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Amp Effects + Distortion

post #1 of 26
Thread Starter 

Is it really possible for an amp to change the frequency response? As in make the mids recessed, treble emphasized, etc. Is that what coloration is? I notice messing with the EQ changes the "color" of the sound, for reasons I can't really understand. 

 

Oh and how do tube amps distort the sound exactly? 

post #2 of 26
Thread Starter 

Hmm no one answered yet. Is my question too stupid? 

post #3 of 26

Tube amplifiers are a bit more complex than that. Tubes can change the frequency response outright, but you also have to consider the nature of the power tube and the output transformer when it is driving a load. Just because a loudspeaker is rated at 8 ohms, doesn't mean it maintains that across the frequency spectrum. The same with the amplifier. Read up on impedance and Zobel networks.

 

http://en.wikipedia.org/wiki/Electrical_impedance

 

http://en.wikipedia.org/wiki/Zobel_network

post #4 of 26
Quote:
Originally Posted by NimbleTurtle View Post

Hmm no one answered yet. Is my question too stupid? 

 

Hey, it's a good question

I suspect we are too stupid to give you a reasonable answer!  LOL!redface.gif

 

Tube amps generally have a higher output impedance than solid state amps.

The higher output impedance can interact with speakers to change the apparent frequency response and and the apparent "tightness" of the bass, i.e. the bass may sound fatter, fuller.

Some Tube amps have a fair amount of second order harmonic distortion which can make the amp sound fuller, more romantic, more lush.

These are just some generalities, random thoughts and my genius, inspired opinions (LOL!).................YMMV!

post #5 of 26
Just about any reasonably good solid state amp should provide a flat response. The things that don't necessarily have a flat response are speakers (and the rooms they're in) and to a lesser extent headphones.

Equalizers are just very precise tone controls. Instead of just adjusting bass and treble, you can pick specific frequencies and boost or cut them.
Edited by bigshot - 8/18/12 at 10:53am
post #6 of 26

I have referenced the Carver Stereophile challenge - where a $600 Carver amp is nulled by Bob Carver (with RadioShack parts overnite in his hotel room) against a highly respected, SOTA tube amp

 

after adjusting frequency response and output impedance to match, Stereophile's "Golden Ears" couldn't tell the difference in blind listening

 

note - in their own listening room, with their own choice of source, speakers - and as experienced professionals taking money for making fine distinctions by listening the "test stress" argument doesn't work so well

 

 

so while the literal "all amps sound the same" is a strawman - amps can differ in frequency response and output damping by enough to be audibly distinguished under DBT conditions

 

but as understood and controllable differences it is "uninteresting" in an engineering sense - it means designers just build in EQ to give their amps unique "voices" - not that there is some mysterious superiority of audiophile tweaks, parts or tubes vs SS in amplifiers

 

"Carver Challenge" info/discussion:
diyAudio Forums - Blind Listening Tests & Amplifiers - Page 22

 

 

original Sterophile article:

 

http://www.stereophile.com/features/the_carver_challenge/

 


Edited by jcx - 8/18/12 at 2:38pm
post #7 of 26
Quote:
Originally Posted by jcx View Post

I have referenced the Carver Stereophile challenge - where a $600 Carver amp is nulled by Bob Carver (with RadioShack parts overnite in his hotel room) against a highly respected, SOTA tube amp

 

after adjusting frequency response and output impedance to match, Stereophile's "Golden Ears" couldn't tell the difference in blind listening

 

note - in their own listening room, with their own choice of source, speakers - and as experienced professionals taking money for making fine distinctions by listening the "test stress" argument doesn't work so well

 

 

so the literal "all amps sound the same" is a strawman - amps can differ in frequency response and output damping by enough to be audibly distinguished under DBT conditions

 

but as a understood and controllable difference it is "uninteresting" in an engineering sense - it means designers just build in EQ to give their amps unique "voices" - not that there is some mysterious superiority of audiophile tweaks, parts or tubes vs SS in amplifiers

 

"Carver Challenge" info/discussion:
diyAudio Forums - Blind Listening Tests & Amplifiers - Page 22

 

 

original Sterophile article:

 

http://www.stereophile.com/features/the_carver_challenge/

 

Apologies if this is a bit off in any way.

 

Taking the Carver model, is it possible to apply this to either "ToTL" dynamics, orthos, or stats? And has this been attempted, if so, it never seems to be talked about.

post #8 of 26
Quote:
Originally Posted by jcx View Post

so while the literal "all amps sound the same" is a strawman - amps can differ in frequency response and output damping by enough to be audibly distinguished under DBT conditions

Solid state amps all sound the same. Tube amps are all over the place. It's possible to hobble a solid state amp in just the right way and get it to perform like a tube amp, but there isn't much call for that. The amps you buy are calibrated for flat response with minimal distortion. That guarantees they'll sound the same.
post #9 of 26
Quote:
Originally Posted by paradoxper View Post

Apologies if this is a bit off in any way.

