Do amplifiers sound the same??

[mtrycrafts]

To take room placement out of the equation, couldn't you just swap the two amps and do the comparison again? If you observe the same results for the same amp using the opposite speaker, then clearly the room placement didn't make the change...

--nw

Sorry, this will not work either. Everything is against you: bias, acoustic memory, etc.

 

[annunaki]

Hey guys, I think some may be missing the point of this post. There probably are audible differences between amplifiers, such as some of you have explained. I am basically saying that the difference is explainable, due one or a combination of the reasons I have given. It is not that one amplifier just sounds better than the other, period.

 

[Dan Banquer]

"I agree with all but #3. A greater amount of distortion will not be created unless the amp is of bad design. A low output impedance and high damping factor will take care of this."

That's what supposed to happen but I suspect that it isn't. From some of the data I have taken and some of the stuff I have listened to make me question just how many amps out there maintain that low output impedance over power and frequency.
d.b.

 

[mtrycrafts]

... just how many amps out there maintain that low output impedance over power and frequency.
d.b.

Why would impedance be power dependent?

 

[Dan Banquer]

One of the issues not discussed in audio is what happens with power amps using unregulated supplies and what happens to transistors when the supply voltage varies.
If we note the data books for transistors we find a gain bandwdth spec for a certain voltage actross the transistor, if the supply voltage chages then the gain bandwidth changes. Assuming that is the case then we have a feedback loop which is set for a certain gain bandwidth trying to hit a moving target, becasue the supply rails are moving up and down depending on load and the gainbandwidth is changing on the transistors.
So if all the above is true and the feedback loop is trying to hit a moving target, then I would expect variations over power and frequency.
Just to add a bit more to mix; when an amplifier is driving a reactive load the voltage and current are out of phase in the output drivers of the amp. If we are using a voltage feedback loop, as we usually do, then we have just exacerbated the problem stated above due to the reactive load.
I also suspect that if bias current through the outputs is for some reason getting lower under higher power conditions then this may also add to the problem.


Are we having fun yet?
d.b.

 

[MacManNM]

Bad amplifiers sound way different. All good solid state amplifiers sound pretty much the same. Most of the coloring comes from the pre-amp. Now, due to design, some amps may sound different (i.e McIntosh autoformer output). But these traits are measurable. McIntosh is the only SS amp that I can think of that uses anything like that. Most other SS amps are Direct coupled. This means as long as they are of reasonable design, they will sound identical.

 

[mtrycrafts]

One of the issues not discussed in audio is what happens with power amps using unregulated supplies and what happens to transistors when the supply voltage varies.
If we note the data books for transistors we find a gain bandwdth spec for a certain voltage actross the transistor, if the supply voltage chages then the gain bandwidth changes. Assuming that is the case then we have a feedback loop which is set for a certain gain bandwidth trying to hit a moving target, becasue the supply rails are moving up and down depending on load and the gainbandwidth is changing on the transistors.
So if all the above is true and the feedback loop is trying to hit a moving target, then I would expect variations over power and frequency.
Just to add a bit more to mix; when an amplifier is driving a reactive load the voltage and current are out of phase in the output drivers of the amp. If we are using a voltage feedback loop, as we usually do, then we have just exacerbated the problem stated above due to the reactive load.
I also suspect that if bias current through the outputs is for some reason getting lower under higher power conditions then this may also add to the problem.
Are we having fun yet?
d.b.

Yes, we are having fun that is why we are here, no

So, power and frequency is affected by sagging line, if the caps cannot handle the duration, right? But I still don't see how the output impedance changes because of decreased power? Or, am I missing something here, a good possibility

 

[Dan Banquer]

This is not about power or frequency reponse: it's about non uniform behavior in power amplifers as it relates to output impedance and distortion at higher power levels.
d.b.

 

[MacManNM]

This is not about power or frequency reponse: it's about non uniform behavior in power amplifers as it relates to output impedance and distortion at higher power levels.
d.b.

I believe that you are trying to say, that due to the change in rail voltage biasing on transistors is going to change, hence causing the output Z to become unstable. When this happens, the damping factor of the amp is drastically changed,along with many other things.

Chain reaction.

 

[Dan Banquer]

Biasing on the output transistors may well be a factor (heat due to higher power levels), but the original issue and I think one of the more important ones is the change in gain bandwidth of the transistors when the power supply voltage changes.
d.b.

 

[Votrax]

Actually for quite a few years they've been using some sophisticated biasing techniques so the effects of temperature and voltage swings are minimal. They typically use a transistor as a constant current source to set the bias current. My Sony ES uses darlington transistors with built in temperature compensation diodes which work quite effectively.

 

[Dan Banquer]

That kind of packaging may help but there will inevitably still be a thermal lag. I would think mainly that the packaging that Sony uses would help speed assembly. When I was making amps I used some better thermal coefficent insulators and had the tracking transistor mounted very close to the hottest running (PNP) transistors also using the better thermal corfficent insulators. It works pretty well, but certainly not perfect.
d.b.

 

[hifiman]

Many, many years ago when Stereo Review was published, Julian Hirsch made the claim that amps sound the same. I haven't owned a lot of amps, but of the few that I have owned I never noticed a difference.

 

[mulester7]

Bad amplifiers sound way different. All good solid state amplifiers sound pretty much the same. Most of the coloring comes from the pre-amp. Now, due to design, some amps may sound different (i.e McIntosh autoformer output). But these traits are measurable. McIntosh is the only SS amp that I can think of that uses anything like that. Most other SS amps are Direct coupled. This means as long as they are of reasonable design, they will sound identical.

.....Mac, just a comment....I just got off the phone with McIntosh in New York by the 800# listed, and a guy in the lab section named Joe P-something-Italian name, said the autoformer section on McIntosh amps effects the sound you hear in no way whatsoever.....

.....you guys do whatever you think is best concerning augmenting your receiver with extra channels of outboard amplification.....

 

[mtrycrafts]

.....you guys do whatever you think is best concerning augmenting your receiver with extra channels of outboard amplification.....

I guess you will not add external amps?

 

[mtrycrafts]

When this happens, the damping factor of the amp is drastically changed,along with many other things.

Chain reaction.

Drastically? That would depend on the frequency this happens at, speakers impedance and the amps impedance change. What is drastic to you?

 

[mulester7]

.....guys, I see there's two posts before this one....what the two posts say I don't know....that's all I can tell you, so what does THAT tell you?....I'm going to enjoy coming to this site much more now, I'm confident....we've hashed the merit of slave amps enough, I won't be listening to your stuff, so do what you will concerning YOUR reference levels....over.....