Good sounding overdriven fets?

[Earthscum]

So, I've played around a little bit with overdriving fets. Obviously, the preceding circuit has a lot of effect on the sound, so I never thought to audition different fet devices... more of sticking a buffer at the end to kill a bit of the high frequency shrill that the filter doesn't quite get. I like MPF102's in this spot... I'm guessing it's mostly to do with how the output impedance interacts with the decoupling cap and volume pot afterwards?

Anyhoo... I had built a clean boost with a MPSA13, jacked up the gain to just below where I could hear it clip, and hooked a Jfet gain (fetzer, to be exact, with J201). I was surprised at the distortion... but it still had that 'transistor' sound to it. I measured my source voltage, and it just happened to be the same as a 1N5818 I was playing with, so I subbed the diode for the source resistor. I got better sounding distortion out of it (and a bit more of it).

So far, every time I've slapped it together, I use a 10k on the drain, and a 1N5818 on the source, and it sounds the same with every J201 I use. Voltages seem to all come in around 4.5-6 without changing Rd... not bad. So is it the diode capacitance that is shaving off that 'shrillness'? Or that the diode Vf changes with the (impedance?) resistance.

So, what I'm wondering is, what are some other "good" sounding fets? I already know about (and love!) CMOS distortions. Are BS170's decent sounding when overdriven? What I have to play with (for about a week and a half) is NTE490, J201, MPF102, CD4007, IRF510. I like the 510 and a schottky or Ge for clippers. Never purposely tried overdriving a mosfet, though. Just used the body diode, or for gain stages.

[jcgss77]

2N5484

I have heard a distortion built around these and it is the best I have heard.  I like high-gain circuits and I liked this one better than the Dr. Boogey recordings.  As soon as I find the link, I will edit this post.

[space_ryerson]

2N5484

I have heard a distortion built around these and it is the best I have heard.  I like high-gain circuits and I liked this one better than the Dr. Boogey recordings.  As soon as I find the link, I will edit this post.

The preamp section of the old Randall RG series amps uses 2N5484's as well.

[petemoore]

  1 well worded question. Approach the component purely from sound-creation viewpoint...all components sound a little bit like components, use the ones you like the sound of !
  So, I've played around a little bit with overdriving fets.
  Naturally.
  Obviously, the preceding circuit has a lot of effect on the sound, so I never thought to audition different fet devices... more of sticking a buffer at the end to kill a bit of the high frequency shrill that the filter doesn't quite get. I like MPF102's in this spot... I'm guessing it's mostly to do with how the output impedance interacts with the decoupling cap and volume pot afterwards?
  Perhaps the way they bias with only 9v's to start with..compared to Jfets that make higher amplification factors.
  Anyhoo... I had built a clean boost with a MPSA13, jacked up the gain to just below where I could hear it clip, and hooked a Jfet gain (fetzer, to be exact, with J201). I was surprised at the distortion... but it still had that 'transistor' sound to it. I measured my source voltage, and it just happened to be the same as a 1N5818 I was playing with, so I subbed the diode for the source resistor. I got better sounding distortion out of it (and a bit more of it).
  Way to experiment with stick a diode in there, sounds like the experiment was a good result getter.
  So far, every time I've slapped it together, I use a 10k on the drain, and a 1N5818 on the source, and it sounds the same with every J201 I use. Voltages seem to all come in around 4.5-6 without changing Rd... not bad. So is it the diode capacitance that is shaving off that 'shrillness'? Or that the diode Vf changes with the (impedance?) resistance.
  Your tests tells it better than my interpretation about questions related to them.
If only the diode for resistor swap makes it sound good, then it is good. There's no diode capacitence that I know of, it is essentially a full-range/DC switch. Transistor frequency response change as a result of circuit alteration [say 'it is now distorting more', or amplifying with a larger X].
  So, what I'm wondering is, what are some other "good" sounding fets? I already know about (and love!) CMOS distortions. Are BS170's decent sounding when overdriven? What I have to play with (for about a week and a half) is NTE490, J201, MPF102, CD4007, IRF510. I like the 510 and a schottky or Ge for clippers. Never purposely tried overdriving a mosfet, though. Just used the body diode, or for gain stages.
   2n5457.
  J201's are easier to get within their parameters for what I like from Fet at >9v, barring Jfet Fetzer article fodder, excellent read / testing fixture that sorts Jfets for what matters to us with small signal effects like this.
 
 

[fuzzo]

I build a fet overdrive , "personal" design , and sounds really cool !

In my opinion the harder thing when you make a gain circuit is the "tone" , you have to find the perfect match you want playing on the frequencies before and after the distortion/Overdrive stage . In general , basses will give you a muddy and fuzzer sound , you have to cut them really early in the circuit to keep the sound clear and clean.

also , take a look at the amp's preamp schematic , can give some good points.

