Adapting transistor circuits to Tubes

[swinginguitar]

I've seen the JFET for 12ax7 substitution, but has anyone tried it the other way? As in adapting well known stompbox circuits to use preamp tubes instead of ICs or Xsistors?

[asatbluesboy]

A Big Muff with tubes? Count me in.

[emstin1]

I'm no expert, but it seems like it would work.  After all, the transistor was invented to replace tubes.  Maybe not in all circuits though.  Imagine the mojo!

[R.G.]

I do know people who have tried it. Including me...  

In general, transistor circuit may or may not go well into a tube implementation. It can be done, but it's not as simple as just subbing in a tube. It will often require a full redesign to get the tube to do something similar.

I *did* once do a paper design of a digital delay implemented with tubes.   It required several tens of *thousands* of dual triodes and its own electrical substation to provide the megawatts of power.

Needless to say, I didn't breadboard it.  

A big muff with tubes would not sound all that different from a big muff with transistors, unfortunately. The way the clipping is set up, what you hear is how the diodes clip, not how the transistors clip. So a tube version would still hear the diodes; probably not what you had in mind.

Magic (including the mojo branch of the family) does exist. However, it exists only inside the heads of humans, not in the real physical world.

Unfortunately, it's not possible to get tube (or germanium, or vintage, or...) sound just by rubbing tubes or germanium transistors onto circuits.  Mother Nature is not that simple.

[swinginguitar]

Thanks RG.

What I was getting at is I have a potential tube amp buld in the works, but will have an extra 1/2 triode sitting there doing nothing so I thought "what if I could wrap a marshall in a box type circuit around that tube stage".

[emstin1]

I *did* once do a paper design of a digital delay implemented with tubes.   It required several tens of *thousands* of dual triodes and its own electrical substation to provide the megawatts of power.

Seriously though, I'd imagine that boost stages (or whatever the technical term) would be easiest to implement with tubes.  Most tube pedals I've seen need more than 9v to run though. 

[tubelectron]

After servicing, building and designing for 30 years with tubes Audio, Musical instruments and RF circuits, and more recently experimenting with solid-state...

Magic (including the mojo branch of the family) does exist. However, it exists only inside the heads of humans, not in the real physical world.

Unfortunately, it's not possible to get tube (or germanium, or vintage, or...) sound just by rubbing tubes or germanium transistors onto circuits.  Mother Nature is not that simple.

... I couldn't agree more with Mr Keen's statement !

A+!

[Mike Burgundy]

What I was getting at is I have a potential tube amp buld in the works, but will have an extra 1/2 triode sitting there doing nothing so I thought "what if I could wrap a marshall in a box type circuit around that tube stage".

Okay, maybe switch in an extra boost stage with specific voicing either at the front, before the tonestack or before the phase shift (if there is one)/power amp for that extra kick?

[frequencycentral]

If you use a transistor PSO you could have the spare stage doing tremolo. Or add another dual triode and you can use the three stages to do optical vibrato.

[aron]

It might be the coolest LOOKING Big Muff. Possibly the most dangerous too depending on the build.

[tubelectron]

A Big Muff with tubes? Count me in.

Here's a kind of Tube Big Muff quickly designed - I think that only one 12AX7 section is enough (Gain 1 or Gain 2) - the gain pots are tandem, and would be preferably LOG, but it's a matter of test. This circuit is untested, but should work, at least with one section. With two sections, you will certainly have huge overdrive/fuzz effect, may be not very controlable and noisy... Of course, tweaking is probably necessary on the interstage caps value and pots taper, as good shielding and grounding is compulsory.



A+!

[anchovie]

What I was getting at is I have a potential tube amp buld in the works, but will have an extra 1/2 triode sitting there doing nothing so I thought "what if I could wrap a marshall in a box type circuit around that tube stage".

You could have a switchable Soldano-style "cold clipper" stage (the one with the 39K cathode resistor) to get extra distortion.

[petemoore]

  Mu Amp...always wanted to/never tried it with tubes.
   Correctly wired=it self biases, the Jfet version certainly is a nice stage to have around/work with.
  Just seemed an apt ''adaptation'' for a guitar tube amp effect.
   I thought of locating a power supply and enough open space in a chassis to start up some Mu-work, an amp here could have Mu>Mosfet source follower. I guess it'd sound pretty good since the mu can have lots of gain and distorts a little and'd be about the last in the chain. that and a Strato-or Fetzer boost...I just never got around to doing it, it'd require resistive divider and associated filtering, this would be re-arranging the B+'s/extending high current ground wires, and pushing the PS filtercaps outside their near-star-ground area, on a new rebuild it might be worth making room for a Tube Mu tryout.