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Old 26th January 2013, 02:09 PM   #8271
gootee is offline gootee  United States
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Originally Posted by a.wayne View Post
Well i guess we have to get ole D into music first , then we can discuss sound..

@Gootee ,

Tom whats this mystery amp putting out 1k into 1ohm ...?
Adcom GFA-585.

I wanted to see what it would take to make the Maggies distort. The 585's 400W into 4 Ohms rating enabled it to do that, without lighting up its clipping indicators.

I also learned that my Vandersteen 2Ce speakers have red lights behind the socks, which start to flash when there's an overtemp condition. <grin>

Last edited by gootee; 26th January 2013 at 02:13 PM.
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Old 26th January 2013, 02:28 PM   #8272
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I have a Pr and yes they will drive 1 ohm , but i could never wrap myself around its sonics , favoring to use The Threshold S500 , PS Audio 200cx or the Krell Ksa200..

The adcom does have alot of drive and did see off the A21 in My setup , a friend now has one (a21) powering his 3.6 , we have not done any comparisons in his setup as yet ....
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On the floor looking at the great ones and drooling ..... :

Last edited by a.wayne; 26th January 2013 at 02:32 PM.
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Old 26th January 2013, 06:37 PM   #8273
gootee is offline gootee  United States
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I am basically still just dabbling with lower-cost used power amps and speakers, as I get back into consumer audio. I also plan to end up with three or four complete systems that I can give to my grown children. I acquired a small armada of Adcom 545II, 535II, two of each, and Hafler 220, and half a dozen late 70s-80s HK and Luxman, which were all incredibly low-priced. I'm still sampling speakers, theoretically. But after the Magnepans arrived, the sense of urgency for sampling others was diminished greatly.

With all of these amps, I am planning to try building some line-level active crossovers to experiment with bi-amping and tri-amping.

Last edited by gootee; 26th January 2013 at 06:47 PM.
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Old 26th January 2013, 10:27 PM   #8274
fas42 is online now fas42  Australia
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Originally Posted by dvv View Post
Since you have no obligations, you can't really fail, Frank. You can get there or not, in which case I'll just go on using what I already have.

Obviously, I'd prefer you to get there eventually.

If you'd like a few shots of what I did with the car, just drop me a line at dvv@beograd.com .
I would say just about everyone in audio has an agenda or two, some of which are tied up with ego, . One of my personal agendas is to get the most out of every recording I have, and everything is sacrified, ultimately, to that goal.

If I were in your shoes, how I would approach this situation is as follows: someone reckons conventional volume controls are a problem, so before I do anything else I would confirm whether such is the case for me; in the other words, whether I can hear this as a problem. And how I would do it is like this: get my best setup, find what a good, average volume is for assessing my best test recordings. Then measure what the resistances are for the pot at that setting, and swap out the pot with fixed value, decent quality resistors. Yes, eliminate the volume control! For a short while, anyway ... Obviously, listen like crazy, see what you think; and then reverse the swap, go back to the pot, and listen again. If you hear a clear difference then your path is set, most likely ...

When doing the listening I would do it in a relaxed, not highly focused way ... which way sounds more "right"?

The recordings I use to test with are key, the best I find are those what are considered bad by most people: heavily processed, lots of artifical echo, excessive high frequency content - these are very hard going on systems with problems, give the game away immediately. Personally, a conventional volume control renders these sort of recordings almost impossible to listen to, that's how bad the distortion effect is for me.

Frank
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Old 27th January 2013, 12:38 AM   #8275
fas42 is online now fas42  Australia
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I've come across a few descriptions of what audio working properly should sound like - rare, usually only achieved with very expensive gear and lots of costly twiddling and optimising. This is not necessary, but is a technique that will work at the moment, with the current thinking of most people.

A taste of what it sounds like for some: State of the Art in D.C. | The Absolute Sound

Frank
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Old 27th January 2013, 02:45 AM   #8276
gootee is offline gootee  United States
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Quote:
Originally Posted by a.wayne View Post
I have a Pr and yes they will drive 1 ohm , but i could never wrap myself around its sonics , favoring to use The Threshold S500 , PS Audio 200cx or the Krell Ksa200..

The adcom does have alot of drive and did see off the A21 in My setup , a friend now has one (a21) powering his 3.6 , we have not done any comparisons in his setup as yet ....
Personally, I think that the Adcoms that I have are very, very good, and the 585 is the best of them, by a small but noticeable margin (and the huge power capability increases that margin).

Maybe I should mention again that my goal is the most-faithful reproduction of the source (whether I like "the sound of it" or not).

The Maggies and the Vandersteen 2Ce and some Thiels that I have are all fairly transparent and revealing, when kept within a reasonable range of operating conditions (which turns out to be fairly wide, usually). And I must have been very lucky with my exact room configuration because the accuracy is spellbinding, and the sound is exquisite, and simply gorgeous; everything is much better, maybe twice as good, the way I have it arranged now, when compared to arranging things differently, in the same room.

Anyway, I compared quite a few amplifiers and receivers (maybe 12 or more?), over the last two years. (This might be meaningless, or perhaps laughable, to those who know the truly high-end equipment, which I do not. But anyone who wants a very large quality/cost ratio, and relatively-low cost, might appreciate it.) Truthfully, I loved them all, but, of course, I had only purchased models that I thought would be excellent. However, the HK 560 (circa 1978), a Luxman 1050 (and I think also the 1120), and the Adcom GFA-585, seemed to have some extra magic to them, although the Adcom GFA-545II was also very, very good. (And except for the 585, they were all under $200, I think, and some were much closer to $100. I figured that even if I used only the cabinets and transformers, for DIY projects, the prices would not be bad.)

