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-   -   How Would You Change This Soildstate Circuit To Tube (http://www.diyaudio.com/forums/tubes-valves/110472-how-would-you-change-soildstate-circuit-tube.html)

prorms 21st October 2007 04:09 PM

How Would You Change This Soildstate Circuit To Tube
 
2 Attachment(s)
HOW WOULD YOU CHANGE THIS SOILDSTATE CIRCUIT TO TUBE??
ALSO IAM NOT SURE WHAT TUBES TO USE I can only go as high
13.5 v and -13.5 v I would like to keep the circuit with same out put leval and input leval this preamp section is for a guitar

Jeb-D. 21st October 2007 04:48 PM

Well,
It would be best to alter the power supply so you get +27V instead of +/- 13.5

check out these tubes that run on low voltage:
http://www.duntemann.com/12vtubes/12vtubesindex.htm

There is also a subminiature called a 6088 that will run on low voltages. But, the 6088 can only be used as a gain stage, it wouldn't make a good output buffer.

Miles Prower 21st October 2007 05:41 PM

Re: How Would You Change This Soildstate Circuit To Tube
 
Quote:

Originally posted by prorms
HOW WOULD YOU CHANGE THIS SOILDSTATE CIRCUIT TO TUBE??
ALSO IAM NOT SURE WHAT TUBES TO USE I can only go as high
13.5 v and -13.5 v I would like to keep the circuit with same out put leval and input leval this preamp section is for a guitar

That's not difficult at all. You could use something like a CCS loaded 6SF5 for gain, a trioded 6AU6 for the output cathode follower (or a 12DW7 that includes a high-u triode for gain and a medium-u triode for the follower) and add gNFB to set the closed loop gain. If it's essential to keep the noninverting aspect, then use a 12AX7 to make a differential, along with the cathode follower and add the NFB.

If you need to keep the Vo down, then simply tap off the cathode follower's Rk.

Tim__x 21st October 2007 05:49 PM

To start with, the solidstate design you posted is horrible. I wouldn't try to copy it with tubes. Secondly, to copy it with tubes would be a whole lot of work.
What you actually want to do is design a tube circuit that performs a similar function. But again, it's a horrible design.

What are you trying to do? What function do you want this circuit to perform?

Tim__x 21st October 2007 05:53 PM

Rereading your post I see you did say what you want.

This design has a gain the increases with frequency at 6db/oct until it equals the open loop gain of the opamp. It also has a very low input impedance (0 ohms, only the reactance of the capacitor). You'd be better off to find a already made tube guitar pre design, there are thousands out there.

prorms 21st October 2007 10:01 PM

is thier way get something close to design 12vdc would be alot easyer then 27v also iam real look for something that preamp with nice clean signal aldoes in opamp it goes about 50mV to 2.5v
in the gain stage


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