Do different amps sound different? (1 Viewer)

[Mike SJ]

"I'm certainly not someone who thinks the color of an amp affects its sound. My point was that the perception of the sound of an amp can be affected by psychological factors"

I understand, I just wanted it to be clear that you werent making a blanket statement to include you, me, or hopefully anyone here at HTF. Yes I agree, the perception of the sound of an amp can be affected by psychological factors.

 

[Claude M]

it wasn't till I swapped to the Norhs and ran the same 3 amps that I noticed a different sound between amps.

 

[Yogi]

Norhs probably have a lowish impedance that likes to interact with your amps more than the other speaker does. Thats why I like speakers with high impedance like these

since they don't interact audibly with amps. I wish all speakers had an impedance curve like this.

 

[Mike SJ]

what speakers are those BTW?

PS and which is better for an amp, a high impedence output ot a lower one. I have a B&K which the spec sheet says they all have 22k ohms and mine has 33k ohms or something close to that. which is better and could you explain why?

 

[Yogi]

Those are Von Schweikert VR2s.

The impedance numbers that you are quoting are for the input impedance at the preamp inputs of your amps (the higher the better upto a point since it makes the life of the preamp driving it, easier). I am talking about the output impedance at the speaker terminals of the amps which is better if its lower.

 

[Mike SJ]

"I am talking about the output impedance at the speaker terminals of the amps which is better if its lower. "

yeah I know, that was just a spec that I didnt really understand. thanks.

so the Von Schweikert site says something like the speaker is 8 ohms, 5 min. And if you run them off a 4 ohm amp? I guess your last post about speakers not audibly interacting with amps... a bit over my head

 

[David Judah]

Here's some guys who definitely think amps sound different(go to the last couple of pages), but I'm sure some will have problems with their testing methodology.

DJ

 

[Claude M]

hey Yogi, you nailed it. I just dug up the specs for those speakers. I can emailed them to you if you'd like. the impedence graph shows they get pretty high in the lower frequencies (close to 64 ohms at 50HZ). From 2k to 20k HZR almost flat at 8 ohms, 200hz to 1K hz the reach close to 16 ohms.

 

[Mike SJ]

looks like we need an official HTF power amp shootout

 

[Shane Martin]

Amps sound different to me. But I'm not going to contribute much more to the dead horse of a subject that this is. I'm sure we'll talk beer in about a few posts and so and then the dead horse of blind testing is brought out by the same people who troll the same threads.

It's a dead horse. Let's move on.

 

[Chu Gai]

If we confine ourselves to solid state amps with low output impedances (high damping factors) then RobertR's #6 post, if read carefully is entirely correct. However, that does not mean that Andrew Pratt's post #8 is necessarily incorrect. What appears to be a paradox or a clashing of views, needs more explanation to understand why both are correct. To that end, I'll disagree with Mike SJ's comment that speakers are not part of the equations and hopefully illustrate below, why they are indeed so.

It's my position that one first should choose their speakers wisely and only then go looking for a receiver or an amp. The reason is really quite simple as the speaker's sensitivity, impedance curve, phase, and the type of music you listen to as well as the volume dictate where your attention should be directed. I recommend that people read the following article from Stereophile to get a better handle on this: http://www.stereophile.com/features/99/index.html

Specifications regretfully shed little insight on how an amp will perform. Saying a car has 245 hp tells you nothing about how it accelerates, what kind of a load it can pull, etc. Dyno readouts are far more informative. Life is always wonderful when you're getting your numbers from a static 8 ohm resistor or taking measurements at 1 kHz. Unfortunately they don't tell how an amp will perform into a dynamic load. To some extent this problem is being addressed by some review magazines and sites with measurements being taken into simulated speaker loads. However we need more of this with more taxing loads.

Audible differences can arise from a variety of reasons of which I'll list a few.
1) An amp can have an inadequate power supply and/or insufficiently large capacitors. Under situations that call for current, the amp can simply run out of current or be borderline. How an amp behaves under those conditions is anyone's guess. It might sound dull or muddy as Mr. Pratt noted. And if you think about it, it's no wonder. The amp can no longer deliver enough current to accurately reproduce the low frequencies. If it doesn't have enough current to reproduce those accurately, it's not a far stretch to imagine it won't do justice with the rest of the program material. OTOH, it might start generating signficant amounts of audible distortion products. Does the word harsh or strident ring a bell here with people?

2) An amp can simply start to run out of voltage. Many of the same issues as noted in 1) can occur. Clipping is a funny thing and you can read more about it at Rane's website where this matter was studied a bit more thoroughly.

