what is this amp really - "Digitech" AS-0476

george a

Member
2002-05-06 1:12 pm
oz
Hi All

I recently picked up for peanuts a power amp described as a "Digitech" AA-0476.

No time to have test driven it yet....but am expecting it to be rubbish...

The case is very soild any probably alone worth the price i paid.
I am searching for any info on the amp - beyond claimed spec's etc.
I's supposedly some 70-80w /channel and I probably originally sold by a mob here in Australia known as Jaycar - essentially and electronics parts and "stuff" outlet.
Google search shows up only a few references - sale on ebay and power spec's and thats about it.

Upon opening is up I find a toroid transformer - 38-0-38v sized at about 300VA by the looks -
and output transistors as a single 2sc5200 2sa1943 per side.

Any ideas anybody?

or any suggestions as to amp design i can pursue to fill the case.

BTW it has 2 pc fans drawing air through the case and over the heatsink.

Will not be suitable for a Class A amp of any sort I suspect.

I already have a couple of Hafler dh200's and a Pass A5 clone. (sweet)

Many thanks in advance..
 
With the price of the 2SC5200 in the US I would doubt if Salt Lake City Digitech is involved. They would probably get a better deal on On Semi parts. Probably tiny (at first) SLC Digitech didn't apply for Australia trademark protection or didn't have many lawyers looking for lawsuits there to protect the trademark. If they didn't word their trademark application broadly, and only protected effect units, then selling a Digitech amp might be legal anywhere anyway.
Liking cheap speaker protection circuits, ie one positively biased >3300 uf capacitor between transistors and speaker, I like the Salas G amp as my next project. http://www.diyaudio.com/forums/solid-state/229120-g-amp.html I was going to build dynakit ST120 clones, but they take an 8 transistor djoffe cold current bias control board to tame crossover distortion. On perfboard, that is a lot of wires. Then there is always the LM3886, see the datasheet for schematics, but I'm having trouble finding heat sink insulators for those IC's at newark or mouser that are big enough. Everything is either TO220 , TO3 or undescribed dimensionally.
If you don't mind melting your speaker if you make a mistake, this looks interesting. http://www.diyaudio.com/forums/solid-state/230766-ultra-performance-amp.html
Or spend 6 months developing an effective speaker disconnect circuit like I have just been doing for a 1.3 kw amp. Welding the contacts together is so expensive to test for. Or build a mosfet relay board for this little (300 va) amp. Not nearly so expensive at 50 amps short circuit current.
 
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george a

Member
2002-05-06 1:12 pm
oz
Hi

Copy of Internals attached.
At the top of the photo are the various input/output sockets.
The multi cable in the middle of the pcb lead to a front panel containing 2 gain control + power /overload / clip indicators.
Semi compliment includes:
2sc5200 2sa1943 2n2073 2n5401 2n5551

As yet I haven't had a chance to listen to it .....
 

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