Tube Driver with FETs

[Doug_H]

I don't idolize or demonize device types. I've heard great/terrible sounding tube & ss circuits. I also don't buy into the generalization that "starved plate" circuits have to sound bad. My 6ak6 pentode driver sounds good, but it just compresses too much for band use. I would guess it is the screen circuits in 2 pentode stgs causing that but anyway...

In the end it is everything working together as a system, and headroom, gain , freq response, & harmonics that determine whether something sounds "good" or "bad", regardless of what is inside or what voltage it's running at.

IMO, of course.

Doug

[aron]

Doug's right of course, it's the implementation, ok, I have never heard an "implementation" of a tube circuit that sounds significantly better than solid state in a pedal. I took a listen to the EH product and it does sound good. I would need to hear it in person to know if it was really any better than any other pedal.

Those who were involved in the beta testing of it on the Duncan forum are just raving over it.  I want to try one myself.

Have you ever heard anyone not rave over "secret" pedal they were testing? It's part of the fun of having something that no one else has. I bet it does sound good though.

The Tillman pre-amp looks like a buffer of sorts.  Am I right?  Or does his pre-amp have more gain than a buffer?

Apparently 3db - it's coming off the drain, not the source.

In retrospect, perhaps it is the fact that there are simply less people making tube pedals than solid state. I keep getting amazed at SS when I hear stuff that Joe Davisson and Gus and others put out.

[Doug_H]

And I run in circles, too.  The only pedal I ever even use anymore is basically an LPB-2. 

Yeah, I'm back to my Rangemaster, NPN Boost, and (on the "non booster loop") Shaka IV. After all the junk I've come up with and other stuff I've played with I keep coming back to those 2 simple boosters and I'm pretty happy.

Doug

[vanhansen]

Those who were involved in the beta testing of it on the Duncan forum are just raving over it.  I want to try one myself.

Have you ever heard anyone not rave over "secret" pedal they were testing? It's part of the fun of having something that no one else has. I bet it does sound good though.

Actually, the folks over there are pretty honest with the Duncan folks.  If it doesn't sound right, they let them know about it.  It's a cool group.  Much different than here, but cool nonetheless.

The Tillman pre-amp looks like a buffer of sorts.  Am I right?  Or does his pre-amp have more gain than a buffer?

Apparently 3db - it's coming off the drain, not the source.

Oh yeah, it is.  I didn't notice that right away.    Funny how the simple circuits can hide the obvious.

In retrospect, perhaps it is the fact that there are simply less people making tube pedals than solid state. I keep getting amazed at SS when I hear stuff that Joe Davisson and Gus and others put out.

There's some SS stuff out there that just flat out rocks, some of it being modelling.  Tech 21, Roland Cube amps, the new Peavey stuff.  The tone has gotten better.  I still love my little Crate from the 90's.  But to me, tubes have the tone.  I guess it's the warmth that I like about 'em.

Speaking of running in circles.  I went from having no pedals, to half a dozen plus an effects rack back down to just a couple.  Now it's a delay, chorus and a buffer in the effects loop and a booster of some sort and wah out front.  Right now the Rangemaster clone I just built has the stage so to speak.

[PharaohAmps]

Yes, I've heard a pre-amp before the invertor.  Sounds horrible actually.  The tubes in the SFX-03 Twin Tube Classic are 6021 dual triode tubes instead of 12AX7's.  It's claimed to be a 100% tube signal path with high plate voltage.  Those who were involved in the beta testing of it on the Duncan forum are just raving over it.  I want to try one myself.

A 6021 is a nuvistor, like the ones in some tube mics or the Nano Head from Z.Vex.  They're lower gain than a 12AX7, closer to a 12AT7 IIRC.

http://frank.pocnet.net/sheets/137/6/6021.pdf

They're real small, and would fit in a pedal OK.  Problem is, they're a real pain to get in and out of their little sockets and there aren't many subs or options to choose from.  If you build a pedal that uses the same B9A basing as a 12AX7, you can sub in lots of different tubes with varying mu and response characteristics.  My pentode based pedal can use either remote-cutoff pentodes or sharp-cutoff, and has some little jumpers inside to tune it further for different tubes.  I think Siegmund made a pedal with nuvistors, and I've heard guys rave both good and bad about it.  I know I sold Class-A Boost pedals to at least two guys with those Siegmund pedals, so that must tell you something.

I've said for years that at least 50% of the distortion from a classic type (BF / Tweed Fender / Marshall / Vox) amp is from driving the PI.  In fact, if I ever do a tube distortion pedal of any kind, I'll put in something to simulate the PI.  Gotta have it.  And if you're doing a master on a tube amp, you need to put it post-PI for sure.

Matt Farrow

[mojotron]

I actually did build a Tube Driver with FETs, but it seemed like the tone circuit on the Tube Driver needs to be tweaked for use with something like a J201 in a Fetzer Valve... I hated the sound, but it could have been tweaked to sound decent.

In short, I really like the sound of the original Tube Driver for some things - and I believe some people like EJ use it for more of a band-pass filter with some minor clipping (uses it with the tone knobs turned fully CCW, vol and gain set to 3-5 - roughly low to mid setting). So, I don't know if when people use the TD in a different context they don't like the sound of the original TD, or if it's a matter of not having a wide range of good sounds.... but the original TD is great for some things IMO, but not a lot of things...

