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Hi Kevin, could you use the LL1660SAM PP as a single ended parafeed primary, and phase splitting secondary transformer, wired 4.5:1+1. The C coils wired in series on the primary, with the A and B coils in parallel on the secondaries? This would be the preamp stage coupling transformer, in an integrated amp.
The parafeed preamp single ended tube would be a 6n1p-ev, the 1660S would split phase and couple to 6n6p drivers. I assume that since the inductance adds while the capacitance halves when running 2 coils in series that I'd have a very high inductance primary, with relatively low capacitance, so bandwidth shouldn't be a problem. However, it seems as if with the 7K Rp of the 6n1p, that resonance peaking would occur. If so, do you think proper selection of grid leak resistors, on the 6n6ps, would take care of any resonance peaking?
If this is feasible, please check out my math, as I'm still not real confident with transformers. If I was swinging 50VPP on the 6n1p-ev then each coil of the secondary would be swinging 11.11VPP, and the 6n6p driver tube would see a reflected impedance of about 346 ohms from the 6n1p. Is this scheme workable, or a bad idea?
twystd
I wouldn't think that the resonance peaking would be that serious for a 7K source feeding a transformer for which a 15K source is "optimum" . You can always dampen high frequency resonances with a resistive load, but usually it's not a good thing sonically. Your idea is a perfectly good one, but start out without the heavy duty loads and see how it goes.
Kevin Carter
K&K Audio
www.kandkaudio.com
I thought that since the 2 primaries are in series that the optimum load would be 30K instead of 15K. Yes I was thinking of trying it with no load at all first, but just wanted to see if the load mismatch might be too much to correct. I guess I must have the math right about the voltage swing and reflected impedance of the 6n1p-ev. Thanks for your help.
twystd
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