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In Reply to: RE: Great Post Dennis... posted by drlowmu on July 12, 2012 at 05:39:13
SET:...more musically revealing...more sensitive to musician's attitudes and emotions...better replicator of musical depth and layering...
PP: CMR Common Mode Rejection in push-pull amp naturally rejects artifacts of music that look like hum noise or distortion...PP processes the music...
Does anyone really think all of this is gospel ? Jeff, my old friend, do you think this is all true fact ? Come on, now, let us decipher some of this; shall we ?
The opinions about more musically revealing, more sensitive to emotion and attitude plus a better replicator of musical depth and layering, sound just like my PP Triode amps using an IT and NFB (no neg fdbk). In fact, my PP amps have more dynamic contrast (thus dynamic range), better depth and layering(much more involving 3D EFX described as holographic), plus they are clearly a better conveyor of the speed and the action of each instrument within any musical selection; compared to many SE amps used on my same systems. Of course, this is opinion. In yours or Dennis's system, your's or Dennis's opinion is what matters.
There is no inherently better topology, nor inherently better tube vs. solid state. System synergy can create fantastic sound in anyone's home. Despite this being the SET forum, there is no SEPentode, triodes, tubes vs. transistors or PP forum. So, this forum is where we often meet and greet.
I have no doubt that your topology and Dennis's topologies have many virtues, sonically. Even spec wise; though we all know many of the specs are inadequate, some of your specs could be admirable. Leaving out any discussion of CMR, a truly theoretical mumbo jumbo description originally intended to describe power supply rejection, how about distortion ? Specs being inadequate, to be sure, it is said the SE amp has higher even order distortion than PP. Okay; and this higher magnitude even order distortion came to be known as euphonic, compared to the lower odd order distortion in PP ? Euphonic; what a pleasant term. What a pleasant effect. Is it any wonder we all strive for euphonious playback ? Even if we prefer other terms, like accurate and detailed, better replicator, more musically revealing, even more flowery words, don't we all strive for musicality and harmonious music reproduced in our homes ? Yes; we all strive for euphonic playback.
Regardless of what type of distortions or the magnitudes of these distortions, none of us usually bring any distortion meters, signal generators or spectrum analyzers when we evaluate systems for the purposes of long-term listenability. We rely on our ears, most of the time; as it should be. Most importantly, any topology, even including ss amps, can create a very musical sound when synergistically chosen within a system approach. There is no reason, for any of us, to drill into anyone else's minds, that their particular approach makes any and all others not as good. Let us all enjoy the music...
Follow Ups:
Hi,
Thanks for informative subjective opinions (to all), it helps me decide which way my investigations go. And on that, nice to know that people are actually building stuff.
Andy, I can also recommend that you try the JJ 2A3 tubes, if you're concerned about matching, I can recommend Bob at Eurotubes.com, I bought a quad 5 years ago and they still all bias up the same, and they were also the most cost effective vendor, even half way round the globe.
PP vs SE, I suspect theres alot more to it that meets the average load. I did and do like 71A SE to PP 2A3 grids into 6k6p-p. Cracker-Jack. But you need a good IT. Lundahl doesn't, Bud Purvine does and no doubt theres a suitable UTC unit that fits more than well.
Foregoing the IT and the splitter and running direct coupled to the SE OP stage was better again, clearly.. but I can appreciate other could be preferred.
I also prefer Garfish to Whiting, others will disagree.. but disagree with what exactly?. Its just a preference, and thats all it is.
Liked what Dennis had to say about bias shift with Vf potential, yes. Could be lessened by some extent, at least to my thinking, by using a CT AC supply -1.25vAC - 0 - +1.25vAC.. who really wants a Rk or Ck anyway?.
At any rate, I'm sure most would agree that its nice to be interested in something that can reward you with satisfaction. And I think that less people can attest to the same as time goes by.
Hey, Thanks.
Shane
Your sense of humor and common sense is refreshing-- and fun!
One thing you might understand-- in my own case-- I've been in audio for a long, long time.
During that time, I've always had access to the best audio amps, preamps, wiring and speakers-- for at least the last 50 years.
I was into Ham Radio, built all my own equipment, ran commercial broadcast stations, designed , serviced, and built movie theatres across half the USA, and worked in L.A. recording venues..
In the early days, the first thing one did to an amp was disable the NFB. Next thing-- in those days-- was better signal handling caps. That included speaker crossovers which normally used Band-Aid packages for caps in passive crossovers. One could get monster improvements in the ALTEC theatre speakers-- for example-- by calling up Rel-Cap, (right in town!) and getting some film caps that were actually designed for speakers.
We had all kinds of amps to play with, and had the money to buy more.
It quickly became obvious that "pro" amps and "Hi-Fi" amps were usually sort of opposites. All were Push-Pull (except for the W.E. Model 91)-- some worked and some didn't. They all had to have major work to sound OK.
In the 60's, finally-- parts that were fairly good had become available to the population-- not just to "pro" users. Many people took available amps as far as they could go-- examples were Dynaco, Citation, McIntosh, Marantz, ALTEC (tube), and a whole pile of Scott, Fisher, and whatever else you want to remember.
NONE of those amps EVER performed well enough to convince a listener-- on any speaker-- no matter how good-- no matter how well modified the amp was-- not one could convince me, or others that we were listening to anything other than equipment that was struggling.
The culprit was amp power supplies-- designed to reduce hum-- and for nothing else useful at all. Those things guaranteed current starvation of all driving
elements, and even screwed-up operation of the output stages-- to some extent. Regardless of power rating, ALL of those amps had NO POWER.
That wasn't all! They also screwed-up Rhythm, Pace, and Timing-- big time.
Today, a few people still try to fix-up this stuff. The results are often far better than the originals, but they still fall very short of actually reproducing music.
A few of us got busy and studied all aspects of amp design, and we first threw-out everything that was not needed. The result was two-stage direct coupling without NFB. The next thing was to assure adequate current availability to the driver stage-- regardless of operating condition.
The next thing was to stop "snubbing" voltage-driven dynamics-- a practice that was robbing music of its "wow" and "fun-factor".. We soon learned to make circuits VERY High-Impedance, put minimal loading on them, but provide them with LOW Impedance POWER.
The rest was implementation-- good chassis design, floating parts in 3-dimensions, using really heavy, sonically excellent conductors, using the best parts, floating iron parts on brass. Using parts of the chassis as isolation platforms. Not much was overlooked!
Today, the results are spectacularly good at reproducing what's been recorded by the best Studios.
That was what we were after the whole time.
---Dennis---
...A few of us got busy and studied all aspects of amp design, and we first threw-out everything that was not needed. The result was........> >
Hi Dennis,
This sounds a very, very familiar scenario and probably one we all went through. The thing is there's a LOT of ways of finishing the sentence! My own would be:
"... putting all indirectly heated tubes back in drawers or on ebay and only using DHTs right through, only using polypropylene caps in power supplies, avoiding all caps in the signal path and as cathode bypasses (except for the output stage), using filament bias, direct coupling where possible, only using transformers or plate chokes on plates of tubes......... and so on
Andy
Nice, Andy!
---Dennis---
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