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Does anyone use Paraphase inverters?

2/9/2005 5:23 AM
Dave Z
Does anyone use Paraphase inverters?
OK I just finished reading the Glass Audio articles on deisgning an amplifier....and they cover the paraphase inverter. you don't see these much in amp designs and I wonder why?
2/9/2005 8:36 AM
Bruce /Mission Amps

I always thought "paraphase inverter" was just another name for a push pull driver.  
Guitar amps use a few different types of push pull drivers but the classic single triode phase inverter is not used by many amp builders any more as it has zero gain.  
2/9/2005 7:25 PM
" not used by many amp builders any more as it has zero gain."
ooo ooo ooo! a chance to pull Bruce's chain :D ...a gain of 1 or 0.9 maybe...but seriously, I have an old phono amp with an early paraphase inverter similar to Fig.12.30A in RDH4. There's a note there indicating that 'Paraphase' covers a large number of different circuit arrangements, so it's not really descriptive enough. The inverter in my Stromberg-Carlson has a gain of roughly 8 and is not balanced. It sounds good enough for me though. It's configuration is like a 5C3 Deluxe, but with a 6SN7 and different resistor values.
2/9/2005 12:33 PM
Chris @ CMW amps
I do
Did build a Gretsch/early 50s tweed style amp some time ago with such driver... crunch!!! It does imbalance pretty soon but you do get lots of even harmonics and a thick midrange.  
Have a look at some Fender 5 A-D x schematics to see some examples in schematics.  
More parts then a cathodyne-splitter ( so more $ ) and not as balanced as a good designed LTP PI.  
Give it a try in a "vintage" style ( simple pre-amp, not too many stages and fancy tonestacks ) old pa-amp or project-amp.  
Hope this helps,  
2/9/2005 6:47 PM
Dave Z
OK thanks
that may work with what I have in mind. Looking to do something quirky.
2/9/2005 8:20 PM
Greg Simon
Re: Does anyone use Paraphase inverters?
You're talking about the old style paraphase inverter that was used in some of the old Fenders and Gibsons, etc? There were two styles that Fender used, one of which is self-balancing. There is also a see-saw inverter, which is similar to those. There is a great book by Norman Crowhurst that goes into the pros and cons of different inverters and he mentions those in there. I forget the name offhand but I can find the name of the book if you want it? I also read somewhere that with modern components, those type of inverters can be made to balance pretty well, but not as good as a LTP. I'm using a see-saw type in a project amp. It was in there already when I got it (CONN organ power amp chassis) and I'll use it at first since it is simpler that way. If I don't like it, then I'll go with something different.  
2/9/2005 10:29 PM
Dave Z

I'm reading the Glass Audio articles, they mention paraphase and floating paraphase, which theoretically self-balance. I'm wondering what the advantage of the long-tailed is - better balance? more gain?  
Anyway I may try one of these just to hear an UNbalanced PI.
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