Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: ALL212 on March 28, 2015, 06:12:09 AM
-
Inspired by other posts but recently by richmi in the gallery:
I replaced the last 270 ohm resistor with the Triad C-7x and "tipped" the last cap with a 1uf Clarity Cap. Hope to add the Cree diode in there someday but for now this will do.
I got lucky on the mounting hardware as being a packrat sometimes pays off. I had the screws and standoffs already in my possession and just had to add the holes to the chassis. I'm going to see if I can find more of those (they come from a dual monitor stand we use at our offices) and if so, will offer up what I find here.
Need some time to listen but no smoke on power up so we're going forward!
From the front:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi905.photobucket.com%2Falbums%2Fac253%2Fall212212%2FDSC_2857_zps91vmy66g.jpg&hash=51b25b484fcef4ca4d55c400ec294345d7cbbda8) (http://s905.photobucket.com/user/all212212/media/DSC_2857_zps91vmy66g.jpg.html)
From the back:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi905.photobucket.com%2Falbums%2Fac253%2Fall212212%2FDSC_2860_zpsoellrn36.jpg&hash=9650979b46c7272762111615063b4bb43f937bb8) (http://s905.photobucket.com/user/all212212/media/DSC_2860_zpsoellrn36.jpg.html)
Full underside:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi905.photobucket.com%2Falbums%2Fac253%2Fall212212%2FDSC_2862_zpsfbf0qsdd.jpg&hash=a9d1f47c1fa37659261924d67e18a22f3a2ec279) (http://s905.photobucket.com/user/all212212/media/DSC_2862_zpsfbf0qsdd.jpg.html)
From the top - new holes just above the t'former holes and a bit to the left. Transformer holes are 1/4" too close together to use.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi905.photobucket.com%2Falbums%2Fac253%2Fall212212%2FDSC_2866_zpsij6shnif.jpg&hash=5787f5fc435614dc64be42f9c37018c44fc47304) (http://s905.photobucket.com/user/all212212/media/DSC_2866_zpsij6shnif.jpg.html)
-
Further upgrades following member Richmi:
Cree diode board added. I didn't drill anything and I think it was Lee Hankins that just let it hang on the wires but I superglued a standoff and then wired it so it already sat correctly on the standoff - then superglued it to the standoff. Kindof a combination of both. If the superglue does let go it won't go anywhere as the wires have it.
I used the "recliner" look for soldering them to the board:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi905.photobucket.com%2Falbums%2Fac253%2Fall212212%2FDSC_2870_zpsnrrddccm.jpg&hash=5f58a8b5130ef49cd627da736739ac64f2553eb1) (http://s905.photobucket.com/user/all212212/media/DSC_2870_zpsnrrddccm.jpg.html)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi905.photobucket.com%2Falbums%2Fac253%2Fall212212%2FDSC_2872_zps3umi7s1f.jpg&hash=f49bbc999fc67a746f7616dc95b4d80082db3a00) (http://s905.photobucket.com/user/all212212/media/DSC_2872_zps3umi7s1f.jpg.html)
Smoothed the overall sound out very nicely. Bass is noticeably better, darker background.
Nice! Thanks guys.
-
I'm interested in installing the choke too but as you've noted, real estate under the hood is tight if there's much in the way of mods and I suspect that a choke is not a typical builder's first mods
-
If you have the speedball installed what I did comes in just short of the depth of the speedball. The fun part is figuring out how to mount that and then grabbing a drill and hitting your top plate. The unsoldering/soldering portion isn't to bad.
If you are a beginner stay away from the Cree diodes - that nice shiny part with the hole in it is hot and I'm guessing if you ground those out some magic smoke could be released.
-
After you installed the CREE DIODES did you noticed any difference in sound?
Thanks
-
'cause it all about dat bass bout dat bass no trouble...
Blacker background.
I'd call what I hear smoother. Definition, soundstage, "air" around the voices. It's just that good!
1) Original Crack good,
2) modded crack better - signal path stuff
3) Built a SEX and liked it better than the modded Crack.
4) Upgraded Crack power supply as above and SEX is sitting on the shelf wondering WTF just happened!! :'(
-
So i'am not imagining/dreaming about what i heard few hours ago after i installed the CREE DIODES.
