BA 99v output impedance and output transformers

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greenmanhumming
Posts: 117
Joined: Tue Apr 10, 2007 1:19 am

BA 99v output impedance and output transformers

Post by greenmanhumming »

I have some LL5402 output transformers, are they suitable as a 1:1 OT for a BA with 99v?

www.lundahl.se/pdfs/datash/5402.pdf

it seems to work OK. any thoughts?

what is the output impedance of the BA with single 99v? should I adjust some output resistors?

the LL5402 seems to like low z operation, it wasn't very happy with my valve output of about 200-300 ohms, but it seems OK on the BA

I also have some sowter 3955 that work ok, but the LL5402 sounds better and has less loss.

the 5402 is so transparent its not always easy to tell its there actually, not sure that quite what I was going for!

chrisp
Posts: 184
Joined: Sun Mar 04, 2007 11:46 am
Location: Sydney, Australia

Re: BA 99v output impedance and output transformers

Post by chrisp »

Output impedance is 10K looking at the schemo. While the LL5402 is specified for a different opamp design, there's no reason why it couldn't work well - how did you wire it all up?
Chris P
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I do lots of things. I believe eclectic skills are best.

greenmanhumming
Posts: 117
Joined: Tue Apr 10, 2007 1:19 am

Re: BA 99v output impedance and output transformers

Post by greenmanhumming »

the output is loaded with 10k resistors, but i imagine the actual output impedance of the opamp is very low,like 25ohms or something.

i wired the 5402 series-parallel for 1:1 same as the datasheet but without the feedback drive circuit.

I had earlier tried it 2:1 in a valve pre, but it was a bit tonally skewed to the treble, probably not high enough impedance, even though its into a 10k input, i guess the transformer itself needs more windings to work properly at hi z

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