My son, who is now 22, also loves music. He used my systems, daily, but, by chance, almost never when I was around, because our schedules differed. We didn't talk about the systems, for many months. But one day we did, and without me mentioning which ones I favored, he named the same three or four that I named above. (I'm pretty sure that he "borrowed" one of the Luxmans, when he moved out of here, even though I had already given him a Hafler DH-220.)

I am still looking for a big pair of Magnepan speakers, probably the MG-3.6/R, hopefully within a half day's drive.

I still think that the decoupling and reservoir capacitors are the main key to the sound reproduction's accuracy and imaging, since they are the actual "signal path", and the high-current signal path is probably a little more unforgiving than the small-signal path. And I would guess that not enough attention has been paid to the details of the cap-current signal path, so far.

I have ben dabbling at developing methods for analyzing and designing decoupling capacitor configurations, and also reservoir cap and power/ground rail configurations. But I suspect that's the wrong paradigm. The caps and their impedance at the output devices ARE the amplifier, or at least they bound its capabilities.

Therefore, my next DIY project will probably be a power amplifier (maybe even just a power output stage), centered around Terry Given-style capacitor-array power/ground-plane boards, and the details of the design of their connections to the power output devices could be a major focus area.

Maybe something like this: Large arrays of large capacitors on large unbroken copper planes (maybe 15x15 1000 uF array per rail), an un-etched two-sided PCB with power on one side and ground on the other, one for each rail (or one for both rails, with two half-planes on one side, for power), just one drill hole per cap with copper removed around edge, NO traces, all copper; "lots of current, under pressure, with almost no constrictions"; about 0.5 nH or less inductance seen by power device connections, with less than 10 mOhms total impedance seen at output devices, maybe significantly less.

Output circuits might be on a small PCB mounted parallel to the back side of the cap array board, only a few millimeters away, and over the area where the two power planes almost touch. Power and ground connections will be able to go directly to the planes, with almost-insignificant connection lengths. No other reservoir or decoupling capacitors will be necessary; power supply and decoupling caps "all in one". To really do it right, I might eventually have to mount a whole amp assembly right on each speaker driver's shortest-possible connections.

Last edited by gootee; 27th January 2013 at 03:08 AM.
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Old 27th January 2013, 03:05 AM   #8277
fas42 is online now fas42  Australia
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Originally Posted by gootee View Post
Output circuits might be on a small PCB mounted parallel to the back side of the cap array board, only a few millimeters away, and over the area where the two power planes almost touch. Power and ground connections will be able to go directly to the planes, with almost-insignificant connection lengths. No other reservoir or decoupling capacitors will be necessary; power supply and decoupling caps "all in one". To really do it right, I might eventually have to mount a whole amp assembly right on each speaker driver's shortest-possible connections.
I'm p*ssed off at the moment, did a decent reply to you, Tom, and it went down the browser gurgler. In essence, I like your thinking here, my DIY chip amp used a lot of these ideas, successfully ...

That "wide range of operating conditions" will improve, that's the main benefit, to be able to go from an almost inaudible whisper to deafening, live music levels with tonality intact -- the amp being fed from healthy power rails is key to making this happen ...

Frank
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Old 27th January 2013, 03:34 AM   #8278
gootee is offline gootee  United States
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Originally Posted by fas42 View Post
I'm p*ssed off at the moment, did a decent reply to you, Tom, and it went down the browser gurgler. In essence, I like your thinking here, my DIY chip amp used a lot of these ideas, successfully ...

That "wide range of operating conditions" will improve, that's the main benefit, to be able to go from an almost inaudible whisper to deafening, live music levels with tonality intact -- the amp being fed from healthy power rails is key to making this happen ...

Frank
Been THERE. I feel for you. Now I always right-click, select all, and copy, before posting. And if it's more than a half-hour's work I usually pop open Notepad or Wordpad, to make a safety copy.

Go listen to your reference track, for a while. I just did and I feel better for you already. <grin>

Last edited by gootee; 27th January 2013 at 03:40 AM.
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Old 27th January 2013, 03:55 AM   #8279
fas42 is online now fas42  Australia
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Originally Posted by gootee View Post
Been THERE. I feel for you. Now I always right-click, select all, and copy, before posting. And if it's more than a half-hour's work I usually pop open Notepad or Wordpad, to make a safety copy.

Go listen to your reference track, for a while. I just did and I feel better for you already. <grin>
It wasn't even like that, I only wanted to click the Italic button and it was "just out of reach" and somehow the manouvering managed to trigger a refresh ... ya just give up at times ...

Anyway, one of the things I mentioned before I was "rudely interrupted" was to think carefully about separating the decoupling into "dirty" and "clean" areas. The dirty, at some distance from the output circuitry, has the "grunt", capacity to handle the bass needs, is where the big current spikes occur; and the clean area, absolutely on top of the amplifying parts, has the quality devices to handle the high frequency transients. That 10 m.ohms or better is a good target ...

Frank
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Old 27th January 2013, 04:52 AM   #8280
fas42 is online now fas42  Australia
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Tom, sorry to do this, but I was curious about the Adcom amp you mentioned, found the service manual for the GFA-585, and it doesn't appear to have the grunt you mentioned. 400W into 4 ohms, as a continuous rating, is the best the manufacturer offers.

On the power supply side you can see why, only 36,000uF smoothing for each rail; significantly more would be needed for continuous power into heavier loads ...

,
Frank
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