SOHA help...
Dec 12, 2007 at 3:39 PM Thread Starter Post #1 of 11

bhostinsky

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On my basic kit SOHA from Glass Jar Audio, I recently changed C2 & C14 to the WIMA MKP 10's and a 5963 nos tube. The resulting sound is awful and borderline brutal. There is more air and detail, but the sound is really harsh. There is probably 20+ hours on both the tube and the caps, and it has warmed up some. Any idea how long it takes for these components to break in, or should they be done breaking in after that amount of time?

Has anyone tried the RCA Clear Tops in these amps? I'm thinking about trying them in the other 2 SOHA's that I have for home use.

Thanks,
Brian
 
Dec 12, 2007 at 4:07 PM Post #2 of 11

headphonejunkie

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I did not like cleartops with grados. I am using an amperex orange globe I got on ebay. This sounds real nice. They are supposed to be made by mullard from the 70's.
 
Dec 12, 2007 at 4:11 PM Post #3 of 11

tomb

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Quote:

Originally Posted by bhostinsky /img/forum/go_quote.gif
On my basic kit SOHA from Glass Jar Audio, I recently changed C2 & C14 to the WIMA MKP 10's and a 5963 nos tube. The resulting sound is awful and borderline brutal. There is more air and detail, but the sound is really harsh. There is probably 20+ hours on both the tube and the caps, and it has warmed up some. Any idea how long it takes for these components to break in, or should they be done breaking in after that amount of time?

Has anyone tried the RCA Clear Tops in these amps? I'm thinking about trying them in the other 2 SOHA's that I have for home use.

Thanks,
Brian



IMHO, something else may be wrong. I have used the combination you mention many times and it happens to be one of my favorites.

Did you re-bias the tube when you switched it? Every tube is different. Depending on how different, it could be operating with a very small voltage swing and largely clipping. Different sides of the tube may have very different biases, also.

Or, it could be a bad tube or just not broken in. Sometimes the old NOS tubes have a case of air infiltration from sitting on the shelf for decades. It may take up to a week sometimes for the getter to burn out all the gas.

Just a few guesses to look at perhaps ...

EDIT: The Wima's are immediate - no break-in required. They are very flat, with only the slightest tendency of some grain in the mids and highs, or perhaps a bit of the telltale film cap "squeekiness", but my ears aren't good enough to hear that.
 
Dec 12, 2007 at 5:03 PM Post #4 of 11

ericj

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I have a whole bunch of 5963's that were sold to me as "RCA" which are extremely harsh sounding. They aren't cleartops, though. And they have the most microphonic of all possible getter designs.
 
Dec 12, 2007 at 6:38 PM Post #5 of 11

bhostinsky

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I'm definitely noticing the squeekiness, which was part of my concern, since I got it even with the both the 5963 and the super warm GE 12au7a that I had in it for quite some time. After a few weeks the original Xicons film caps seemed to warm up, guess I was hoping the Wima's would do the same. I would really like to keep them in since they provide a much better presentation to the music.

I guess the tube just needs some serious break-in time to loose the harshness. It's biased to the 40v stated in the build. Would higher be better?

Thanks,
Brian
 
Dec 12, 2007 at 6:53 PM Post #6 of 11

tomb

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Quote:

Originally Posted by bhostinsky /img/forum/go_quote.gif
<snip>It's biased to the 40v stated in the build. Would higher be better?


NO. That would make it worse.

It could still be a bad tube. The recommendation of the 5963 was usually specific to a GE, but there are other brands that still do pretty well.. As Ericj states, there are some examples that are not as consistently good in the SOHA. Even if GE or whatever - there is always the chance that you got a bad one.
 
Dec 12, 2007 at 7:33 PM Post #7 of 11

bhostinsky

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Sorry, I didn't realize I forgot to mention the brand of the tube. It's a GE 5963. I have 2 and they're both really really bright. I just put my headphones on after letting the amp run for the past 6 hours and it definitely sounds better, but still incredibly bright. The headphones I'm using are AKG K55 (need closed cans for work) and the K701's. I'm hoping another hundred hours or so would do the trick for the tube.

After doing an extensive search on the boards, I think I'm going to try the Mundorf caps. Can anyone recomend a shop to get them as well as model number (or something like that)? I've tried the Auricaps and they're nice, but I read the Mundorfs can be a little warmer, and that sounds like music to my ears.

Two other things I should probably mention is that the output resistors are Vishay's and the opamp is a OPA2134. This amp is not going to get the JISBOS boards since it's for work.

Thanks,
Brian
 
Dec 12, 2007 at 8:18 PM Post #8 of 11

stixx

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Quote:

I think I'm going to try the Mundorf caps


Before you get Mundorf caps I would definitely try another tube. The impact on sound of a different tube for sure is much greater than exchanging an mkp cap for another mkp cap...

Wima's are very flat = neutral, and a standard Mundorf is pretty much the same unless you want to spend big bucks on the upscale Mundorf's... But whether putting silver or gold in your signal chain at work makes that much of a difference is up to you to decide...
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Dec 13, 2007 at 12:14 AM Post #9 of 11

bhostinsky

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I just happened to notice that both of the GE 5963's that I have are extremely microphonic, have some background tube noise. Every other tube I have is dead quiet in both respects, I can tap on the tube glass and no noise with other tubes. Could these be bad tubes or are the 5963's just like that?

As for the caps, I think I'll just stay with them Wimas and go for higher end on the ones I use at home with the 701's.

Thanks,
Brian
 
Dec 13, 2007 at 12:30 AM Post #10 of 11

tomb

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Quote:

Originally Posted by bhostinsky /img/forum/go_quote.gif
I just happened to notice that both of the GE 5963's that I have are extremely microphonic, have some background tube noise. Every other tube I have is dead quiet in both respects, I can tap on the tube glass and no noise with other tubes. Could these be bad tubes or are the 5963's just like that?

As for the caps, I think I'll just stay with them Wimas and go for higher end on the ones I use at home with the 701's.

Thanks,
Brian



Nah - no tube is "just" microphonic. They're bad.

I think it's something in the mechanical construction that got messed up. When the tube glass was blown and the parts encapsulated - there was a small chance that the plates or grid or something ended up touching the sides of the tube so that any touch resulted in reverberation. Just my own personal theory, but I've seen tubes with getters that ended up bent down over the plates and the microphonics were horrible.

It's not something that was ever a regular thing, thank goodness - unless you get someone that purchased a whole batch that way and is re-selling them. I've heard of that happening, too.
 
Dec 13, 2007 at 12:40 AM Post #11 of 11

bhostinsky

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Thanks Tomb. I was kind of afraid of that. I read somewhere about some tubes being microphonic until they properly break in. Will try to grab some others to see if that eliminates the problem.
 

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