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Amp Specs esp. DampFactor : Citation, Adcom, etc.

Howdy,
I don't know if these specs are available, above and beyond the typically published stuff, but I'm trying to make some decisions about reworking my HT (I've posted some other threads) and I'd like some specs. to help make some decisions. What I'd like to know is if there is somewhere I could find the specs for the Citation 7.1, 5.1, Adcom GFA-545s and 555s, and a few others I'll list later. Basically, I've got the Citation 7s and a 5, but I might augment this system.

I've got some specs, such as what is available in the Citation manual, but there are only a few specs there. For instance, I don't believe that Citation lists a Damping Factor for the 7.1 or 5.1 and I'd love to know this. If I can, I'd like to compile a spreadsheet that I'll share for comparison. I know that much of this may simply not be available. Do I need to compile a list of specs that I'm looking for perhaps? I'm hoping that there might be a broader specs sheet, say for dealers instead of consumers?

Thank you everyone,
Aaron
aewhistory
almarg's avatar
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almarg
9,670 posts
 
Some folks are passionately against using specs in judging equipment and others, albeit a smaller group IMO, are just a passionate that specs/performance should be measurable. Personally, I'm a military historian and tend to be analytical, so while I can appreciate both sides of the debate, the end result frustrates me. So my main question is in trying to understand the two sides, or rather how do I reconcile these two positions?
My feeling is that the proper reconciliation of those two positions is that an understanding and assessment of specs is both useful and necessary in RULING OUT component selections that would be poor matches to either other components in the system (e.g., impedance incompatibilities, gain or level mismatches, etc.) or to the listener's requirements (e.g., peak volume capability, deep bass extension, physical characteristics, etc.). That hopefully allows the potential candidates to be narrowed down to a manageable number, and may allow some expensive mistakes to be avoided.

The list of remaining candidates can then be further narrowed either by listening, or if that is not possible by careful assessment of reviews and user comments (with grains of salt liberally applied).

Best regards,
-- Al
dob
577 posts
 
I am sure that in future, the set of measurments will predict fully amplifier behaivor.

Today, however, many measurments are meaningless or obtained by using dubious techniques design to improve measurments results and not sound.

Today, there are very few measurments which can preedict accurately what to expect e.g. headroom, bandwidth, lowest impedance the amplifier is stable and may be a few more.
THD is not but distortion spectrum will tell me a lot.

At any rate, DF is the ratio of speaker input impedance to amplifier output impedance at given frequency (I think 100 Hz but not sure) and can be achived, as Kijanki said by using deep slow negative feedback. I saw amplifiers, mostly class D with DF > 6000 which could not drive difficult load speakers.

I would suggest to trust "a bit" professional reviewers but more the amplifier's owners review - however, critically i.e. to see what speakers were used, what front end was used etc.
atmasphere's avatar
atmasphere
11,901 posts
 
Some folks are passionately against using specs in judging equipment and others, albeit a smaller group IMO, are just a passionate that specs/performance should be measurable. Personally, I'm a military historian and tend to be analytical, so while I can appreciate both sides of the debate, the end result frustrates me. So my main question is in trying to understand the two sides, or rather how do I reconcile these two positions?

This is actually fairly simple. The answer is that the specs were devised about 40-45 years ago, when very little was known about how the human ear perceives sound. A lot of research has been done since then, but none of it has been incorporated into the tradition of measurement, and so we have the experience of not being able to tell much of anything about the sound of the amp from its spec.

IOW, we don't measure what is important to the human ear.

This is what has led to the objectivist/subjectivist debate, although the issue is a bit larger and more complex than that. See
http://www.atma-sphere.com/papers/paradigm_paper2.html
for more information.

Just a FWIW, Damping factor is the least of your worries in any solid state amp. I would not worry about distortion either, Kijanki is correct in his initial post.
kijanki's avatar
kijanki
4,432 posts
 
"we don't measure what is important to the human ear"

Atmasphere - absolutely true but how we can measure it? I don't know how to measure amp's music power or how to measure TIM distortion or how to guarantee synergy with the speakers. Is there anything we can do (new standards) or it will be always black magic?
atmasphere's avatar
atmasphere
11,901 posts
 
I think there is. This is just my opinion of course, but I think we need a standard signal burst, one that last for about 1 second or so, that is completely non-repetative.

The instrument would then compare the amplifier's output to the original. The result would be examined for odd-ordered harmonics so a listener fatigue/brightness rating can be assigned. Then the lower ordered harmonics can be analyzed so a low-order coloration (warmth, caramel, syrupy) value can be assigned.

It would be nice to do this with a variety of test loads, both linear and nonlinear.

That's where *I'd* like to start anyway. I think there is no reason why such a test could not be devised- the compute power for that is pretty common these days.
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