Digitech AA-0479. Better than expected.

[surprisetech]

I need a fill-in PA Power Amp for a while because I decided to refurbish my trusty old DIY amp which is built around a pair of EA 150W kit amps from circa 1988.

 

Came across a Digitech AA-0479 in very good condition available close by and at only $79 figured it was worth a try.  150WRMS x2 @8Ohms.  200WRMS x2 @4Ohms.

After cleaning out the dust I had a good look around and must say I'm pretty impressed with the whole thing.  The design and layout overall appears to be quite sound.  It's a rugged design and the build quality is very good.  Component quality was also a nice surprise for the most part, with most of the electrolytics being recognized reliable brands and only a handful of caps that might be of suspect quality.

 

I powered it up and checked the output to make sure no DC present.  All good, so I connected it up and gave it a run.  Sounds quite good, but one channel has a little bit of hum.  Turned out that two of those unrecognized-brand caps are the preamp PS filter caps and the old brown glue issue had struck one of the leads on one of them, leaving it O/C.  Given the amps age, I was planning to replace the electros anyway and they're already on their way from Mouser.

Had a look under the main board and it was nice & clean, no sign of heat stress and the quality of all the solder joints is also very good.

 

Interested to know if anyone has any experience with this beast or a copy of the schematic, but for now I thought I'd just post a few pics to show why I'm pretty happy with it for the price.

[LogicprObe]

 

That seems a great buy to me.

 

(I didn't think there were any of those EA amps still in service!)

[surprisetech]

16 hours ago, LogicprObe said:

 

That seems a great buy to me.

 

(I didn't think there were any of those EA amps still in service!)

 

Thanks, didn't have much spare cash when I built the EA kits, but I had access to some surplus bits from work, so the heatsinking is overkill, transformer is over spec'd and the PS filter caps are 15,000uF 100V Philips which I check every couple of years to make sure the C & ESR are still good.  It's never been worked too hard either.  I've always had efficient speakers; two DIY pairs in the past, but I moved to a pair of Samson Auro D15s a couple of years ago to cut down the weight for the sake of my back & shoulders!

 

When both amps are back in service it will be interesting to see which one ends up being the spare.  I'll post pics of the DIY amp innards when the refurb is finished.  I'm keeping an open mind.

[LogicprObe]

 

I was mulling this over later and I think I mistook them for the ETI 100w amp that blew up all the time!