Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Paul Birkeland on June 20, 2019, 09:21:06 AM
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For those who can hear their computer working away through their Crack or who are using a powerline ethernet kit and hear lots of clicking and static, a ground breaker installed in place of the buss wire between the chassis and the ground tab of the IEC power entry module will very likely solve this issue. I recommend using a diode that's rated for at least 2A, and the voltage isn't particularly important. Part number STTH2R06 looks to be a solid choice. I do not recommend using a Schottky diode here.
I've attached a photo of how this is retrofitted into a Crack.
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Would this work on any of the other kits? I have a S.E.X. that has this issue. I use an ifi USB filter that works, but it would be nice to bypass that.
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This is very cool.
@PB: can you explain how it works?
It doesn't make sense to me. Two ideal diodes paralleled with reversed polarities would do nothing, right? All current/voltage would pass unimpeded in either direction. So I figure it must work ONLY BECAUSE real world diodes are non-ideal.
I've seen ground loop breakers that employ a diode bridge with a resistor and cap to greatly reduce ground loops - but you're using only the diode bridge. Does the tiny amount of resistance and capacitance of the diodes do the trick? Or is something else at work here?
many thanks,
Derek
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Would this work on any of the other kits? I have a S.E.X. that has this issue. I use an ifi USB filter that works, but it would be nice to bypass that.
Give it a shot and let us know!
@PB: can you explain how it works?
It separates the safety ground by the voltage drop of one diode (in either direction).
All current/voltage would pass unimpeded in either direction. So I figure it must work ONLY BECAUSE real world diodes are non-ideal.
Yes, a perfect diode wouldn't allow this arrangement to work.
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Many thanks PB.
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A little more specifically, if you have a small AC voltage, say 100mV, the diodes present a pretty large impedance and this is what's broken. If you have more than about 0.7V of anything AC or DC, then the diodes will start to short that out.
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I do not recommend using a Schottky diode here.
@PB: why not a Schottky?
Many thanks, Derek
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My Crack w/SB is dead silent, but marked in case come across some noisy tubes.
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@PB: why not a Schottky?
You want the forward voltage drop to be significantly higher than the magnitude of the noise you're dealing with. The low forward voltage drop of a Schottky diode in this instance is a bit of a disadvantage.
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Ah, yes. That makes sense. Thanks.
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I’m thinking about giving this a shot. Is there any amp in the lineup where this would be unsafe or a bad idea? I assume not but don’t want to make a costly mistake.
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I don't see issues doing this with any of our products. I do also plan to test whether a UF4007 can throw a 20A breaker and survive, as this could also be a suitable part to use.
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I picked up a dozen or so and will probably add them to every kit next time any of them are on the bench for one reason or another.
Any downsides to doing it besides the minimal effort and cost?
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In the event of a catastrophic failure, you may need to check and replace the diodes.
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Ok, I’ll just shoot for no catastrophic failures then ;)
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Installed this last night and all seems to be well so far. One caveat for folks wanting to try this in the future - the ground tab opening gets pretty congested with the two buss wires and the twisted leads of the diodes. Prepare for some cussing and finagling. It definitely helped to clear all the extant solder out of the hole first.
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Hello,
This is a mod I would like to try as I have always had a bit of noise from my PC audio.
That said, I am essentially a beginner with this stuff. I built a Crack + Speedball and had no issues. However, to mod my crack I'm a bit lost. I have an original Crack and not 1.1. Your picture looks a bit different than mine does. Mine looks exactly like in this picture - https://i.imgur.com/ZknbokI.png . This is pulled from the original crack manual, as my Crack is on currently and hot.. haha. But, it looks the same.
How would I go about performing this mod? Also, do you need 2 x STTH2R06 diodes?
Sorry for my ignorance and thanks!
HMF
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There is no difference in installing the diodes in the Crack 1.0 vs. 1.1. Both amps have a piece of buss wire from the IEC power entry ground to the chassis solder lug. This is cut out, then the diodes are soldered in its place.
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There is no difference in installing the diodes in the Crack 1.0 vs. 1.1. Both amps have a piece of buss wire from the IEC power entry ground to the chassis solder lug. This is cut out, then the diodes are soldered in its place.
Ahhh. So you leave the buss wire going from the chassis soler lug -> terminal 16L, and replace the buss wire going from the chassis solder lug to the IEC power entry ground with the 2 diodes?
In that case.. easy peasy.
I was confused about the black wire in the original posts attached pciture running into the chassis solder lug, as I don't have that present on my Crack. Wanted to make sure I wasn't missing something.
Thanks for the reply.
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Yes, that's all you need to do.
-PB
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Yes, the 1N5408 would work well.
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Implemented this on my Speedballed Crack, which had been exhibiting clicking due to the mesh extender I installed. The fix worked like a charm. Thanks, Paul!
Joe.
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This mod removed the noise I was getting from my DAC. Thanks for this great mod PB!
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This is the best $2 you can spend on the Crack. Perhaps it would be worth including these diodes with the kit and adding the mod into the manual.
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This is the best $2 you can spend on the Crack. Perhaps it would be worth including these diodes with the kit and adding the mod into the manual.
I concur 8)
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I sure do like having the safety ground connected with a solid piece of wire when a component is being powered on for the first time!
