Simple fun question,
Why build a tube amp that sounds like a transistor amp. If the tube amp matches the transistor/SS levels of distortion then the transistor or SS amp will be cheaper to build.
Put another way the SS amp outperforms the tube amp in all measured parameters, but I'll build a tube amp to match it because I want to use tubes.
Or I'll build a tube amp and then mod it until it matches the SS amp. Because that's the sound I like..😀
Regards
M. Gregg
Why build a tube amp that sounds like a transistor amp. If the tube amp matches the transistor/SS levels of distortion then the transistor or SS amp will be cheaper to build.
Put another way the SS amp outperforms the tube amp in all measured parameters, but I'll build a tube amp to match it because I want to use tubes.
Or I'll build a tube amp and then mod it until it matches the SS amp. Because that's the sound I like..😀
Regards
M. Gregg
How can I add low level crossover distortion to a valve amp, and then ensure that in the output it gets differentiated so that although very small it is very peaky?
I guess I would need a Class B output, running fairly cold, lots of forward gain and heavy feedback. The stability problems could get interesting!
How can I add a small DC offset to the output of a valve amp?
I guess I would need a Class B output, running fairly cold, lots of forward gain and heavy feedback. The stability problems could get interesting!
How can I add a small DC offset to the output of a valve amp?
A well made and good design SS amp has negligible Xover distortion and definitely no DC offset.
To introduce Xover distortion why not add a pair of diodes in parallel but electrically opposed in series with your loud speaker. Then you can make it behave like a poor quality SS amp.
Silly!
To introduce Xover distortion why not add a pair of diodes in parallel but electrically opposed in series with your loud speaker. Then you can make it behave like a poor quality SS amp.
Silly!
Actually, my SS amps sound better than my tube amp at 1% THD. But the tube amp has taken two lightning strikes with the result I had to replace the power switch and turn off pop capacitor. The tube amp lasted most of 40 years with octal e-caps and decennial power tubes, and I have yet to get more than a year performance out of any of the SS amps.
I'd like to get the tube sound down to .03% THD, and KevinKR says his triple triode driver board from classicvalve.ca will do it.
Two of the SS amps have internal connection problems at those wimpy little voltages they use on the input stages, which is one more reason the ST70 is waaay more reliable than solid state. The solid state witch hunt starts again with the rains of October. Last winter I found a bad solder joint in the PV-1.3k which had been whanging the output to 160 VDC and burning out the DC protection circuit since 1994 when it left the factory. Wimpy op amps, too **** sensitive to a cold soldering iron. The 1998 CS800s blows the breaker, probably has bad special order short e-caps buried inside the steel power supply enclosure which is required to keep the switching power supply from howling into the speaker. Tricky cheap transistors need a lot of help to work right.
I'd like to get the tube sound down to .03% THD, and KevinKR says his triple triode driver board from classicvalve.ca will do it.
Two of the SS amps have internal connection problems at those wimpy little voltages they use on the input stages, which is one more reason the ST70 is waaay more reliable than solid state. The solid state witch hunt starts again with the rains of October. Last winter I found a bad solder joint in the PV-1.3k which had been whanging the output to 160 VDC and burning out the DC protection circuit since 1994 when it left the factory. Wimpy op amps, too **** sensitive to a cold soldering iron. The 1998 CS800s blows the breaker, probably has bad special order short e-caps buried inside the steel power supply enclosure which is required to keep the switching power supply from howling into the speaker. Tricky cheap transistors need a lot of help to work right.
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Been there; done that. For one project, I wrapped some 20dbv of gNFB around a hollow state design, and, indeed, it sounded just like any run-of-the-mill SS amp. Cutting that back to some 7.0dbv of gNFB sounded much better.
For another project, I included variable gNFB (0 -- 13dbv). Turn the gNFB all the way up, and the sound is definitely tending towards "solid statey" sound.
Measure what parameters? There is very little correlation between THD figures and listener satisfaction. It all depends on what harmonics are present. Lower order harmonics are less disturbing than higher order harmonics, for example. If THD were the be-all and end-all of sonic performance, we'd have attained Audio Nirvana a long time ago. THD makes for good marketing department braggin' points, but little else.
Can you point me to specific claim, I don't remember making such claims about the driver upgrade board, it may be consistent with measurements I did 20+ yrs ago on a unit, and at something like 1W @ 1kHz, but I have not checked, and it does not sound reasonable for higher powers at higher/lower frequencies. The design is licensed and I have nothing to do with the day to day operations over there. (Serious health issue makes focusing elsewhere much more important.)
No question it is a big improvement over the original design, and back in the day I sold about a 100 of these boards before ceasing operation.
Probably best to PM and I will try to get to the bottom of this.
The .03% number comes from the manual for the solid state amp I want my tube amp to sound like, the CS800s. What you said to Zigzagflux about the triple triode board you designed for the ST70 was "a big improvement" or something. If I bought one for my original ST70 I wouldn't be measuring, I'd just be looking for less pitch instability on top octave Steinway piano solos. Or less buzz on tinkly bells. Probably I'm hearing 10-14 khz IM distortion , since I'm deaf above 14 khz.
Actually, I don't want to cut up the ST70 that badly, it is the only hifi amp that works most of the time if the e-caps and rectifier are up to date. I might build a clone with triodeelectronics transformers and your board some day for a test. (The Hammond organ tube amps soldier on even if output power is down to 10% it seems).
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