[tomb]

Ok that makes sense, without the 50k it was way worse but it's still not ideal, I was under the impression that using a 100k pot to begin with would allow for a little more play, but I guess I was wrong. Thanks for all the help.

Nope. You get more noise with a 100K pot.

 

[RanDiesel]

I built the SSMH 12AU7 version about 2 years ago and have been using it happily until recently I noticed that the left channel was really quiet compared to the right channel. So I cracked it open and found a bloated capacitor, C5 (63v 470uF) to be specific. I am wondering if this is just bad luck with these nichicon caps I found on ebay or if I could possibly have caused it with heat or a short? Seems like if it was a short it would have happened right away.

 

[vapman]

I built the SSMH 12AU7 version about 2 years ago and have been using it happily until recently I noticed that the left channel was really quiet compared to the right channel. So I cracked it open and found a bloated capacitor, C5 (63v 470uF) to be specific. I am wondering if this is just bad luck with these nichicon caps I found on ebay or if I could possibly have caused it with heat or a short? Seems like if it was a short it would have happened right away.

Ebay caps sound sketchy. I would only buy caps from a distributor personally.

Even good cap brands can fail and this design has been safe and stable for many, is your enclosure not allowing heat to vent properly?

 

[RanDiesel]

Ebay caps sound sketchy. I would only buy caps from a distributor personally.

Even good cap brands can fail and this design has been safe and stable for many, is your enclosure not allowing heat to vent properly?

 
It was an ebay store front and not a random guy, and at the time Mouser didn't have the nichicon caps I wanted. The enclosure is the standard one in the BOM for the 12AU7 build. There are no air holes besides the ones that the mosfets poke thru to the heat sinks. I suppose I could add air holes but I am starting to think I just got a bad cap. Here is a pic:

 

[vapman]

Duds show up even in good brands once in a while... weird that they were on ebay and not on site. I would replace it and should be ok after that...

 

[RanDiesel]

Actually, that specific voltage is difficult to find. Do you think a 50v version would work? Found this one:
http://www.mouser.com/ProductDetail/Nichicon/UKZ1H471MHM/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oiS%252b9HFuzN1rI%3d

 

[Danthrax]

It's not recommended to run below 63v for safety reasons and I they do not make a KZ series capacitor with 470uF above 50v 330uF is the max for 100v I ended up getting one of these: http://www.mouser.com/ProductDetail/Nichicon/UFG1J471MHM/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oi7zPc9z1C2rY%3d for the 470uF I needed. EDIT: ignore that the 12au7 build doesn't appear to use a 48v power supply like the 19j6 build so I would think 50v is safe as they recommend a minimum of 16v, leading me to think a 25v would also work but I'm not sure what benefit that would give you. If that was a 470uF 100v KZ capacitor that you already had in there it could very well be likely that it was indeed fake (unless this was a cap that previously existed and has since been discontinued) and in that case I would recommend replacing any that you had in use...

 

[RanDiesel]

  It's not recommended to run below 63v for safety reasons and I they do not make a KZ series capacitor with 470uF above 50v 330uF is the max for 100v I ended up getting one of these: http://www.mouser.com/ProductDetail/Nichicon/UFG1J471MHM/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oi7zPc9z1C2rY%3d for the 470uF I needed. EDIT: ignore that the 12au7 build doesn't appear to use a 48v power supply like the 19j6 build so I would think 50v is safe as they recommend a minimum of 16v, leading me to think a 25v would also work but I'm not sure what benefit that would give you. If that was a 470uF 100v KZ capacitor that you already had in there it could very well be likely that it was indeed fake (unless this was a cap that previously existed and has since been discontinued) and in that case I would recommend replacing any that you had in use...

 
So the capacitor I was using in there was a FG series one just like the one you have in your striked out post.
 
I will just order the same one again this time from Mouser, since I really don't want to completely dismantle my amp to replace both caps to the 50v versions. As you can see in the picture I have each channel on its own perf board so I can just yank one and fix it. Thanks for all the help.

 

[tomb]

 

  It's not recommended to run below 63v for safety reasons and I they do not make a KZ series capacitor with 470uF above 50v 330uF is the max for 100v I ended up getting one of these: http://www.mouser.com/ProductDetail/Nichicon/UFG1J471MHM/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oi7zPc9z1C2rY%3d for the 470uF I needed. EDIT: ignore that the 12au7 build doesn't appear to use a 48v power supply like the 19j6 build so I would think 50v is safe as they recommend a minimum of 16v, leading me to think a 25v would also work but I'm not sure what benefit that would give you. If that was a 470uF 100v KZ capacitor that you already had in there it could very well be likely that it was indeed fake (unless this was a cap that previously existed and has since been discontinued) and in that case I would recommend replacing any that you had in use...

 
So the capacitor I was using in there was a FG series one just like the one you have in your striked out post.
 
I will just order the same one again this time from Mouser, since I really don't want to completely dismantle my amp to replace both caps to the 50v versions. As you can see in the picture I have each channel on its own perf board so I can just yank one and fix it. Thanks for all the help.

 
Those are not FG caps in that photo.  FG's are exactly opposite of that color scheme - they are gold with a black stripe (as in Nichicon Muse Fine Gold).
 
