Fully Discrete 400 / 700 Driver Circuit (Full Comp Only)

[laatsch55]

Lee,

I added a hole bunch of new links to my previous post over the last hour and your response.

Here is another one.

ftp://ftp.dcaudiovisuel.com/dca/AudioPrecision/ATS1A-DD_GPIB_Prog_Ref_Manual_rev2.pdf

Please let me know if any of it helps.

Ed

This one applies, but I'm not to sure what it does. Is it an alternate method to control the analyzer?

 

[oldphaser]

Ed,
My 700 already has upgraded supply caps.... Mallory 20000uF/100VDC (125VDC surge). Also, I am using 15024's and 15025's for drivers and outputs.

Nick,

These kind of details are good to know.

Do you have any old 9,800uF capacitors laying around that you could re-install temporarily in order to perform the signal-to-noise ratio and dynamic headroom tests, etc...as I mentioned in my previous post? Likewise, I would be curious to see what the dynamic headroom with the 20,000uF capacitors are in comparison.

Ed

 

[THD+N]

Ed,
I'll have some time this weekend to swap out those caps and perform more tests.

 

[Gibsonian]

I would then suggest when performing subjective testing that one states the manufacturer, and model number of the speakers..... The speaker placement.... The size of the room.... The artist and song(s).... etc.... Better yet maybe do what many well known amplifier designers do and that is to perform listening tests at 1W with a pair of headphones. In which case you can remove the room acoustics and some of the variables. Notable designers like Dan D'Agostino, John Curl and Nelson Pass all use headphones at approximately 1W to evaluate the amplifiers they are designing. By the way, most amplifier use is between 1W and 40 Watts. Nelson Pass has a website and it is http://www.firstwatt.com. "Dick Olsher famously remarked that the first watt is the most important watt".

Perhaps we all need to also buy a copy of J. Gordon Holt's (former publisher of Stereophile) book "The Audio Glossary" which has terms and definitions.
(It will cost you around $75+ for a used copy)
Here is a link to some of the terms re-published in 1993. https://www.stereophile.com/reference/50/index.html

Did I stir the kettle enough? LOL!

Ed

Don't think we need Holts book quite yet. Think talking about how these amps compare to one another soundwise is quite helpful when you dont have access. If I went by specs alone I wouldn't own PL amps, that's for sure. I sure dont need to know all the room dims, song played etc. And headphones or speakers are fine!

 

[Northwinds]

I have never subscribed to using headphones to test an amp. It's not a real world thing to me as I use a big honkin' set of speakers and I make use of far more then 1w. No one who buys a monster amp is going to plug headphones into it to listen because then what is the point of all the power, dynamics and headroom? No freaking amp in the World is going to sound the same in the zillion different listening areas people have across the world. Different speakers, different preamp etc... all make a headphone test a moot point to the average listener. Headphones do not represent real room listening, not even approximately

 

[THD+N]

I concur (with Northwinds), for the most part. I believe the logic behind using headphones for amp design/evaluation is to:

1. Isolate your ears from the listening environment, so you can only hear the amp.
2. Evaluate the noise floor of the circuitry.
3. Listen for any type of audible distortion at low levels that may be indicative of problems at higher power levels/frequencies.
4. Since head phones are usually just a single diaphragm, there are no passive crossover artifacts to contaminate the signal from the amp under evaluation.

I understand that Nelson Pass has a set of La Scala's too for amp evaluation at his company or home. The high sensitivity reveals a lot of detail at low power.

 

[THD+N]

Perhaps we all need to also buy a copy of J. Gordon Holt's (former publisher of Stereophile) book "The Audio Glossary" which has terms and definitions.
(It will cost you around $75+ for a used copy)

I also have an extra copy of the Audio Encyclopedia by Tremaine, if anyone is interested. It is in fair shape. They are going for about $150 and up, but I'll let this one go for $100 due to its age and wear.

 

[oldphaser]

........I believe the logic behind using headphones for amp design/evaluation is to:
1. Isolate your ears from the listening environment, so you can only hear the amp.
2. Evaluate the noise floor of the circuitry.
3. Listen for any type of audible distortion at low levels that may be indicative of problems at higher power levels/frequencies.
4. Since head phones are usually just a single diaphragm, there are no passive crossover artifacts to contaminate the signal from the amp under evaluation.

Nick,

Well said!
Your explanation of some of the variables one is trying to isolate is what I meant to say in better detail.

In one of my prior posts on this thread, I didn't mean to infer that testing at 1W with headphones was the only tool in a designer's toolbox. However it may be a starting point that we may all may more easily duplicate. To be sure, I am willing to bet the designer’s perform objective testing with measurement and test equipment as well as subjective testing with their own preferred loudspeakers, music, etc.

In order for us to do subjective testing (listening tests), I had suggested that we might also obtain Mr. Holt's book "The Audio Glossary". In his book, he has terms and definitions for those subjective words audio reviewers like to use when performing listening tests. I suggested this so that we could more effectively communicate to each other by using the same terms and definitions. Otherwise, when someone says something sounds a particular we may not understand one another. (Lawyers love it when we pay them to argue over what a term in a contract means like the word "reasonable" in a home lease agreement).

I am just trying to get us all closer to one another in the words we use when we perform our appraisals. In this case, how an amplifier sounds.

Golden ears unite!

Ed

 

[Fishoz]

"Golden ears unite!"

Hear! Hear!