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The Woo Audio 2 - Page 12

post #166 of 1026
Quote:
Originally Posted by HeadphoneAddict View Post
You guys should be thinking about a WA22 now. Balanced, yum.

I needed speaker out as well (for Stax transformer and K1000), so it was between a Beta 22 or a Eddie Current ZDT. Tubes won...
They always do. You've made me wait in line by taking the last one, you know.
post #167 of 1026
Quote:
Originally Posted by HeadphoneAddict View Post
You guys should be thinking about a WA22 now. Balanced, yum.

I needed speaker out as well (for Stax transformer and K1000), so it was between a Beta 22 or a Eddie Current ZDT. Tubes won...
I know that people were requesting a balanced woo amp, but is it actually in the works?
post #168 of 1026
Quote:
Originally Posted by number1sixerfan View Post
I know that people were requesting a balanced woo amp, but is it actually in the works?
Yes, a prototype version was at a meet.
post #169 of 1026
Quote:
Originally Posted by number1sixerfan View Post
I know that people were requesting a balanced woo amp, but is it actually in the works?
Woo Audio 22 Fully Balanced Headphone Tube Amplifier

The prototype was at the NYC meet.

http://www.head-fi.org/forums/f45/of...thread-415713/
post #170 of 1026
Quote:
My gut feeling (nontechnical) is that I don't think that mismatched tubes would cause loud hum
The sellers said that the tubes (the 5998 pair a couple months ago and the 6N13S more recently) tested 100% and were matched, but within each tube the two triode sections were not matched. That said, I unfortunately do not know enough about the inner workings of tubes or how these issues could manifest

Any ideas what could cause these symptoms? Amp turns on and works fine, tubes slow start to glow like normal, as they do so a hum appears in both channels, even when the input selector is in the "mute" position. Hum is constant, not affected by volume dial position.
post #171 of 1026
You might write to Jack about the hum problem. There was a version of the 5998 that had closely matched triodes - the 2399, but as I recall, Skylab did not feel the sound was strikingly different.

I guess my point is that matched triodes probably wasn't a characteristic of the 5998, and that may not be the problem. The only hum I've had with my WA2 is from one oar two substitutes for the 6DJ8s I had been trying. The power tubes - a lot of different varieties - have all been essentially silent.

As for low impedance, the WA2 sounds terrific with my D2000s.
post #172 of 1026
I cannot imagine how unmatched sections would be causing hum. Most of my 5998's are pretty well matched, but I have some 6AS7G's that are not, and in my DV337 at least this does not cause problems.

You do have some power tubes that do not hum in your WA2, yes?
post #173 of 1026
Quote:
You do have some power tubes that do not hum in your WA2, yes?
Yes - such as a NOS pair of TS 5998's and GE 5998A. When I took out the 6N13S and put those in it is dead quiet. Ditto for the 5998's from a few weeks ago which I returned - hum when in the amp, silent when replaced with the 5998A's.
post #174 of 1026
Change of plans! I will be using either the 6 or the 2 for the L3000.
post #175 of 1026
Quote:
Originally Posted by number1sixerfan View Post
Change of plans! I will be using either the 6 or the 2 for the L3000.
Impedance on the L3000 is 48 ohms, so it should be a better match with the WA2 than the W5000s (40 ohms).
post #176 of 1026
Quote:
Originally Posted by xenithon View Post
Yes - such as a NOS pair of TS 5998's and GE 5998A. When I took out the 6N13S and put those in it is dead quiet. Ditto for the 5998's from a few weeks ago which I returned - hum when in the amp, silent when replaced with the 5998A's.
So other than the tubes being flat out bad, the only thing I can think is that the pins are dirty. Did you clean them by any chance?
post #177 of 1026
No, but oddly enough......well, let me take a step back. I did some experimentation last night:
- had in a pair of known-to-be-good (ktbg) 5998A tubes
- took out one of the tubes and put in one of the 6N13S tubes
- tested both with and without music; no hum, jet black background, music played perfectly
- swapped tubes around (i.e. swapped them between the two sockets); no hum
- took out that 6N13S and put in the 2nd one, while keeping the same ktbg 5998A in
- at first, no hum; but when I switched off the amp a hum/noise appeared (in the left channel; with the 6N13S installed in the left socket)
- switched on again and hum slowly appeared; also reacted to tapping the chassis of the amp

This seems to point to one of the 6N13S tubes being bad - microphonic, and possibly also cathode/heater leakage? I initially said "oddly enough" because one of the 6N13S tubes has a pretty loose base (loose from the glass) and dirty-looking pins. That however is the good tube; the one which is not loose and with clean pins is the bad one.

I also got a reply from Jack who said that tubes can (and often do) test 100% but have noise/hum. In other words, the tube tester can only tell so much - perfect test does not guarantee quiet tubes.
post #178 of 1026
That all makes sense -I still suggest using a contact cleaner on the pins.
post #179 of 1026
Skylab - you may know you've had me hunting down some brown base GEC/Marconi tubes; which are of course just a myth ....

...I wanted to ask if you have used - and your thoughts on - the 7236 tubes (e.g., Cetron, Sylvania)?
post #180 of 1026
I have a pair of Tung-Sol 7236's, and they sound good, although they are on the more forward/bright/lean side than the 6AS7G or 5998.
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