Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: fullmetal on May 23, 2011, 02:06:41 AM
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Hey everyone, I have had a crack for about a month now, and since it is my first amp I am continually amazed at how awesome music sounds. However I have begun to notice quite a bit noise when there is no music playing. Is this normal? I usually cant tell when music is playing, unless it gets really low and then I can hear the humming in the background. Would this be fixed with the speedball upgrade? I use Decibel for a music player, HRT MSII DAC, blue jean rca, beyerdynamic dt990 600ohm.
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Listening to it now it just started humming so much I could feel the vibration. I accidentally left it on all night last night, could that be a problem?
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Leaving it on should never be a problem unless something has failed. Vibrating could mean that a tube is drawing too much current. Start by taking the voltage measurements and let us know if anything seems way off. As Grainger mentions it could be a solder joint that opened up, or it could be a tube going south.
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Ok, I will do that. The hum is much more pronounced on the right side.
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Funny that I found this thread just now, I was thinking about the background hum in my amp as well. It is very low though still audible if there is no music at all and during silent passages with very few instruments. I don't think there is something wrong however, I just wanted to know if there is a hum present in these amplifiers or if they should be dead quiet? The latter seems a bit unnatural since I know how much my guitar amp hums.....
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My crack with speedball and stock tubes is very very quiet into shorted inputs, no hum at all. With some of the 6AS7 there is a tiny bit of hum, it can be made worse by adding a 6SN7. But even at it's worst it is still hardly discernible and when you ply music I do not notice it except between tracks or very quiet passages.
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Is it normal for it to be more pronounced on one side or does that indicate a problem? When I get a chance I will go over it and check the voltage measurements and probably just buy the speedball upgrade.
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I had a bad tube that had a raised noise floor on one channel.
Just listening to mine now I realised that if the source on my pre-amp was the iPod I'd get a slightly raised noise floor that isn't there with my dac. It could be a number of things until you've eliminated some steps - have you swapped the input cable around (l/r to r/l)? That at least narrows down the fault to the amp.
Dac > Speedball > 600Ω headphones is dead silent on mine.
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Yes, to be sure of the noise floor you have to remember that it can be coming in ahead of the amp. So the best way to listen to the noise floor is with the inputs shorted with shorting jacks. That way you will only heard noise generated by the amp.
Fullmetal, have your tried different tubes? That would be one important test to make after you make the voltage checks. If a simple tube swap doesn't solve it - since your problem is dominant in one channel you should probably go over the solder joints concentrating on the connections on the side with the noisy channel. It makes the most sense to solve this problem explicitly rather than hoping that installing the upgrade will solve it.
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I do not have another set of tubes to swap out. I hope that is not the issue as I just got the kit a month ago. What are shorting jacks? Thank you for the replies, hopefully I will get some voltage readings soon.
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Would you believe it?
I just switched off my pre-amp power supply and power amp (both Naim) for the first time in months and bongo. One channel with a raised noise floor on my input tube... Grr, I only had that E80CC in for a few days as well, it was working perfectly. Both the Crack and Naim system are connected to the same mains but the crack was turned off at the time, could it be coincidence?
:(
Luckily my faithful CV4003 is still working a-okay.
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All voltage readings checked out. And Doc the reason I thought the speedball might be a good route is this is the only Crack I have ever heard so maybe the noise floor is normal.
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I would suggest trying different tubes next. Contact Eileen tomorrow and she can send out a set to try. queen at bottlehead dot com
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Maybe this can help... I finished my build the weekend before this past one. I built the Crack stock with the excpetion of using Mills resistors in place of the stock cement/wirewounds and used an Alps Blue Velvet volume pot. The amp is, for all intents and purposes, silent. I was and still am incredibly impressed with the lack of any preceptible background noise. I havent shorted the inputs to check whether the background is actually "black", but in terms of normal listening, there is nothing there. For all intents and purposes, it's silent (Speedball must be really impressive).
My point is that the amp, in stock form, is capable of a near silent background during normal listening (including quiet passages and pauses in the music). I use the word near as a qualifier only because an auidophiles description of silent may be different from mine, but you get the point I think. So follow the advice of the more knowledgable folks who have offered suggestions.
For the record, my main phones are Beyer 990's (250 ohm).
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I expect that the sensitivity and impedance of the phones used will affect the level of noise you hear. That is, in addition to the tubes as Doc mentioned already.
