selecting SE OPT

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selecting SE OPT

Postby nyazzip » Fri Jan 18, 2013 12:57 am

so...i am finally getting around to getting an adequate output transformer for my rh84 experiment... the one i have been using is the much maligned OPT from the cheap epiphone guitar amps. i am wondering, even though it is overkill, would it be better to get the largest wattage OPT i can find? i'm thinking about getting the 15 watter. as long as i have to pay shipping and such, i don't mind spending ten extra bucks for the big one. are there any detriments to my thinking...?
also, i may (very likely)want to experiment with larger SE amps down the road. is 5K/8r a flexible ratio transformer, or am i likely to be locked in to few choices? i'm not quite sure how to research this so i thought i'd ask here
...also i am finally going to bite the bullet and get me a proper 10H choke. all this from Edcor....
(love)
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Re: selecting SE OPT

Postby Geek » Fri Jan 18, 2013 2:29 am

I would (and always do) do that.

Larger cores afford more inductance, better current capability before saturating and extended bass response.

A CXSE would be overkill ;)
(but the 2A3 amps I build with them do go to 7Hz [:) (lol) )

Cheers!
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Re: selecting SE OPT

Postby Shannon Parks » Fri Jan 18, 2013 5:28 am

I second everything Gregg says. Also remember that distortion with lower inductance transformers skyrockets below 50Hz due to fluctuating saturation. When the grid is 0V at 20Hz you are saturated and have crap output, while it swings to the other end it isn't bad (unless you are in the knee of the curve then you'll have more distortion). It's probably more of a problem than bandwidth. Fortunately it doesn't sound bad. (c)

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Re: selecting SE OPT

Postby nyazzip » Fri Jan 18, 2013 4:42 pm

Thanks for the input. Hey geek, you happy with the 2a3?
?..any schems available...?
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Re: selecting SE OPT

Postby Geek » Fri Jan 18, 2013 5:21 pm

The 2A3's I've built have blown me away more than any other amp I've heard.

The biggie:
http://geek.scorpiorising.ca/GeeK_ZonE/ ... pic=4444.0

And attached is a 2A3 I rebuilt for a client. He got a "pan" of Swedish iron for dirt cheap and said to me, "can you do something with this?". So I did :))

Cheers!
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2A3_rebuild.png
Simple 2A3
2A3_rebuild.png (43.85 KiB) Viewed 2104 times
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Re: selecting SE OPT

Postby nyazzip » Sat Jan 19, 2013 5:44 pm

ah thanks. those 2a3 builds are a little expensive-looking for me, for now. plus the 2a3s want a 3k primary.....
edcor stuff ordered! now the loooooong wait begins i guess...
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Re: selecting SE OPT

Postby Geek » Sat Jan 19, 2013 7:42 pm

Your raw basic 2A3 build is about the same cost of a Dynaco kit in parts. The iron is the most expensive part, as usual.

That XPWR183-120 I had specifically designed by Edcor for 2A3 projects and is a regular item on their list [:)

As for 2A3's, you know the el-cheapo Sovtek ones? Sound friggin AWESOME! (love)
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Re: selecting SE OPT

Postby nyazzip » Thu Feb 28, 2013 5:43 pm

update: finally got the edcor goods today! a 10h choke, a 10w/5k SE, and a 15w/5k SE......
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