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Old 24th November 2008, 04:19 AM   #1
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Default Question re: chokes

I do not fully understand the concept of chokes. when I am looking on digikey they were asking me about the dc resistance and current. Which parameters would be ideal for removing hum/buzz in a tube amp? the audio stage, not the power.

Would a 120ohms be appropriate? I read that amongst these forums. However all digikey items are rated down to 10mA which I really doubt thats enough.

Thanks!
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Old 24th November 2008, 05:10 AM   #2
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Hi,

The parameter good for removing buzz is the inductance (in henries). 10H is a good general start.

The gague of wire and length used determines the resistance. The smaller the core, the more turns needed for given inductance, hence the higher the resistance and lower the current rating.

Digikey does not have power supply chokes.

What you're looking for is a supplier of Hammond chokes, as they will likely be the best bang for the buck.

The cheap overseas chokes half the time aren't gapped for DC and are woefully overrated (I have some here common as dirt sold as 90mA DC that aren't gapped at all and wound with 36AWG [good for 36mA continuous] wire!!!), so you want to avoid those.


Cheers!
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Old 24th November 2008, 05:26 AM   #3
athos56 is offline athos56  United States
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Angela.com has the best prices on Hammond transformers I've found online.
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Old 24th November 2008, 06:48 AM   #4
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Quote:
Originally posted by Geek
Digikey does not have power supply chokes.
Actually, they do.
http://search.digikey.com/scripts/Dk...l?name=154G-ND
So does Mouser
http://mouser.com/Search/ProductDeta...KrtnBU2w%3d%3d

Neither generally have great prices, though the difference is often lower than the shipping from elsewhere if you are ordering other stuff. That is, if you need lots of Digikey/Mouser stuff and only one Hammond piece, you are often better off getting it through Digikey/Mouser than paying the additional shipping elsewhere. Neither have that many in stock, though I think Mouser is better in this regard.


Quote:
Originally posted by athos56
Angela.com has the best prices on Hammond transformers I've found online.
Radiodaze.com might be better, and you don't have to deal with Angela shipping weirdness or attitude.

Also, Handmade is closing out their Hammond and you might find a deal: http://www.hndme.com/productcart/pc/...idCategory=107
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Old 24th November 2008, 07:12 AM   #5
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Quote:
Originally posted by dsavitsk


Actually, they do.
http://search.digikey.com/scripts/Dk...l?name=154G-ND
Well, I'll be darned.

Showing all non-stock here. Best to get at another place unless he has an account.


Quote:
Originally posted by dsavitsk
So does Mouser
http://mouser.com/Search/ProductDeta...KrtnBU2w%3d%3d
Fellas, notice his location.... suggesting Mouser is bad: FedEx + Canuck = $$$$$$$$$$ brokerage

Though if he can find a dealer to ship USPS, then that would be cool, as he can get it cheaper than up here even with the extra postage

Cheers!
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Old 24th November 2008, 08:13 PM   #6
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would I be looking for something like this?
http://www.hndme.com/productcart/pc/...&idproduct=348
thanks for the headsup on the deal though, I'd probably get a pair of their output transformers too
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Old 24th November 2008, 09:18 PM   #7
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There is a good idea for hum/buzz: Cap 1-2 mkf paralell to the choke
Try.....
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Old 24th November 2008, 10:27 PM   #8
pageboy is offline pageboy  United States
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Mouser does ship via USPS. You can choose which shipping service you want to use from them. I ordered some parts from them recently for my Fisher 400, and had the package shipped USPS.
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Old 24th November 2008, 10:33 PM   #9
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actually solely for cost reasons, im trying to stick to them because their output transformers are on discount =P I figured the hammonds are better than those 18$ ones mentioned else where on this forum. im not sure what you mean azazello with mkf.

thx

edit: btw! whoowhoo! im outta probation =)
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Old 25th November 2008, 12:08 AM   #10
chrish is offline chrish  Australia
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If you are talking about Edcor as the $18 ones, then you might want to check out this page Tubelab tests hammond and edcor transformers . Edcore is good value for money.
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