An Amp Sonics side-thread

[Brett]

first of all, damping factor can never be too high. ideally it should be ininite.

Dave has already covered this. Nelson Pass has covered it even better.

you do have a point that if you run an AB amp at 0.1% of its power it may have poor distortion and noise performance there ... but at 10% of its power an amp will typically have better performance than at 90%.

So with my high efficiency speakers, down in the low power region the amplifiers will spend most of their time working in, the AB design will sound worse. Wow, I've only known that for 20 years.

yes there is still every reason to build efficient speakers but there is no reason to use 2 watt amps.

At about 104dB from >200Hz, why do I need more than 7W in a modest room? A large SS AB amp isn't much more energy efficient and sounds worse.
Currently <200Hz is 35W AB, but will likely be replaced sometime in the future with a switchable 20/40W class A design as I have all the parts on hand.

 

[vasyachkin]

I have my own PA's, all built by me so I understand. Please explain the relevance to domestic reproductive systems.

There are many superbly designed and implemented class A amplifiers out there.

Build efficient speakers, then the size and class of the amplification becomes a much smaller issue, with far fewer compromises. By efficient I mean >96dB, preferrably 100dB. Compromise is in size and sometimes cost.

what i meant regarding home versus PA systems is that at home its not a business so its not about the bottom line. lets say you determine that you need 50W per channel, then there is nothing stopping you from using a 500W per channel amp and you can forget about clipping. you cannot do this for PA because then you will have to explain why you're wasting money that is not yours. so the PA amp i have has a "soft clipping" option (switch) for example, but in practice i don't need it because of the headroom.

as far as building 96db to 100db speakers my position is this. all things being equal i will always prefer a more efficient speaker, but if i have to make any compromises in performance to get the extra efficiency i will not go for it. there are 8000 watt amps (Crown I-Tech, class D) that sound good enough to cover bass in an active system and there are slightly less powerful amps, say 7000 watt (QSC Powerlight, Class H) which are good for covering the rest of the frequency range. as such 96 to 100db efficiency is a luxury, not a necessity.

 

[vasyachkin]

In practise you will never get a damping factor much over 20. You also have to ask how a very high DF is achieved.

i think my amp has DF of about 500. i believe DF is achieved through large amount of negative feedback.

i know Pass has beef with NFB but i dont.

are you going to call me a heretic and burn me at the stake ?

 

[jdlech]

So does your class A amp also double as a toaster oven or room heater?

Just kidding, really.

If I could have two 40W all class A amps for normal listening, I would. I agree that in a normal entertainment room, 40W would be adequate for 99% of the time. And ceteris paribus, class A naturally has less distortion than AB or C.

Why two? I normally run a DSP.

 

[Brett]

what i meant regarding home versus PA systems is that at home its not a business so its not about the bottom line. lets say you determine that you need 50W per channel, then there is nothing stopping you from using a 500W per channel amp and you can forget about clipping.

It depends on where you're willing to compromise. I would rather have a lower SPL, through better amps into more efficient speakers, than dynamic power compression with AB amps into less efficient speakers. Been there, done that.

as far as building 96db to 100db speakers my position is this. all things being equal i will always prefer a more efficient speaker, but if i have to make any compromises in performance to get the extra efficiency ... {snip}....as such 96 to 100db efficiency is a luxury, not a necessity.

Depending upon how the lower eff system is implemented, there may be a whole raft of compromises. I've posted on it before, and I just can't be bothered rehashing it today.

Luxury, no. I build these systems both for the enjoyment of listening to them and the experience of the build, so they provide pleasure and other benefits on other levels, such as increased knowledge through experience and research. These things are not luxuries in my universe.

i think my amp has DF of about 500. i believe DF is achieved through large amount of negative feedback ... and i happen to think NFB is not evil.

Not in the real world it won't be. Add connectors and even modest cables and it drops significantly.

 

[Brett]

If I could have two 40W all class A amps for normal listening, I would. I agree that in a normal entertainment room, 40W would be adequate for 99% of the time.

Why two? I run a DSP.

Heat is not an issue. The room has good natural ventilation.

What's the DSP got to do with it?

Single amped, in my system, it would be more than enough.

I'm quad amped, or will be soon;
20-60: SS PA amp
60-200: 35W tube AB, to be replaced with 20/40W class A
200-1k5: 7W PP class A tube
>1k5: same amp.

All of this was built, except for a few passives, with the parts I already own.

 

[vasyachkin]

Not in the real world it won't be. Add connectors and even modest cables and it drops significantly.

well if you count the resistance of cables its going to drop from 500 to about 20 indeed

and if you count the resistance of the voice coil then it will drop to below 1

what is your point ?

DF is certainly not the parameter on which to judge an amplifier and yet high-tech amps generally have it higher. i believe Crown I-Tech has it at about 1000 or more.

i would agree that DF of about 20 is enough in practice, but i would feel safer buying an amp with DF of 1000 because typically only very high performance amps have that.

 

[AJinFLA]

Almost all SS AB amps sound the same to me, whether an old Rotel or yamaha, or the Quest, QSC,or Yamaha high power designs I use in my PA's.

Under double blind conditions?

Generally, not that great, especially when you're running very high efficiency systems.

Really? Earl Geddes used a $150 AB Costco Pioneer to demo his rather efficient Summas. Tom Danley uses AB as well with his even more efficient Synergy Horns. I wonder why they are not hearing such fidelity losses as you? Here is a thread where Earl discussed his measurement methods
Geddes on distortion measurements. Are you using such measurement techniques? Maybe the ones like Bob Cordell uses?

Distortion is worse at low levels with an AB amp (any type) because nonlinearity increases areound zero. High eff speakers make this much more obvious.

