Chassis looking for an amp

[tvrgeek]

I have a couple of Hafler 220's and 120's Reasonable amps, but my wife likes my Rotel's better, so I thought I would recycle the chassis, heatsinks, and transformer for a DIY. Leach is an option, but the SS thread recommended a gainclone of some type. 50 to 100W, not a big deal. Any recommendations on the best executed chip-amp as has been beat up by this forum?

I have a spare B&K 140 too, but as with the small heatsink, I thought I would use it for a class D.

[Stormrider]

Don't destroy vintage amplifiers. If you don't like them, sell them to someone that does and buy new a new chassis for your project.

[tvrgeek]

My basic inclination, but 220's are dime-a-dozen and I can't buy a chassis, heatsinks and transformer for what one costs. They are good amps. Not great amps, and not rare. (Well, the 120 is and I had to pay for it.) I was originally looking at the Hafler mods ( 800 posts strong), but by the time they finish, it is not a Hafler either. Most are based on total new cards that are expensive or no longer available.

I still may just sell them if I can't find a design I am in love with. A better course may be POOGING some Rotel's that are better to start with, or sell everything I own and buy a Bryston, but what fun is that?

I would entertain offers I guess, but that was not the intent of the post.

[planet10]

Isn't the volatge from a Hafler transformer a bit high for chip amp?

I too have a Hafler chassis (no boards or transformer came with it... used for parts on restoring another)

dave

[woody]

Those transformers give about 60v + and - after the bridge rectifier and caps.

[Stormrider]

My P230's (basically a DH220) have ~64Vdc rails, usable for a Leach, but higher than Leach recommends for the stock design. The DH120 has ~54Vdc rails, way too high for a chipamp. I think the person building a chipamp into one of these amps had an SE120. The SE120 is basically the same as a DH120 but it's transformer has 240V taps in primary for international use. Using the 240V taps at 120V would result in ~27Vdc rails which is good for an LM3886.

If you have a regular DH120 you're stuck with mosfets.

[gootee]

Maybe you could "stack" two chipamps between +/-60, and get +/-30 or so for each one. :-)

But I think I'd just use a different power transformer.

Mauro Pensa's "MyRef C" seems like it would be really great. There are some huge threads about it, here in the Chipamps forum. I would also look up Carlosfm's snubberized regulated power supply.

I'd also like to try paralleling two or three beefy chipamps (per channel), and putting them all inside the feedback loop of a good opamp. The greater current-dumping capability should make them able to drive just about anything, very well, giving, for example, excellent response from bass drivers that have large impedance dips, and highly-capacitive loads for that matter. I've simulated several such designs of my own, and the topology using the paralleled chipamps as a "power booster" amp inside an opamp's feedback loop looks like it should be fantastic.

Also, something with a topology like a Howland Current Pump, but with paralleled chipamps inside an opamp's feedback loop, looks like it could be very interesting, and worth trying, too.

Chipamps are pretty coool, because it's so quick and easy to throw test amps together, since there are relatively few parts. And they're basically just like giant opamps, which allows a designer to focus more on other parts of the design. I like the LM1875, LM3875, and LM3886. But I would suggest going to national.com and looking at all of their audio products, and the application notes.

Have fun,

Tom

[tvrgeek]

"Have fun,"

The entire point! Thanks. Someone mentioned some "sym" something too.