New at runoffgroove.com: Professor Tweed

[B Tremblay]

One question: Does the tone control give a wide range from bright to dark? (I suspect it does) because playing a strat through a super reverb, I find a lot of pedals too bright/harsh. I always have to add extra tone filtering and I don't usually like the end results.

I used a Tele bridge pup extensively when we were developing/testing the Professor and found the Tone control to have a very useful range.  At the lowest Tone setting the punch is still present, but much smoother than the usual twang.  The treble bleed cap preserves brightness at the low gain settings as Mark Hammer described earlier, so it doesn't get really dark when playing clean.

[Mark Hammer]

imho a presence control plays its best role, when deriving the F.B. signal from the actual power output at the speaker...

I certainly can't speak from experience, but I would lean towards your view, if only because the output transformer and speaker play a factor in what it is that is being fed back through the loop.

As to the properties of the tone control, call me crazy, but in the 28 years that this has been my main amp, I can't think of many times where I found the tone control a shortcoming on how I wanted to sound.  Indeed, sometimes I wonder if the pot hasn't rusted in place because I simply don't move it most of the time.  On the other hand, I'm the sort of guy who likes to have more flexibility in tonal control on the guitar itself, and via pedals.

Still, that being said, there have probably been a number of FET-based projects posted, involving mu-amps or other topographies, where insertion of a tone control like this around a gain/attenuation pot earlier in the circuit might be interesting and worthwhile pursuing, particularly insomuch as it permits for variable treble accentuation at lower drive settings.

[RDV]

Yes. I'd like to place an order please? I'd like a one of your lovely J-Fet simulations please? One of my Supro "Super".

Here's the schem file(thank you schematic heaven!):
http://www1.korksoft.com/%7Eschem/bargainbin/gretsch6150.pdf

Please & Thank You!

RDV

[B Tremblay]

Yes. I'd like to place an order please? I'd like a one of your lovely J-Fet simulations please? One of my Supro "Super"

The coolest feature of Doug's method is the ease of converting to FETs.  Read the Professor Tweed article for the technique.

Take a stab at it on your own and if you get stuck, we'll help you out.

[Doug H]

Well, this isn't really "my method" or anything but I appreciate all the kudos guys.  I was inspired by Jack's use of the minibooster with the mini-tubes, as well as his use of JFETs in the Fet-Muff, and Brian Mena's work among others.  In all honesty the Meteor was a hack, just a brute-force approach of blindly subbing fets in a tube circuit (at 9v) to see what would happen.

My only comment about the NFB loop is I would think you would take it from the "speaker" (your output LPF).

But man, that sure sounds tweedy! I have some soundclips of a strat through a 5E3 and hear some similarities.

Nice work!

Doug

[B Tremblay]

Regarding Supro amps, I should probably mention that we've already developed a terrific-sounding FET emulation of my Supro 16T, which is not too different from the Super.

We've been debating whether to release it; we don't want to be over-saturating the market with emulations, especially since the 16T and Princeton amps share a similar circuit and tone.

Our goal is not to be the leaders in the FET emulation field, but rather to help teach the technique to the DIY-FX community with examples such as the Thunderchief, Matchbox, Fetzer Valve, and Professor Tweed.

[puretube]

wanna know a secret?

[B Tremblay]

Well, this isn't really "my method" or anything but I appreciate all the kudos guys.

They're quite well deserved, since your "brute force" approach just happens to work beautifully!

I hope that more people will apply the technique to the vast number of tube amp schematics now available on the web.  Creating a pedal version of a favorite amp (or using various stages from different circuits to develop an original design) is much less mysterious and daunting thanks to your work.

[Ed G.]

hmm...can you say Dumble???

[RDV]

wanna know a secret?

YES!

RDV

[Phorhas]

mmmm... Dumble...

I had an Idea: take a range master and stick it before a fetser-valve type thingy right to a mini-booster type thingy... to emulate an over-driven-amp-with-a-hot-pocker-stuck-up-it's-*ss...

Blues Braeker ClapTone?

Well, what ya say? I'm so busy right now so I can't seem to find the time and check it out... if it tickles anybody's fancy, be my guess...I wonder what that will sound like...

[petemoore]

The Fetzer will probably behave Jfet Smooth, once it's wired correctly.
 The Rangemaster thing...not quite so fast, you might want to work with this one for a time er two.
 Messing with bias, trying out different transistors helps find stable bias and tone.
 These boosters are good fun stages to have around and experiment with. 1 2 3...Distortion, you can always separate them if they're not getting along, two on one board usually do ok.
 Problem is with a PNP, it's meant extra battery for me.

[Gary]

hmm...can you say Dumble???

Ed,

We worked out a draft for the '97 Dumble ODS and an earlier '70s model.  There's a lot of jfets in there and it will require a bigger board, but I'd love to see if you take it somewhere.  I don't think we ever breadboarded it.  Since these things seem to work right off the bat, I'll bet you can get it going.  Please let us know if you do.

puretube,
What is that secret?  The curiosity is killing me.

On the subject of where the feedback loop is taken from, I tend to like the sound better if the feedback is taken from the last coupling cap.  For some reason, it seems more "lively" than going straight from the drain.  As Doug says, you can go from just infront of the master volume control.  That setup seems to sound a little thicker to me, which can be good.  We've stuck with tapping from the output side of the last drain cap for no particular reason.  There is a lot of room for experimeting here, as you are crudely trying to emulate the output transformer and the effect of the speaker(s).  There are arguments that can be made for taking the tap from just about anywhere.

[Doug H]

mmmm... Dumble...

I had an Idea: take a range master and stick it before a fetser-valve type thingy right to a mini-booster type thingy... to emulate an over-driven-amp-with-a-hot-pocker-stuck-up-it's-*ss...

Blues Braeker ClapTone?

Well, what ya say? I'm so busy right now so I can't seem to find the time and check it out... if it tickles anybody's fancy, be my guess...I wonder what that will sound like...

3-4 yrs ago there was a diy-er that designed a pedal with a si rangemaster driving a couple miniboosters. The web site is gone and I can't remember the name of it but it had the word "ballz" in it.  That's all I remember, I used to have the schem but I don't think I do anymore. Anyway, he had a few sound clips and it sounded pretty nice from what I remember.

Doug

[Mark Hammer]

T'wer the Ballz Booster by Alexandro Charissis, and I'm looking at it right now.

[Doug H]

T'wer the Ballz Booster by Alexandro Charissis, and I'm looking at it right now.

That's it!

Doug

[Johan]

this method seems very interesting, perhaps I should make a version of MY favorite amp..Orange Graphic-80 ( think early AC-DC )
I remember seeing a schematic for Trace-Elliot a few years ago doing it this way to make an amp with two channels, Marshall and Fender style. I didnt reflect on it then, but obviusly I should have... allthou they run their amp at 24volts ( I think ), the aproach was very simillar.
I think the trace amp was called either Speed-twinn or trident..I also think I have the schematic at work...

Johan

[keko]

All around the article you talk about using MPF102´s.

How does it compares to 2N5457? They are the only ones I've got around, so, is it worth it building it with those and only those in mind?

Great release...again!

[B Tremblay]

How does it compares to 2N5457? They are the only ones I've got around, so, is it worth it building it with those and only those in mind?

The circuit has been tested with 2N5457 and the results were quite close to using MPF102.

[Torchy]

While on the subject of "pet" amps, anyone got/investigated the Hughes&Kettner Tri-Amp ??

Saw it demo'd by a guy called Thomas Blug (?) and sounded awesome ...