Fulltone OCD

[RDV]

Out of all honesty, I thought it sounded nothing like the OCD.  It sounded to me more like a lower gain version of the BSIAB II

I've got both in my pedalboard and I can tell you that they sound and feel very different. It probably illustrates Bwanasonic's point that it's hard to judge a pedal's merit based on samples.

RDV

[Ge_Whiz]

you know, i would have thought boutique builders would stray away from the standard tubescreamer thing, and explore the world of fets or cmos...i would take a peppermill over a TS anyday...

Yeah, me too. Maybe the IC in the OCD is a fake - and all the real circuitry is inside the pots.    :!:

[stm]

Maybe the OCD is just a kind of RAT clone, as the Full-drive is a TS clone.  Just guessing here.  Can you point to where the picture of the unit is?  Are there any visible TO-92 trannies/JFETs besides the OpAmp?

[dosmun]

The OCD's are "gooped"

[bwanasonic]

Maybe the OCD is just a kind of RAT clone, as the Full-drive is a TS clone.  Just guessing here.

If someone had posted a clip of one of the runoffgroove JFET amp based circuits before the circuits were posted ( say the english channel, or the thunderchief), what would you have guessed the architecture was? Just another TS or RAT clone? How close to actual circuit do you think you would have guessed. My guess is most people would've had no idea. Current guesses at the OCDs architecture based on sounclips are probably just as clueless.

Granted, Mr. Fuller is not known for original designs, but...

Kerry M

[mojotron]

you know, i would have thought boutique builders would stray away from the standard tubescreamer thing, and explore the world of fets or cmos...i would take a peppermill over a TS anyday...

I would too!!

But, actually, I have found that the classic effects are popular because they do a lot of things right. So, if my customer needs a wheel, I build them something shaped like a wheel - that does a lot of other new cool things that they can accept. I think this is how you have to approach making products about 60-70% of the time. The other 30% is spent doing research, and building the more interesting stuff, because that represents the customers for boutique pedals - about than 3/4 want a "better-than" product, the rest want something new and cool....

The funny thing is that, if you have to describe your effect to a shop owner, you have to conceptialize it in terms of what they can sell - otherwise they might not even listen to it. So the shop owner that has just bearly survived 2001-2004 here in the US, is very conservative right now... There are exceptions, and I'm really just getting started - but this is my experience. So, while not trying to clone anything, what I do is approach building products where I take something like a tone control from here, or I use an IC in this configuration from this circuit.... because that method lends itself to building something someone else can promote/sell and the customer would comfortable with the sound/controls..

I don't see this as a compromise, but more of a way to approach supporting the more interesting stuff.. So, although I flame some big pedal makers as much as anyone, in reallity - I'm likely using the same approach they are - I guess I'm just trying to be a little more "custom" than others, and be a nice person along the way....  

[RDV]

Maybe he cloned a Hotcake.

I'm grasping.

RDV

[Ed G.]

My guess: Fet stages with an opamp-based active tone control.

[amz-fx]

If someone had posted a clip of one of the runoffgroove JFET amp based circuits before the circuits were posted ( say the english channel, or the thunderchief), what would you have guessed the architecture was?

I probably could have guessed, and I'm going to explain why...

In 2001, I bought a commercially produced overdrive pedal from a stompbox dealer and then traced the circuit. It is shown below, with many of the component values removed so it cannot be cloned but enough of them left in so you will get the idea:



In 2004, this schematic appeared online:



Amazingly similar, yes? How did that happen? Well, the idea of imitating a specific amp topolgy is not new...  my Mini-Tubes preamp (from 1999) was closely modeled after a Marshall 50w Lead amp, and before that the Fet Muff (1995) had gain stages that are similar to a classic Bassman.  Even further back, Fender, Ibanez and Roland made jfet-based amplifiers with tube-like design characteristics. The idea has been percolating for years.

So...  if a new pedal appears and it  has a jfet emulation of a classic amp model, is it (1) an clone of a circuit found online, (2) a clone of a previously released commercial pedal, (3) independently developed, or (4) none of the above?  Great minds think alike?  maybe, maybe not.

There's no point in speculating... but there are plenty of cool circuits available freely on the Internet to keep everyone busy building stompboxes until the next millenium. Build something!!!  

Best regards, Jack

[bwanasonic]

I probably could have guessed, and I'm going to explain why...

I forgot to say "except maybe Jack Orman" :wink:  

I'd be real interested in knowing what pedal your talking about if it's readily available...

There's no point in speculating...

That was the point I was trying to make.

Kerry M

[stm]

Jack, is it possible that on the 2001 pedal where you drew the two caps on the source pin of the second JFET, they are in fact connected one to JFET 1 and the other to JFET2 ?