That is why i asked first.
Thanks
-
Tell me of your dreams, Usul...
What did you hear?
-
Exactly what you described above except for the soundstage i can't tell the difference.
-
BTW i just turned the amp off so i can take some photo later.
-
Here is mine.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fcdn.head-fi.org%2Fa%2Fa8%2F900x900px-LL-a8c7dc2c_DSC_4034.jpeg&hash=cd69e46eb0db1ff91986dd2d4a52e982f696a25b)
-
I'll try and be nice to our northern neighbor...but it's gonna be tough... ::)
I like the "no holes in the board" approach with just snugging it down - nice!
Ok - maybe soundstage isn't what I've got. Separation between those things that are making the music. Each instrument and vocal is placed very specifically, back ground is so black that the room acoustics are amazing.
Guitar lead in on Jethro Tulls Aqualung track 7 "My God" - I've listened to this many times and never heard it like this.
Alan Parsons Project, Edgar Allen Poe - another album I've listened too many times and I just get the silly grin... 8)
-
No worries. ;)
I LOVE HOLES......... ;D
First thing i noticed the first time i fired up my crack after i installed the Cree Diodes is the Separation and even quieter background and the bass and how smooth sounding it is.
-
What tubes are you using? And what headphones?
Stalker alert!! :o
-
nice modding ALL! What do the cree diodes do for sound?
-
nice modding ALL! What do the cree diodes do for sound?
Can I just call it "Magic" and get away with it? ::)
Keep in mind that within 10 days I did the choke, bypass and Cree's so there wasn't a bunch of listening time with the cree's out of the mod.
With all three changes:
Bass is better, tighter, deeper. Background is inky dark - you hear the room acoustics without effort. Placement of individuals and instruments is precise.
This "minor" mod goes a long way in proving the design of this headphone amp is spot on. Very nice job Doc!
-
Very interesting. I'm going to have to try it! Anything to make my Crack sound better!
James
-
Please be careful of the Cree's - that silver tab is live and is a heatsink so you shouldn't cover them and they cannot touch anything - ever!
-
What tubes are you using? And what headphones?
Stalker alert!! :o
Chatham 6AS7G and Tung-Sol 6SN7GTB(Tall Bottle),HD650 and DT 880 600R.
-
You converted yours to use the 6SN7's?! Nice! Much better than 12AU7's?
I've got a RCA long black plate 5963, Tung-Sol5998 with HD650. Source is a Squeezebox Duet with a Stello DA-220.
Just bought another Crack kit. Going to use it for testing and then, maybe, what I think I'll call a BAC (Big A$$ Crack).
-
This topic has encouraged me to add the Cree diodes to my already quite modified Crack (speedball, choke, output and last power supply film capacitors). I wasn't expecting as much improvement as it turned out to be. Still having difficulty putting my finger on it, but the Crees make it definitely sound better to my ears.
-
i'm interested in modding my crack with the cree diodes But where do i get the board ??
-
You can get the pcb from PartsConnexion.
Here is a reference to the thread where this was first posted - http://bottlehead.com/smf/index.php?topic=7215.0. You can find a link to the pcb in there.
-
Parts Connexion have been out of stock since last year and I can't find a similar alternative. Is there an alternative pcb that could be used ?
Thank you!
James
-
Odd - I clicked on the link I provided in richmi's thread and it does not look out-of-stock to me.
Link ot the pcb - http://www.partsconnexion.com/product26996.html
-
Hi Gunter,
Yes Parts Connexion don't seem to have any real-time stock control, so I just place an order and then they email me and let me know if any items are out of stock. They have been out of stock of these since late last year. I've checked in with them every 5 weeks or so, but no luck. They mentioned that everything is still way behind after Chinese new year. I'm not in a hurry but thought I would check here just in case....
I think I'm sorted now - this community is awesome. :)
-
Yes Parts Connexion don't seem to have any real-time stock control, so I just place an order and then they email me and let me know if any items are out of stock.
That's right, they don't have real-time stock availability, you have to ask.
-
For anyone curious, I e-mailed Parts Connexion and they told me the PCB for this mod is back in stock!
Google "Discrete Bridge Rectifier PCB - TYPE 2 (TO-220 Radial Style)," and it's the second link.
