Experimental Design

[analag]

Using a miniature tube (6021) and a +/-60V supply I plan to build a high headroom, high output swinging opamp, for line-amping or maybe DI work.
I have made an excellent model of this tube, based off of my stash so my sim should be close to real world.

 

[CJ]

What is the MPS p/n? It will take that much voltage?

Plus 1 for using tubes
Minus 1 for no iron.

If you can get glass and sand to sound good together, you be one bad mofo.
If not, you be one Leo Fender. (Musicman was hy-brid, sounded semi OK, Johnny Winter liked it, but he looks like walking death nowdays, have you seen that skinny albino?)

Have you seen Tube Tech vac tube op amp circuit?

Have you tried the 6021 in place of 6072 in mic pre type circuit?>
Might be cheap alternate fr med mu twin 9 pinner.

 

[analag]

I actually got a mic with a 6021 in place of a 6072 in it.
As for the iron....think of it as a Opamp which is what it, and you can put iron at the input, output or both. With a 1:10 input iron, (2) of these hybrid thingy, stick a pot between the them and a 600:600 output iron, we could have ourselves a nice mic pre.

 

[CJ]

You might try a reverse pwr supply, come into the tubes with full B+, then knock it down with a pi section for the latter transistor stages so you do not need heat sinks.

 

[Gus]

check the rode NTK schematic at group DIY. I kind of like that circuit in microphones

 

[cuelist]

What is the reasoning behind tubes as the inout pair and the remainder being solid state?

From the strength / weaknesses of tubes / solid state would it not make more sense to use tube as the voltage amplifier and use transistors for input and output?

Just a thought...

 

[PRR]

Input stage gain is around unity. That's not wrong, just unusual.

Input offset will be near 100mV, unless you are very lucky. It will be much larger for a minute after cold-start, won't settle to a few mV of final value for a half hour. It may be drifting for months. It takes a long time for my VTVM to settle-in after a tube change; over a year before I don't have to diddle the trim every day. That's not a fatal flaw, just something you have to deal with.

 

[ioaudio]

can somebody explain that circuit to in more detail? i think its very interesting, but i dont understand it, and i think there are others who cant really understand.

 

[analag]

http://www.dibsplace.com/dibsed/CIRCATS/je-990.pdf
Take a look at the 990 schemo, you will notice it's basically the same thing with a tube replacing the differential or transconductance stage. Voltage rails are also beefed up to accomodate the tube and to allow much greater output swing capability than is associated with normal opamps.

analag