Will this work for an EL84 push pull?

[zobsky]

will this work for a EL84 push pull?

The EL84/6Bq5 has low drive requirements. Would something like this work well (theoretically) since I have all the tubes and transformers lying around:

[CD player]-->[low mu triode (eg. 12B4A with myu of 6)] -->[coupling cap]-->[cinemag CMLI-15/15B] --> [EL84 push-pull]-->[OPT]

cinemag transformer link: http://www.cinemag.biz/line_input/CMLI-15-15B.pdf

I'm not sure what the allowable signal voltage swing and current capabilities are with this transformer, despite looking at the spec sheets (or maybe I don't understand how to translate insertion loss and input level in dB to volts 🙂 ).


Thanks

 

[Wavebourn]

Mo then plenty!

It will give you about 10V swing on 20 Hz with 1% distortions. Use CCS and source follower for triode load if you don't want "sweet" distortions from "voltage controlled variable resistor" triode.

 

[zobsky]

Thanks, .. I also have pairs of #27 and #37 tubes which I can use as input/driver tubes (somewhat higher mu of about 9 but less current driver of ~ 5mA ). Would these be better, from a design and sonic aspect, .. from someone who has worked with them.

 

[Wavebourn]

Actually you need a very low gain of a voltage amplification, so only feedback deepth will depend on tubes. Use the cheapest you have.

 

[rdf]

If that were my pile of parts I'ld be inclined to investigate putting the Cinemag at the very front, doubling out the 12B4As and maybe running them fixed bias. BTW, I don't see a secondary centre tap on that model, how would use it as a phase splitter?

 

[zobsky]

If that were my pile of parts I'ld be inclined to investigate putting the Cinemag at the very front, doubling out the 12B4As and maybe running them fixed bias. BTW, I don't see a secondary centre tap on that model, how would use it as a phase splitter?

Your suggestion is similar to a suggestion SY had for me a long time ago
( http://www.diyaudio.com/forums/showthread.php?postid=315504#post315504 ) . Now that I'm planning an easier to drive push pull project, I was wondering whether using the transformer after the input tube will work.

Re. phase splitting, ... I think a resistive divider was reccomended (see post linked )


P.S. don't know if this is obvious, .. but essentially, the big goal is to see if I can build an optimal 2 stage push pull amp, ..hence the choice of the (relatively easy to drive) EL84 as the power tube and the 12B4A (or other suitable tube) as a high current input / driver.