I ordered mine and will post my impressions once installed. Happy listening and take care!
-
Is there a possibility use cree without the board? I've already changed the stocks with telefunken byt238, want to try these cree.
-
One of our moderators posted that replacing any one of the existing diodes with just one Cree would do the job. I've done it to one of my kits - maybe the Reduction? You just have to be very careful of placement because of the tab. Remember that they do have to go in the correct way.
Might be best to start a new thread so that you get attention to this before doing it?
-
One of our moderators posted that replacing any one of the existing diodes with just one Cree would do the job. ...
This is not technically true. You can add a Schottky between the bridge of 4 diodes and the first filter cap, and that is widely thought to be effective.
-
Has anyone looked at the effect of this on a scope?
-
a year ago...somewhere in there... I bought another Crack and built it stock. Tried using my o'scope but it was not up to the task. I don't know the make/model but I didn't see any difference in wave forms. Now - I might not have been looking in the right place or had the scope on the right settings but I did have fun playing around, just no useable results.
My ears told me something good happened when I put that diode board in with the Cree's on the Crack.
Thanks Paul for the clarification on the right way to add a single Cree. (I'd best turn my Reduction over and see exactly what I did under there!)
Here's what I did under there... Solitary cap, red leg to furthest back resistor.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi905.photobucket.com%2Falbums%2Fac253%2Fall212212%2FDSC_2923_zpsqe8ffmnm.jpg&hash=102fded2aa8785fb313a26a401b248a4fedd4233) (http://s905.photobucket.com/user/all212212/media/DSC_2923_zpsqe8ffmnm.jpg.html)
-
You want to look at the power supply. Right at that first cap would be a good place. Maybe on the heater secondary too. Look for spikes. The UF4007 is an ultrafast recovery diode and should have only a very tiny recovery spike. The Schottky should have none. Will the Schottky remove a spike from another diode? I dunno about that. People have used tube rectifiers after a SS diode because they are slooow and thus filter out the quick spike. They do the same for the musical transients.
-
I cant get my head around that single diode in series, wouldn't it just conduct all the time being forward biased?
-
Here is a site with some information on reverse recovery, which applies to non-Schottky diodes:
http://electronics.stackexchange.com/questions/13912/what-is-the-reverse-recovery-time-in-diode
The reverse recovery happens very quickly, which causes noise of a buzzy nature that radiates as radio waves and infects nearby circuits.
Schottky diodes (and vacuum diodes) do not have this mechanism, so they prevent the recovery from happening rapidly when placed in series with a regular junction diode - making the recovery spike insignificant.
-
It was the single schottky diode after a rectifier bridge that i don't understand, how could it possibly make any difference?
W2AEW did a great video demonstrating reverse recovery here, he is worth subscribing to as all his videos are great, though some get into RF voodoo which is over my head.
https://www.youtube.com/watch?v=SBqLOrlA7QI (https://www.youtube.com/watch?v=SBqLOrlA7QI)
-
For anyone curious, I e-mailed Parts Connexion and they told me the PCB for this mod is back in stock!
Google "Discrete Bridge Rectifier PCB - TYPE 2 (TO-220 Radial Style)," and it's the second link.
I ordered mine and will post my impressions once installed. Happy listening and take care!
What is the total cost including shipping and handling for the rectifier PCB? I'm reading from Parts Connexion FAQ that a $5 handling charge will be included if order is less than $25. So the cost of the board will be $1.95 + $5 handling + ~$6 shipping?
-
Did I just hear that? Holy mackerel!!
-
You've replaced the stock diodes with the board/Cree's?
Ya...you probably did just hear (or not hear the noise) that! 8)
-
So help me understand this all...is the idea of replacing the diodes a good thing or a not so good thing? Based on some of the comments and concerns that Doc posted I am concerned and a bit confused. I would like to try this but not unless its really been "scoped" out....
Alex
-
Alex, I do not believe that using Cree diodes improves the sound in Bottlehead gear, I have a bad habit of using the Cree's in most of my builds because they look "cool" not because they might improve the sound quality.
Lee Hankins
-
I just tried them out because they are relatively cheap (like 10$), everyone who tried them was so wild about them and the diode bridge PCB is on promo but more importantly available at the moment at Partsconnexion.
