j-FET / Triode Phono front-end

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Cressy Snr
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#286 Re: j-FET / Triode Phono front-end

Post by Cressy Snr »

I don’t need to tune my OTL for 1% 2nd harmonic. It already produces that by the time it reaches 200mW :lol: :lol: :lol:
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IslandPink
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#287 Re: j-FET / Triode Phono front-end

Post by IslandPink »

izzy wizzy wrote: Sat May 04, 2019 1:53 pm
Do you think you were tuning for "1% negative phase 2nd harmonic"?
I don't think so, but then my system would already have some 2nd-harmonic.
I remember that I had a first set-up and then a modified set-up that I preferred. Andrew set up a quick Spice model, the first set up on Spice showed essentially no distortion, the preferred set-up showed a 2nd-harmonic peak at 70dB down. The difference in perceived tonal quality was quite significant.
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izzy wizzy
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#288 Re: j-FET / Triode Phono front-end

Post by izzy wizzy »

IslandPink wrote: Sat May 04, 2019 2:10 pm
izzy wizzy wrote: Sat May 04, 2019 1:53 pm
Do you think you were tuning for "1% negative phase 2nd harmonic"?
I don't think so, but then my system would already have some 2nd-harmonic.
I remember that I had a first set-up and then a modified set-up that I preferred. Andrew set up a quick Spice model, the first set up on Spice showed essentially no distortion, the preferred set-up showed a 2nd-harmonic peak at 70dB down. The difference in perceived tonal quality was quite significant.
Nick mentioned something like that when tuning one of his amps.

I saw something similar in the sim for the output on my phono in that the imbalance of the diff stage with a small tail was a similar harmonic profile to a single ended stage where if the tail had a CCS to force better balance, the 2nd fell away.

It's amazing how so little can make a difference.
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