Fulltone - OCD  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.

Postby JHS » 13 Sep 2007, 14:34

Pulldown Rs suck treble and kill dynamics, it's a fact. Take a simple FF, OCD or SHO and stuck a 1M, 4,7M 10M between the input wire and ground and listen to the tone. I can hear a audible difference, no matter what guitar I plugged in and when the amp is set up for a clean sound.
On a already distorting amp it's less audible but the sound is more undefined and the string-to-string definition is not as good with a pulldown R as without it.

The absence of a the pulldown R in the OCD is one reasen for the clear, cutting highend response.

The LF353 sounds nothing like a 082 and the same circuit-layout means nothing. An old JRC 4558D has the same layout as a new NJM 4558D but the sound is different due to modern production technologies. The JRC072BD sound different compared to the stock JRC072 due to it's lower slewrate, both have the same internal layout.

JHS
JHS
Cap Cooler
 
Posts: 484
Joined: 14 Jul 2007, 12:20
Has thanked: 0 time
Have thanks: 3 times

Postby MKB » 13 Sep 2007, 15:03

analogguru wrote:
IMO what you are paying Fulltone for is the ears and knowledge to combine such tiny mojo effects together to make a superior whole.


No....: You pay for that that you are so stupid to believe the mojo-lies which are spreaded around and that you believe this Mojo-unit will improve your skills.

When you listen to zeppellin, purple, moore, chaquico, knopfler: they sounded without fuller or zvex.... they sounded much better than 99,99 % of what I listen today WITH Zvex, Fuller & Co (and clones).

analogguru


All I know is the OCD has the best transparency and dynamics by far than any other distortion or overdrive pedal I've built or heard since I started building and playing in 1981 (the year I received my electronics degree). And he has a few mods in it, in particular component choice, that I haven't read about since reading the internet effects boards in 2000. His tricks took the stock VLOD (which was flat and bad sounding) into another realm altogether. He has the ears and perception to design and build such a thing, and that is to be respected. He doesn't advertise any of his mojo tweaks, so hype doesn't have anything to do with it, at least in my case.

I would have bought one, but there are no dealers anywhere around here. I actually built one to see if I would be interested at all, and the one I built turned out so good that I now have no interest to buy one. I can't imagine a real one would be any better.

Why can't we just say he did a great job on this one, regardless of what we think of him?
MKB
Breadboard Brother
 
Posts: 92
Joined: 06 Sep 2007, 13:03
Location: USA
Has thanked: 0 time
Have thanks: 0 time

Postby analogguru » 13 Sep 2007, 16:07

An old JRC 4558D has the same layout as a new NJM 4558D


except one additional diode in the new one.....

Why can't we just say he did a great job on this one, regardless of what we think of him?


1.) I don´t know how much he contributed to the design, maybe it was even an employee like with the Fat-boost.
2.) I don´t have a problem with the possible fact that it should sound good or perfect.... The Klon worshippers will have it, or the Maxon OD-820 worshippers or the Zvex ...or the... or the...
3.) I only listened to some sound-samples which I found on the web of glorified pedals and sorry, they sounded like shit compared to the mentioned guitarists. Maybe this sharp, dirty, muddy undefined "punky" distortion is fashion now, but for $250,-- or more I am awiting a "one-trick-pony" which sounds much better, especially when played through a tube-amp.

analogguru
There´s a sucker born every minute - and too many of them end up in the bootweak pedal biz.
analogguru
Old Solderhand
 
Posts: 3285
Joined: 26 Jun 2007, 14:58
Has thanked: 0 time
Have thanks: 116 times

Postby JHS » 13 Sep 2007, 16:34

The OCDs and most of his FXs are perfect voiced for any kind of vintage guitar and most NM amps, the downside, they are sounding worse with middy and compressed highgain PUs like a SH4/11 and most DiMarzio PUs or newer high gain amps.

Landgraff has an excellent ear too, all of his boxes sound sterile on low volume but on stage level his DOD cuts through, the sounds gets lost after a few meters with a FD-2 or other TS-clones in front of an amp.

