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Question about using rectifier tube or not
Question about using rectifier tube or not
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Old 28th July 2018, 10:31 PM   #11
pblix is offline pblix  United States
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Another reason people in Hifi like to use tube rectifier is the gradual rise of B+ at power-on. This gives the other tubes time to heat up without full HV on the plates. Some say this extends tube life. For tube amps with solid-state rectifier you can install a standby switch or a timer/relay to circumvent this issue. I'm a firm believer in SS rectifiers.

BTW, for guitar amps, you can achieve the same thing by using a relatively large resistance in the PI filter. More current draw -> more sag. YMMV
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Old 28th July 2018, 10:39 PM   #12
Galu is online now Galu  Scotland
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Originally Posted by pblix View Post
BTW, for guitar amps, you can achieve the same thing by using a relatively large resistance in the PI filter. More current draw -> more sag. YMMV
Correct for a class AB amp, but won't work for class A (see my earlier post #7).
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Old 28th July 2018, 11:13 PM   #13
Wavebourn is offline Wavebourn  United States
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Question about using rectifier tube or not
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Originally Posted by Galu View Post
I never used the word 'only'!
Neither you tried for yourself.

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Originally Posted by Galu View Post
To be clear, overdriving a valve amp produces both even and odd harmonics.
Not if it is a well balanced amp.

Please read my complete description above. And google for Fourier Transforms, it helps more than repeating after "Gurus".

PS: it is not a theoretical question to me. Reading such "Gurus" and their pupils, people demand from me to design for them amps that add "euphonic even order harmonics". However, I can add square-law rectifiers to signal path, but they would spit on me then. And I would loose all respect to myself.
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Old 28th July 2018, 11:38 PM   #14
PRR is offline PRR  United States
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Originally Posted by Wavebourn View Post
..Nothing produces second order only harmonics....
Right. But Fender's input stages are cold-biased to work over a long range of even-order flavor before they break into odd-order. The output stages are strongly odd-order. The player has some control of how much of which via various gain knobs and playing level.

Playing a turned-down 20W amp at the sub-Watt level, even my wax ears can hear the 2nd order in the Fenderish preamp (on a 2-preamp Ampeg where the other side was dead-clean). Of course when you play the 20W amp at "40++ Watts!", there's "no" 2nd, your ears are full of odd-order products.

The rectifier is like the stitching on a baseball. Some things, tradition over-rides all else, change is not welcome.
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Old 29th July 2018, 12:12 AM   #15
6A3sUMMER is offline 6A3sUMMER  United States
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I believe that overdriving an SE guitar amp (i.e. a 6V6 champ) sounds a lot different than overdriving a push pull guitar amp.

Perhaps some of you guitar amp players can tell me if that is generally true for both moderately overdriven, and for strongly overdriven amps.

Last edited by 6A3sUMMER; 29th July 2018 at 12:14 AM.
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Old 29th July 2018, 12:18 AM   #16
PRR is offline PRR  United States
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Originally Posted by 6A3sUMMER View Post
I believe that overdriving an SE guitar amp (i.e. a 6V6 champ) sounds a lot different than overdriving a push pull guitar amp....
Different, but the SE job still goes grossly odd-order when OVER-driven.
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Old 29th July 2018, 12:22 AM   #17
pblix is offline pblix  United States
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Quote:
Originally Posted by Galu View Post
Correct for a class AB amp, but won't work for class A (see my earlier post #7).
Yeah, you already said that in post #7.
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Old 29th July 2018, 12:27 AM   #18
Wavebourn is offline Wavebourn  United States
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Question about using rectifier tube or not
Quote:
Originally Posted by PRR View Post
Right. But Fender's input stages are cold-biased to work over a long range of even-order flavor before they break into odd-order. The output stages are strongly odd-order. The player has some control of how much of which via various gain knobs and playing level.

Playing a turned-down 20W amp at the sub-Watt level, even my wax ears can hear the 2nd order in the Fenderish preamp (on a 2-preamp Ampeg where the other side was dead-clean). Of course when you play the 20W amp at "40++ Watts!", there's "no" 2nd, your ears are full of odd-order products.

The rectifier is like the stitching on a baseball. Some things, tradition over-rides all else, change is not welcome.
Back in 70'Th I organized a laboratory where we experimented with sounds designing synthesizers, guitar effect, and other musical stuff. The only way to generate even only harmonics was a direct synthesis. No distortions can ever provide even order harmonics only. A quadrature rectifier, 2'nd order only (of course, never ideal) can be used to get 2'Nd order distortions, but not 2'N2, 4'Th, etc...

And, as I mentioned above (if you ever read that), the real guitar string wobbles. It makes distorted sound more alive than a dull sound of an electric guitar string without any added distortions.

When I played a solo guitar, I made for myself a pedal with variable distortions, from clean, through soft a-symmetric, to hard symmetric distortions. It was very convenient to express feelings.
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Old 29th July 2018, 01:31 AM   #19
Galu is online now Galu  Scotland
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Originally Posted by Wavebourn View Post
Please read my complete description above. And google for Fourier Transforms, it helps more than repeating after "Gurus".
I did read your complete description.

You introduced several factors which can influence the harmonic structure of an amplifier's output signal and I've listed them below to prove I was paying attention!

Symmetrical/asymmetrical distortion; clipping; the non-sinusoidal vibration of guitar strings; attenuation by tone (?) control; overdrive.

All very interesting, but each factor would benefit from further amplification (pun intended!).

P.S. I have no need to google 'Fourier Transform' as I was introduced to the topic many years ago when but a lad at university!

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Originally Posted by pblix View Post
Yeah, you already said that in post #7.

Sorry, I wasn't getting at you - just making sure that owners of single ended amps don't attempt to introduce sag.
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Old 29th July 2018, 02:08 AM   #20
Wavebourn is offline Wavebourn  United States
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Question about using rectifier tube or not
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Originally Posted by Galu View Post
Sorry, I wasn't getting at you - just making sure that owners of single ended amps don't attempt to introduce sag.
What about Fender Champion? ;-)

I even went further with my "Microchamp" project.
Attached Images
File Type: jpg microchamp-5.jpg (132.3 KB, 95 views)
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Nothing in the universe is perfect. The ideal things are the ones that are most optimal. Optimization criteria, what matters. When I hear "No Compromise Design", I want to take a sledgehammer and test how impact-proof it is.

Last edited by Wavebourn; 29th July 2018 at 02:11 AM.
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