Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: W5FH on October 25, 2022, 02:27:55 pm
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I searched previous posts on this site in regards to the HiWatt DR-103 phase inverter circuit, namely the single (ECC83) triode section V3b that is supplying a fixed voltage bias to the phase inverter V4 grids (ECC81). This circuit is very interesting to me, especially after reading some favorable comments about the low distortion operation of the phase inverter. I would appreciate any comments or guidance on whether to utilize this form of P/I biasing.
Thanks all.
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Hiwatt decided to use a fixed bias LTP PI rather than the more common bootstrapped bias LTP PI. Any sonic difference would be due to this circuit difference.
V3B is a totally unnecessary cathode follower circuit. I think Hiwatt just didn't want to have an unused triode. Dave could have done it like this with the same results. Then he could have added a killer Trem-O-Nator with the extra triode. :l2:
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V3B is a totally unnecessary cathode follower circuit.
Yes, on paper, but it seemed to me that lower source Z of the active v-divider added some positive to the overall sonic character especially when pushing the LTPI hard in that amp. At least it seemed that way to my old ears when another forum member and I experimented with that ckt. years ago. Bypassing and cold(er) biasing V3a added A LOT overdrive character as well, not that there's much of that to begin with.
--Pete
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Thanks for all replies -
I was curious if the active voltage divider would have sonic properties apart from a resistive divider, very interesting. I guess what I meant to ask, or should have asked - - is there any advantage to a fixed bias LTP P/I as compared to the normally used cathode biased version?