JHS
JHS
Cap Cooler
 
Posts: 484
Joined: 14 Jul 2007, 12:20
Has thanked: 0 time
Have thanks: 3 times

Postby DougH » 13 Sep 2007, 21:44

I heard an OCD in person and it didn't distinguish itself one way or another to me. Just another distortion pedal... The construction however was very good and this is how Fuller distinguishes himself AFAIC.

I use 1M pulldowns on all my builds and have never heard an audible difference other than stopping the switch pop. Never... And I've tested it on the breadboard every time I design something.

I don't know how accurate any of the schematics shown thus far are. But they appear to me to be more of an accumulation of tricks and "mojo-itis" than any kind of sound engineering.

In general I would say there are basically two paths you can take when you design a pedal. One- start with a goal in mind, what you want to achieve as well as a basic idea of the types of components you want to use. Then you design the circuit using design principles that have been used since the dawn of electronics. After that you put it on the breadboard and tweak the hell out of it until you hear what you want to hear.

The second method is to take an existing circuit and immediately throw it on the breadboard. Then you basically step off into the ether and throw every trick you have in the book at it. Hit it with a rubber chicken a few times, throw some fairy dust on it, and get out the black cat bone. Then when you arrive at something you like, you are there, man. Voila- your newest creation. And I guess you call that "art" or something- whatever...

And of course there are infinite shades of gray between the two extremes. But the more boutique schems I see, the more I see them leaning towards Method 2. Otherwise I don't see how you account for the low ESR film cap in parallel with the electro filter cap trick in a friggin' 9 volt circuit, for example... And the endless scrutinizing and agonizing over cap types in a 9v circuit. And on and on...

I just don't have much respect for Method 2 "designers" or their "design process". It's certainly not a very straightforward method. I know I can get as much or more bang for the buck with far less components using Method 1.

And BTW... Probably the reason it doesn't sound good with the gain past 12 o'clock is due to headroom exhaustion. The simple fix is to design less gain into the op amp stage. And if a builder doesn't understand that fix, he shouldn't call himself a "designer"...

For this message the author DougH has received thanks: 3
juice2 (27 Apr 2018, 07:37), modman (22 May 2012, 10:06), premiumplus (07 Mar 2014, 17:16)
DougH
Transistor Tuner
 
Posts: 1104
Joined: 18 Aug 2007, 05:53
Has thanked: 4 times
Have thanks: 23 times

Postby Jim777 » 13 Sep 2007, 22:19

The OCD has a 470k input resistor. So why not 1meg or higher? Probably because that's what's in the voodoolab. You could easily raise the value of that resistor and I'm sure you would hear a difference. How would a 10meg pulldown resistor turn it to mud? Are you saying it has a different effect because it's on the other side of the input cap? 10meg-470k there's a big difference. I'm pretty sure you can hear the effect of it so how far do you take it? The best thing would be to have active pickups or preamp in your guitar. You may like that or you may not.
Jim777
 
Posts: 32
Joined: 20 Aug 2007, 03:21
Has thanked: 0 time
Have thanks: 0 time

Postby Jim777 » 17 Sep 2007, 00:49

OK back on topic....I havn't tried this internal diode mosfet thing yet does it sound any different to a bog standard diode?
Jim777
 
Posts: 32
Joined: 20 Aug 2007, 03:21
Has thanked: 0 time
Have thanks: 0 time

Postby briggs » 18 Sep 2007, 13:36

It isn't a "rule", just a request jg.

I breadboarded JHS's version the other day. It sounded nice. ~Not my favorite OD sound though.

EDIT: I'm looking at the wrong scheme :roll:

AG: Can you explain to me how the blocking diode in the shaka clipping arrangement effects the sound? I'm clueless?
Last edited by briggs on 18 Sep 2007, 13:39, edited 1 time in total.
Image

I am Klon.
User avatar
briggs
Tube Twister
 
Posts: 1997
Joined: 12 Jul 2007, 11:02
Location: Breaking into Heaven.
Has thanked: 30 times
Have thanks: 124 times

Postby briggs » 18 Sep 2007, 22:18

How is the HP/LP switch working here? I'm overlooking something I know...
Image

I am Klon.
User avatar
briggs
Tube Twister
 
Posts: 1997
Joined: 12 Jul 2007, 11:02
Location: Breaking into Heaven.
Has thanked: 30 times
Have thanks: 124 times

Postby MKB » 19 Sep 2007, 12:58

briggs wrote:How is the HP/LP switch working here? I'm overlooking something I know...