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How about SF51-B diodes? Do those make the cut?
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Those are going to have leads that are quite fat, and it wouldn't surprise me if you couldn't get one properly attached to the #8 solder lug.
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I asked because I used those years ago when I built my Crack amp. Aside from the fat leads are their electrical parameters suited to the task?
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I asked because I used those years ago when I built my Crack amp. Aside from the fat leads are their electrical parameters suited to the task?
Yes, electrically they would be fine for isolation. Hopefully you didn't use them in place of the UF4007s in the power supply though!
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No, using them in the power supply would not have been good, not for those diodes and not for the rest of the amp.
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@PB - I recognize that this mod was only intended to deal with the bigger (noisier) problem of junk on the power lines (for those that have this problem) and not meant to be a fix-all for all types of noise. But I'm wondering whether this would prevent rfi/emi induced currents picked up by shielding from draining to earth ground?
I was thinking a tiny cap in parallel might provide a workaround a la Broskie and others for high frequency noise, but this wouldn't provide a path for lower frequency noise to drain (e.g., currents induced by a PT or power supply chokes).
Any thoughts?
I like the idea of the protection this simple mod provides. But I don't have discernible noise on my mains - although I do believe my sound take a sight hit when my son is watching tv. At the same time, I don't want to do anything that compromises all the other "protection" I've built in with extra shielding and drains to ground.
many thanks, Derek
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You could certainly put a 0.1uF ceramic cap across the diodes.
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Thanks PB. My concern, perhaps (likely) based on misunderstanding, is that this would work well for higher frequency noise -- e.g, 10kHz+ -- but less well for 60/120Hz transformer noise caught by shielding to which a 0.1uF cap would present an effective resistance in the 1000's of Ohms. Does this matter? Or does even such low frequency noise signal, having nowhere else to go, pass directly to earth ground even if provided only a highly resistive (reactive) path to earth ground?
many thanks again, Derek
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The cap would indeed create a short circuit for high frequency noise from the chassis to the earth ground. Of course, you don't want to create too good of a short, otherwise the noise we are attempting to block will be passed by the cap, and thus defeat the purpose of the diodes in the first place.
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It just occurred to me that there is relatively easy solution for dealing with lots of shielding that needs wiring to ground: install your two-diode mod, but isolate the shielding from chassis ground and wire the shield drains directly to the earth ground lug of the iec inlet.
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You can do that or move the diodes to between the audio ground and the chassis ground.
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That's an even better idea! Thanks PB.
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I've just put in the diode mod and have to say the results were not much short of a revelation. Full volume from the PC and full volume on my MkI crack and it's so silent I think I'm missing something! All of those tiny twitters and buzzes are gone. As a test, I played this at about half volume (HD600) and the silence at the end really enhanced the performance. If Steven Wilson is an unknown name to you please listen. If you're not emotionally drained at the end I'm sort of sorry for you.
https://www.youtube.com/watch?v=tMfGp79fJCQ
Thanks, PB. This should be added to the original build IMO. Just a few pence for such a good result. It's also a good incentive for me to get the Speedball fitted
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I don't see issues doing this with any of our products. I do also plan to test whether a UF4007 can throw a 20A breaker and survive, as this could also be a suitable part to use.
PB, what's the result of this experiment? As i have some leftover uf4007's from my original Crack build and am planning on reusing them..
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The peak current rating of the UF4007 is sufficient that this seems less concerning than it once did. I wouldn't be concerned about using them in this application.
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Would a pair of 1N5402 diodes be suitable? They were the only ones I managed to find locally
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They could be a little bit on the large side physically, but electrically they will work OK.
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You were not wrong! a bit of a tight fit but now it is totally silent with nothing playing, even with the volume turned up full and positioned next to my router
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Worked like a charm 8) Thanks PB
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Can this mod be installed on an Eros v1 and Mainline as well?
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Can this mod be installed on an Eros v1 and Mainline as well?
I don't see issues doing this with any of our products. I do also plan to test whether a UF4007 can throw a 20A breaker and survive, as this could also be a suitable part to use.
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Thanks, I seems to have missed that info.
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Are you feeding your Eros with a signal from a computer? If not, then I would not install this in a phono preamp.
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Yes, the 1N5408 would work well.
Hey there! Just picked up some of the above diodes, but the leads seem mighty thick - and double thick once twisted - wondering whether ill be able to attach to the ground etc effectively. So, my question: do the STTH2R06 diodes have skinnier leads?
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Yes, they would have skinnier leads.
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I'd love to try this mod, but the only diodes I've got on hand are 1N4001, which are rated to 1A.
It's been quite a while since I built my crack, but can you confirm for this beginner that I should find a different set of diodes to use?
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The peak current capability of the 1N4001 is 30A, which is more than enough to get the job done.
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Hi - would 1N5408 work here? Rated at 3A and 1000V? the datasheet says it's a rectifier diode. I'm not sure if that's a problem in this application?
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The peak/surge current is 125A, so no problems there.
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A little more specifically, if you have a small AC voltage, say 100mV, the diodes present a pretty large impedance and this is what's broken. If you have more than about 0.7V of anything AC or DC, then the diodes will start to short that out.
Forgive my ignorance, but am I understanding this correctly?
It sounds like this will prevent voltage under 0.7V from passing through the diode bridge.
