simple 2 knob hi gain distortion..collaboration?

[deadastronaut]

removed by rob..ha ha...

[tubelectron]

Hi deadastronaut,

Yes : mass is ground... Sorry.

The Dr Boogie schematics looks like if there was here a "tube-to-FET substitution"...  If it behaves like the equivalent tube circuit, the 1st stage gives clean gain, and the 2nd, 3rd and 4th gives a "progressive clipping distribution" between the different stages : it explains many of the inter-stage RC filters and attenuators, in order to obtain touch-sensitive and stable distortion, good sustain and decay. Let me say that it is not so easy to achieve (with tubes), by experience, mainly if you want a very broad range of overdrive while staying consistent at any gain level, and particularly at the low levels.

A+!

[deadastronaut]

removed by rob....of no use...

[B Tremblay]

I don't know if you drew that schematic originally, but I'd appreciate it if builders did not use runoffgroove.com's schematic symbols for other circuits to prevent confusion: http://www.diystompboxes.com/smfforum/index.php?topic=44909.0

[deadastronaut]

i have no idea....it was on google...didnt mean to offend.......!..

i dont remember seeing a dr boogie on runoffgroove?..

[B Tremblay]

No offense was taken.  That thread is quite old (downright ancient in terms of "teh intarwebz") and since this thread is getting a lot of views, I figured it was a good spot to mention it.

[Wild E]

Hi Rob, I now have $.02 to throw into the pot. Experimenting with values might get some good sounds, but it could take a while. I'm a big fan of the fetzer valve article at http://www.runoffgroove.com/index.html to help learn about biasing fet's. It'll sidetrack you for a bit but should help. After you read the article I would say set your source resistor to Idss then vary Vd between 1/2 V+ and Vp untill you get that sweet spot. You can omit the gate cap if you want. As  a note from experience, two fetzer valves set at Vp is too much so I would set the second one closer to 1/2 V+.
I plan to try your 1 fet version as soon as I get the parts I'm missing, it sounds great!

[Wild E]

I think B Tremblay has ESP! He posted while I was typing about his site. too funny.

[deadastronaut]

Hi Rob, I now have $.02 to throw into the pot. Experimenting with values might get some good sounds, but it could take a while. I'm a big fan of the fetzer valve article at http://www.runoffgroove.com/index.html to help learn about biasing fet's. It'll sidetrack you for a bit but should help. After you read the article I would say set your source resistor to Idss then vary Vd between 1/2 V+ and Vp untill you get that sweet spot. You can omit the gate cap if you want. As  a note from experience, two fetzer valves set at Vp is too much so I would set the second one closer to 1/2 V+.
I plan to try your 1 fet version as soon as I get the parts I'm missing, it sounds great!

cheers mike..yeah i need to actually learn that stuff , and put the time in...instead of guessing and trial and error etc..

its such terminology as 'idss' that gets me!..whats that mean?...sorry for dumbass questions!..

i'll read it, and stuff it in my head ok...cheers mike. thanks. rob. (good luck with he 1 fet its great!)..ijust want a bit more gritn gain..(i am greedy)..lol.

[deadastronaut]

I think B Tremblay has ESP! He posted while I was typing about his site. too funny.

yeah must have... ive been told off. ..but fair play to him i didnt know it was his stuff!..

edit: cheers mike.for the link..great article...a must read for a dumbass like me ha ha...

[Wild E]

It took me a couple of times for it to sink in, but I guess I'm a "catch on quick after a long time " kinda guy. Give it a read or two, it will help.

[tubelectron]

Hi again deadastronaut,

would this give hi gain distortion ?..or would it be like the boogie a matter of doing all sections..!..

As you guessed it, I am more specialized about tubes, so my answer is subject to validation, as we spoke about FETs here :

I think that what you've circled is nothing more than a "cascode"-type hi-gain stage (invented in the tube era), but again, it is not designed to give distorsion but hi-gain in order to drive the following stages, which will then deliver the distortion.

It is very difficult to obtain good distortion in a single stage preamp (tube or transistor). You can try to tweak the bias and the voltage, but you will usually obtain a bad fuzz tone, with an abrupt decay (you know what I mean, I guess). If you add diode clipper to that single stage, then you will have more coherent overdrive-sounding distortion (have a trial with the simple-to-die Electra distortion to get an idea), but it is not hi-gain highly distorted pattern as I heard it on your samples. Sorry, you need multi-stage design !

A+!

[deadastronaut]

Hi again deadastronaut,

would this give hi gain distortion ?..or would it be like the boogie a matter of doing all sections..!..

