DCAudioDIY.com

...but I've been there a lot of times!

Anyway, hello, I'm Bill Waslo, ran into this forum via a link on another forum... I'm an audio DIYer, formerly from Ohio, now in Portland, Oregon. I'm also a programmer, have done a number of audio measurement systems ("IMP", "LAUD", "Praxis", and "OmniMic") as well as the free crossover design program "XSim". And various spreadsheets for audio things, particularly about Synergy Horns (the Danley type, not the Klipsch Synergy models).

I registered here because I wanted to comment about choke-fed amplifiers in the thread http://www.dcaudiodiy.com/phpBB3/viewtopic.php?f=4&t=536. I've designed and built a number of these type amps. An older one will be in an upcoming issue of Linear Audio. So, maybe after I've done my introduction here, I'll be allowed to comment?

Hi Bill:

You are certainly welcome here. That is the amp that David and I built. I am a long time user of LAUD and that application was used in testing the amp. Way back I also did an article in Audio Amateur or Speaker Builder, I don't remember which on a protection circuit to guard the sound cards when using LAUD. The article on that amp has been accepted for publication by AudioXpress but I don't have a publication date yet. Hope to hear more from you in the future.

Tom

Hi Bill,

I sent you those British papers on cepstrum analysis back when you were developing IMP.

Hi Pooge,

I think I remember (was a long time back, though, and my memory is turning to mush on a lot of stuff anymore!).

Hi Tom,

I managed to comment on the choke-fed amp thread, even posted a schematic and photo. Can you tell me where you got your chokes? I'ts hard to find anything above 35mH and 5A DC handling.

Bill:

They were wound by hand. I used laminations I recovered from some old transformers. What a job. I used paint stripper since some of them were dipped in what appeared to be epoxy. Then I actually found the best way to clean them was to use hot water and Tide. A dip in alcohol helped dry then and then I used a final dip in some acetone with just a smidge of oil to prevent rust. If I figured my time at about $1/hr I had a fortune in them. I'll never do that again. I also wound the power supply choke by hand.

Tom

OK, thanks. Guess I'm not going to go that route!

BTW, the chokes I used in the bigger amps were Triad C-49U
http://catalog.triadmagnetics.com/Asset/C-49U.pdf.

I'd have liked something with about double the inductance or more, but these actually turned out to work pretty well and I haven't had any problems with bass from the amps. Not too terribly expensive, but heavy buggers. Shipping cost gets up near the cost of the chokes.

The power supply choke was 30 mH, 7A, .23 ohms DCR. The output chokes were 100 mH, 5A, .74 ohms DCR. Here are curves of the chokes from a curve tracer with a DC step signal.

Tom

Hammond makes 100mH at 5A & 10A (195T5 & 195T10) chokes, and one that's 150mH at 3A (193V)....

Roscoe

_________________
I can explain it to you, but I can’t understand it for you.

Thanks, hadn't seen those.

The 10A 100mH looks very nice... but the price (OUCH). And weighs 35 lbs, but I guess that's to be expected.