I presume the noise coming from a nearby PC/USB DAC is somehow linked to small changes in voltage sent through the power cable, and somehow this small resistance will prevent these changes from translating into the audio signal.
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It's not exactly a resistance, it's more of an open circuit below a certain threshold.
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I had severe noise problems with two different Crack amplifiers that I had acquired no matter what DAC I used as long as the main source was my computer's USB port. Tried ALL my USB ports including a powered and unpowered USB hub too. Regardless, the noise was very much available and loud especially when I started playing a video game on my PC or did anything that put my GPU to work. Used at least 6 or 7 different models and brands of DAC. Then I found out the same happened with other tube amplifiers too (DV and woo) so it was definitely my system. Tried a myriad of USB noise reduction gizmo from iFi. Tried all sorts of fancy power cords both for my Crack and my PC to no avail. Some of these would reduce the noise a little bit or change its nature somewhat but it was still there and in full force! Ultimately did the resistor mod suggested here and just like magic, all the noise disappeared... But I couldn't find a similarly simple solution for other tube amps, so continued my troubleshooting steps until I came across this magical USB isolator after having read about it on various forums:
https://hifimediy.com/product/hifime-high-speed-usb-isolator/. The noise is now completely eliminated with all my tune amps. I have tried it with an Topping E30 and SMSL SU-8 v2, Khadas Tone Board, and a few other DACs I can't even remember in combination with my two non-Crack tube amps and no noise whatsoever... Now I've been tempted to remove the resistors from my Crack to test it with this to see if the noise will be gone, but don't feel adventurous enough.......yet.
Sorry for the super long post, but it was driving me crazy trying to eliminate the weird noise problem I was having, so I figured I'd share some of what I went through and what ultimately worked for me in case it can also help someone else out.
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For the purpose of this mod, you can think of a diode as erecting a barrier that is approx. 700 mV tall: @700 mV and below, no current flows, but everything above 700 mV passes over the barrier. (The "height" of the barrier, called the diode's "forward voltage" -- the minimum voltage required to turn the diode "on" and permit voltage and current to pass, varies a bit by type of diode). This applies to a "forward biased" diode - i.e., one where the anode is more positively charged than the cathode (banded end). Because the mod uses two "reverse paralleled" diodes, there is a forward-biased diode in each direction: to earth ground and from earth ground -- so it blocks sub-700 mV currents in both directions.
In reality, the "barrier" is sloped and some small amount of current makes it through when the applied voltage is less than 700 mV. See attached graph, and specifically the region to the right of the X,Y origin.
cheers, Derek
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One thing I have noticed after doing the diode mod is that my tubes, especially the power tube, doesn't get as brightly lit as before or as compared to when I use the same power tube in another tube amp. As you can tell from my posts, I severely lack technical knowledge in this area, but is this a general side effect of this mod?
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One thing I have noticed after doing the diode mod is that my tubes, especially the power tube, doesn't get as brightly lit as before or as compared to when I use the same power tube in another tube amp. As you can tell from my posts, I severely lack technical knowledge in this area, but is this a general side effect of this mod?
No, not at all. That would tend to indicate a loose connection in the amp that may have been bumped when you installed the mods. I would go back in and do a DC voltage check and start a new thread if anything is off. The twisted pair of wires that goes to B7/B8 makes the 6080 glow, and if one of those wires is loose on either end, it will not glow nearly as brightly.
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For the purpose of this mod, you can think of a diode as erecting a barrier that is approx. 700 mV tall: @700 mV and below, no current flows, but everything above 700 mV passes over the barrier. (The "height" of the barrier, called the diode's "forward voltage" -- the minimum voltage required to turn the diode "on" and permit voltage and current to pass, varies a bit by type of diode). This applies to a "forward biased" diode - i.e., one where the anode is more positively charged than the cathode (banded end). Because the mod uses two "reverse paralleled" diodes, there is a forward-biased diode in each direction: to earth ground and from earth ground -- so it blocks sub-700 mV currents in both directions.
In reality, the "barrier" is sloped and some small amount of current makes it through when the applied voltage is less than 700 mV. See attached graph, and specifically the region to the right of the X,Y origin.
cheers, Derek
Oh wow, thanks! That graph helped me understand it better. This implies small voltages over ground can cause noise, I don't really understand why but I'm going to try and find out.
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This implies small voltages over ground can cause noise, I don't really understand why but I'm going to try and find out.
The maximum peak signal voltage you could send into a Crack with the volume control all the way up is 1.5V. If you have 500mV peak of noise current because of a polluted ground, that's not a small voltage at all!
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The maximum peak signal voltage you could send into a Crack with the volume control all the way up is 1.5V. If you have 500mV peak of noise current because of a polluted ground, that's not a small voltage at all!
Hmm, interesting. I was thinking it had to be related to 120 AC volts somehow due to the connection to the main power input. I think I need to take a step back and figure out how the audio signal differs from the 120 AC in, and how the ground differs and can affect the audio. I believe the simple answer is the noise is coming from the audio input rather than the power input, therefore the voltage is significantly lower.