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Apologies for the slight thread-jack.
When I turn on the crack with the E80CC in I get a inrush type hiss in the right channel, then it dies down completely before the same happens on the left a second or two later (but the hiss stays at a noticeable level). Is this indicative of something?
I've noticed that in general when I power on one channel usually comes up first and also when powering down, I guess this is normal? Could the E80CC have suffered in some manner because of this?
I quite liked the sound of it and am considering replacing it, is it a lost cause though or just a bad experience? My other tubes seem perfect fwiw.
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Might try cleaning the tube pins, Scotchbrite works well. Then insert and remove the tubes 5 or 6X to clean the sockets.
Delta, try leaving the tube running for a few days, see if the hiss cooks off...John
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I just finished my speedball upgrade yesterday and with the exception of soldering one of the 2907A transistors where one of the 2222A was suppose to go everything is working. I discovered my mistake shortly after doing it and set it right. However, my amp is no longer as "black" quiet as it was before. There is definitely a low background hum that seems to be unaffected by the volume control and a pronounced buzzing that comes in between 75-100% volume. I've had a good look and most of the ground contacts and the soldering seems solid. Any thoughts on where I should start to troubleshoot?
Thanks.
Mark
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If the transistors got power before the mistake was discovered, I would start by replacing the 2N2907 and 2N2222 that were installed in the wrong places. They may have been damaged and that could be creating the noise. Other than that the other idea would be to go over all of the new solder joints that were created with the upgrade with a hot iron and reflow them.
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If you didn't power it up before swapping the transistors rewet all the solder joints for the Speedball upgrade connections to and from the circuit and to and from the circuit board first. If that doesn't help then try the boards themselves.
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Thanks for the quick replies. I discovered the mistake while I was still building the boards, about 10 seconds after I'd soldered the wrong one in place and clipped the leads. Oh well, lesson learned. Check twice, solder once. After reflowing the solder joints on the new connections that seems to have solved the worst of the hum. I still have some buzz at the top end of the volume but it isn't where I do my listening so I can live with it.
With the music going, it sounds great. iMac > MusicHall Dac25.2 > Crack > Beyer DT-990 (250 ohm)
Thanks again for a great kit, I feel another expensive hobby coming on.
Mark.
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Be certain to move the iMac away from the amp as all computers create noise.
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I've noticed that in general when I power on one channel usually comes up first and also when powering down, I guess this is normal? Could the E80CC have suffered in some manner because of this?
Is this normal behaviour? I'm wondering if the E80CC because of it's slightly different requirements to the E82CC's might actually be fine and maybe it's something else, especially as the hiss starts quite loud in the right channel then reduces to nothing and then starts up in the left channel and reduces to a quiet level. It's like it is repeating but doesn't get enough something to reduce the left channel down all the way...
I'm hung up on this tube now. I'm concerned if I buy another, it will just do the same. Tx
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Yes, one tube heating and coming on faster than the other is normal. If you have two slower tubes in the same channel, like in a Paramount, it is even more dramatic.
If you don't get sound in 10s that isn't normal.
Deltaunit, you might have a fellow Bottlehead in your town. If so you might not have to buy a tube to check it out.
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Thanks Grainger, I'm based in the UK, Bristol to be exact, so it might be a long shot but if there's anyone with a E80CC in the area - get in touch! :)
I'm thinking I just wasn't aware of the hiss at first, it is quite quiet and negligible against daytime noise (I also didn't plug my HDs in until after it was on to be safe so wouldn't have heard the rushing sound) so I probably just missed it at first. It was sold as being 100% though so I've just contacted the seller, just to see what comes of it.
Has anyone had a totally silent E80CC I wonder? Hope so, I'm on a mission now!
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... a pronounced buzzing that comes in between 75-100% volume...
This is often a sign of RF interference; the upper range setting on a log taper volume control provides the highest impedance at the input grid and the greatest susceptibility to electric field capacitively coupled noise. In some cases it is actually television signals, at 30Hz (US) frame rate with lots of harmonics. Light dimmers, cell phones, electric motors, various appliances that you or the neighbors may be using, are other possible sources. Just a thought.
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Yes, that would make sense given where the amp is located and the rats nest of AC, computers, home theater gack and general crap that is in that part of my apartment. Thanks again for the help.
mark.
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Replaced the 12AU7 and...silence! Thanks for the help!