 

Taking the Carver model, is it possible to apply this to either "ToTL" dynamics, orthos, or stats? And has this been attempted, if so, it never seems to be talked about.

 

I don't think I understand what you're saying. Are you talking about EQ and tweeking a low-end headphone/speaker to sound like a higher-end model?

post #10 of 26
Quote:
Originally Posted by OJNeg View Post

 

I don't think I understand what you're saying. Are you talking about EQ and tweeking a low-end headphone/speaker to sound like a higher-end model?

In short yes. Furthermore, to EQ/tweak, etc to such an extent that DBT provides others not being able to differentiate the low-end

with the higher-end

post #11 of 26
Quote:
Originally Posted by jcx View Post

I have referenced the Carver Stereophile challenge - where a $600 Carver amp is nulled by Bob Carver (with RadioShack parts overnite in his hotel room) against a highly respected, SOTA tube amp

 

after adjusting frequency response and output impedance to match, Stereophile's "Golden Ears" couldn't tell the difference in blind listening

 

note - in their own listening room, with their own choice of source, speakers - and as experienced professionals taking money for making fine distinctions by listening the "test stress" argument doesn't work so well

 

 

so while the literal "all amps sound the same" is a strawman - amps can differ in frequency response and output damping by enough to be audibly distinguished under DBT conditions

 

but as understood and controllable differences it is "uninteresting" in an engineering sense - it means designers just build in EQ to give their amps unique "voices" - not that there is some mysterious superiority of audiophile tweaks, parts or tubes vs SS in amplifiers

 

"Carver Challenge" info/discussion:
diyAudio Forums - Blind Listening Tests & Amplifiers - Page 22

 

 

original Sterophile article:

 

http://www.stereophile.com/features/the_carver_challenge/

 

 

I've heard of the Carver challenge and it's pretty telling. From what I understand, all he had to do was match impedance and tweek a little to get it to sound like the tube amp's transfer function. Did he have to adjust for added harmonics that the vacuum tube design would have introduced? Or were those not audible enough to make a difference to the listeners?

post #12 of 26

In your opinion....................

 

Quote:
Originally Posted by bigshot View Post


Solid state amps all sound the same. Tube amps are all over the place. It's possible to hobble a solid state amp in just the right way and get it to perform like a tube amp, but there isn't much call for that. The amps you buy are calibrated for flat response with minimal distortion. That guarantees they'll sound the same.
post #13 of 26

details of the Carver-Stereophile challenge were deliberately obscured - I think somewhere it is mentioned that Caver may have made ~ minor change to the feedback - in addition to the added output parts

 

the tube amp wasn't identified to spare the manufacturer's reputation - but could have been push-pull to get the power rating - so may have had very little 2nd harmonic to begin with

 

we can build SS or Tube amps that do have "sound" effects - it is easier, cheaper to build "transparent" SS amps than with Tubes

post #14 of 26
Quote:
Originally Posted by jcx View Post

details of the Carver-Stereophile challenge were deliberately obscured - I think somewhere it is mentioned that Caver may have made ~ minor change to the feedback - in addition to the added output parts

 

the tube amp wasn't identified to spare the manufacturer's reputation - but could have been push-pull to get the power rating - so may have had very little 2nd harmonic to begin with

 

we can build SS or Tube amps that do have "sound" effects - it is easier, cheaper to build "transparent" SS amps than with Tubes

 

Seems like there was an adjustment for distortion.  Notably, it seems to have been tuned on a dummy load rather than on the speakers.

 

Quote:
Neither LA nor I had any idea what "adjustments" would be involved, but I, for one, was convinced that the area that would ultimately stymie Bob was that of harmonic distortion content. I have long believed that some of the major sonic differences between amplifiers were related to the relative and absolute amplitudes of their harmonic distortion components. (It is known, for example, that the amplitude of the high-order harmonics—the third, fourth, fifth, and sixth harmonics—become progressively weakened in the signal from a tubed component, and remain relatively constant from a solid-state device.) I was a little shaken when I learned that a half-dozen small potentiometers that Bob had wired into his amplifier were "distortion pots," which enabled him to change the amplitude of any "spurious" harmonic as desired, independently of the other harmonics!

 

 

With some tube amps, particularly at some output range, you may not have to bother, but probably the reference here had some significant "character" to speak of.

post #15 of 26
Quote:
Originally Posted by jcx View Post

details of the Carver-Stereophile challenge were deliberately obscured - I think somewhere it is mentioned that Caver may have made ~ minor change to the feedback - in addition to the added output parts

 

the tube amp wasn't identified to spare the manufacturer's reputation - but could have been push-pull to get the power rating - so may have had very little 2nd harmonic to begin with

 

we can build SS or Tube amps that do have "sound" effects - it is easier, cheaper to build "transparent" SS amps than with Tubes

 

Do push-pull tube amps have lower harmonics (compared to single-ended) in general? How come?

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