I've been doing some experimenting to try and understand the way this noise is introduced. First I've realized there are two noises:
1. Can be heard with nothing plugged in but the headphone and power, but I have to turn the volume way up. It's a constant buzz that is audible after about halfway, more present in the left side. I'm going to guess this is either a ground loop buzz, or there are some weak solder joints. I think the ground loop occurs when nearby stuff is plugged into a different outlet or something? This amp is on top of a PC and next to a monitor, which are all plugged into the same power conditioner. I don't really know enough about this to determine much about it.
2. Needs a signal into RCA.
2a. If I connect them and touch my fingers to the other side I get a buzz, I'm guessing this is a ground loop caused by my body.
2b. When plugged into my DAC output I get intermittent little buzzing, similar to the cell phone interference sound, but lacking a distinct pattern. The DAC is powered via laptop currently, which runs on battery and is charged by the same outlet, but not on a power conditioner. The sound is present regardless of the laptop being plugged into an outlet, guessing this is something related to the battery of the laptop sending something over the 3.3V USB powering the dac.
2c. When I plug the interface into my main PC USB, the noise is drastically reduced in volume. This PC is plugged into the power conditioner. I'm guessing here, it's the same 3.3V sending noise, but due to a better PSU installed in the system it's more stable.
I've been reading up on ground loop hum, and will continue to try and learn more about this. It's one thing to know how to install a fix for noise, it's another to understand why it fixes it. I'm very interested in the why of it all. Thanks for the info on this.
I just got the pair of rectifiers today for this mod, going to install them after work.
BTW: The longer I use this amp the more I am enjoying it. Sometimes the bass notes hit so nicely, I'm extremely happy with this amp and have greatly enjoyed building it myself. The active community on these forums is a very nice bonus to it all.
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1. Can be heard with nothing plugged in but the headphone and power, but I have to turn the volume way up. It's a constant buzz that is audible after about halfway, more present in the left side. I'm going to guess this is either a ground loop buzz, or there are some weak solder joints. I think the ground loop occurs when nearby stuff is plugged into a different outlet or something? This amp is on top of a PC and next to a monitor, which are all plugged into the same power conditioner. I don't really know enough about this to determine much about it.
This is covered in the sticky FAQ on this forum. With open inputs and high input impedance, turning the volume control up with nothing plugged in is just amplifying ambient grunge.
I've been reading up on ground loop hum, and will continue to try and learn more about this. It's one thing to know how to install a fix for noise, it's another to understand why it fixes it. I'm very interested in the why of it all. Thanks for the info on this.
It's more about when two grounds aren't in perfect agreement with each other, and in this case when you have the ground in the Crack that is really solidly earthed and another ground via USB that has a few hundred mV of noise riding on it. If those two meet, that few hundred mV of noise becomes signal current as it seeks earth in the Crack, or it doesn't if it can't follow that loop (with the anti-phase diodes). When we put out our own DAC, we were very careful to only use the USB power as an indicator that something was plugged into the USB socket and nothing else!
BTW: The longer I use this amp the more I am enjoying it. Sometimes the bass notes hit so nicely, I'm extremely happy with this amp and have greatly enjoyed building it myself. The active community on these forums is a very nice bonus to it all.
We are certainly here to help.
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Just installed the mod, works like a charm. Zero noise picked up from DAC, via laptop or PC connection. I even turned the knob all the way up and still nothing.
Great stuff, thanks Paul!
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I don't know what kind of voodoo magic was involved in this modification idea, but all I can say is that it works 100%. I just wish I had done it sooner.
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As I posted after I had added the diodes to my Crack with great success, IMO they should be provided as part of the original build. If nothing else it would cut out a lot of posts from unhappy owners. Costing just a few cents, it's a no brainer.
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I should point out that it does not always work for every situation. The ways of hum and noise are many and varied!
But yes, it is included in the new Moreplay preamp.
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RL207 or UF4007? I have both on hand. The RL207 isn't a fast recovery. Does it matter?
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Either one is OK, the RL207 would be a worse rectifier than the UF4007, but would be slightly better in this position.
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Either one is OK, the RL207 would be a worse rectifier than the UF4007, but would be slightly better in this position.
What characteristic makes the RL207 "better" than the UF4007 for this duty? The higher current and peak current ratings?
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You can use either, the RL207 has a very high peak current rating, and that's not necessarily a bad thing.
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Thanks Paul. I have a surprisingly very low amount of "hash" present in both the Crack and a Hybrid tube headphone amp when hooked up to my DAC. It's only present in the Hybrid when the DAC is run through the Foreplay before the Hybrid. DAC direct to hybrid and the hybrid is silent. It's present in the Crack either direct from the DAC or through the Foreplay first. Only slightly worse when the Foreplay is in the mix. But really, it's low level either way. Plan on installing the diodes in both the Foreplay and Crack to see if I can get rid of it. But I'm considering myself lucky because it's really low level as it is.
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Ive got some DAC noise on my SEX with some of my headphones. And I was wondering if I need to include both ground leads connected to the ground of the inlet plug for it to have the desired effect?
NVM, theres only one going to the inlet ground..
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The diodes replace the IEC earth to chassis lug connection, nothing else.
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https://www.mouser.ie/datasheet/2/358/typ_DEH-1275811.pdf (https://www.mouser.ie/datasheet/2/358/typ_DEH-1275811.pdf)
Came across these on Mouser, they are targeted at the mhz range but i wonder if they would suffice to stop ground loops in audio equipment?
