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Old 15th September 2005, 04:50 AM   #1
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Default Audio Reasearch

Just out of curiosity, has anyone DIYed any audio reasearch equipment?
From my limited knowledge I know that the brand is pretty good.
I was quite surprised to find schematics on the internet so I was wondering if anyone cloned anything, and if anyone did how does it sound compared to other commercial and DIY stuff?



Thanks
Lawrence
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Old 15th September 2005, 11:48 AM   #2
EC8010 is offline EC8010  United Kingdom
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There's a reason why Audio Research diagrams are easily found. The clever bit in their power amplifiers is not in the diagram but in the output transformer. Try a different output transformer and the amplifier will almost certainly oscillate.
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Old 15th September 2005, 01:44 PM   #3
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I've built the phono sections of SP3, SP6 and SP10. Not bad for high NFB commercial equipment.
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Old 15th September 2005, 02:30 PM   #4
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Me too. I cloned an SP3 years ago. Worked fine compared side-by-side with the real thing. For power amps, EC8010 is right about the special output transfomers. ARC certainly doesn't need to use off-the-shelf Hammond transformers. They have the volume and resources to design and subcontract whatever they need. Their schematics are good teaching tools. You can watch the progression through the years, especially in power supply regulation techniques.
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Old 15th September 2005, 04:41 PM   #5
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I clonned SP8 long time ago but with beefed PS reg ;
without too much modesty- good DIY preamp always can run circles around it ; and my PTP "clone"was better sounding than original
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Old 15th September 2005, 04:50 PM   #6
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Quote:
Originally posted by EC8010
There's a reason why Audio Research diagrams are easily found. The clever bit in their power amplifiers is not in the diagram but in the output transformer. Try a different output transformer and the amplifier will almost certainly oscillate.
The compensation scheme is certainly quite specific. But every time I see one of those schematics, I have a Franz-Joseph moment and think, "Too many parts!"
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Old 15th September 2005, 06:21 PM   #7
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Quote:
Originally posted by SY


The compensation scheme is certainly quite specific. But every time I see one of those schematics, I have a Franz-Joseph moment and think, "Too many parts!"
...that's what happens when you have fulltime salaried engineers sitting around trying to look usefull. I am especially leary of those Rev. a, b, and c jobbers; you know they didn't take any parts out.
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Old 18th September 2005, 05:47 AM   #8
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Years back, the fact that Bill Johnston made circuitry available truly impressed me. It took me three years to locate a pair of output transformers which whilst wound in New Zealand, appeared to take the Williamson ideals to the limit. They have a three inch stack of super-silicon steel, and end-bells caste in aluminium. They are big, big, big, nearly eight inches deep...

I copied the D76 circuit with the tube-realised screen-voltage regulation via op-amp, ECC81, and a KT88. Just loved the comments re why does a power amplifier have three out-put tubes............Will never forget the first "power-on" experiment when the only loudspeaker I could put my hands on was a tiny unit from a mantle-radio,,,couldn't here nothing - no hum whatsoever,,,the wet-finger trick and the poor speaker-cone reversed itself.....Nearly fifteen years later these self-same copies of AR circuitry are my stile to emotional bliss....[just one hiccup when one of the ICs burst)

I copied the SP10 - yes, two chassis and twelve ECC88s..... fabulous. Elsewhere I have commented upon the seemingly-held belief that this circuit is hard on ECC88s. Not true down-here, but I admit to including a mains-filter in the pre-amp. Voltage-readings meet Bill's figures - the thing justs plays - havn't changed a thing - tubes must be six+++ years old.....

I have even played with his [Johnson's) mosfet regulation circuitry using the IPF830...this works too!!!!

(My SP10-copy followed the modification-circuitry where the upper tube in the line-stage was biased from the output cathode)

My personal thoughts are: Triodes, triodes, triodes....with ultra-linear transformers being really naughty for output-stages....I am really-grossed with Quad circuitry where feed-back is provided via the cathode-winding.........Like a baker's daughter, I have dough in both hands..........Have wound some really-nice OPs for 320Bs SE, yet have gone the other-way for PP triodes with cathode-feed-back. Hey!!!!!! Dinner-calll...............

G
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Old 18th September 2005, 11:49 AM   #9
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I still have the SP3 knockoff I built -- maybe it was 15 years ago -- I also rehabbed a Dynaco ST70 with the AR boards from the article in Audio Amateur -- it really didn't sound that much better than the ST70 (but I was able to sell it for a fortune on EBay.)

At one time you could just call up Audio Research, mail them a couple bucks and voila manual and schematics.
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Old 18th September 2005, 12:35 PM   #10
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Quote:
Originally posted by Graeme
{lot's o' stuff}
Wow.
Not a big fan of the 6DJ8 'sound' myself, but always wanted to hear an SP10. Ever had a chance to compare it to other designs/executions?
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