Always needing to know why Dave :^)

http://f1.pg.photos.yahoo.com/ph/the_hurdy_gurdyman/detail?.dir=/6d5d&.dnm=5289.jpg

• Scott schematic

Thanks for the link, that's cool.

I couldn't see it very well, but maybe if I downloaded it and put it in an image viewer it is high enough resolution it would be crystal clear. Still, from what I could see, it looked like the basic amplifier was a pretty clean push-pull circuit and the "spaghetti-looking mess of circuitry" was mostly tone control circuits. When set flat or disabled, they wouldn't impact the sound at all. So it may be that the design is actually pretty basic and not alarming even to the low-parts-count purist.

Then there is also the issue that a filter isn't necessarily made more pure by having a low parts count. If the components are linear and the load perfectly resistive, that's one thing. But if the load is not resistive, particularly if it is also non-linear, then a simple filter is often horribly wrong. In that case, a more pure filter is one that is more complex and compensates for load variations. I don't see that as being much of the case here, because it's really more of a loudspeaker issue than anything else. It's something to consider when making passive crossover components. But I thought it worth mentioning in the context of "circuit simplicity" verses "response purity." These two things aren't necessarily related.

And then there's one more thing. This one makes me wince, but I think it's still important to say. Think about how many people make comments about a sound system they are particularly fond of, saying it sounds better than live, or words to that effect. If something sounds "better" than the original source, then it must be "different" than that source. If the goal is accurate reproduction, then this would seem to be a bad thing. Something was added that enhanced the original, or something that wasn't particularly good in the original was removed. But the enhancement was a change, and kept the reproduction from being true to the original.

I really like what Siegfried Linkwitz says about the job of a good sound system being its ability to provide an illusion of reality. For many years, I strived to keep things as close to the original as possible, and I still think that's a worthy goal. But after reading his comments, I realized that he's right - No matter how much effort is placed in maintaining "accuracy," it's all an illusion. And being so, the fact is that the best facsimile is the one that is perceived as being best. This is where objective measurement and subjective perception meet.

I guess the bottom line is that if this amplifier has done it for you, then the engineers have met their goal. Whatever inaccuracies are present don't seem to be noticable to you, and the things it does right, it must do very right. So maybe it isn't flawed after all.

Wayne

A nice side effect of those subsonic filters is that I don't get massive uncontrolled woofer fluntuations when playing warped records, even with an open baffle.

Not sure why my schematic pic is fuzzy. I think maybe Yahoo photos doesn't have good enough resolution. You'd think that, being free, you should get great quality! Free just isn't what it used to be.

Dave :^)

BTW, I've noticed the same harshness in the upper mids on my Scott amp. It's small, but there. It seems to be more noticable on some speakers then others. I've heard it is caused by the cera-caps that are used throughout the curcuitry. Replacing these with good poly caps should cure this. I have replaced just the output coupling caps and have noticed a small improvement. One of these days I'll get around to replacing the rest.

Dave

If you want your final amp (yeah right...you KNOW you have the bug and NOTHING is final), i would suggest an amp that is built new, with high quality parts. Should cost you between $500-$2000 in parts, depending on what kind of speakers you have, what circuit topology you need, etc.

I agree with Dave's post below that output trannies sound slighlty better after being broken in. THis is typically a 1000 hours or so, depending on the iron. After that, in my OPINION, the differences will be almost too subtle to bother about.

hope this helps.
-akhilesh

-akhilesh