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Old 26th July 2012, 01:51 AM   #1351
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I have 4 of these heat sinks. Possible to get another amp out of these heat sink?
It's smaller than I said before. 5x3.5x3 inches.
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Old 26th July 2012, 02:47 AM   #1352
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Those are nice sinks. I wouldn't have any problem
putting 4 of them to work.

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Old 26th July 2012, 03:08 AM   #1353
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Any hints Mr Pass? Stick with another 2sk82 SIT amp or something else?
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Old 26th July 2012, 12:35 PM   #1354
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You could use those for lots of things. If you don't have the actual spec, I'd estimate one to be around .8-1.0 C/W.

Incidentally, the SIT scales reasonably well, which is to say: for a smaller amp use a little less Vds, and a little less idle current. This requires a little more experimentation on your part but isn't a big deal. For a starting point, just change them in proportion and see what you get. This also works well with the inductor-loaded versions, which have the benefit of greater efficiency.
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Old 26th July 2012, 02:30 PM   #1355
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Quote:
This also works well with the inductor-loaded versions, which have the benefit of greater efficiency.
Thanks Mike. Inductor version looks interesting. Also, interestingly enough, my first electronics book back before the Internet, described class A amps with an inductor or transformer to improve effeceincey at better than 20%.
I think it said 45-50%, which sounds high (to me) for class A.

Juanitox mentioned a Hammond 193 choke. There are several versions of based on voltage or current rating. They can go up to 3 amps.
I think it's the 193v. The choke would have to be able to handle at least 3A, correct?
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Old 26th July 2012, 02:49 PM   #1356
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You could theoretically acheive 50% efficiency, but there are always some losses in the inductor.

Additional info:

Quote:
Originally Posted by Michael Rothacher View Post
I've forgotten who I promised this to, but here's the info on the Hammond 193V.

Not bad, and we get a nice efficency boost from the lower DCR iron core. You can put those 24V supplies to use now. I didn't experience any loss of inductance at 2A (or the rated 3A for that matter).

You could even run this one with a 20V supply @ 1.4A for a nice little 7W amp with 2% THD at full power.

No, I haven't listened to them. The measurements are in the pdf. Have fun.
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Old 26th July 2012, 03:05 PM   #1357
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I have 2 big Antek audio 18v power tranformers meant for an F5...they only really need one.
Too much fun!!

thx!

V~
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Old 26th July 2012, 03:48 PM   #1358
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There are a couple of open frame chokes with better specs and are dirt cheap. There's a $45 difference. Sounds too good to be true. Somethings off. Core type?

Quote:
A big spool of magnet wire isn’t exactly an ideal inductor and there will be some DC resistance and other losses. My spool of magnet wired measured around 110 millihenries and the DC resistance was 5-6 ohms. Lower resistance and more inductance would be nice but we work with what we have.
List of Hammond Transformers


# L A R Vdc Lbs $$

156B 1.5mH 5A 0.07 400 .50 $14.25

157D 1mH 10A 0.038 400 1.0 $16.25
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Old 26th July 2012, 03:53 PM   #1359
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Quote:
Originally Posted by vdi_nenna View Post
Something's off. Core type?
Inductance.

100+ mH is kinda the minimum here.
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Old 26th July 2012, 04:00 PM   #1360
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I see. Top chart is Henrys, bottom chart is mH. Sorry.
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