Pretty much all the voltage will run across those caps if a short occurs - that's 48VDC using the Cisco power supply.  However, no one would spec 50V caps in that scenario.  2V is just too small a safety factor.  It's why we went with 63V.  Electrolytics are made in definite voltage rating increments - 16V, 25V, 35V, 50V, 63V, etc.  I can't comment if you are using a different power supply, but use of a 12AU7 tube wouldn't change anything in that regard if the same power supply were used.
 
Also, the 16V rating you refer to is for the cathode bias capacitors.  There is very little voltage across those capacitors.  We need to be careful about which capacitor is which, here.

 

[RanDiesel]

   
Those are not FG caps in that photo.  FG's are exactly opposite of that color scheme - they are gold with a black stripe (as in Nichicon Muse Fine Gold).
 
Pretty much all the voltage will run across those caps if a short occurs - that's 48VDC using the Cisco power supply.  However, no one would spec 50V caps in that scenario.  2V is just too small a safety factor.  It's why we went with 63V.  Electrolytics are made in definite voltage rating increments - 16V, 25V, 35V, 50V, 63V, etc.  I can't comment if you are using a different power supply, but use of a 12AU7 tube wouldn't change anything in that regard if the same power supply were used.
 
Also, the 16V rating you refer to is for the cathode bias capacitors.  There is very little voltage across those capacitors.  We need to be careful about which capacitor is which, here.

Ah, yes, I see that now, thank you! Luckily I hadn't clicked the checkout button yet. As I read the descriptions on these different capacitor series, I wonder if the difference between the KW series and FG series would be noticeable. The description certainly makes it seem like I would get "a rich sound in the bass register", according to Nichicon. I realize that any SQ questions are purely subjective, but I figured I would ask anyways since these capacitors are very close to the output

 

[tomb]

KW's are power caps, only. If these are at the output, you'll definitely do better with the FG's.

 

[Danthrax]

   
Those are not FG caps in that photo.  FG's are exactly opposite of that color scheme - they are gold with a black stripe (as in Nichicon Muse Fine Gold).
 
Pretty much all the voltage will run across those caps if a short occurs - that's 48VDC using the Cisco power supply.  However, no one would spec 50V caps in that scenario.  2V is just too small a safety factor.  It's why we went with 63V.  Electrolytics are made in definite voltage rating increments - 16V, 25V, 35V, 50V, 63V, etc.  I can't comment if you are using a different power supply, but use of a 12AU7 tube wouldn't change anything in that regard if the same power supply were used.
 
Also, the 16V rating you refer to is for the cathode bias capacitors.  There is very little voltage across those capacitors.  We need to be careful about which capacitor is which, here.

Oh yeah you're right, apparently whatever design I was looking at was incorrect. I wonder if his use of the 50v kz cap lead to it's premature death. I would definitely go with the FG cap that I crossed out instead of the KZ. tomb what would the effect of running 2 lower uF KZ caps in parallel have on the signal quality? I know that in theory it would be equivalent capacity but in practice I'm guessing there is a reason not to do that.

 

[tomb]

Well, paralleling electrolytic capacitors in a power supply is done all the time. In the signal path, however, electrolytics always sound worse than the alternatives (even compared to output transformers). That includes "boutique, audio-quality" electrolytics as well. So, if a 2nd cap is used in the signal path, it's almost alwayssome sort of film bypass, which can take over passing most frequencies and relegate the electrolytic to the lower frequencies. Whether it really happens that way or not is a subject of debate. It's not something that can be objectively tested with current technology/understanding. Some combinations work well, others do not.

 

[Nathan P]

Another Fred Starving Student joins the fray! I used Wima Polypropylene film caps, but a smaller size than what comes in the Beezar kit since the Fred PC boards are a bit different. In hindsight, I could have easily bent the leads and fit the larger caps for 3a and 5a. Ah well, I have another whole board to build with different components to see what differences I can hear.  
 



 
Initially had one of my caps polarity messed up but switched that around and it's working great. Aside from the fact that I wired my L/R backwards on the input side.
 
I'll fix that and I think I may swap out the 50k resistor prior to the pot to a 100k... I'm getting some channel imbalance and methinks using more of the volume will ameliorate that somewhat. Then it's time to get my case finished.
 
So far I'm not super super loving the sound of the GE tubes I grabbed. It's sounding just a bit thin in instrumentals. Vocals are cutting through like crazy though. Even without a case background noise is negligible so I have high hopes for a practically zero noise floor once buttoned up.
 
Question-I picked the Nichicon output caps based off of the BOM here:http://www.diyforums.org/SSMH/SSMHbom.php They appear to be the same used in the Beezar kit from photos. Would replacing these with the FG series net any real improvement? I'm also curious why C7/8 is recommended to be a signal quality cap. I chose a basic Panasonic since it's an optional cathode bypass. Is something special going on here that I'm missing?
 
For anyone wanting to use a parts list for this, it's here: https://www.mouser.com/ProjectManager/ProjectDetail.aspx?State=EDIT&ProjectGUID=ED556D7D-F5AA-4079-B0F2-385EB79A7395 I used all vishay metal film resistors as well. Note-I made at least two orders from Mouser. I'm not sure if I added everything from that so double check if you use it. Everything is labelled so that if you get one of Fred's boards you can drop in where the packages tell you to.
 
-Nathan

 

[tomb]

Signal goes through the cathode bypass, that's why signal-quality caps (Muse ES) are used.