Regards,

STM

P.D. When I saw the circuit my first thought was: "hey, this commercial pedal is a clone of the English Channel"; then I realized it is from at least three years before the E.C., so we are talking here about a happy coincidence of taking a VOX amplifier as the basis for a JFET emulator... Makes you think about "fast judgements"  :oops:

[mikeb]

When I saw the circuit my first thought was: "hey, this commercial pedal is a clone of the English Channel"; then I realized it is from at least three years before the E.C., so we are talking here about a happy coincidence of taking a VOX amplifier as the basis for a JFET emulator... Makes you think about "fast judgements"  :oops:

There's obviously no way the 'commercial pedal' could be a clone of the EC. The other way around, on the other hand ....
:shock:

Mike

[B Tremblay]

Here's the story of the FET-based amp emulator circuits released by runoffgroove.com:

Doug Hammond released his Meteor circuit, based on the Trainwreck A9.  He wrote to me last year after the English Channel was posted at runoffgroove.com and said: "[T]he Menatone Top Boost in a Can... ...was my original inspiration to try using CS JFET stages for the Meteor."

Gary Burchett decided to apply the same approach to the Marshall 100W Super Lead.  We'd already been using FETs in the Odie and Peppermill circuits, so it felt like a natural progression.  He shared his results with me and we released it as the Thunderchief.

Based on the overwhelmingly positive reception of the Thunderchief, we realized that there were other amps that might produce interesting results.  Over a few months last year, we developed the Matchbox, Professor Tweed, Eighteen, Supreaux, English Channel, Uno, Flipster, and Umble.  We chose the "parent" tube amp circuits based on popularity among players.

All those circuits use the same approach that Doug first shared with us.  Once Gary and I decided that it was time to move on to other projects, other forum members have applied that "formula" to create their own FET-based amp emulator circuits.

[Steve C]

Here's the story of the FET-based amp emulator circuits released by runoffgroove.com:

All those circuits use the same approach that Doug first shared with us.  Once Gary and I decided that it was time to move on to other projects, other forum members have applied that "formula" to create their own FET-based amp emulator circuits.

I remember this one too:

http://diystompboxes.com/sboxforum/viewtopic.php?t=10986&highlight=miniboogie

[amz-fx]

Here's the story of the FET-based amp emulator circuits released by runoffgroove.com

Just so no one misses the point of the story I posted...  it is an example of how, once you know the "technique", it is easy for two independently produced conversions of an amp to look very similar...  so just as there is a commercial pedal(s) that emulates an AC30, for example, the next guy (ROG) using the technique will likely produce one very similar, even when done on their own...  which also means that if another commercial pedal comes out and it looks like one of the Runoffgroove designs, that doesn't mean it is a copy of it and not developed by the boutique manufacturer...  or it could be copied from the prior available commercial pedal, or designed by one of us behind the scenes, and so on.  My common source jfet amp emulations from the 1990s look much like those posted, with just a few differences.   :shock:    Things are not always what they seem...

regards, Jack

[B Tremblay]

...it is an example of how, once you know the "technique", it is easy for two independently produced conversions of an amp to look very similar...

Exactly!

The archived thread that Steve C referenced is another chapter in this saga.  I have absolutely no recollection of that discussion (the subject wouldn't have caught my eye, but that's another matter entirely) and even if had read it, I wasn't savvy enough to grasp the concept at that time.

When Gary sent the first draft of the Thunderchief to me, I had no understanding of tube amp topology.  My "eureka!" moment occurred when he suggested that I draw out a FET-based stompbox version of an amp.  Then it all clicked into place...

[Steve C]

My "eureka!" moment

I had one of those shortly after that thread when I was looking at some of Jack's schematics and realized he'd already covered it.  So I went on to something else.  My first intention was to make an analog version of a POD (Line 6).  It could be done with all the different amp sims that are out.   :wink:

[WGTP]

I certainly appreciate the efforts of Doug, Gary, Brian, Jack, etc. who brought that technigue to the board, even if it has been done before and in other places, I don't think most of us here knew about it.

It greatly increased my ability to understand tube amp schematics and the differences between real tubes and Jfets.  

It appears a lot of this stuff has been around for decades and most of us are just finding out about it.  I still wish I had known about this stuff in '73 and most of it was around then, if I could have found and understood it.  

We are blessed with some great EDUCATORS hear on the board, I suspect some of them are professionals at it.  

[amz-fx]

is it possible that on the 2001 pedal where you drew the two caps on the source pin of the second JFET, they are in fact connected one to JFET 1 and the other to JFET2 ?

Yes, that's possible...  I'll have to look back at my original sketch.

I remember this one too:
http://diystompboxes.com/sboxforum/viewtopic.php?t=10986&highlight=miniboogie

Excellent link Steve.  That shows how the same technique was discussed in this very forum back in 2003.   I'm sure my boogie conversion looks much like yours.  

One note: no matter how good it is compared to other pedals, a simple jfet imitation of an amp model doesn't quite capture the full essence of a nice tube amp...  there is still something missing.

regards, Jack

[puretube]

:shock: