Audio Design amps – Newly discovered treasure

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energyandair

Active Member
I just bought an Audio Design Model One preamp, and a matching Model 20A Power amp circa 1981; both in great condition and complete with Operating/Service manuals and boxes.

The design is simple, the build quality appears excellent and there are some unusual design features. (Eg Provision for externally interchangeable phono cartridge loading capacitors)

The appearance is nicely understated. The front panels are milled from 10mm (3/8”) aluminum and then painted with an extremely durable grey finish. From the color, you might think they were NAD but the build and sound are at a different level. The metal control knobs are recessed into the face plate with the finest tolerances I’ve seen on audio equipment.

They have far fewer switches and controls than was normal practice in 1981, and 26 years later this might be one of the reasons that they sound so good. Internally it appears that they used widely available components with tight tolerances plus a few individually matched components where they couldn’t get tight enough tolerances off the shelf.

The seller bought them new from the designer, Howie Brown, who he knew from the University of Waterloo.

The manuals are very useful but have a few inconsistencies and I could find almost nothing about the amps on the net. I did however find a reference in the Stereophile master index “Audio Design 20A (Holt) VI-6”. If anyone can send me a copy of the article, I would really appreciate it.

So far I find them more than good to listen to with silent background, good dynamics, clear highs, good on voice, strong clear bass and no listening fatigue. I’ll report again when I’ve had a chance to listen over a longer period and see how they stack up against my other components.

David
 

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Looks like extremely good build quality to me. I think you're in for a treat with that combo.

any idea what power output the amp is rated at? What class it is?
 
jpdylon said:
Looks like extremely good build quality to me. I think you're in for a treat with that combo.

any idea what power output the amp is rated at? What class it is?
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The manual is a bit confusing on this because in some places it says 10A and in others 20A, sometimes on the same page. I believe that there may have been a 10A, a 20A and a 30A.and I think that the 10A references in this manual may be typos.

The Spec is labeled 10A and shows:
Both channels driven: 8 ohms - 100W, 4 ohms - 185W
One channel driven: 8 ohms - 120W, 4 ohms - 200W, 2 ohms - 350W

The schematic is labeled 20A and shows 53.5V rail voltages and if I am reading it right the output transistors are Q200 and Q 201 (2 each per channel) with the parts list showing Q200, Q 201 - Transistor, 2N3773, TO-3

I’ll weigh the unit and check the rail voltages and output transistor when I have a chance.

David
 
maxkelley said:
They sure look like a nice treasure! Where'd you get these from? And yes, they almost look NAD-like.
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I found them locally through a local internet site that seems to carry more stuff than the local Craigslist.

David
 
The model one preamplifier is a good design. I bought one for 75 bucks and replaced the power caps with black gates and more storage (higher microfarad count) and replaced the opamps with Burr brown 2132?? Analog devices op275's or National semiconductor high end op amps-can't remember which ones but pin for pin compatible with the original tlo72's? 5532??
Sounds absolutely fantastic!!!- remember the opamps are the heart of any device-I'd put it up against many new high end preamps- not using right now because there is a loose connection that I haven't quite figured out and one side cuts out occasionally- but when I used it in place of my primaluna prologue 3 into my Mark Levinson amp it sounded wonderful and slightly tighter bass than the primaluna. well woth the effort
 
I've got the predesesor to the 10A/20A/30A series, the PA100 sitting in my storage room in it's original box. It delivers 100 wpc in stereo and drive a 2 ohm load, Even in it's Bridged Mono Mode where it produces 350 watts it will still drive a 4 Ohm load. It seams to have a slightly dark tone with an almost Tube like smoothness, yet retains all the detail and speed expected of any high end SS Amp today. It does THUMP bigtime at start-up and power down though.

For 20 years I was using it with a NAD 1600 Preamp/Tuner and it sounded good. One day I connected up my Denon 1500II CD Player's variable Audio output directly to the PA100. I could not believe the deference in SQ when I took the Preamp out. Now it sounded like the good stuff I hear in Audio stores from a 25 year old amp. I was using a pair of Energy Pro-22 monitor speakers at the time that never sounded so good.

When I decided to upgrade my amps, I wanted a good preamp, remote controll and keep the great sound so I bought a Bryston B100SST Integrated. I connected the preamp section of the Bryston to the PA100 just to see how much better the new amp was. While the Bryston has much better imaging/soundstage, with a more Neutral sound (vs slightly dark for the Audio Design) in most other respects the Audio Design gave up nothing, including the powerfull controlled Bass Bryston is known for.
 
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