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So even without the speedball upgrade the amplifier is supposed to be dead quiet? Because mine still gives of a low hum though it is impossible to hear when there is music playing as there's almost always some kind of background hum on the records themselves...
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So even without the speedball upgrade the amplifier is supposed to be dead quiet? Because mine still gives of a low hum though it is impossible to hear when there is music playing as there's almost always some kind of background hum on the records themselves...
Have you tried a different source, like perhaps a CD player just to check? I assume you're spinning vinyl since you stated "records". Im far from being an expert but my Crack is stock, no speedball, only an Alps blue velvet pot and Mills resistors in place of the stock cements and it is dead quiet, no hum no hiss. My source is a digital music player and I recently added an old AH Tjoeb CDP as well and it is quiet with both. I may be off base but I would think that eliminating the source itself as the culprit would be a logical first step.
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Hi Viktor,
Does the hum go away when you turn the volume down all the way? What headphones are you using?
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Hi! No the hum doesn't go away when I turn it down, it is basically constant regardless of volume level. I'm not using vinyl at the moment, feeding it from the computer with a music streamer II. Also, I'm using HD650 headphones. Maybe it is something with the tubes, I don't know if I can muster going through all the solderings either.....And since all the measurements were correct it is a bit confusing!
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Low hum levels aren't always directly correlated to bad solder joints. I would suggest trying different tubes if you have not done so already, as my hunch is that is the most likely source if the hum. There is also a small chance that the amp is picking up the hum from a power transformer on a nearby piece of gear - if there is another power trans nearby.
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Ahh, okay! Unfortunaly I don't have any other tubes nearby, I'll see if it is possible to pick some up here in Sweden and try them out as well!
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Viktor,
Doc supplies nice and new tube sockets with his kits. But who knows when they were made. There might be a little dirt/tarnish in the tube sockets. Try removing and re-inserting the tubes 6 or 7 times to see if this cleans both the tube pins and socket. It is easy, quick and often effective for noise.
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You have given me that advice several times no and I still haven't done it properly.... :( Of course I have taken them out and put them back in I think at least four times in total. Maybe I should also try with some de-oxidation/grease/super-duper oil as well. I have one here at home that I've used on contacts in my computers with success so maybe that could be worth a try also. I'll report back with my findings!
Thanks for all the help, most helpfull forum ever!
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Viktor, Ive never been to Sweden but I would suspect that it's possible that one of the musical instrument retail stores would sell some new production tubes ... if there are any close to you. 12AX7 seems to be most popular pre-amp tube in newer production tube guitar amps but you never know. Maybe worth a shot to make some phone calls.
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Yesterday I took the big tube out and cleaned the pins for a bit then put it back in. The background hum was the same but I still listened to some music then all of a sudden all I can here is static, I was very afraid I'd destroyed my HD650 but fortunaly they seem ok. Then when I tried to turn the amp back on and listened with my SR60 ( my test headphones from here on ) there were no static at all and everything worked as before. I'm getting very vexed by this irregular behaviour, today I'm going to go trough the solderings once again as there is one part that I did a bit weir, its two of the connections for the 6080 where I put one wire to the bottom hole and the other one above, I don't think this should be a problem by maybe it is worth a try to put the both trough the same hole.... We'll see how it goes.
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Viktor,
You have two problems, the background hum and the crackling noise.
There are a number of things that can cause hum. A ground that is not well soldered becomes an "Ohmic" connection. That can be checked by touching up all the ground connections.
Another thing that might cause the background hum is the AC heaters to the tubes. They should be twisted well and flat against the top plate. The heater wires should be routed so they cross the signal wires at a 90 degree angle.
A loose ground or signal wire in your interconnects can cause hum... see the list goes on. Have you checked with the inputs grounded? (I think, can't remember all the posts in this thread, I think that your hum doesn't go away when the volume is all the way down. That eliminates anything upstream of the volume control.)
The noise might be the tube, swapping it for another, one at a time, can eliminate that. You will most likely roll tubes soon anyway so check the "Tube Rolling w/Crack" thread. It is always good to eliminate the tubes as the source of a problem.
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Greatful for all the advice! I did a small checkup today and resoldered some connections including the first ones I did, seems a bit lower now but not completely gone. Are the ground connections the ones with black cable? I know that the ground often is black but not completely sure in this case!
