"diode-less" overdrive ???

[frank_p]

Angry beard ?

[liquids]

I do not have in favor the mos-fets, finding that they sound inexplicably somewhat harsh and uneven harmonically on the trials I have made, the last one being a clone of a traced-from-an-original MG "Sexy Drive" pedal (which uses cascading J201 and 2N5457 fets). But it would be time for me to start new trials on that field...

A+!

I happen to agree with you about mosfets - it's not so much a filtering thing, but in the way they recover from clipping that I find harsh.

Re-try jfet mu-amps, SRRP jfets, and the like.  Don't be afraid of strong filtering - cut bass pre-clipping, post-clipping active bass boost & active treble cut.

[liquids]

Also wanted to note that - since you seem to love the sound of warm tubes - I've done a fair amount of work with tube preamp designs (i.e. soldano, Dr Z, etc) minus any marshall/fender/vox type tone controls, alongside jfet distortion/overdrive.

I've typed this out before but, I found that cascading even tube stages for clipping and then dialing it down to guitar-output strength of signal (like a pedal) and running it into an amp, it's unsatisfactory...by itself.

Cascading tube stages benefit from needing at least two stages (at standard amp voltages) before any clipping occurs, typically with a passive control between them to dial in clipping. Also grid resistor sare typically already there on the stock schematics, and they are taming down treble, keeping the grids from getting all unstable and nasty when driven hard.

Most jfet designs ignore these differences.  They're different beasts surely, but fets can clip easily at the sight of a single guitar note when producing notable gain. They also produce a lot of highs happily, if you don't tame it down just the same as tubes, but few designs make use of any significant resistance at the gate of the device.

I found that cascading tube stages run like a preamp/pedal benefitted greatly from active EQ post-clipping, when run into an amp's input like a pedal is, just as the jfet pedals I work with also benefit from it.  

Semiconductors are a lot simpler to work with when it comes to stompboxes, so I stick with them for distortion/OD!

With semiconductors - don't be limited to 9v - just like with tubes, jfets tonality and the character of clipping and gain changes as V+ goes up or down (IMO).

[WGTP]

I will respectfully have to disagree with you about Mosfets.  To me they have a glassy, edgy, (Zvex says Blizzardy) "Character" to them that is more like tubes really sound than the smoother Jfets.  For some reason I have had trouble getting along with Jfets until recently, unless they were in a Mu/Srrp.  My current bread board has a mix of BS170's and J201's and may be the best yet.  

[oh7hhi]

Hi!

Maybe OP should try the Blackstone Appliances Mosfet Overdrive.
I build one for a friend two years ago and it's still in his board .

Very bluesy and singing tone, someone could say "Dumble-like"...

OK - I see (thanks !) - it's more or less an improved Hot Tubes / Tube Sound Fuzz design. Circa 20 years ago, I have been given a mint Hot Tubes from EH (that I sold stupidly for peanuts) and I remember that it worked better on organ than on guitar...

I do not have in favor the mos-fets, finding that they sound inexplicably somewhat harsh and uneven harmonically on the trials I have made, the last one being a clone of a traced-from-an-original MG "Sexy Drive" pedal (which uses cascading J201 and 2N5457 fets). But it would be time for me to start new trials on that field...

A+!

http://www.youtube.com/watch?v=dZ-KnOZvFP0

Doesn't sound harsh to me ... But to each his own .

[liquids]

No...doesn't sound harsh.  Sound muffled and honky, primarily.       But the OKKO diablo is JFETs and I find it can sound pretty awful, just the same...

I should say that I was nitpicking about MOSFETs...I think diode feedback loop clipping recovers from clipping in a harsh manner.  But TS's don't ususally sound harsh to me in a vacuum...

I'm speaking of the subtleties of what I hear with clipping, naked without filtering. 

I generally prefer JFET mu-amps/srrp configurations, but I also think the amount of high end they can sometimes produce at above 9v is ridiculous without filtering...yet I happen to like the way they clip and recover from clipping under specific configurations, and work around the things I dislike.

I'd also simultaneously say that with the right filtering (which is the critical element to the sound of clipping IMO), one can probably make nearly any device configuration sound favorable....again, my preference for JFETs over other devices is on a personal and subjective level...and ask me again in 5 years. 

I personally stopped working with discrete MOSFET clipping after I sold my Zvex BOR, then built a BSIAB and then breadboarded a BoR clone...I came away feeling like cascading discrete mosfet stages for clipping was nice when clipping, but the recovery was harsh/abrupt.

It was years ago, I've learned quite a lot since then, and I may have even screwed something up, but that was what I felt at the time, all other variables NOT being equal.       Sorry if I hurt anyone's feelings by saying something less than flattering about MOSFETS. 

[tubelectron]

Well...

1 - I always have some problems with sound description vocabulary... Sorry ! About Fets circuits I tested, I found that the harmonics sounded uneven, a kind of "bad ringing, bad frequency beat", like with the Marshall BluesBreaker pedal 1st issue (TL072) that I had (and got rid), something at the opposite of what you hear with a RAT (LM308N), a DOD250 (4558), for example... I should have made and record spectrum analysis at the time, but I was lazy !