What I ended up doing with this was scavenging the FETized-TD parts and mod-ing a BSIABII's first and third stage to get a little less gain and more low end - and that pedal can sound a lot like my old TD w/my favorite tube - only better IMO because it seems to have a much broader range of "good sounds" - although it's not very "BSIAB-ish" anymore.

[mojotron]

And I run in circles, too.  The only pedal I ever even use anymore is basically an LPB-2. 

Yeah, I'm back to my Rangemaster, NPN Boost, and (on the "non booster loop") Shaka IV. After all the junk I've come up with and other stuff I've played with I keep coming back to those 2 simple boosters and I'm pretty happy.

Doug

I spend a lot of time these days with just a FuzzFace (1 of 10 or so..  ), a strat and an amp.

[Johan]

I don't idolize or demonize device types. I've heard great/terrible sounding tube & ss circuits. I also don't buy into the generalization that "starved plate" circuits have to sound bad. My 6ak6 pentode driver sounds good, but it just compresses too much for band use. I would guess it is the screen circuits in 2 pentode stgs causing that but anyway...

In the end it is everything working together as a system, and headroom, gain , freq response, & harmonics that determine whether something sounds "good" or "bad", regardless of what is inside or what voltage it's running at.

IMO, of course.

Doug

..the problem with most starved plate circuits is that little or no attention is put on the effect of "space charge"..basicly, when runing starved, the grid loads up with negative DC, changing the Mu of the tube ( the very principle behind vari-mu compressors..) . you can overcome this, at least to a great degree, by tying the gridresistor to a positive bias ( as in Aron's Chacka tube )  or to the B+ as in the "tube driver" or feeding it with a fixed dc-bias/ low-z output, but you need to know when and how much...just pull out your VOM and mesure the DC-voltage on the grid of any "standard" tubecircuit when it running "starved" and you'll see what I'm talking about...and then you still have to take into account that the linear region of the tube is severly limmited when running at low voltage..

...I guess that could be a project/challange for the next time my sweetie is away..

johan

[aron]

I think Siegmund made a pedal with nuvistors, and I've heard guys rave both good and bad about it.  I know I sold Class-A Boost pedals to at least two guys with those Siegmund pedals, so that must tell you something.

OK, look, take what I say with a grain of salt.... I played that pedal, it was not very good (to me). I didn't break up really well, it sounded very flabby and to me was not good for anything but really low gain.

As soon as you said this, I remembered that pedal. Remember though, that I could have played a defective one or he could have improved it by now (I think my friend got it right when it came out).

[aron]

Here's a site I found while looking searching the 6021:

http://amps.zugster.net/articles/tube-pedals

[MartyMart]

aron, this guy makes some killer sounding pedals ...
http://www.owenelectronics.co.uk/9916.html

The space charge distortion is very, very nice   
( The 12AX7 is not just a light bulb )
He's also a very helpful and friendly guy

MM.

[Paul Marossy]

I personally like the starved tube sound. In all of these starved tube distortion circuits, the distortion is created by a SS device anyways (AFAIK). That is followed by the preamp tube, which is forced to operate in its non-linear region. But, I like the combination. It's like most other circuits, they're not good for everything or palatable for everyone's taste.

The ones that operate at higher plate voltages, like the Matchless Hot Box seem to be highly prized. But, it's a big bulky thing that has to be plugged into the wall...

[Doug_H]

.and then you still have to take into account that the linear region of the tube is severly limmited when running at low voltage..

The BKButler circuit compensates for this somewhat with low gain tube stages (low value plate resistors, etc). Some of the starved tube pedal designs I've seen appear to be pretty awful in this regard- the gain is just way too high. But that's just a hunch. I haven't tried them. (I did experiment with high gain stages with the BK circuit on the breadboard and it sounded pretty bad.) For some reason I remember having difficulty controlling freq rsp with the low voltage stuff. IIRC it was tricky controlling the flab but not sounding too thin. There are limitations to starved plates, as there are with any methods.

Doug

[aron]

aron, this guy makes some killer sounding pedals ...

Aha but it's not all tube. One 12AX7 is not enough for a good medium to full overdrive AFAIK. That one sounds like it's a mix of solid state and tube. Sounds like it would be good though.

[wampcat1]

http://www.national.com/an/AN/AN-32.pdf

[EDIT]: posted here for the newcomers... 

I had forgotten about that -- I remember seeing that on Jacks site a while back.

[puretube]

...I've said for years that at least 50% of the distortion from a classic type (BF / Tweed Fender / Marshall / Vox) amp is from driving the PI.  In fact, if I ever do a tube distortion pedal of any kind, I'll put in something to simulate the PI.  Gotta have it...

Matt Farrow

nice read

[puretube]

Tap the end of a preamp and listen to that tube overdriven sound before it hits the phase inverter and you might be surprised.

imho, this looks to me a bit like: plugging a guitar into a home-HiFi...


mind also, that there are some nice single-ended amps out there...

[vanhansen]

...I've said for years that at least 50% of the distortion from a classic type (BF / Tweed Fender / Marshall / Vox) amp is from driving the PI.  In fact, if I ever do a tube distortion pedal of any kind, I'll put in something to simulate the PI.  Gotta have it...

Matt Farrow

nice read

That is an excellent read. Thanks, Ton.