[MichaelFranks]

A friend's old AA headamp finally bit the dust, does anyone know if AA gear is still serviceable? Any reputable techs on the board have experience with these?

Thanks!

 

[sacd lover]

Quote:

Originally Posted by MichaelFranks A friend's old AA headamp finally bit the dust, does anyone know if AA gear is still serviceable? Any reputable techs on the board have experience with these? Thanks!

The last I knew the tech for AA (Dusty) now works for Channel Island Audio. If he still works there he would likely be able to offer some assistance.

www.ciaudio.com

 

[rickcr42]

check the faq section of the audio asylum and download the service manual for the Audio Alchemy DTI something something DAC which has the basic circuit of the amp (it is the output section of the DAC,a single OP176 to current pump output stage).

Not much can go wrong other than power supply or output stage failure so I would try and first see if the regulators are putting out the correct voltage with a voltmeter then use a signal tracer working from the output stage back to find where the problem is.It could be as simple as oxidised power inlet pins requiring cleaning with a good contact cleaner-always a good idea with vintage equipment

good luck,actually a nice little amp

 

[rickcr42]

BTW-hopefully it is not the opamps which are the now obsolete and hard to find OP176's, a single but better version of the OP275

 

[elrod-tom]

Quote:

Originally Posted by rickcr42 good luck,actually a nice little amp

I would have to agree...a VERY nice little amp. Runs class A pretty much all the time.

Downside - it throws off heat like nobody's business, especially when hooked up to a PSII. A buddy of mine actually had a heat-sink mounted to the top of his. I'm thinking that, long-term, it's probably going to be subject to breakdown because of all that heat.

I actually had a thought about acquiring one, taking it out of its casing, and finding something that was more effective in terms of cooling. Even an open enclosure with an external fan. But that seemed like a lot of trouble.

Still though, well worth trying to get it repaired. Like rickcr42 said, nice amp.

 

[rickcr42]

Quote:

I actually had a thought about acquiring one, taking it out of its casing, and finding something that was more effective in terms of cooling. Even an open enclosure with an external fan. But that seemed like a lot of trouble.

The fix for that is to add transistor heat sinks and a DIP Pack IC cooler.

A small heat sink that mounts on top of the chip.The downside is trying to aquire the thermal bonding agent to attach the heat sink to the chip in small quanitiies.there may be a source out there but it has so far eluded me.(needed for some ceramic package LH0033 buffers)

Another opetion/or as an addition to the above is to drill holes in the actual casing.Since AA made their products as a pcb mounted to the panels it is a simple process to slide the entire "guts" out of the extrusion (the main chassis) for modifying .

Once the extrusion is separated you can take masking tape and cover the top then make a grid pattern with a pencil.At every point the lines bisect you drill a hole for venting.after deburring the edges with a small file take a black soft felt tip pen,the old benzine stinker type,and jam it into the holes to cover up the exposed aluminum.Once dried re-assemble the whole shootin' match back into a usable amp but now with some serious cooling.

BTW-there IS a place that has obsolete parts in small quantities in case it is the opamps that are toast.Not real cheap but the amp is worth saving if possible.

 

[MichaelFranks]

Thanks for the tips guys!

Anything beyond a simple fuse change is probably out of my league, i guess I was looking for people who have serviced AA products in the past, I was aware that dusty is still making equipment, but the bill for a 12 year old 200$ amplifier could easily exceed the cost of another used unit

If you know of any reputable DIYers who would be willing to undertake such a project, chime in!

 

[Oink1]

Quote:

Originally Posted by rickcr42 A small heat sink that mounts on top of the chip.The downside is trying to aquire the thermal bonding agent to attach the heat sink to the chip in small quanitiies.there may be a source out there but it has so far eluded me.(needed for some ceramic package LH0033 buffers)

Have you thought about something like this rick? $12 from here (random supplier...)

 

[rickcr42]

Quote:

Have you thought about something like this rick? $12 from here (random supplier...)

have you used this product man ?

and if so,is the adhesive quality good ?

I need a tight bond.One that will not come loose during shipping (we all know how thew mail treats packages

)

 

[Oink1]

Quote:

Originally Posted by rickcr42 have you used this product man ? and if so,is the adhesive quality good ? I need a tight bond.One that will not come loose during shipping (we all know how thew mail treats packages )

I've never used the adhesive but i know people who have (sticking ram sinks to VC's) and by all accounts it sticks like a mofo!

(the site also warns it's permanent) I use the Arctic Silver thermal compound on my CPU and VC and it's very good stuff.If you want a less permanent soloution get the CPU paste and apply it to most of the chip bar the four corners where you should apply 4 dots of superglue - push your sinks into place and you're good to go!

 

[rickcr42]

I want "forever".Thanks man.

Michael :

Maybe you can have a local "geek" run some simple power supply voltage tests to eliminate that as the problem.It would be a shame not to repair the amp if the issues are minor but at the same time not wanting to spend long green is understandable when you could most likely pick up another on ebay for less than the repairs if extensive.

But as I said before,it really is a nice little amp and the added Headroom Crossfeed is no slouch either.Other than an actual Headroom amp there are only two products i know of that use that crossfeed topology,the best crossfeed out there if you like that sort of thing (I do).

If you eventually decide not to repair the amp contact me and maybe we can deal

 

[Oink1]

Quote:

Originally Posted by rickcr42 I want "forever".Thanks man.

No problem - glad to help

 

[some1x]

About the Arctic Alumina Epoxy,
My old Radeon 8500's heatsink was held in place with the Arctic Alumina Epoxy. It is still in place after 3 years (quite an accomplishment especially since the copper heatsink is fairly heavy and is facing downwards).

http://www.targetpc.com/hardware/cooling/adhesive/

 

[garybx]

Pardon me for piggybacking on this thread, but does anyone know the power supply specs for the AA HPA? I finally found my unit in a box of old stuff, but I couldn't find the PS and the unit doesn't have any voltage or other info on the back.

Thanks!
Gary

 

[rickcr42]

The Audio Alchemy products were made with external power supplies meant to power more than one device if desired so they all shared the same basic ps connection scheme for compatibility.....

At the bottom of this page http://www.audioasylum.com/scripts/d.pl?audio/faq.html

...is the schematic for both the DAC-In-the-Box and the DDE-3 DAC.If your amp has the mini-phone jack then download the DITB file.If it has the Mini-DIN (multiple contact pins) then download the DDE file.

The schematics will show the power supply connections to the device which will allow you to modify a power supply voltage and current for use with the amp.

BUT BE CAREFUL !

attaching a reverse polarity may damge the amp if the regulators do not have reverse polarity protection diodes.

hope this helps

rickmonster