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Old 27th January 2013, 05:04 AM   #8281
a.wayne is offline a.wayne  United States
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The 565 will drive a 1 ohm load , i think it has a 1.7k transformer and 10pr outputs / monobloc, I just did not like the sonics vs my other amps, it is a power house thou ....

I think i said 585 before, my error it was the 565 mono units i jad meant to say , no the 585 wont go there ....


Last edited by a.wayne; 27th January 2013 at 05:11 AM.
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Old 27th January 2013, 05:24 AM   #8282
fas42 is offline fas42  Australia
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Yes, I'm sure it will handle low impedance loads, but for me a true measure is whether it can be done continuously, until the output devices start to overheat and the protection cuts in. Even the 4ohm continuous rating only holds if an optional fan assembly is fitted, which I suspect the majority won't have.

The good thing about the Adcom is that it has decent voltage drive, 80V rails which helps to give it good headroom on transients. I still have a Perreaux 2150B, with 90V rails, but originally with relatively weak smoothing caps; the lack in the latter makes all the difference ... the first heavy duty tweaking I did, years and years ago, was to rip this out, and add a vast array of small, paralleled caps, I think about 4 x the original capacity ...

Frank

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Old 27th January 2013, 07:30 AM   #8283
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Originally Posted by a.wayne View Post
The 565 will drive a 1 ohm load , i think it has a 1.7k transformer and 10pr outputs / monobloc, I just did not like the sonics vs my other amps, it is a power house thou ....

I think i said 585 before, my error it was the 565 mono units i jad meant to say , no the 585 wont go there ....

The 585 is essentially two 565s in one case, but with only one (really-huge) transformer.

I can't identify any "sonics" when listening to it. It seems extremely neutral and transparent. But maybe I'm too old and my high-frequency hearing ability is too far gone. It sounds literally identical to the Luxman 1050 and HK 560 that I mentioned, when all else is equal; just extremely clear and clean, with perfect imaging. None of them contribute anything of their own, to the sound, as far as I can tell.

There is at least one known problem with the 585 and 565: A bad batch of some well-known high-end 220 uF caps was used on the servo boards, which began to leak. If that happened, you might have been starting to get DC on the outputs, which might have biased your speaker motors off-center, changing the sound.

Walt Jung was on the design team for those amps and has posted here on diyaudio about the servo board cap problem.
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Old 27th January 2013, 08:17 AM   #8284
dvv is offline dvv  Serbia
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@Tom, @Frank

I've mentioned this before, but just in case you didn't catch it ...

One of the oldest trick in the book, and one of the first I came across, was introduced by the Japanese tweakers. They called it a composite cap.

The reasoning is that each and every material used for capacitors has its own properties, weaknesses and strong points, and essentially that none is perfect. To get nearer to perfection, one should combine three materials, for example, polyester, polyprolyene and polycarbonate. Say you need a 3 uF cap somewhere - put one of each in parallel for the best audible result. If they cannot be of equal value, then make sure that the fastest among them (polycarbonate) has the largest value.

In my day, I experimented quite a bit with this and I think they are definitely on to something. No single value I ever used could match a composite one, even if by a small bit.

My general feeling is that the best decoupling capacitor is the one not there, i.e. I am pro DC servo arrangements, I am not against cap coipling, but if I'm going to do it, it will definitely be a composite cap. It's not like you need tons of them.

@Frank

What you propose for critical listening is what I have been doing for decades now. Honestly, I haven't come up with a better method yet.

Regarding chip power amps, a friend of mine is kinda nuts about them and has been fooling around with them for quite some time. I have heard some of his work, and truth be told, some of the results he obtained are impossible to ignore, simply because they sounded really very, very good.

His best work was an amp with a Nat Semi chip power amp, I think around 50 WRMS/8 Ohms, which was preceeded by a FET input op amp as a buffer, and he was generous with both the main electrolytics and on board local power supply decoupling. Now, that one made many other much more expensive amps sweat tryuing to cach up at room volume, and I should mention his speakers do someting like 91 dB/2,83V/1m, meaning reasonably efficient.

Another friend bought via the Internet one of those DIY boards which use Nat Semi's all-but-the-output-stage driver chips. The actual output used four pairs of 2SC5200/2SA1943 trannies, and with 22,000 uF/63V caps per power line (88,000 uF total), he did obtain some rather good results.

The point is, there are a lot of worthwhile options floating around.
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Old 27th January 2013, 08:47 AM   #8285
fas42 is offline fas42  Australia
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Quote:
Originally Posted by dvv View Post
What you propose for critical listening is what I have been doing for decades now. Honestly, I haven't come up with a better method yet.
Good to hear ...

Quote:
Regarding chip power amps, a friend of mine is kinda nuts about them and has been fooling around with them for quite some time. I have heard some of his work, and truth be told, some of the results he obtained are impossible to ignore, simply because they sounded really very, very good.

