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In Reply to: RE: curious... posted by Ralph on July 04, 2012 at 10:20:04
Well, let's see: Yes-- I borrowed the whole engine diagnostic lab. (the use of it).
Yes on all of number two.
Both, and square wave also. Most telling is just to run a known recording for a set period of time at a standardized AVERAGE SPL.
I had the lab for a few days-- it was a weekend, so I ran a different amp every time I came into the lab-- after it had been quiet for a time.
I might mention that heat buildup in the VC quickly gets out of the way once power is off. It also quickly dissipates during listening if you switch from one amp to another that contains more on-time music signals and less out-of-time-sequence power.
Once we realized that we could do this, we were able to run through more amplifiers-- if one had allowed TOTAL cooldown-- say overnight, then we could not have run them all.
The solution was to subject SOME amps-- the ones we really liked-- or had showed up really bad, and we thought that one should get a re-run, then those examples would get run in the morning-- when all had not been running, or afternoon if we had chosen to let things stop for a few hours.
Most of that extra attention was not really needed-- if you just switched amps while running-- and equalized SPL levels for each one, you could quickly observe temp. differences. Actually, once familiar with the procedure, I liked doing it that way better.
It was really cool to put on a better amp and watch the temps drop-- then, just for kicks, crank things up-- see how loud we could get before we saw the higher temps again. To me, that was fun, and running amp changes during play was even better-- as we could see temp changes occurring as we played.
All that was necessary was to calculate the watt levels going into the speaker-- at the same SPL, and watch the temps change! Real cool.
Amps ranged from 2% heat all the way up to 97% heat. The second best amp that was tested was a WAVAC from Japan. It had a positive-bias, A2 output stage-- a DHT that was High-Mu.
The data remains informal (but scientific to me). I make no claims about it, and so am keeping it non-published. I only mentioned the heat% in VCs because I think it helps us to understand that a music signal must be presented to a speaker in time-correct form, or it will produce mostly heat. You'll still be able to drive the speaker-- but the ultimate in fidelity will not be achieved, and you'll need far more power to get the same SPL..
I think that the stage that drives the output device must be designed for the speaker to be used.
I regard (conceptually) an output stage not so much as an amplifier-- I regard it as a slave-- a modulated coupling device that is between the power supply and the speaker.
It is transferring the driver-stage's characteristics into the speaker at a higher power level.
You must match the driver-stage characteristics to the speaker. All the output stage should do is program power supply energy into the speaker in absolute conformance with the driver-stage's dictates..
This statement explains why a low power amp can out-power a much larger amp IF the low-power amp has a lot of Power Supply energy available. All that is happening is that the output tube is sampling that High-Power PS-- what you HEAR is that High-Power Supply-- the output device may only be capable of a watt or so-- but it can momentarily couple a MUCH LARGER PS into the speaker when that is called for.
The driver stage is critical-- it cannot be allowed to mis-program the output stage/power supply/speaker combo.
Most decent amps outputs can connect well to a speaker-- within reason-- within their types range.
In a SET amplifier, it is the driver stage behind that, and the power supplies behind all the active devices that determines-- mostly-- what we hear from a speaker.
---Dennis---
Follow Ups:
Hi Dennis !
Here is my few comments and personal conclusion to yours topic :
a)- You say all that things about that different amps produce different level of generated heat on the (load)speaker VC .
b)- And you say that musical signal have to be presented in correct time in to the load(speaker).
My personal conclusion is that both of yours observation is correct ! , but I think that both effects is also very tightly connected to the amp Slew Rate characteristic , respectively to amp output power signal Rise time speed rate vs. amp output power signal Fall down time speed rate characteristic .
Performing famous 10Khz square wave signal amp test you can only partially check that , since the real music signal have quit different shape .
c) You say - I think that the stage that drives the output device must be designed for the speaker to be used.
My personal conclusion that this yours claim is here correct to , but is also tightly connected to implementation of DC coupled driver tube to the output device ( triode ) ,in order to achieve the best possible amp sonics , but anyway I think you have to take care where that output device (triode) tiny grid peak music signal AC currents actually flow & finish , I think it is always better to be directed via to the load(speaker)rather than to goes somewhere else .
d) You say -I regard (conceptually) an output stage not so much as an amplifier -- I regard it as a slave-- a modulated coupling device that is between the power supply and the speaker.