3) An amp that has inadequate phase margin for a given speaker's impedance and phase can go into oscillation. Typically this results in elevated temperatures and the generation of harmonics, some of which are ultrasonic and can fry a tweeter (or the other way around) and some of which are in the audible range. The thing is, it's a non-linear phenomenon. At a particular volume one might not hear any problems.

4) Amps or receivers that employ current limiting are not always designed so well. Anyone's who has seen the old protection message come up has more than a passing familiarity with that. As the unit approaches it's current limit, greater amounts of distortion products are created and of course, depending on their order and what's playing, various negative comments come out...harsh, grainy, etc.

5) Users, in an attempt to squeeze every last bit of performance out of their speaker wires, even if it's inaudible, turn to vendors or home brew recipes (braiding Cat5) that have significantly more capacitance than regular old 12 gauge. Look for the review in a recent Stereophile where Kalman Rubinson used Alpha Goertz's speaker wire (a nasty wire IMO) and drove an Adcom into shutdown.

These negative results are sometimes blamed on things that have nothing to do with the problem like metal tweeters. Now that's not to say that all metal tweeters are wonderful but it just might be that the reason the harshness went away was because Speaker B, which has a silk tweeter, also has a crossover network that limits HF hash. One needs to dig deeper to get good answers.

It's my opinion, that people looking for amps generally ought to more strongly consider those above the entry level from most manufacturers. They seem to be more solidly built with better power supplies and less likely to give grief.

As far as putting up the Samson against that Krell...I wouldn't, but I'd put up a variety of pro amps from QSC, Crown, Carvin, etc. any day of the week driving nasty low impedance loads and feel pretty confident I've got enough current to execute Osama.

David, you know damned well that testing methodology was egregiously flawed and was quite self serving.

 

[David Judah]

Yea, especially if you're an ATI or Bryston owner.

DJ

 

[Chu Gai]

No kidding! I might have missed a reply in that thread that you referenced David but I'd asked for clarification of the calibration procedure and the order the amps were stacked. Maybe they ducked. The results showed no consistency although a trend was attempted to be forced based on the limited amount of responses. It also wouldn't have been so hard to put up a blind of some sort and simply refer to the amps as Amp A, Amp B, etc.

Bryston will be here 5 years from now and they'll be servicing your 9 year old amp under warranty that you can sell for a pretty good price. The question is can Gemstone say the same?

 

[Yogi]

I couldn't have said it better, Chu. The thing is not many people realize these limiting conditions are often exceeded in amps in day to day use under normal operating conditions so a general statement like all amps sound alike if driven in their linear range under such and such condition etc etc...is true only in a very narrow sense. When real speaker loads are interacting with amps/receivers playing at theater levels saying that a $100 receiver sounds the same as a 10K 600W monoblock is hilarious at best.

 

[Chu Gai]

Well true, but then you take some 98 dB efficient speakers and you could play them with a KLH receiver and have power to spare. Hell some time ago I wrote how I'd taken a Sansui receiver (mid 70's) over to a person's house and we hooked it up to some Avantegardes. The receiver didn't break a sweat and what can I say...the setup, while wierd, was quite 'musical'.

I do hope people click on that Stereophile link...it's helpful I think.

 

[Ricky T]

Chu,

Nice post on reasons for audible differences. Do you make your posts in Word and cut & paste sometimes (to save time) I think a Sansui receiver from the mid 70's was/is highend stuff.

 

[Shane Martin]

I will say that Chu's post was pretty good and Yogi's follow up was good too.
Yes and the stuff is built more robust than todays standards.

 

[Mike SJ]

"To that end, I'll disagree with Mike SJ's comment that speakers are not part of the equations ..."

Chu, I understand that IN THE END the amps must 'adapt' with each speaker they are sending signals too, in a simple sense. All I was trying to do was eliminate as many variable from the equation, and just look at what is actually within the amps that cause changes in sound. I understand the basics on impedence and such. just trying to clarify.

 

[Andrew Pratt]

I'm pretty sure that's exactly what's going on with my HK and Rotel amps as the HK's numbers aren't that strong when you compare its 4 and 8 ohm ratings indicating a weaker P/S where as the Rotel's is much better and are known for generous P/S and large cap's. I also know my mains ohm rating dip's quite low at some points which will clearly stress the weaker P/S'd amp.

 

[Yogi]

Or you could hook them up to a 50W/ch tube amp and have a rocking setup with power to spare too

Its too bad that most speakers today are not designed to be that efficient. The average speaker efficiency today is around 89-90 db efficient and so most receivers will struggle to keep up with them in a moderately sized HT. Also isn't speaker efficiency and impedance not always go together? Meaning an efficient speaker could still dip down below 4ohms in the lower registers to tax the KLH receiver out of juice in spite of its high efficiency? Am I right Chu?