LL1674 and 56 linestage update

K&K Audio / Lundahl Transformers

Welcome! Need support, you got it. Or share youe ideas and experiences.

Just a brief update for those who are interested...
The disclaimer! I still haven't received my parafeed capacitors, or the mosfets to replace my mje350 ccs, so my experiments are very limited and sub optimal.
Last night I measured the inductance of the windings between connection points 7-6 and 9-10 on the LL1674 using my cheap (and nasty) inductance meter. The meter only tests at 200hz and the results are +/- 5%. 19.5H was measured for each of the two windings.
From what I've read about parafeed designs, if you double the inductance of the parafeed transformer, and you can halve the value of the parafeed capacitor, you will get a similar frequency response. Previously I had windings 7-6 and 9-10 in parallel which gave an overall inductance of about 10H. Placing these same windings in series gave me 40H.
At present, my basic (sub optimal) circuit is:
B+=260v
Anode R = 47k ohm
Cathode R=1.35K ohm
Parafeed transformer with windings 6-7 and 9-10 in series
Parafeed cap = 4.4uF
Just changing the transformer windings from parallel to series connection had a much larger effect than I was expecting. Bass response is flatter than before with a -0.7db point at 20hz. I expected that effect however, the treble is also much flatter than before with a -0.6db point at 20kHz. I suspect that there is something going on with parasitic capacitance which will need further investigation....
When are my large parafeed caps going to arrive!?!
Kind Regards
Andrew

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Topic - LL1674 and 56 linestage update - Drewaudio 12:31:41 04/01/05 (0)

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