Okay the cracking popping sound is still there though and the background hum is there as well. I think I'll order some new tubes and test those before doing anything further so I can rule that part out at least.
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Another source of noise could be the source you feed into your Crack. If it is too close it might inject noise/hum into the circuit downstream of the volume control. Checking this costs nothing just move the source or any other electronic device away from the Crack.
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I have done that to no avail sadly. Right now I'm listening to some music and tapped the 6080-tube slightly and the sound went away completely in the right channel. I know about microphonics but didn't know it it should be this apparent. I will report back when I get the tubes, ordered a 6AS7GA (mostly based on looks...) and a TAD 12AU7WA. Also found a store in germany so I should get them fairly fast!
Cheers
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It sounds promising that tapping the tube remedied the noise, atleast in the one channel. Promising in that you just may simply have a bad tube. I learned a good while ago that it's always a good idea to have a few spare tubes on hand. Even if they are inexpensive newer production tubes or cheaper used or NOS tubes. The spares may not be your tubes of choice but atleast they get you up and running if a tube goes south. Reading through the forum threads regarding troubleshooting, seems like Doc nails it on the head most every time. If he thinks it's a problem tube, it's probably a problem tube.
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Let's second Laudanum's suggestion. For trouble shooting purposes a pair of tubes you hate are a thousand times better than a questionable tube you love.
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Laudanum: The cracking noise didn't go away, the noise went away completely which further strenghtens my and also Doc's thoughts that it is a bad tube. Found a store located in germany so I'll probably have them next week or so! :)
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Okay the tubes arrived yesterday and now I've tested both of them, changing the 6080 the crackling noises went away but the background hum was still there though slightly lower. Chaning the 12AU7 tube the amp is now dead silent as far as I can tell! :)
The big 6080-tube looks alot more like the Bottlehead logo so that's nice! I also think the sound is a tad better but than could just as well be placebo...
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Viktor,
Tubes should look cool too! As I just posted in another thread, Elcraigo's about Paramour 76 driver conversion, one of the reasons I like the 76 as a driver on my Paramours is that they are a slightly shorter and similarly shaped tube as the 2A3.
I'm glad the problems went away. Now for some serious tube rolling. There is a very long thread on tube rolling in Crack that has some good suggestions.
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Okay the tubes arrived yesterday and now I've tested both of them, changing the 6080 the crackling noises went away but the background hum was still there though slightly lower. Chaning the 12AU7 tube the amp is now dead silent as far as I can tell! :)
The big 6080-tube looks alot more like the Bottlehead logo so that's nice! I also think the sound is a tad better but than could just as well be placebo...
FANTASTIC NEWS!!! 2 problem tubes, who woulda thunk it, but it happens. The heaters are AC and I know there are some 12AX7's that tend to produce hum with ac heater supply (The Svetlana 12AX7 new production tubes back close to a decade ago come immediately to mind). I wonder if there are any specific 12AU7's, old or new production that are particularly susceptible to it.
Anyway, Viktor, I would highly suggest looking for some deals on ebay, or elswehere, for some tubes, atleast as spares if money is tight. Many NOS or good UOS 12AU7 and 6080 / 6AS7 types are inexpensive with very good deals to be had. The telefunken, Amperex, Mullard etc. 12AU7 types can fetch a good deal more, but there are even deals to be had there (not as much for Telefunken) if you want to try some.
For example, I recently picked up a Silvertone labeled Amperex (Herleen) that tested NOS range for 5 dollars (US). There are quite a few European based tube sellers on ebay with the more "botique" tubes so shipping cost would be less for you. But some very good steals and deals can be found from North American sellers that would offset the bit of additional shipping cost. Those tubes you dont favor you can turn around and resell if you want to.
Anyway, glad your Crack amp is up and running now.
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Yeah I thought it was a bit weird to but seriously it does seem like that's the case since it's working now. Who knows, the box was a bit damage when it arrived to me, it could have taken a hit during transfer that damaged the tubes!?
After all I'm just glad it's finally working, it will take some time before doing some serious tube-rolling after this business but I will definitely check ebay for some good deals, thanks for the tip!
By the way, here's a hipstamatic pic of the amp where you can see the look of the tube! Sorry for all the OT :(
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Viktor, I dont doubt that both tubes were bad. Just bad luck, that's all. Your problems sound like they are in the past and you can now just enjoy the music.