Redesigning Tube-Based Circuits to Transistor-Based Circuits

[mimmotronics]

I've stumbled upon a book called Electronic Circuits Manual by John Markus from a local estate sale. It's basically an encyclopedia of circuit designs and I believe it was written in the 70s. As such, a lot of the circuits are Tube-Based.

I'm wondering if anyone has any tips on converting a tube-based circuit design into something transistor-based?

[diegocw]

http://runoffgroove.com/fetzervalve.html
This great site could help!


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[PRR]

> stumbled upon a book called Electronic Circuits Manual by John Markus

https://archive.org/details/ModernElectronicCircuitsReferenceManual

Marcus did a bunch of these; you may find others by clicking his name on the Archive.org page.

Most were under-described throw-away tidbits. Very few directly relate to audio, though everything is grist for the mill. I've read about 2,500 pages of Marcus collations and got about 2.5 amusing ideas.

[mimmotronics]

Thank you diegocw! Added to bookmarks!

PRR, awesome! That is true, a lot of the circuits described are mostly throw-away as applied to audio, but I figure there are some things to scavenge from them (even if its just 2.5  ) Thanks for the find!

[amptramp]

I'm wondering if anyone has any tips on converting a tube-based circuit design into something transistor-based?

First step - do away with the heater/filament wiring.  Wasn't that helpful?

N-channel JFET's are quite a bit like tubes but that does not mean you can pull out a tube and install a JFET without making wholesale changes in the design.  If you look at a tube stage as a functional block, it may be easier to reorganize it as an op-amp circuit.

Some of us in the antique radio restoration game have come up with plug-in transistor equivalents to tubes such as this 1L6 pentagrid converter replacement:



Just to help you follow, pins 1 and 7 are the filament, pin 2 is the plate, pin 3 is the oscillator second grid, pin 4 is the oscillator first grid, pin 5 is the screen grid and pin 6 is the signal input grid.

a type 01A triode simulator is described here:

http://www.greenhillsgf.com/Project_SS-Tubes.htm

The fact that some people have done this does not mean it is the wisest course of action for someone building an audio device.  Tubes, FET's and bipolar transistors all have different transfer functions so even if you could get something that worked, it might not sound the same.