To my ears the Cree SiC Schottky's sound like a nice upgrade both in noise and clarity, but why?
Most seem to think reverse recovery current (or better the lack thereof) is responsible for the goodness (but at "only" 50/60Hz AC... why?), maybe other properties like lower forward voltage drop, ... could be playing a role?
Bear in mind that everyone with one or more Crees already had a choke installed beforehand, which affects pretty much everything in front of the reservoir cap.
-
You want to look at the power supply. Right at that first cap would be a good place. Maybe on the heater secondary too. Look for spikes. The UF4007 is an ultrafast recovery diode and should have only a very tiny recovery spike. The Schottky should have none. Will the Schottky remove a spike from another diode? I dunno about that. People have used tube rectifiers after a SS diode because they are slooow and thus filter out the quick spike. They do the same for the musical transients.
Anyone tried this?
-
Are you asking if anyone has looked for spikes on the heater secondary?
-
Yes.
*And i don't see what could be done about it if there was. Other than better wind the wires. Shielding the heater wires...
-
The point is if you are seeing spikes anywhere you might want to change to a rectifier that puts out a smaller spike or no spike in the B+ supply. One could also try implementing an RRSF filter between the heater secondary and the tube sockets. This is tricky because you are pretty much limited to caps without any R or L, since they will add too much resistance to the circuit and the heater voltage won't be right.
This is why we went with the UF4007s. If the rectifier is quiet there is no spike that needs to be filtered.
-
I know I'm a bit behind here in terms of the age of the thread, but I've just fitted the Cree based rectifier in my Crack, and can immediately recommend it.
Cheap, quick, and no doubt that it is now pulling more detail than I was hearing before. I can't really argue with hearing new things.
:)
-
pardon my ignorance, but is there BOM for the parts needs for the Cree/schottky rectifier mod?
Any instructions too? I sort of get it from the pics for the cree/board, but I'm not sure about the Schottky diode.
This seems like an easy, inexpensive mod that I would like to try.
thanks.
-
This should be it.
http://www.partsconnexion.com/product26996.html
or Google "Discrete Bridge Rectifier PCB - TYPE 2 (TO-220 Radial Style),"
If they're out let me know - I bought a few extra the last time.
-
If you want to go all out, I thread the hole in each diode via a tap, and then screw a nylon bolt through each diode, spaced 1/4 " apart.
-
This should be it.
http://www.partsconnexion.com/product26996.html
or Google "Discrete Bridge Rectifier PCB - TYPE 2 (TO-220 Radial Style),"
If they're out let me know - I bought a few extra the last time.
thanks. That's the board. What cree diodes are needed? And what Schottky diode is needed?
-
Slow down - do some research...
Cree is the brand name, shottkey is the component type.
http://www.partsconnexion.com/product7559.html
Disclaimer - any information supplied is what I used under my own guidance. Your ability to loosen the magic smoke is entirely up to your own skill level.
You need to read through the thread all the way carefully. Especially noting that if you install these wrong or are not careful in what you're doing you can shock yourself or destroy the components.
-
Slow down - do some research...
Cree is the brand name, shottkey is the component type.
http://www.partsconnexion.com/product7559.html
Disclaimer - any information supplied is what I used under my own guidance. Your ability to loosen the magic smoke is entirely up to your own skill level.
You need to read through the thread all the way carefully. Especially noting that if you install these wrong or are not careful in what you're doing you can shock yourself or destroy the components.
Got it. I was schooled on Head-fo too. I'm a-learnin'. I've recently learned which way goes up on the tubes!
-
Ok. I got my board and diodes. I would just like to verify the next steps.
1) Remove the 4 rectifiers at 18,19,20, and 21.
2) Wire the board as show in the diagram below. I will probably just glue a nylon spacer to the bottom of the board and then to plate like shown earlier in this thread.
I assume the wires should be twisted to the board, also as shown in some of the earlier posted pictures.
Is this diagram correct?
https://cdn.head-fi.org/g/9937481_l.jpg (https://cdn.head-fi.org/g/9937481_l.jpg)
-
Looks good.
-
Looks good.