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I accidentally ordered a few STTH2R06A, rather than STTH2R06. I have attached here: https://imgur.com/a/ieMnrfB
Can I use these in place of the the non-A variant? E.G. something like this https://imgur.com/mVpuFLf
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I would absolutely not use surface mount diodes in this application.
Order 1N4001, 1N4002, 1N4003, 1N4004, 1N4005, 1N4006, 1N4007, UF4001/2/3/4/5/6/7.
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https://www.mouser.ie/datasheet/2/358/typ_DEH-1275811.pdf (https://www.mouser.ie/datasheet/2/358/typ_DEH-1275811.pdf)
Came across these on Mouser, they are targeted at the mhz range but i wonder if they would suffice to stop ground loops in audio equipment?
They are 25 freaking dollars each if you buy 50 at a time!
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They are 25 freaking dollars each if you buy 50 at a time!
Neat idea though. And if they actually work for breaking ground loops, they might be worth it for a lot of people.
One could also just install a tiny inductor between the earth ground and chassis ground, but I can't find a high current rated one on Mouser. These are all a lot cheaper than the Schurter thingy, but none are rated for much more than 5A, and most for a lot less: http://www.mouser.com/Passive-Components/Inductors-Chokes-Coils/Fixed-Inductors/_/N-wpczZ1yzvvqx?P=1z0z819Z1z0z7l5Z1z0wohhZ1yzjx1iZ1z0wqhyZ1z0jky5Z1z0wqh6Z1yzjx12Z1z0wognZ1z0wqobZ1z0wqgxZ1yyt8gaZ1z0wqhwZ1yztq3uZ1yyt8f1Z1z0woglZ1z0wqo9Z1yzmpecZ1z0wkc2Z1z0j7djZ1z0wqhsZ1yxadcvZ1z0j5rrZ1z0wogjZ1z0wqo1Z1yztpvpZ1yi47jgZ1z0wkc1Z1z0wqhqZ1z0jkw7Z1yu90k7Z1yzuwe3Z1z0woghZ1z0wqo0Z1z0woh9Z1yvgg2oZ1yzuvkkZ1z0wqhoZ1yzakszZ1yxh8woZ1yy85mjZ1y9gfh8Z1z0wogfZ1z0wqppZ1z0wpgmZ1yu90l4Z1z0wfhjZ1z0wqhnZ1yzuvk8Z1yy7e5iZ1z0wqn1Z1yzsc00&Keyword=inductor&FS=True (http://www.mouser.com/Passive-Components/Inductors-Chokes-Coils/Fixed-Inductors/_/N-wpczZ1yzvvqx?P=1z0z819Z1z0z7l5Z1z0wohhZ1yzjx1iZ1z0wqhyZ1z0jky5Z1z0wqh6Z1yzjx12Z1z0wognZ1z0wqobZ1z0wqgxZ1yyt8gaZ1z0wqhwZ1yztq3uZ1yyt8f1Z1z0woglZ1z0wqo9Z1yzmpecZ1z0wkc2Z1z0j7djZ1z0wqhsZ1yxadcvZ1z0j5rrZ1z0wogjZ1z0wqo1Z1yztpvpZ1yi47jgZ1z0wkc1Z1z0wqhqZ1z0jkw7Z1yu90k7Z1yzuwe3Z1z0woghZ1z0wqo0Z1z0woh9Z1yvgg2oZ1yzuvkkZ1z0wqhoZ1yzakszZ1yxh8woZ1yy85mjZ1y9gfh8Z1z0wogfZ1z0wqppZ1z0wpgmZ1yu90l4Z1z0wfhjZ1z0wqhnZ1yzuvk8Z1yy7e5iZ1z0wqn1Z1yzsc00&Keyword=inductor&FS=True)
I'm not sure if that would pass electrical code requirements. I'm guessing one probably needs a current rating on the ground connection that is at minimum the same current rating as the breaker at the panel (e.g., 15A or 20A).
cheers, Derek
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I would bet that those would pass 20A and pop a circuit breaker pretty easily.
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Fair point - it only needs to handle the current for a split second.
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Still, I don't think these would get the desired result. For audible noise, these would be a dead short (it's a piece of wire after all) and would only present significant impedance to high frequency noise that wouldn't otherwise be audible, and that we would otherwise want to shunt to earth as effectively as possible.
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Yeah, that makes sense. they'd only be appreciably reactive in the MHz range. The application example diagram in the Schurter datasheet shows them used with a mainframe computer and peripherals.
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I would absolutely not use surface mount diodes in this application.
Order 1N4001, 1N4002, 1N4003, 1N4004, 1N4005, 1N4006, 1N4007, UF4001/2/3/4/5/6/7.
Thank you Paul B, I have ordered some 1N4007 (1A/1200V) following your advice.
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The maximum peak signal voltage you could send into a Crack with the volume control all the way up is 1.5V. If you have 500mV peak of noise current because of a polluted ground, that's not a small voltage at all!
If I understand the paragraph correctly, the noise current is coming from the ground pin in your power outlet / power strip, and the pair of twisted diodes is to block the noise current from entering the Crack, am I correct?
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They are 25 freaking dollars each if you buy 50 at a time!