It basically changes the low end cutoff of the RC filter formed by the switched series resistors, output pot, and output coupling cap. The resistors are parallelled when LP is engaged, meaning Low Pass perhaps? That's the easy and obvious answer.

I suspect there might be some other things going on, like maybe some interaction with the op amp output impedance, or some effect with that unusual tone control. I use mine in that position all the time however, sounds more like an amp IMO. The switch has a real but subtle effect, I like it.
MKB
Breadboard Brother
 
Posts: 92
Joined: 06 Sep 2007, 13:03
Location: USA
Has thanked: 0 time
Have thanks: 0 time

Postby DougH » 19 Sep 2007, 15:38

MKB wrote:
briggs wrote:How is the HP/LP switch working here? I'm overlooking something I know...

It basically changes the low end cutoff of the RC filter formed by the switched series resistors, output pot, and output coupling cap.


If you were tapping the junction between the coupling cap and those resistors for the output, that would make sense. But according to the schematic, those resistors form a LPF with the tone control cap. Which means the "peaky" comments don't make any sense at all to me.


The switch has a real but subtle effect, I like it.


"Subtle" is the operative word here I suspect.

And if you're part of the "mojorific" clique you "get it" and will exaggerate its usefulness. (Not you personally, MKB- just making a general statement...) And if you don't hear it, you just don't "know tone", "have toneful ears", etc... That's the way this cult of personality stuff generally works...

I'm old school: If I flip a switch or turn a knob I expect to hear a change that is direct and unmistakable- not "well I think I sort of heard this", or "maybe if I had spent more $$ on my amp I would hear it" or etc.
DougH
Transistor Tuner
 
Posts: 1104
Joined: 18 Aug 2007, 05:53
Has thanked: 4 times
Have thanks: 23 times

Postby DougH » 19 Sep 2007, 17:56

Re. Passive MOSFET clipping:

The 2n7000 protection diode has a fwd voltage of ~.88v according to the datasheet. This is roughly in the neighborhood of a typical Si diode like a 1n914 at around .7v. I have not compared the two and don't know if there are actual differences in the sound. There *could* be due to comparative softness of the knees, etc but I haven't tried it.

Someone mentioned Aron's Shaka as an example. Understand, the Shaka used the IRF510 or IRF520 which is a power MOSFET, not a small-signal MOSFET like the 2n7000 or BS170. The IRF510/520 protection diode has a fwd voltage of ~2.5v. From my recollection, the IRF510 diode clipping sounded more pleasing to my ears than the typical Ge or Si diode string.

Also, the first person I was aware of that suggested passive MOSFET clipping in a pedal circuit was John Greene (jg on here). Aron reversed the polarity as he preferred the sound of the protection diode clipping and implemented it on his Shaka 3. I got out my Shaka a few days ago and tried it for the first time in a while. It's really a nice sounding overdrive. I would suggest to anyone interested in a good, low noise, no-nonsense overdrive to give it a try.
DougH
Transistor Tuner
 
Posts: 1104
Joined: 18 Aug 2007, 05:53
Has thanked: 4 times
Have thanks: 23 times

Postby lohstah » 20 Sep 2007, 08:37

the effect of that switch is not subtle at all if you ask me...
set to lp, the pedal has gobs of low end, as opposed to hp.
no mojo thing here. :wink:

cheers,
lohstah
lohstah
Solder Soldier
 
Posts: 238
Joined: 08 Jul 2007, 21:08
Has thanked: 202 times
Have thanks: 97 times

Postby DougH » 20 Sep 2007, 12:35

lohstah wrote:the effect of that switch is not subtle at all if you ask me...
set to lp, the pedal has gobs of low end, as opposed to hp.
no mojo thing here. :wink:

cheers,
lohstah


My comments were directed at the posted schematic, which I can't vouch for the accuracy of.