That is a sweeping generalization. There are both good and bad examples of AB design. Claiming that crossover distortion is audible listening to music using every AB design would be unsubstantiated. Unless you have data to show me otherwise.

As well as doing tests, I've also designed, built, tested and measured about a hundred amps over the last few years, so I feel I have some insight into why there are differences between them.

Please share your results with us. Nothing against peer review of data I hope?

cheers,

AJ

 

[planet10]

Under double blind conditions?

And can you show valid double blind tests that show they are all the same?

Or scientific proof that small amps aren't better?

dave

 

[pedroskova]

Under double blind conditions?




Really? Earl Geddes used a $150 AB Costco Pioneer to demo his rather efficient Summas. Tom Danley uses AB as well with his even more efficient Synergy Horns. I wonder why they are not hearing such fidelity losses as you? Here is a thread where Earl discussed his measurement methods
Geddes on distortion measurements. Are you using such measurement techniques? Maybe the ones like Bob Cordell uses?



That is a sweeping generalization. There are both good and bad examples of AB design. Claiming that crossover distortion is audible listening to music using every AB design would be unsubstantiated. Unless you have data to show me otherwise.




Please share your results with us. Nothing against peer review of data I hope?

cheers,

AJ

This belongs in the Audio Asylum's propeller head ward.

 

[planet10]

i believe DF is achieved through large amount of negative feedback.

Can you show us the distrotion spectrum of your amplifier? I bet it has lots of ugly high order components....

dave

 

[pinkmouse]

Personally, having heard lots of PA amps, I have never been able to correlate the level of DF with any consistent subjective sound difference...

 

[MJL21193]

Can you show us the distrotion spectrum of your amplifier? I bet it has lots of ugly high order components....

dave

Hi Dave,

For my own information here, do you mean something like this:

Thanks

 

[Brett]

well if you count the resistance of cables its going to drop from 500 to about 20 indeed

Well, as you're connecting to a speaker that includes cabling and connectors, it's far more appropriate. It's rrelevant what the DF measures with a test resistor across the amplifier terminals.

Under double blind conditions?

Many were. And as I already own all the gear, my biasses are substantially reduced on the non-blind tests.

Really? Earl Geddes used a $150 AB Costco Pioneer to demo his rather efficient Summas. Tom Danley uses AB as well with his even more efficient Synergy Horns. I wonder why they are not hearing such fidelity losses as you? Here is a thread where Earl discussed his measurement methods
Geddes on distortion measurements. Are you using such measurement techniques? Maybe the ones like Bob Cordell uses?

If you note in the linked Geddes thread, I'd mentioned using an HP spec an years ago to try to do something similar, but couldn't get SNR low enough for good repeatable measurements. When I have the time (I'm going back to school this year), I'd love to examine this further.

Because someone finds something adequate for the task, doesn't mean there's not other ways of doing it, some of which may be better.

That is a sweeping generalization. There are both good and bad examples of AB design. Claiming that crossover distortion is audible listening to music using every AB design would be unsubstantiated. Unless you have data to show me otherwise.

I think it's on the mark for the majority of generic AB designs. Show me where it's not by giving some measured examples at low power where I would use it.

Please share your results with us. Nothing against peer review of data I hope?

My data is all in hardcopy in notebooks and I have no interest in spending the time or effort to make it electronic for your review.

 

[AJinFLA]

Almost all SS AB amps sound the same to me, whether an old Rotel or yamaha, or the Quest, QSC,or Yamaha high power designs

Under double blind conditions?

And can you show valid double blind tests that show they are all the same?

Can I show valid double blind tests that they all sound the same to Brett?

Or scientific proof that small amps aren't better?

I am to present scientific proof of your purely subjective contention?

This belongs in the Audio Asylum's propeller head ward.

Then move or re-post it there yourself.

cheers,

AJ

 

[Brett]

Can I show valid double blind tests that they all sound the same to Brett?

Notice earlier I said ALMOST which to you has become all.

 

[AJinFLA]

Notice I am responding directly to Planet 10's question in my post. Notice your ALMOST has become all in his question.

cheers,

AJ

 

[vasyachkin]

Can you show us the distrotion spectrum of your amplifier? I bet it has lots of ugly high order components....

dave

i dont have such data. however why assume that if an amp has less overall distortion that the distortion must be uglier ? and why assume that if an amp has lots of distortion then it must be euphonic ?

thats like saying that a blonde must be dumb or a person with thick glasses must be smart.

i will readily agree that a class H amp will have much uglier distortion than a class A amp, but this has nothing to do with amount of NFB.

as i said before i have nothing against inherently linear class A amps except that they're not very practical. if i could choose between two amps of same power, same price and same THD i would get the class A ... but i will never be offered such a choice

if i have to choose between a class H amp of the power i want and a class A amp with 1/10th the power that i want, then i will go for the H.

 

[planet10]

For my own information here, do you mean something like this:

Yes... looks like a PP amp with little or no 2nd order, but a fair amount of 4th and some higher. Anything above 3rd the ear really finds objectionable, and the lack of 2nd means the 3rd isn't as well masked. An ideal spectrum would have some 2nd, a bit less 3rd, and vanishingly small higher order components.

dave

 

[MJL21193]

Yes... looks like a PP amp with little or no 2nd order, but a fair amount of 4th and some higher. Anything above 3rd the ear really finds objectionable, and the lack of 2nd means the 3rd isn't as well masked. An ideal spectrum would have some 2nd, a bit less 3rd, and vanishingly small higher order components.

dave

Thanks,
Looking at the scale the higher harmonics are about -100db, including the 4th. That's a long way down.

Are you sure this is hard to listen to?