Thanks! Mod installed and crack working. I have no idea if it sounds better as I have no temporal comparison skills, but I'm going to believe is sounds better. Exactly $10 better ;)
-
I'm going to believe is sounds better. Exactly $10 better ;)
Maybe $9.95.
-
Curious to hear the different in diodes myself but the board is forever not available. I see they have an assembled one but it's not using schottky ones. Is it what I need? As a last resort I'll get it just for the board and replace the diodes.
https://www.partsconnexion.com/ASSEM-77727.html
-
I might have a spare or two. Let me know if you still need one.
-
I tried looking at the original thread where this mod was discussed, but it seems like it's either archived or moved. Does anyone have the full instructions? Link to the original: https://bottlehead.com/smf/index.php?topic=7215.0
-
Actually I found this reply in another thread:
Below are some links I have saved for these mods that I intend to do at some point.
For broken links and particularly for images I quite often just do a google image search for something relevant in the threads
Bridge Rectifier
You don't really need the PCB as the circuit is as you would expect and you can replicate on prototyping board or similar.
NB There are reminders that the tabs on the top of the diodes are live and should not touch anything ever.
- PCB - https://www.partsconnexion.com/PCB-77727.html
- Cree Diodes https://www.mouser.co.uk/ProductDetail/Wolfspeed-Cree/CSD01060A?qs=%2Fha2pyFaduha8e7L7P6H8AQPAaWzRYR18hPNYjU5%252Bzc%3D.
- Wiring guide - https://cdn.head-fi.org/g/9937481_l.jpg
Choke
- https://www.mouser.co.uk/ProductDetail/Triad-Magnetics/C-7X?qs=sGAEpiMZZMuMS2dUaCDnDB57UyZo4e84
This replaces one of the two big white 270 Ohm 5W resistors. Most people seem to replace the one between 13L and 15L
Does the "Old Transformer" and "New Transformer" refer to versions of the Crack transformer? I assume so, like a Crack 1.0 or 1.1?
-
Yes, the 1.0 and the 1.1 have different power transformers.
-
Got it, thanks. Filing this away under "future upgrades if they can get the PCB back in stock."
-
Maybe you could just make one with protoboard using wire in place of the traces as Ianp suggests in the quote?
Or maybe the axial style recitifier board (in stock at Parts Connexion) could be made to work by bending the leads of the diodes? https://www.partsconnexion.com/PCB-77726.html (ftp://www.partsconnexion.com/PCB-77726.html)
-
Maybe you could just make one with protoboard using wire in place of the traces as Ianp suggests in the quote?
Or maybe the axial style recitifier board (in stock at Parts Connexion) could be made to work by bending the leads of the diodes? https://www.partsconnexion.com/PCB-77726.html (ftp://www.partsconnexion.com/PCB-77726.html)
The extent of my electrical abilities extends to poorly soldering and following extremely explicit directions written by people way smarter than me; I'm not sure I want to take on protoboards since there's a 95% chance I'll solder my dog to the amp by accident.
I've got some feelers out for the actual PCB, but I might give the other version a shot. Or maybe get the pre-built one and yank out the existing diodes.
-
The extent of my electrical abilities extends to poorly soldering and following extremely explicit directions written by people way smarter than me; I'm not sure I want to take on protoboards since there's a 95% chance I'll solder my dog to the amp by accident.
I've got some feelers out for the actual PCB, but I might give the other version a shot. Or maybe get the pre-built one and yank out the existing diodes.
Solder your dog to the amp....
From a comedy standpoint the fun to be had with that comment is almost limitless.
From an animal cruelty standpoint I'm not going there for any reason.
but that's just funny stuff right there...
-
I really like my dog and would like to keep her separate from the amp for obvious reasons. That's why I'm leaving protoboards to people with a higher IQ than mine (44).
-
Was perusing the Parts Connexion site and just noticed that the radial style rectifier board is back in stock. Grab'em while you can!
-
Maybe you could just make one with protoboard using wire in place of the traces as Ianp suggests in the quote?
Or maybe the axial style recitifier board (in stock at Parts Connexion) could be made to work by bending the leads of the diodes? https://www.partsconnexion.com/PCB-77726.html (ftp://www.partsconnexion.com/PCB-77726.html)
Reviving this suggestion to see if anyone knows. The "Discrete Bridge Rectifier PCB - TYPE 2 (TO-220 Radial Style)" seems to be perpetually out of stock. Does anyone know if that axial version of the rectifier board would work for the cree mod? I can't find any posts of anyone actually using the axial board...
