I don't get the expected power output.

[Alan0354]

I was under the impression that the 6V6S is a more rugged version of the 6V6GT with a higher Pda of 14W, so I guess you can push it a bit harder, but I doubt it would make much of difference SPL-wise.

I gave up on the JJ already, I think that's the end of the road. I am going to try the 6L6 next. Question is in the last post whether the PT can handle the 6L6 reliably.

[nickb]

Ha ha, I am one up over you!!! I have the Tektronix 465......from the late 70s, 10 years newer!!!! And I have a function generator I got from the surplus store for $100. But I think both are plenty for guitar amp. To be honest, I don't even use these often. I had to pull them out from the closet yesterday when you guys here insist on using them.

Now a days, scopes are really cheap, I saw in Fry's they have some digital scope smaller, fancier and faster than mine for less than $500.

Yes, I think so, I put the 8.33 ohm on the 8 ohm tap, this is like 16 ohm on the correct transformer.

I had the fanciest scopes, spectrum analyzers, network analyzers at work back in the days. But in this guitar amp, or even audiophile amps, I really don't think you need any of those. Low distortion has nothing to do with good sounding.

I guess I assumed that Alan being a long term EE would have one or two lying around

No problem - use PC + Audio Card line + attenuator + free FFT software (e.g. Audacity). Kinds clunky but it will work.

And, no this was nothing to do with "low distortion", but just a means of measuring using the same yardstick. Yes, maybe the Webers do give to 20 watts but if it's ten times the distortion I don't think it's a fair comparison.

[nickb]

Mystry solved, I think... Martin Manning posted a comparison of the actual traced 6V6S vs. 6V6GT specsheet on TAG awhile back, it can be seen that the 6V6S is quite a bit less sensitive than the 6V6GT. But I am still puzzled by your measurements, how come it only swing down to 220V? Ditto for the 6V6 which was only a bit better - neither was anywhere near the saturation region of tube...

[ATTACH=CONFIG]29885[/ATTACH]

I think the conclusion may be correct but you have to be careful extrapolating valid conclusions from a single sample, especially given today's manufacturing variability.

[Alan0354]

I guess I assumed that Alan being a long term EE would have one or two lying around

No problem - use PC + Audio Card line + attenuator + free FFT software (e.g. Audacity). Kinds clunky but it will work.

And, no this was nothing to do with "low distortion", but just a means of measuring using the same yardstick. Yes, maybe the Webers do give to 20 watts but if it's ten times the distortion I don't think it's a fair comparison.

Ha ha, I got use to working with minimal. I worked in an analytical company call Charles Evans & Assoc that want to branch out into designing mass spectrometer. They literally hired me to start the engineering. We started with a Tek 465 as the only scope in 1988!!! I had to fight to get a 475 300MHz scope and we had to design pulsing circuits over 300MHz bandwidth!!! So I got used to the lean and mean environment. It was not until 2000 that I venture out to other companies that I was shocked, absolutely shocked how nice their equipments were. A scope that was over 3GHz!!!! HP network analyzer and all!!!

You'll be surprised how much you can do with so little. A lot of people think they need first class equipments to do first class work. I just believe you can do with less. Face it, in guitar amp, how often you pull out a scope? I had it on my desk for a while, then I found that it's just taking up valuable space. I just packed it away until a few days ago when I had to use it.

Hey The whole thing in this thread was because of I had a wrong transformer AND more important, I read the wrong color wire!!!!, No network analyzer or fancy scope can fix stupidity!!!

[soundmasterg]

There was some scuttlebutt when the JJ 6V6S came out that it was more like a 6L6 inside the bottle and that was why it could take the higher voltage. So if it is more like a 6L6 then it will be less sensitive and take more gain to bring it to its full power level. It may also like a lower impedance than a traditional 6V6 too, with a typical 6L6 being half what a typical 6V6 would like to see. I don't know if you tried the JJ into the 4 ohm tap and compared it to the 8 ohm tap power of the Chinese Weber and Ruby 6V6's or not?

Greg

[soundmasterg]

You could always rewire the sockets and try some 7591's too. Those can take the voltage and will give good power and sound, and they are more sensitive than even a 6V6 so they will overdrive easier. You have a choice of the JJ or the EH, with the EH being larger physically and it may not fit in some amps. In my experience the 7591 likes to see about 5000 ohms for a pair so they would be happy with either your 4 ohm or 8 ohm tap most likely.

Greg

[Alan0354]

There was some scuttlebutt when the JJ 6V6S came out that it was more like a 6L6 inside the bottle and that was why it could take the higher voltage. So if it is more like a 6L6 then it will be less sensitive and take more gain to bring it to its full power level. It may also like a lower impedance than a traditional 6V6 too, with a typical 6L6 being half what a typical 6V6 would like to see. I don't know if you tried the JJ into the 4 ohm tap and compared it to the 8 ohm tap power of the Chinese Weber and Ruby 6V6's or not?

Greg

Yes, I tried on different tap of the OT, it is lower power than the Weber across the board. I did verify that I drove the 6V6S to 0 grid and verify that the tube clip when I reach 0 grid. I have plenty of drive to the tube, I verified gain of the tube is not an issue. In fact, that was the first thing I suspect, I even change the PI tube from 12AT7 to 12AX7 to increase gain. It did not make any difference.

No, I don't think the 6V6S is close to 6L6. I did use 6L6 in the amp, with the right tap, I got 30W out of the pair of 6L6.

[Alan0354]

You could always rewire the sockets and try some 7591's too. Those can take the voltage and will give good power and sound, and they are more sensitive than even a 6V6 so they will overdrive easier. You have a choice of the JJ or the EH, with the EH being larger physically and it may not fit in some amps. In my experience the 7591 likes to see about 5000 ohms for a pair so they would be happy with either your 4 ohm or 8 ohm tap most likely.

Greg

Thanks

At this point, I am settling with the Weber 6V6. I already got 22W. I could have got 24W if I leave the +B at 420V. I actually lower the +B to 402V to protect the tube. My PT is spec for 25W max, or else, I would put the 6L6 in and get 30W easily.

Thanks