~$5 from Mouser. Will add one to my next order and measure them against the 10r/.1uf trap i am using in my pre amp.
https://www.mouser.ie/ProductDetail/Schurter/DEHL-10-0001/?qs=%2Fha2pyFaduglz%2FafWzmtwPY7x75HshQWsFSrhm4Ey1uJ9e%252BfusRydw%3D%3D (https://www.mouser.ie/ProductDetail/Schurter/DEHL-10-0001/?qs=%2Fha2pyFaduglz%2FafWzmtwPY7x75HshQWsFSrhm4Ey1uJ9e%252BfusRydw%3D%3D)
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If I understand the paragraph correctly, the noise current is coming from the ground pin in your power outlet / power strip, and the pair of twisted diodes is to block the noise current from entering the Crack, am I correct?
Usually, what we call "ground loop" hum/buzz comes from capacitive coupling from the power transformer primary winding to the signal amp power supply secondary (the high voltage in tube amps). The capacitance is small, on the order of 100pF, so it presents a high impedance at power line frequencies and can be shorted to ground through a 10-ohm resistor.
The diodes are there in case there is a fault that presents a low-impedance source, such as a short from the power line to the signal ground. In normal use, they are not active and have no effect.
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Usually, what we call "ground loop" hum/buzz comes from capacitive coupling from the power transformer primary winding to the signal amp power supply secondary (the high voltage in tube amps). The capacitance is small, on the order of 100pF, so it presents a high impedance at power line frequencies and can be shorted to ground through a 10-ohm resistor.
The diodes are there in case there is a fault that presents a low-impedance source, such as a short from the power line to the signal ground. In normal use, they are not active and have no effect.
Thanks a lot for the explanation, PJ. I could hardly understand what you said, mainly due to my ignorance in electronics.
1.) so the capacitive coupling (first time to hear that coupling in the transformer :) ) from the power transformer primary winding to the secondary windings will pass some small line current (110V 60Hz) to all secondary winding circuits (the 6.3 VAC heater circuit and the 2x0 VAC unrectified B+). But how the capacitive currents are grounded, I can't find any 10-ohm resistor in Crack?
2.) the twisted diodes are breaking the ground loop if I understood PB's 'ground breaker' correctly, so why they are not active and have no effect?
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There are some vintage components that just use a 10 ohm resistor instead of the antiphase diodes. I prefer the diodes a bit because the peak current capabilities are better specified.
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https://en.wikipedia.org/wiki/Ground_loop_(electricity)
The Ground loop (electricity) article on Wikipedia is terribly written, but I think I roughly got the idea of 'ground loop'.
So the RCA cables that connect Crack and DAC form a ground loop (ground of Crack -> Crack chassis -> RCA grounding wires -> DAC chassis -> ground of DAC -> ground of Crack), and the loop acts as a single-turn secondary winding of a transformer. So through induction it will generate some small noise current from ambient magnetic fields - magnetic fields that come from the main power line (60Hz), router, computer, etc.
So the 'ground breaker' diodes from PB will break the ground loop, preventing it from generating noise current thru induction. Am I correct? :)
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It's more about creating a break in the blue line in this image, and mostly breaking the line between the PC and the Crack. What we don't want is for any nasties riding on the earth connection from the PC to travel through the signal cables, into the Crack, then to earth through the Crack. A DAC which has its own power supply and does not rely on USB for power will tend to do this on its own. We used to suggest using a DAC with an optical cable to do this, or SPDIF with a proper input transformer, but the antiphase diodes create an opening in the loop for far less money.
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Thanks a lot, PB, for the image.
I think my understanding of 'ground loop' from the terribly written self-conflicting Wikipedia article is exactly the blue line loop in your image.
My computer and DAC both come with SPDIF. I once tried connecting them via an optical cable, but couldn't hear any difference vs the USB output to DAC. :-[
Then I did some google search, and it seems some people think the SPDIF output from computers is not optimized for HiFi audio, they are designed for data transfer, so the jittering from SPDIF on computers will be very high due to poor clocking. Not too sure about these technical stuff :-[
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It just occurred to me that there is relatively easy solution for dealing with lots of shielding that needs wiring to ground: install your two-diode mod, but isolate the shielding from chassis ground and wire the shield drains directly to the earth ground lug of the iec inlet.
You can do that or move the diodes to between the audio ground and the chassis ground.
That's an even better idea! Thanks PB.
Just intrigued by the talk, but couldn't fully understand it... :-[
I can understand @Deke609's method to wire his Faraday shielding cage to the earth lug of the IEC power socket directly in order to bypass the diode 'ground breaker' and drain the EMI noises captured by the Faraday cage to the ground.
But I couldn't quite understand PB's approach. Where are the audio ground and chassis ground?
I just learned today that the Crack's "ground bus" is grounded thru the 3U/L tab, so should we break the grounding connection there and insert the "ground breaker" there? :)
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Sure, you can go ahead and isolate terminal 3 and install the antiphase diodes between terminal 3 and the chassis.
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Cool, thanks a lot for pointing out the "ground breaker" location for Cracks with Faraday cages, PB!
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Hi there - I'm a newbee for comments to the forum. I built my BHC with Speedball last June; it works well until recently when I notice the following.