As you guessed it, I am more specialized about tubes, so my answer is subject to validation, as we spoke about FETs here :

I think that what you've circled is nothing more than a "cascode"-type hi-gain stage (invented in the tube era), but again, it is not designed to give distorsion but hi-gain in order to drive the following stages, which will then deliver the distortion.

It is very difficult to obtain good distortion in a single stage preamp (tube or transistor). You can try to tweak the bias and the voltage, but you will usually obtain a bad fuzz tone, with an abrupt decay (you know what I mean, I guess). If you add diode clipper to that single stage, then you will have more coherent overdrive-sounding distortion (have a trial with the simple-to-die Electra distortion to get an idea), but it is not hi-gain highly distorted pattern as I heard it on your samples. Sorry, you need multi-stage design !

A+!

cheers again bruno.

i have just been reading the runoffgroove fetzer article suggested by mike...great article...still got to get my head around some of the
terminology/maths etc ..but i can look that up in the faq's...getting more of an idea on how to go about it though!...valve versus fets etc..
i'll get this j201-386 bugger going if it kills me(and my cat!ha ha ).i know theres a serious kick ass sound to be had out of this combination..somehow...someday....

anyone dabbled with this idea?...rough schematics ...etc....


edit: so roughly im looking at sticking a fetzer.(or 2).into a 386?.....

[Wild E]

edit: so roughly im looking at sticking a fetzer.(or 2).into a 386?..... icon_idea icon_idea icon_idea

Pretty much. There is a suggestion for replacing the buffer stage in the Ruby amp with a fetzer valve in their faq section I believe. But it doesn't have to be an exact fetzer, you can drop the miller cap, add the presence cap and play around with the drain trimpot until you get a good sound. It's a good way to get a starting point instead of throwing in some random values.

[deadastronaut]

edit: so roughly im looking at sticking a fetzer.(or 2).into a 386?..... icon_idea icon_idea icon_idea

Pretty much. There is a suggestion for replacing the buffer stage in the Ruby amp with a fetzer valve in their faq section I believe. But it doesn't have to be an exact fetzer, you can drop the miller cap, add the presence cap and play around with the drain trimpot until you get a good sound. It's a good way to get a starting point instead of throwing in some random values.

yeah am going to try this...looks very much the same as the ruby, but hey i'll  have a go....

its always strange looking at diagrams..with no idea of  the sound they produce..!!!...

and yep...ill try and learn instead of the random value..'ready fire then aim' approach!...ha ha..cheers. 

[caspercody]

Rob,
Another thing to look at is the different schematics for amps you like. Look at the different values on each stage, and between stages. From what I have seen so far, almost all pre amp stages of amps have the same layout. just different values on the resistors, and caps. But within each manufacture, their amps all look the same.

[deadastronaut]

Rob,
Another thing to look at is the different schematics for amps you like. Look at the different values on each stage, and between stages. From what I have seen so far, almost all pre amp stages of amps have the same layout. just different values on the resistors, and caps. But within each manufacture, their amps all look the same.

cool...cheers caspercody...i'll look around..for some kick ass amps.....


i just boarded the fetzer valve (slight overdrive crackle) then i put it into a 386 setup as before..got hi gain..but very soft and mushy...no bite to the note..or definition...
fuzz fans might like it... not my cup'o'tea..(very english ha ha)

the journey continues.......might try the lower gain fetzer version after too...

[davidallancole]

It's kind of funny.  I started a thread because I was building a ruby and it has the fizzy decay just like you guys have mentioned.  I have tried everything to get rid of it but it stays.  I am building it on a breadboard and its given me enough promise to build a proper board and put it in an enclosure.  I hope this fixes the decaying fizz since it sounds like not everybody gets this.  I'll probably put a dip socket in so I can switch chips in and out to try to get the fizz to disappear.

[phector2004]

Rob,

have you considered feeding higher voltage into the FET?

i.e. maybe +18V with a trimmer

I had a variant of the first third of Aron's Shaka express + LED clippers breadboarded, made things LOUD when around 13-15V, with distortion, but nothing fuzzy (unless you starve it). Might also have had a lot to do with the 4558 chip though

Edit: gonna try it this week when my 386's come in

[caspercody]

The fizzle sound on a sustained note is from the 386. I have built many distortion pedals based on Jfets, Cmos, and op amps and the only ones that fizzled at the end of a sustained note was the 386 pedal.

oops, also happened on a Jfet build. but that was because I did not bias the Jfet.