2 - The trials that I have made with Fet Qs or ICs were sonically unsuccessful, and the few Fet-based pedals I had in hands were not satisfactory : Marshall BluesBreaker 1st edition (TL072), two boutique MG pedals (with Fet Qs). So I draw the conclusion that Fets didn't matched my playing, and that it needed further trials to see if a better behavior could be achieved. In the meantime, I found that µA741, LM1458, RC4558, LM308 gave more convincing - or rewarding - results, again regarding my playing and gear. So maybe I drawn too fast conclusions !

Also wanted to note that - since you seem to love the sound of warm tubes - I've done a fair amount of work with tube preamp designs (i.e. soldano, Dr Z, etc) minus any marshall/fender/vox type tone controls, alongside jfet distortion/overdrive.

I've typed this out before but, I found that cascading even tube stages for clipping and then dialing it down to guitar-output strength of signal (like a pedal) and running it into an amp, it's unsatisfactory...by itself.

Cascading tube stages benefit from needing at least two stages (at standard amp voltages) before any clipping occurs, typically with a passive control between them to dial in clipping. Also grid resistor sare typically already there on the stock schematics, and they are taming down treble, keeping the grids from getting all unstable and nasty when driven hard.

Yes. I can't agree more, since I concentrated on tube circuits design for 30 years... And I can tell that it is very easy to design bad-sounding tube gear, despite the so-called "Tube Magic" !
Doide clipping is an efficient facility...

Nonetheless, I am planning to try the preamp section of my (wonderful) MKIIA Boogie tamed to guitar level and connected to the input af one of my SF Fender, In order to see if I benefit from the MKIIA overdrive/boost/lead qualities applied to a Fender - the goal being to built that section in a pedal if it sounds as expected... Maybe I will come to the same conclusion as yours : unsatisfactory ! Hope I will find the time to do that soon...

I have made some years ago tube based overdrive pedals combining diode clipper, more or less inspired by my Westbury W-20 "The TUBE". The results are satisfactory, but I must recognize that it's less practical than a 9V battery powered pedal, for a sonic result which is not tremendously superior :





A+!

[WGTP]

No problem with different opinions.  I actually use all methods myself.  I have a breadboard with op-amp clippers (I seem to prefer using 2 stages of LED's for the added dynamics and blinking lights, also Real Mosfet clippers

http://www.aronnelson.com/gallery/main.php/v/WGTP/Moster.jpg.html?g2_imageViewsIndex=1)

one for CMOS distortions and the one for Jfet/Mosfet experiments.  Mu/Srpps Rock, as do the Obsidian, Blackfire and Vulcan of Joe Davisson.  Live I use a a 22w. all tube amp.  Not much of a Fuzz head.  Love it all if it sounds good.  

[DavenPaget]

No problem with different opinions.  I actually use all methods myself.  I have a breadboard with op-amp clippers (I seem to prefer using 2 stages of LED's for the added dynamics and blinking lights, also Real Mosfet clippers

http://www.aronnelson.com/gallery/main.php/v/WGTP/Moster.jpg.html?g2_imageViewsIndex=1)

one for CMOS distortions and the one for Jfet/Mosfet experiments.  Mu/Srpps Rock, as do the Obsidian, Blackfire and Vulcan of Joe Davisson.  Live I use a a 22w. all tube amp.  Not much of a Fuzz head.  Love it all if it sounds good.  

Nice doing you have there .
I generally use my 30W dsp amp for playing and a buffered input box into a regular pc speaker ( not really regular , it's been spruced up . )

[Gus]

Here is a simple low gain with EQ circuit.  Sometimes this sounds good with certain guitars and tube amps


Sometimea an overdrive is best when the amp starting to breakup and you push certain frequencies just a little harder.  Try an EQ between the guitar and amp for an overdrive

[tubelectron]

Gus,

Does this simple low gain with EQ circuit clips by itself, or is it only a tailored frequency booster ?

A+!

[Gus]

tubelectron

I just did an LT spice sim of it.  The sim shows about  +15dB max gain so more of a tailored frequency booster to give a tube amp just a little more drive.  I you were to try it make C2 a 1uf film.  It is an early version of the circuit I have changed some values and should build the next version to test it.
I few friends have the first version and it can sound good with certain guitars and amps often lower powered tube amps.   Sometimes it is not what people want.

[tubelectron]

Thanks Gus,

I think that I'll have a re-try of a "clean" booster (your version in the post above) on my Deluxe Reverb, but I am pretty sure that it won't fill the bill unless I play at loud volume (clean/crunch limit). In that field, the compromise I found was that : a gentle boost - overdriver to help the amp playing at medium level (but still clean) to pass more easily the frontier of dirtyness for a bluesy tone, without increasing the overall volume level too much, the amp being typically a DR or a PR.



I have built one dozen of them (in tin boxes !) for friends, some of them without the OVD control. I never used it too much, in fact, because unlike them, I mostly play in a big Soul and Rhythm'n'Blues band, where I found that the sound requirements are more demanding than in a smaller blues band.

A+!