-
:-[ I have a few of those...just not sure where I put them. If I find them I'll see if the traces look similar to the other board. I've never used those...yet.
-
Reviving this suggestion to see if anyone knows. The "Discrete Bridge Rectifier PCB - TYPE 2 (TO-220 Radial Style)" seems to be perpetually out of stock. Does anyone know if that axial version of the rectifier board would work for the cree mod? I can't find any posts of anyone actually using the axial board...
They got back to me a couple days after I requested they notify me when they’re in stock. I think they’re just ordering them when people ask.
-
Oh ok! I'll contact them and see what happens! I'd definitely prefer to use the board that everyone else is using...
-
There's some new Schottky Diodes available on Mouser, would one of these work instead? If so, better or worse then the previous version?
https://www.mouser.com/new/wolfspeed/wolfspeed-c6d-diodes/
-
There's some new Schottky Diodes available on Mouser, would one of these work instead? If so, better or worse then the previous version?
They are ultimately pretty similar to the 600V/1A parts. The minor differences are not worth the dramatically increased price IMO.
-
Makes sense, I was wondering that too. Maybe in time they'll come down in price and then might be worth it.
-
By the time that happens, there will be another generation or two of Schottky diodes to replace them.
-
That is very true!
-
One more dumb question, if I were able to somehow make room, could I replace both 270/5w PS resisters with two C-7X chokes? Seems like it would be an even better solution based on the research I've done and would remove even more ripple. Or would this be one of those diminishing returns kind of thing?
-
How much ripple do you hear now?
-
I suppose not to much, it's dead quiet, just more of a curiosity.
-
So instead of adding these upgrades to my existing build, I created a new build and incorporated them in. I pretty much followed the original couple of posts, 1uf Clarity Cap on the last PS cap, added the choke and used the Cree diodes. I also added film capacitors. After I did the resistance checks, I was a bit nervous powering it up the first time, so I said a prayer and turned it on and no smoke! I did the voltage checks and they all were within range. Whew!
Anyway, I've been using it for a few days now and it sounds great! It's almost like having the Crack with Speedball, even though there's no speedball. I've got it pared up with my 600 ohm Beyerdynamic DT770 Pros (well more like 550 ohms), but the bass is very good, deep, tight and controlled. The film caps add a smoothness that electrolytic ones don't have.
Anyway, it's a worthwhile upgrade. I went with the Mundorf capacitors, but I'm not sure the sound is $120 better. If I were to do it again, I would probably choose cheaper film caps, maybe the Dayton Audio ones, but that's just my opinion.
I'm planning on adding the speedball over the holiday weekend, so I'll post some pictures once that is done.
-
Ok, changed my mind, here's some initial pictures.
-
Nice build! Got all the stuff inside the box. 8)
-
Thanks! Yeah, I followed the great instructions on this post!
-
So I've been listening to this mod for a few weeks now and I will say I agree that it's "all about dat bass." I have a pair of modded 600 Ohm DT770 Pro's and the bass is deep and tight, but I really hear the sub-bass. In addition I do hear more detail, but I really notice the bass response. So great mod over all!
-
Hi,
I'm just trying to gather safety info about handling capacitors. I know electrolytics can be dangerous when charged and that you should only handle the body of the capacitor unless you know for sure it's discharged. But what about film caps? Do they need to be discharged too before handling freely? If so, will an insulated screwdriver across both terminals (like with an electrolytic) be advisable? Thanks and pardon my ignorance.
-
Don't use a screwdriver. Use a 10K ohm resistor. A screwdriver will spark on a cap with a lot of charge. Film caps of higher values should get the same treatment.
-
Thanks, Doc!
So, should I hold the resistor with insulated pliers, the cap by the body, and then join the leads? Like the attached crude picture?
"Film caps of higher values" ... How high? For example, what about the Crack's 100uF film output caps, or a power supply film bypass cap (2.2uF or less)? Thanks so much again, Doc, and I hope you and Queen Eileen are doing well during this rough time.