Assuming it's right- I'd have to try it on the breadboard. I'm having trouble believing I'll hear a difference in ~20k of Zout, esp with a 500k volume pot hanging off the end. Although I would expect it to react with the tone control cap in the opposite fashion of what has been described. I'll try simming this and see what it looks like. Maybe there's something I'm missing?
Last edited by DougH on 20 Sep 2007, 13:49, edited 1 time in total.
DougH
Transistor Tuner
 
Posts: 1104
Joined: 18 Aug 2007, 05:53
Has thanked: 4 times
Have thanks: 23 times

Postby DougH » 20 Sep 2007, 12:42

One more thing I noticed in the posted "OCD" schematic: The 4.7M hanging off the volume pot wiper on the output is completely superfluous. It serves no purpose at all...

Another example of too many components, and some which do nothing...
DougH
Transistor Tuner
 
Posts: 1104
Joined: 18 Aug 2007, 05:53
Has thanked: 4 times
Have thanks: 23 times

Postby DougH » 20 Sep 2007, 13:32

Here's a couple frequency plots of the "OCD" output stage in "HP" and "LP" mode to compare. I ran an AC simulation in SIMETRIX, swept from 10Hz to 20KHz, 3v peak input signal (with a 4.5v DC bias) into the output stage, fixed the tone control pot at 5k, left out the 56k to simplify, etc... R3 was changed from 33k for "HP" mode to 13.2k for "LP" mode to compare.

http://s14.photobucket.com/albums/a320/Doug_H/Analysis/



It does pretty much what I expected. The resistor reacts with the 47n tone control cap and in "HP" mode rolls off more highs. Yawn...
DougH
Transistor Tuner
 
Posts: 1104
Joined: 18 Aug 2007, 05:53
Has thanked: 4 times
Have thanks: 23 times

Postby indyguitarist » 20 Sep 2007, 13:48

DougH wrote:The second method is to take an existing circuit and immediately throw it on the breadboard. Then you basically step off into the ether and throw every trick you have in the book at it. Hit it with a rubber chicken a few times, throw some fairy dust on it, and get out the black cat bone. Then when you arrive at something you like, you are there, man. Voila- your newest creation. And I guess you call that "art" or something- whatever...



:lol:
indyguitarist
Resistor Ronker
 
Posts: 378
Joined: 11 Jul 2007, 03:25
Has thanked: 0 time
Have thanks: 162 times

Postby cbriere » 20 Sep 2007, 13:54

SW has effect on the high end only.
I simulated with TONE at max (20k) and 5K.



http://i77.photobucket.com/albums/j69/c ... ONE20K.jpg


http://i77.photobucket.com/albums/j69/c ... TONE5K.jpg
cbriere
Breadboard Brother
 
Posts: 121
Joined: 24 Aug 2007, 13:30
Location: québec, canada
Has thanked: 0 time
Have thanks: 8 times

Postby DougH » 20 Sep 2007, 13:59

What does your sim schematic look like?

edit: Your results pretty much concur with mine except for the open/closed switch positions. I agree that it does not affect low freq response at all. It's a LPF.
Last edited by DougH on 20 Sep 2007, 14:50, edited 1 time in total.
DougH
Transistor Tuner
 
Posts: 1104
Joined: 18 Aug 2007, 05:53
Has thanked: 4 times
Have thanks: 23 times

Postby briggs » 20 Sep 2007, 14:10

Bit OT here. What software are you guys using for simulation? I need to get myself a copy!
Image

I am Klon.
User avatar
briggs
Tube Twister
 
Posts: 1997
Joined: 12 Jul 2007, 11:02
Location: Breaking into Heaven.
Has thanked: 30 times
Have thanks: 124 times

PreviousNext

Return to Boutique Stompboxes dissected...

Who is online

Users browsing this forum: polarbee, sego91 and 20 guests