I notice/hear/feel a 'static electricity' type shock in the right channel of my new (2 mos) ZMF headphone. It is winter, dry and lots of static all over my gear. I rolled a new tube and thought it went away. Rolled another one and it's still there. Zach at ZMF has not experienced before.
Has anyone had this happen to them? Would the fix that Paul started with this thread solve this?
Thanks - and if I'm doing anything wrong in the forum comments (style, quotes, etc.) let me know that as well.
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Is this noise present with nothing plugged into the RCA jacks on the Crack and the volume pot turned all the way down?
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Thanks Paul - I will try to replicate it under that condition. I will also try another headphone/cable to see what the result might be.
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So I pulled my last comment - I simply cannot replicate my static shock/energy jolt in the right channel of my headphone.
I tried Paul's suggestion of unplugging the inputs from my Crack with volume at zero; no static shock resulted.
I also tried to replicate with different tubes, on different days (even other days when static was present in the day) and could get no shock through the headphone, even though there would have otherwise been a static electric charge when I touched other parts of my equipment.
Must have been the tubes that was in place on the day. :-(
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For the purpose of this mod, you can think of a diode as erecting a barrier that is approx. 700 mV tall: @700 mV and below, no current flows, but everything above 700 mV passes over the barrier. (The "height" of the barrier, called the diode's "forward voltage" -- the minimum voltage required to turn the diode "on" and permit voltage and current to pass, varies a bit by type of diode). This applies to a "forward biased" diode - i.e., one where the anode is more positively charged than the cathode (banded end). Because the mod uses two "reverse paralleled" diodes, there is a forward-biased diode in each direction: to earth ground and from earth ground -- so it blocks sub-700 mV currents in both directions.
In reality, the "barrier" is sloped and some small amount of current makes it through when the applied voltage is less than 700 mV. See attached graph, and specifically the region to the right of the X,Y origin.
cheers, Derek
And there it is. An explanation simple enough for me to understand!. thanks PB for the brilliant Mod. and thanks to Derek for lifting the veil!
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Hi, I am currently trying this mod on my Extended Foreplay 3. I am using 1N4004 diodes.
There is a drain wire from the power switch cable connecting the IEC power entry to the first ground lug and then it continues to the ground lug from the power transformer.
When I do the mod I am assuming I need to clip the drain wire between the IEC and the first ground lug but leave a connection between the first ground lug and the transformer ground lug. This is how it is done in the Crack.
I am wondering if it would be better to route the drain wire from the power switch directly to the transformer ground lug and not to the IEC ground? The photo just shows my layout nothing soldered yet and no clipped leads yet. If somebody can confirm that I would appreciative it. Thanks, Best, Stefan
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That should work the way you have it setup.
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Thanks Paul, this mod works wonders did it on my Crack as well.
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That works for noise control, but is not as safe as it should be. The chassis plate and transformer cores should be bonded to the safety ground with no interruptions; the ground lift should occur between the signal ground and chassis; i.e. at terminal 28.
That's a pretty inconvenient location, unfortunately - a great many wires go to that terminal. It will be tricky!
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Thank you Paul, indeed terminal 28 would be tricky. PB said on the first page of this thread:
I don't see issues doing this with any of our products. I do also plan to test whether a UF4007 can throw a 20A breaker and survive, as this could also be a suitable part to use.
If you are saying that this mod is not the safest for the Foreplay then I would consider reversing it, it's nice without the noise but I rather would go the safe route.
Could you or PB confirm the safety of this mod? Thanks, Best, Stefan
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This is a workaround for older kits. For new kits, we separate the audio ground and the chassis plate with the antiphase diode arrangement plus some other parts, and this is the safest choice. For our older kits that are not designed from the start to have these parts, the solutions are less than ideal. It would take a very catastrophic failure (like say replacing the power cord on your electric clothes dryer with the power cord plugged into the wall, then dropping the bare end of the power cord onto your Foreplay's chassis plate) to cause problems with the diodes installed, but it is remotely possible.
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Hello,
Just finished my stock Crack build and I’ve discovered through process of elimination that my crack produced a static noise whenever my FIIO K5 Pro external DAC/amp’s USB is connected to my desktop computer. The static increases in volume when the volume on the crack is increased but not when the DAC/amp’s volume is increased.
I’m pretty confident that my solder joints are good, as tapping on the unit produces no distortion or anything audible.
I’m wondering if using an optical connection would resolve the issue.
I would greatly appreciate any advice or help anyone is able to offer regarding this issue.
Thanks I’m advance.
Tom
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An optical connection will resolve the issue, or there's this:
https://forum.bottlehead.com/index.php?topic=11676.0 (https://forum.bottlehead.com/index.php?topic=11676.0)
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Aha!
I had read that thread as it sounded similar and wondered, but did not want to assume.
I think I will move forward with adding a ground breaker, thank you much!
Would you mind explaining why this is happening and how this fixes it? I found it interesting because whenever I moved my computer mouse I could cause a noise in addition to the background static.
Tom
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The diodes create some separation between the Crack earth and the earth of the computer, which will interrupt the flow of low level noise that would otherwise be there.
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Okay gotcha. Was trying to read a bit about the anti parallel diodes.
Thanks a bunch Paul!
Tom
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I want to try this on my SEX kit. I also have USB noise on my odac.
I drew a picture of what I think needs to be done. So basically I solder the twisted diodes at the red points and the black line represents the twisted diodes. Anything I am missing?