-
If you get a 10W resistor for discharging caps, you can use an insulated pair of pliers to hold the body of the resistor to discharge things. You don't want to do that with a small metal film resistor, as you'd likely crunch through the outer coating of the resistor by grabbing it with the pliers.
-
Thanks, Paul!
I'll look into getting a 10K ohm 10W resistor to do the job.
Specifically, I'm looking to roll a couple of film bypass caps (1uF 400-800V) onto my last power supply film cap. With this extra time, I'm upping the dose of my crack addiction... I just want to see if I can tell any differences easily, or at all.
Please see attached picture. I plan to use copper alligator clips with the bypass caps for easy swapping back and forth. How would you go about doing this safely? After shutting off the amp, should I join the resistor to the caps' leads while the bypass cap is clipped on, or should I wear rubber gloves to detach the alligator clips, then use the resistor to discharge the bypass cap? Thanks for your time! :)
-
The way I do it is to hold the resistor with insulated needlenose pliers by the body, then discharge the power supply to the chassis. It's a lot easier to do it that way rather than trying to get a big 10W resistor connected between B+ and ground.
-
Thanks! But where specifically on the power supply would you touch the resistor's lead to? Please see photo.
-
You'll probably find that it's super easy to use terminal 5 on the octal socket.
-
Okay, just to be clear, the process for safe cap discharge goes:
1) Power off amp
2) Touch 10K ohm resistor to octal terminal 5 & anywhere on chassis (please see photo to verify)
3) freely handle alligator clips or leads of any cap in the amp
...or for a specific cap, touch resistor ends to each lead of the cap to be handled.
-
More digging led to my finding this post by Paul Joppa (about discharging 220uF 250V PS caps):
________________________________________________________________________
Re: Building a capacitor discharger - what size resistor to use?
« Reply #1 on: January 26, 2012, 12:07:35 PM »
"Perhaps we should look for a resistor that will survive even if the circuit is still accidentally powered. Let's say you want to use a 5-watt resistor; then since power equals voltage squared over resistance, the minimum resistance is 8000 ohms. The time constant RC is less than 2 seconds, so if you leave it connected for 10 seconds (5 time constants) the voltage will decay by a factor of 175 (e to the 5th power) - i.e. to a bit over a volt. 10K is probably easier to find.
"For a 1 watt resistor, you'd need 40K and it would take 50 seconds to discharge. I'm not that patient, myself."
________________________________________________________________________
So, again, to be perfectly clear, the process for safe cap discharge should go:
1) Power off amp
2) Touch 5W 10K ohm resistor to octal terminal 5 & anywhere on chassis for 10 seconds (please see photo to verify)
3) freely handle alligator clips or leads of any cap in the amp
...or for a specific cap, touch resistor ends to each lead of the cap to be handled for at least 10 seconds.
Is this correct? Thanks for bearing with me. :)
-
You're missing the step where you take your meter and measure the DC voltage left in the supply.
For a power supply like the Crack, I don't worry much if there's 10V or less left in the supply, that's low enough for me. In a low voltage power supply with tens of thousands of micro-farads of capacitance, that isn't necessarily the case.
-
Here's my take on some free form soldering to replace the rectifier diodes with Cree Schottky diodes.
Each diode runs at around 31.5ºC after an hour or so of use. The copper legs are bound in place with a single strand of very thin wire then soldered in place. There's a bit of UV cure resin thrown in for extra mechanical strength.
I wasn't entirely sure this was a good idea when I started but I think it turned out pretty well. There are sound improvements to be heard in term of less weird high pitched noises which I'd attributed to RFI - maybe it was just a dodgy solder joint - I guess I'll never know for sure. This plus some bypass caps, diode grounding, a shield for the 12AU7 and an alps pot have take the crack as far as I want to. Maybe one day I'll take it all out and try each step in a different order to figure out where the biggest gains were had.
The noise floor is incredibly low and the sound is exactly where I want it. I find myself listening all day long.
-
in term of less weird high pitched noises which I'd attributed to RFI
diode grounding
If you implemented the modification to use antiphase diodes to break the signal ground and earth, then that would get rid of weird high pitch noises.
