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RE: curious...




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---


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