OPT options

for the DIY ST35, the Dynakit and every other PP EL84

OPT options

Postby jetpack » Mon Jan 27, 2014 7:39 pm

Hi All.
I'm thinking about trying to build an ST35. I'm looking at the following James output transformers:
JS-6238HS, 8kOhm primary Z, DC current 100mA, 30W, 5Hz-80kHz (1dB).
Any thoughts on whether this is suitable or if it is an overkill? The next step down is a 20W version with 90mA.
Thanks!
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Re: OPT options

Postby Shannon Parks » Tue Jan 28, 2014 5:26 am

I think those look great. Just watch your phasing, as Murphy's Law states you'll get it backwards on a new amp 100% of the time. (lol)
Also, I see Screen taps for the Ultra-Linear connections which is a must, but do you know the ratio %? It does change things some. Here's a read:
viewtopic.php?t=4169

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Re: OPT options

Postby Geek » Tue Jan 28, 2014 6:43 am

Shannon Parks wrote:Just watch your phasing, as Murphy's Law states you'll get it backwards on a new amp 100% of the time. (lol)


Yep!

I use a dummy load and o'scope for power-up and am rewarded with a squarewave every time (sick) (lol)

Cheers!
-= Gregg =-
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Re: OPT options

Postby jetpack » Wed Jan 29, 2014 2:32 am

Great thread about the % winding for the primary tap! Thanks. Thanks for the tip about using a dummy load for the first power up to check for phase too. Forums like this certainly help those of us with less knowledge achieve enjoyable results.
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