-
If you implemented the modification to use antiphase diodes to break the signal ground and earth, then that would get rid of weird high pitch noises.
Hi Paul, I did! They removed some of the noises but not entirely. I ended up putting a sheet of aluminium insulating foil up on a wall and that got nearly all of it (I look like a loon, but 100% the government can't see my thoughts anymore ;))... in all seriousness there's a cell tower about 100 feet from our house.
I made each change separately - tube shield, antiphase diodes to ground, bypass cap, cree diodes and finally an additional bypass cap. The noises stopped after the cree diodes but I already had the caps at this point (2.2uf and 220nf I believe) so I added the to the final electrolytic. I think the tube shield had the largest effect but it made some other subtle sounds more apparent.
I was done... in reality I'm going to add some copper shielding inside the case - as fond as I am of the silver foil it's starting to attract the wrong kind of attention.
-
In all seriousness, that first pic looks like art. A "found object" sculpture: a cyborg centaur. If it ever fails, you can sell it as a postmodern commentary on the state of the individual in the age of automation, digitization, miniaturization ...
cheers, Derek
-
In all seriousness, that first pic looks like art. A "found object" sculpture: a cyborg centaur. If it ever fails, you can sell it as a postmodern commentary on the state of the individual in the age of automation, digitization, miniaturization ...
Sounds like I could have my retirement fund sorted with a few well timed, elaborate failures ;)
-
So something else you could try regarding the cell tower. Install one end of a Z5U cap to each tab on each RCA jack. Twist the free ends together, then run a wire from those ends to the ground tab on the IEC power entry module.
-
@baseonmars
Way cool implementation of the diodes!! Should I build another Crack I think I’d use your method.
-
Speaking of cree diodes! When installing the diodes (using the pic I found earlier in the thread for wiring) am I removing the exising wiring to the power? I believe 18 and 19L?
-
So something else you could try regarding the cell tower. Install one end of a Z5U cap to each tab on each RCA jack. Twist the free ends together, then run a wire from those ends to the ground tab on the IEC power entry module.
Hey Paul, so... I had more or less given up on getting rid of the last night until one night when I heard it, whilst in bed and with ear plugs in. It must be tinnitus that sounds similar to RFI. I feel like a bit of an idiot but figured I'd come clean in case there are others out there chasing after the last bit of noise.
For what it's worth the diodes and tube shield did have a measurable difference on noise floor/RFI reduction, but the last bit was definitely in my head/ear.
-
I have a cell tower about 500 feet away from my house and it has never been a problem
Now if I could say the same for the shitty power I get...John
-
PCB - https://www.partsconnexion.com/PCB-77727.html
Cree Diodes https://www.mouser.co.uk/ProductDetail/Wolfspeed-Cree/CSD01060A?qs=%2Fha2pyFaduha8e7L7P6H8AQPAaWzRYR18hPNYjU5%252Bzc%3D
Is partsconnexion the only place to get the PCB?
Also, it's been a while since these were released. Are these still the Cree Diodes to use or is there something else out there?
-
For the Crack if you're having trouble finding the 1A/600V Cree diodes, there are higher current versions that you can substitute.
-
PCB - https://www.partsconnexion.com/PCB-77727.html
Cree Diodes https://www.mouser.co.uk/ProductDetail/Wolfspeed-Cree/CSD01060A?qs=%2Fha2pyFaduha8e7L7P6H8AQPAaWzRYR18hPNYjU5%252Bzc%3D
Is partsconnexion the only place to get the PCB?
Also, it's been a while since these were released. Are these still the Cree Diodes to use or is there something else out there?
Those ones are what I think most people used, but you could try these: https://www.mouser.com/ProductDetail/Wolfspeed-Cree/C6D04065A?qs=%2Fha2pyFadujYuAKy3YnKTEHyWCBrjYBu8BL2A6RZVomCRp63dgtoXQ%3D%3D
-
Thanks for the help guys. I am going to try those cree diodes that you suggested Tim!
-
No need to change the values on the caps in the power supply when added choke(s) ?
-
No.
-
Hi guys. I'm buying some Cree Diodes from PartsConnexion. Can I use 1A 600V?
-
Hi guys. I'm buying some Cree Diodes from PartsConnexion. Can I use 1A 600V?
Yes.