does anybody know of any simple yet good tube opamp circuits? i am pretty new to this so i want to find something simple that works good. i want to replace the opamps in a tone control circuit with tube circuits, if thats even possible. i think it is. maybe not? i dont know. help would be appreciated.
I think Bob Pease (of National semiconductor) has written an article or two on the early days of vacuum tube op-amps.
Ralphie,
Take a look at this recent thread.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=36157&highlight=
A very nice active tone control circuit built around 12AX7s is discussed.
You could "copy" a discrete part FET opamp circuit. The I/P circuitry of opamps is a differential topology that (big surprise 😉 ) was 1st developed using vacuum triodes.
IMO, Max Robinson's Baxandall circuitry described in the thread is what you should build.
Take a look at this recent thread.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=36157&highlight=
A very nice active tone control circuit built around 12AX7s is discussed.
You could "copy" a discrete part FET opamp circuit. The I/P circuitry of opamps is a differential topology that (big surprise 😉 ) was 1st developed using vacuum triodes.
IMO, Max Robinson's Baxandall circuitry described in the thread is what you should build.
Don't forget the old Tektronix Type "O" plug-in for 500 series scopes, was a fancy tube op-amp. I even have one still, good for plotting xfmr. and inductor hysteresis curves (configured as an integrator).
Don
Don
Hi,
For a classical feedback Baxandall tone control you don’t need an op-amp, just an inverting gain stage. If you keep maximum bass boost/cut and treble boost/cut moderate to say + and – 10 dB (who needs more?) a gain of 20 to 30 will suffice. At the moment I am working on a new tube pre-amp with tone control. Simulations with a 6DJ8 as mu follower (gain = 30) seems promising so far. But I haven’t built anything yet, so I am hesitating putting up a premature circuit here.
Cheers 😉
For a classical feedback Baxandall tone control you don’t need an op-amp, just an inverting gain stage. If you keep maximum bass boost/cut and treble boost/cut moderate to say + and – 10 dB (who needs more?) a gain of 20 to 30 will suffice. At the moment I am working on a new tube pre-amp with tone control. Simulations with a 6DJ8 as mu follower (gain = 30) seems promising so far. But I haven’t built anything yet, so I am hesitating putting up a premature circuit here.
Cheers 😉
Philbrick manual download page,all at once (75MB) or by section
http://www.analog.com/library/analogDialogue/archives/philbrick/computing_amplifiers.html
HeadWize Design Series Paper with the Barbour and Forsell tube opamps plus the borbely Hybrid Tube/Mosfet Op Amp
http://headwize.com/projects/showfile.php?file=opamp_prj.htm
http://www.analog.com/library/analogDialogue/archives/philbrick/computing_amplifiers.html
HeadWize Design Series Paper with the Barbour and Forsell tube opamps plus the borbely Hybrid Tube/Mosfet Op Amp
http://headwize.com/projects/showfile.php?file=opamp_prj.htm
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