Also currently looking at the 1n4007 for this mod. Anyone have a better recommendation? I guess the ones Paul mentioned are all good for this.
Does this look correct?
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1N4007 will do the job. The little piece of bus wire going from the solder lug on the chassis up to the IEC power entry module needs to be removed in the process as well, as the diodes are taking its place.
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Thanks Paul, if I understand correctly just the single piece of bus wire going up to the IEC power entry module should be removed.
The 2 other pieces of bus wire should remain, correct?
Also should I reverse the polarity of the diodes like in your original picture?
Much appreciated.
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Yes, the piece of bus wire wire going to the earth lug on the IEC power entry module is removed and replaced by the pair of diodes. The diodes need to be wired antiphase.
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Totally needed for me. Also worked like a charm!!!
Like, static, that changes pitch depending on the screen. Pulled the RCA, and dead quiet, so I knew the noise was after the Crack. And now....holy flippin' motherlovin' cow!!! It made my HD650s come to life!!!
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Hi there,
I've been reading this thread (and others) and didn't find my situation covered.
My Crack + Speedball produces crackling/noise on the left channel. Only power and headphones are plugged in, nothing on the RCA jacks. Turning the volume pot doesn't affect this.
All joints seem fine, poking around and re-heating many didn't make a difference.
What I've observed: my laptop (and monitor etc) are sitting right beside the Crack.
a) unplugging the laptop (and all other devices in this room) from power doesn't affect the crackling
b) unplugging the laptop AND moving it 4-5meter away: the crackling stops
Could this be solved through the suggested diode mod as well?
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You may be picking up pollution through the air. Does the noise go away if your laptop is running on batteries?
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Thanks for your quick response.
No, the noise is present as long as the laptop sits right beside it. Whether the laptop is battery powered or plugged into power doesn't affect the crackling.
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If you turn the laptop to airplane mode, does the noise go away?
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Yes it does!
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I would recommend purchasing a 0.1uF X7R capacitor (leaded, not a surface mount/smt). Solder that between the ground shell of the red RCA jack and terminal 22. That may or may not solve the problem, but it's a cheap experiment to try.
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Assuming I got the right part: it didn't solve the noise.
Now, with the Crack sitting besides the non-airplane-mode laptop,
a) when no RCA jacks are plugged in: audible hum on both channels, increases when volume is turned up. Masks the initial left channel crackling.
b) with RCA jacks plugged in (either to a cellphone or another grounded DAC): the audible hum mentioned above is gone - but the left channel crackling remains
The good news is: just 50-60cm of distance between laptop and Crack will reduce the left-channel-crackle to almost nothing. I'll just re-arrange my setup and take the capacitator out again :-)
PS I can't seem to insert the attached image. The capacitator reading is 104KH 250VMY. It's attached to terminal 22 and the ground lug of the red RCA jack.
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That is not an X7R cap, and yes, it may indeed matter.
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I just wanted to chime in that:
- Crack baseline: All sorts of CPU noise from ground loop from my DAC (SMSL D300) clearly audible at around 30-40% on the volume knob. Unplugging USB cable from DAC would remove all noise.
- Crack + Speedball: Would hear the same CPU noise at ~20% volume. Was driving me nuts!
- Crack + Speedball + anti-phase STTH2R06: Same CPU noise barely audible at 100% volume.
Given that I listen at 15-25% (depending on album), I'm very happy to report that thanks to the mod, I am listening to pure silence in between tracks and silent moments!
Thanks for making this a sticky, and the easy $1.24 + 5 minute fix!
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Worked perfectly on my Crackatwoa!
I have an Audiolab M-Dac connected to my PC via USB and prior to this, there was noise leak at 0% volume (could still hear music), an audible background noise past 75% volume and moving my mouse on the screen caused background noise as well.
Now 0% volume silences all sound, volume knob turned to 100% has no background noise, and no more background noises with my mouse.
Was getting ready to replace my DAC prior to finding this fix.
Paid $2.02 at Digikey for two STTH2R06.
Thank you!
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Hello,
I want to add this modification to my Crack, since I get a lot of loud noise through usb whenever my pc is working on some demanding program.
I've been looking for the STTH2R06 but I can't find them around my area and the shipping costs are pretty high. I've bought a handful of 1N4007 instead since they were mentioned here before.
Before I proceed with the mod I just wanted to ask for confirmation that these diodes would work fine, since looking them up they seem to measure 1A (I'm rather clueless when it comes to these components). Am I good to go?
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They have a sufficient surge rating to handle the duty there in case of failure, so go ahead and use them.
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Just wanted people to know this worked perfect for my SEX kit. In terms of how to do it, just disconnect the skinny wire connected to E on the top left corner (Look at page 25 of your Terminal Identification photo), you don't even need to cut the wire, just unsolder the wire, twist the diodes in opposite directions together making sure it doesn't short on anything else and "voila" no noise at all if you have it connected to your DAC.
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I would absolutely not use surface mount diodes in this application.
Order 1N4001, 1N4002, 1N4003, 1N4004, 1N4005, 1N4006, 1N4007, UF4001/2/3/4/5/6/7.
Any reason to pick one over the other or all going to do the exact same job?
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They are all about the same in this application.