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bullpeters 22nd August 2012 04:51 AM

Phase inverter, your comments welcomed!
2 Attachment(s)
I was recently given this hand drawn schematic from some that has a lot more experience then me. I would like some opinions. I have attached the exsisting inverter as well. Sorry that the file is sideways, cant seem to turn it and I didnt draw it so sorry for that as well!!!
It is proposed as an positive alternative to the current Long Tailed Pair in my EL84 amplifier.There are several missing values that i could use help with those as well

DF96 22nd August 2012 08:50 AM

Two problems with the new circuit:
1. wrong valve - ECC82 is nowhere near as linear as an ECC83
2. wrong bias - it looks like your friend has tried to combine two different LTP bias methods so got it wrong.
There are two LTP phase splitter bias methods which work: the one used by Leak (self-bias), and the one used by Mullard (DC coupling, with the second grid DC coupled to the first grid and AC coupled to ground).

In addition, as the ECC82 has such low mu it needs a CCS as the tail unless you want significant imbalance. The ECC83 has just about high enough mu to get away with just a tail resistor.

Your friend needs to go away and do some more thinking and reading.

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