His best work was an amp with a Nat Semi chip power amp, I think around 50 WRMS/8 Ohms, which was preceeded by a FET input op amp as a buffer, and he was generous with both the main electrolytics and on board local power supply decoupling. Now, that one made many other much more expensive amps sweat tryuing to cach up at room volume, and I should mention his speakers do someting like 91 dB/2,83V/1m, meaning reasonably efficient.
50W amp, 91dB sensitivity is all you need to get impressive sound levels. Currently, the setup here uses 15W chip amps into speakers of that sensitivity, and that creates deafening levels, ringing in the ears with a modern, restricted dynamics recording.

I just mentioned on Curl's Blowtorch thread that a Marshall 350W guitar amp uses just 4 chip amps to do the job well enough for muso's ...

Quote:
The point is, there are a lot of worthwhile options floating around.
Yes, that's the key, there are myriads of ways to get there. Only, from my POV, too many people sabotage their chances of getting impressive sound because of silly shortcomings, little weaknesses that undermine the real potential ..

BTW, that email address you posted didn't work for me, bounced ...

Frank
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Old 27th January 2013, 08:52 AM   #8286
fas42 is offline fas42  Australia
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With paralleling cap's, when needing 3uF, I assume you meant 3 of 1uF units ...?

Frank
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Old 27th January 2013, 10:54 AM   #8287
dvv is offline dvv  Serbia
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Quote:
Originally Posted by fas42 View Post
Good to hear ...


50W amp, 91dB sensitivity is all you need to get impressive sound levels. Currently, the setup here uses 15W chip amps into speakers of that sensitivity, and that creates deafening levels, ringing in the ears with a modern, restricted dynamics recording.

I just mentioned on Curl's Blowtorch thread that a Marshall 350W guitar amp uses just 4 chip amps to do the job well enough for muso's ...


Yes, that's the key, there are myriads of ways to get there. Only, from my POV, too many people sabotage their chances of getting impressive sound because of silly shortcomings, little weaknesses that undermine the real potential ..

BTW, that email address you posted didn't work for me, bounced ...

Frank
Frank, I have two functional e-mail addresses, and they are:

dvv@beograd.com
dvv@bitsyu.net

Both worked this morning just fine.

Regarding amps, I agree, too many people are locked into their point of view beyond redemption.

Not too long ago, if you didn't have a FET input, some would swear it wouldn't even work. Next, there was a FET input with a casocde - again, some people think that's the ONLY way.

I am not trying to dispute the merits of such topologies, but just to spite such people, my HK 6550 uses a simple as can be differential input, and I'll wager it will outshine many with complex circuitry at the input.

So, I need not go outside my own house to verify that any topology, when applied knowingly, will produce good results, more often than not better than many a device slapped together according to current fashon.
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Old 27th January 2013, 10:56 AM   #8288
dvv is offline dvv  Serbia
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Originally Posted by fas42 View Post
With paralleling cap's, when needing 3uF, I assume you meant 3 of 1uF units ...?

Frank
Zigactly! (Drunken Obelix to Asterix in "Ceasar's Laurel Wreath").

If for some reason not possible to obtain with equal values, it was suggested that the largest value used should be polycarbonate. It seems nothing else on this planet can match its extraordinary speed.
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Old 27th January 2013, 12:58 PM   #8289
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by gootee View Post
The 585 is essentially two 565s in one case, but with only one (really-huge) transformer.

I can't identify any "sonics" when listening to it. It seems extremely neutral and transparent. But maybe I'm too old and my high-frequency hearing ability is too far gone. It sounds literally identical to the Luxman 1050 and HK 560 that I mentioned, when all else is equal; just extremely clear and clean, with perfect imaging. None of them contribute anything of their own, to the sound, as far as I can tell.

There is at least one known problem with the 585 and 565: A bad batch of some well-known high-end 220 uF caps was used on the servo boards, which began to leak. If that happened, you might have been starting to get DC on the outputs, which might have biased your speaker motors off-center, changing the sound.

Walt Jung was on the design team for those amps and has posted here on diyaudio about the servo board cap problem.
Well aware and all my adcoms are in tip top shape , no issues anywhere (565,555) fresh caps etc ..

I'm currently redoing the 200cx, Imo the best value in power amps if spending below 1k, you usually can find them in the 500-700 region ..

http://www.stereophile.com/solidpowe...741/index.html

Last edited by a.wayne; 27th January 2013 at 01:02 PM.
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Old 27th January 2013, 03:33 PM   #8290
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Originally Posted by dvv View Post
Zigactly! (Drunken Obelix to Asterix in "Ceasar's Laurel Wreath").

If for some reason not possible to obtain with equal values, it was suggested that the largest value used should be polycarbonate. It seems nothing else on this planet can match its extraordinary speed.
I can't see how a polystyreen cap with a low loss factor could benefit by paralleling it with e.g. a polycarbonate one with much higher dielectric losses. (of course using half values). Just doesn't make sense to me.
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