JJ6V6 in 6L6 amp

[ultra-gain]

Well, to be honest, on that amp a half power switch would be like a half power switch on a drag racer. The XXX is a loud stage amplifier, not a bedroom warrior. If one wants a quiet amp, one should not buy a XXX.

And if half power is all you are after, why fart around with 6V6 tubes? Just disable two of the power tubes. Open their cathode leads.

lol. I was wondering if some one was going to me call out on the obvious. I hear you Ezno. Thought about buying a Weber Power Mass 200. Just figured four 6v6 was cheaper and also gets me lower than half power.

[Chuck H]

Isn't the XXX just a high gain preamp into a clean power amp? In typical use the power tubes are never clipped so their tonal contribution relative to volume is almost moot. Any tonal change heard when the amp is played louder is more likely to be acoustic changes relative to sheer volume in the room and perceived by your ears. That will be lost no matter how the volume is reduced unless there is another tone altering mechanism to the system by which the volume is reduced.

[g1]

Agree with Chuck, I don't think anyone is ever setting these up clean and cranking the master till the power amp breaks up.
All the high gain tones are achieved through preamp distortion. Power amp breakup might even make it sound worse.
So just turning down the master should achieve the volume reduction.

[Chuck H]

I don't think anyone is ever setting these up clean and cranking the master till the power amp breaks up.

I'm not even sure you can. Not by much anyway. I can't determine the gain of the effects loop, but if it's typical then it's under a volt coming out and probably more like half a volt. Then one gain stage and then the PI. And the PI values are very conservative and only offer maybe half the usual gain from this circuit. There's also some minor loading between the loop and the PI. But it's basically one gain stage to a LTP with about half the usual gain feeding signal to the power tubes. It probably can clip. but probably just a little. Very intentionally set up to offer full power without the contribution of power amp clipping.

[ultra-gain]

Isn't the XXX just a high gain preamp into a clean power amp? In typical use the power tubes are never clipped so their tonal contribution relative to volume is almost moot. Any tonal change heard when the amp is played louder is more likely to be acoustic changes relative to sheer volume in the room and perceived by your ears. That will be lost no matter how the volume is reduced unless there is another tone altering mechanism to the system by which the volume is reduced.

I was wondering if that was not the case. The tone comes from the preamp section.

[soundmasterg]

If it was me I'd just add power scaling to that amp. Then you can get the tone you want at any volume you want. Just power scale the power amp and phase inverter. It will even lower the B+ around 15-20V which might help things. See the link below.

Greg

https://www.londonpower.com/power-scaling

[ultra-gain]

If it was me I'd just add power scaling to that amp. Then you can get the tone you want at any volume you want. Just power scale the power amp and phase inverter. It will even lower the B+ around 15-20V which might help things. See the link below.

Greg

https://www.londonpower.com/power-scaling

thanks for the link. I have never heard of this. Probably just use the master volume knob on this amp.

[Chuck H]

thanks for the link. I have never heard of this. Probably just use the master volume knob on this amp.

That IS how the amp was designed to be used. There really is no advantage to the implementation of power scaling for this design.

If you don't use the amp at loud volumes, but prefer it's tone when used that way I might suggest that whatever differences in perception volume puts on the ears might be responsible. You could experiment with different cabinets to see if a final EQ/speaker efficiency change helps. There's a noticeable "feel" that comes with speaker efficiency. Speaker hunting can be an expensive drag though. If you're getting satisfactory tone from it as it is then there's really nothing to consider.

[ultra-gain]

That IS how the amp was designed to be used. There really is no advantage to the implementation of power scaling for this design.

For sure. I see this now. Pretty simple if I just thought about it. All the sweet tone is from the pre-amp section. Thanks to James Brown.

If you don't use the amp at loud volumes, but prefer it's tone when used that way I might suggest that whatever differences in perception volume puts on the ears might be responsible. You could experiment with different cabinets to see if a final EQ/speaker efficiency change helps. There's a noticeable "feel" that comes with speaker efficiency. Speaker hunting can be an expensive drag though. If you're getting satisfactory tone from it as it is then there's really nothing to consider.

Absolutly, Fletcher-Munson curve. Plus just the sheer force of cranking an amp up loud and pushing some air into your chest and the excitement of an electrified guitar at loud levels.

I'm actually stoked on the sounds I'm getting. Still chasing the perfect medal tone though. Baritone guitar -> Seymour Duncan Black Winter(On order)-> Amptweaker Tight Drive-> Triple XXX->4X12 5150 loaded with Sheffield 1200. I have the Seymour Duncan APH-2 in the guitar now. Hoping the Black Winters set it off.

[Helmholtz]

Absolutly, Fletcher-Munson curve.

Actually the Fletcher-Munson curves show that there is insignificant change in hearing frequency response at different loudness levels at least in the guitar frequency range.
As long as the curves of different loudness levels run in parallel, there is no change in frequency response perception.

[Justin Thomas]

But we don't count in such studies. Because, deaf rock stars in some or most frequency ranges, anyway! We make terrible test subjects.

Jusrin

[eschertron]

Actually the Fletcher-Munson curves show that there is insignificant change in hearing frequency response at different loudness levels at least in the guitar frequency range.
As long as the curves of different loudness levels run in parallel, there is no change in frequency response perception.

I have to ask what curves you are looking at? I see a 20dB difference in the 100Hz - 1000Hz decade. IMHO it's the chest-thumping low notes that indicate loudness for most "test subjects". That's why most cheap 'loudness' controls only boost [edit] LOW [/edit] frequencies.

[Helmholtz]

But we don't count in such studies. Because, deaf rock stars in some or most frequency ranges, anyway! We make terrible test subjects.

Jusrin

Well, that means that those deaf rock star need a completely different set of Fletcher-Munsons curves.

[Helmholtz]

I have to ask what curves you are looking at? I see a 20dB difference in the 100Hz - 1000Hz decade. IMHO it's the chest-thumping low notes that indicate loudness for most "test subjects". That's why most cheap 'loudness' controls only boost frequencies.

There's nothing like a 20dB difference between DIFFERENT sound pressure levels. No need to compensate the natural frequency respone of the ear as long as it doesn't change at different sound pressure levels.

[Leo_Gnardo]

But we don't count in such studies. Because, deaf rock stars in some or most frequency ranges, anyway! We make terrible test subjects.

Fletcher's and Munson's great grandkids ought to look into this, because it appears to be true. Calling Doctor Fletcher! Calling Doctor Munson! Bring your audiology test lab and let's find out. Don't forget ear fatigue, temporary threshold shift. Test the morning after the big rock show, then again after 2 weeks of relative silence. Should generate an interesting set of curves. And let's not forget the varying effects of presbycusis, say what. WHAT??? Natural loss of hearing acuity in aging people. Even if they're not so aged. Starts small, almost undetectable in your 20's, definitely noticeable by 40-50's and it's all downhill from there. Hand me my ear horn sonny...