[petemoore]

  Assuming 9v supply:
 Examples of stage[s #1:
 Ge with 7 volt supply = distorts already [or some other way also to do this.
 Jfet with 12v supply = mostly clean [can be done with BJT, Mosfet, Opamp etc.
 Second stage sees stage 1 output, which has been made much stronger by stage 1, so #2 can be made to distort.
 Stage 1 of course has a 'volume control' which is now named 'gain control' because it also adjusts the distortion of stage 2.
 Stage 2 is a Jfet @ 9v. Distorting it's input and/or output may be possible. exp as related to the thread title illicit suggestions: not distorting the input, and lightly distorting the output...to the point where it 'folds' or 'buckles'...[sounds transistorey] then cut back Stage 2 input using stage 1's volume/gain'' control.
 Because 'tube-ey' has such a positive connotation, I can't use it, but ime, tubes pushed real hard at any 1 point do about the same type thing as any other component...still tube-like and all but too much input or expectation of output on ANY type of component makes it sound ''ey'' -ey, or...too much like itself having trouble processing signal for some reason. We'll call the over-distorted Jfet or tube "Transistor-ey" just to make the point that 1 stage hammered super hard with massive input or overly-restricted by limited powersupply makes 'rough' sound.
 Stage 1 and stage two somehow sound smooth now.
 We put a Mu amp in stage 2 and try that out, or a CMOS...
 Or move on to stage 3...similar deal to stage 2 exept the 'third multiple' makes stages 1, 2, and 3 more complicated to make a 'well balanced' gain structure..where none of the transistors is 'folding' or 'buckling', to further illucidate by using example of confused-ing terminology..keep it 'tube-like'...lol.
 Ok:
 9v supply for stage 1, uses Jfet which has no input distortion, perhaps touches of output distortion.
 Say 12v for stage two, we put a voltage regulator on it's supply so we can move the supply voltage up/down, this gives us a bit more room to play with the swing room/distortion characteristics of the output. We put a pregain on it's input in case we want to adjust some other stage 1's output [try Ge for tone-worth experiment, Cmos for Smooth disto or whatever...use two stage/stage 1 approach...buffered input and then voltage gain stage.
 Frequency shaping starts with stage 1 or 2 ?, adding passive components to alter frequency response of course alters gain of said frequencies.
 What goesintacomesoutas...
 I did all the experiments on perf-bread, using various stage 1's including compression. I found having most of the connections soldered solidly made it easier to keep reliablity up while doing stage circuit altering experiments, so some of the stages soon went into boxes to drive the other stages which I had on the testjig as perf-breadboard type circuits...instead of one big sprawling thing...also allowed plugging in various block diagram configurations [Ge>Jfet>Jfet] or {Jfet @8v>2xJfet@9v supply] or {Jfet @3v supply>9VJFet>12vJfet].
 It's easy to get out of the 'sweet zone' parameters in any of the stages, and 2x as difficult to determine which of the latter 2 [or more] stages after stage 1 is making 'transistorey' tone.
 The concept of stepping voltages [as suggested^] is where the new Jfet designs and discoveries will be greatest. Probably because Jfets vary, stepping voltage is a challenge, increasing the # of gain stages blurs the 'vision' of where 'this' distortion occurs [thats the whole idea concept, there is no 1 transistor doing all the work].
 That said, once all the hurdles have been crossed, and the ''large ball goes in the small basket from a good distance''...it's probably worth all the extra set-up and extensive experimentation if taking Jfets where Jfets have never gone before is the goal.
 The concept being similar to what 'rectifier' amps do, multiple stages and stepped supply voltages.
 Otherwise there are skads of documented circuit/variation experiments for single supply 9v, 12v and 18v jfet operations, 5v CMOS was very tone-worthy in experiments but they all burnt [on me.
 
 

[anchovie]

CD4007

I've found these to be a bit fizzy, nothing that a low-pass filter after the clipping stage can't cure though.

[edvard]

What you are doing with the diode is the same thing you'd do with a resistor/electrolytic cap at the source.
It's just holding a voltage at the JFET source terminal; in this case, the voltage is the V_f of the diode.

I'm wondering if the JFET's internal capacitance is what is taming the shrillness, or if it's simply that JFETs distort the signal differently compared to transistors. 

Either way, I like JFET overdrive designs because it's actually difficult to pull raging gain out of them without using multiple stages, making it less tempting to constantly 'up the dose' with op-amp designs until you are left with a distortion instead of the nice tone-ful overdrive you set out to build.