Roughly speaking You are correct here to , but don`t forget that between output device and load(speaker) is OPT , placed like pasive impendance matching device , then you have there bias network circuit around that output/driver devices to , and ...etc , things which usually if is have not designed in proper way can worse the amp sound significantly .
On the end I must say next to :
Personally I`m not the big fun of SE(T) amps ! , but I like & support open mind people like you who want to goes forward and try to make modern & better sounding tube amps following self intuition and ears , but have non conventional design approach to .
And just this to :
I observed that in the far past times many succesfully top SS amps designers have borrowed ideas, concepts & solutions from the early best sounding tube amp designs.
For example :
Mr. John Lindsley Hood has made in the early 60` his famous 10W A class SS amp directly copying famous Williamson PP tube amp concept , later in early 70` many top USA & Japanese SS amp designers have directly copying Futterman OTL tube amps original design solutions , in the recent time many top SS amp designers Worldwide have copying even OTL Circlotron tube amps designs solutions .
Today if I made analysis of relative good sounding & modern SS amp original circuits I can found there many valuable design solution for modern & better sounding tube amp to , so I suggest you to sometime check this advanced SS amp circuits .
And yes , IF is possible attach here your amp schematic ,presented even with out of particular elements values , because if your amp really sound good than no matter what I or anyone else here think , writes ,praise or criticize , final judgement well come from yours customers ears anyway .
Best Regards !
__
Enlightened Evolution-Astral Projection
Wow! All the Way from Yugoslavia! You guys are Oil Dudes!
Welcome to my rantings and (shall we call them discussions?-- yeah, that's better, I think)-- your post is a delight....
Hidden in it are all kinds of cool observations-- you realize, of course, that there are people on here who won't understand a word of it!
To those dudes, I'd say-- "get out more"-- travel! Even within the USA and Canada. Amazing what people are doing-- you just have to find them.
Realize that Americans have had a strong media complex for many years, many of our industries have been geared to already set-up production goals, schedules, etc., and the almighty Dollar has called a lot of the shots.
It's really nobody's own fault, but many of us over here have completely lost the ability to think for ourselves, having become Robots for the System.... Likewise, some "Engineers" have become basically Office Dudes--who use test instruments and known and proven theory over independent thinking.
However, those guys also contribute in meaningful ways to many things, but as a whole, our people have become programmed mentally to the point that they are actually blocking progress, invention, and individual expression on many levels.. THIS in the "Land Of The Free"! Totally amazing. Stand shocked-- and look.
It's a pleasure to find you on the net-- with your unorthodox writing style. Keep it up-- many of us are enjoying this-- your instincts make total sense to me.
A bunch of us are going to show up at Denver's RMAF 2012-- in Room 2020.... and go from there, visiting as many of our fellow exhibitor's showrooms as possible. The whole point is to see how others are doing audio-- not just ourselves.
Keep up your posts-- they're way cool!
---Dennis---
-
~!
The Mind has No Firewall~ U.S. Army War College.
Thanks, Ralph! I read all of it. Thanks for the insightful glimpse into how human beings operate under the stress of making things look good to whomever is judging them!
Historically, that's mostly how we got our audio "engineering" specs-- from politicians! Not only political politicians-- "engineering" politicians!
Same methods! Develop formulas, specifications and applications that make the-- Mistakes Of The Time-- look good on paper.... Of course, those formulas always work and always deliver the results scientifically expected of them-- they accurately deliver the OPINION of the guy who developed the formula!
What the Heck! We somehow manage to stumble around and a few of us think for ourselves, and actually get part way back to physical reality--sometimes, when we can.
GUYS! You will get a Kick out of Ralph's paper-- read it and understand what life on this Planet is really doing to our minds-- as the "experts" in every field tell us how to think, how to engineer-- and how to die their way-- as fools!
We can do better. And, when pushed, we'll do better yet. After you read Ralph's insightful paper, you'll realize why only a few will do it!
---Dennis---
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