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Anybody sketch out the schematic for the final version of the OCD (known variously as 2.01 or 2.1) developed and sold before Fulltone closed it's doors?

bluesky636 wrote: ↑07 Jan 2023, 07:16 Anybody sketch out the schematic for the final version of the OCD (known variously as 2.01 or 2.1) developed and sold before Fulltone closed it's doors?

https://www.pedalpcb.com/product/pcb542/

apparently pedalpcb has it, but no published documentation yet

Hmmm. Yeah. PCB only, no schematic which is what I am looking for.

Thanks tho.

bluesky636 wrote: ↑07 Jan 2023, 07:16 Anybody sketch out the schematic for the final version of the OCD (known variously as 2.01 or 2.1) developed and sold before Fulltone closed it's doors?

This is from an email someone got from Mike -

A few weeks ago I was messing around and found a way to isolate the clipping via a smaller separate pair of caps and boom, I now could tune the amount off bass that passes by the clipping section without triggering it. (source)

Based on that, it sounds like there are capacitors in series with the clipping diodes (MOSFETs). Not sure why you'd need a pair of them, since you could just put one before or after the clippers, but whatever. I might grab one of the v2.01's just to verify, it should be easy to tell what's going on without desoldering anything.

smear wrote: ↑09 Jan 2023, 00:32 https://www.pedalpcb.com/product/pcb542/

apparently pedalpcb has it, but no published documentation yet

That doesn't seem to cover the V2.01, just the V2.

If that's true then restoring the better sound of the pre-1.8 versions can easily be done by using 10µF caps in the PS filter section instead of the new spec 220µF. Fortunately DIYers don't have to abide by RoHS laws.

I don't know what ROH has to do with power supply design.

bluesky636 wrote: ↑13 Jan 2023, 19:49 I don't know what ROH has to do with power supply design.

RoHS mandates what kind of power supplies can be sold. According to the linked sources, only switching types are allowed which can generate noise that non-switching (e.g. transformer) supplies don't have. Without appropriate power supply filtering, the pedal might be noisy. So presumably Fulltone changed the power supply filtering to prevent noise when used with switching power supplies. In other words, he blames RoHS for the proliferation of switching type power supplies which forces him to improve the power supply filtering in his pedals.

In the OCD, one of the filter caps is part of the path to ground through the MOSFET clippers, so they theoretically create a low pass filter which would let more lows be clipped with a larger cap value. I'm not sure I believe that, or perhaps there's more to it that I/we don't know, because I would think that 10µF should already be considerably large enough to let all guitar frequencies be clipped (my calculation is that the knee frequency would be 1.6Hz). 220µF is 22x larger so on paper there would be a big difference, but I'm a little suspicious. This might be just a marketing ploy to combat the negative reception of the 2.0.

Ummm, the majority of pedalboard power supplies use transformers, usually toroidal, all of my home theater equipment use transformer power supplies, and most high end 2-channel stereo equipment use toroidal transformers. All are ROH compliant and sold world wide. Sounds like a pretty lame excuse for changing things.

https://www.rohsguide.com/rohs-faq.htm

ggbb wrote: ↑13 Jan 2023, 19:32 If that's true then restoring the better sound of the pre-1.8 versions can easily be done by using 10µF caps in the PS filter section instead of the new spec 220µF. Fortunately DIYers don't have to abide by RoHS laws.

It was actually v1.7 when the caps were changed from 10uf to 47uf, but they were also bumped up to 220uf in v2.0. However, the power supply filtering has absolutely nothing to do with the amount of bass. The reference voltage acts as audio (AC) ground, and as far as the diodes are concerned there isn't any substantial difference between true ground and virtual ground. Mike is full of nonsense and should know better.

The real reason V2 has more bass is because the filter in the first opamp stage was changed to 3k3/100n, which gives a high-pass corner frequency of 482 Hz. The original V1 was 723 Hz and V1.3 was 1064 Hz, so V2 has more bass than either of them.

aionios wrote: ↑14 Jan 2023, 02:44 The reference voltage acts as audio (AC) ground, and as far as the diodes are concerned there isn't any substantial difference between true ground and virtual ground.

I think the bias filter cap is what allows the DC bias reference point to function as a virtual ground for AC, so as far as AC goes it is part of the circuit. AC seeks ground not Vbias.

Here's a graph of a sim comparing the AC response differences between 1µ, 10µ, 47µ, 100µ, and 220µ values for the bias filter cap in the OCD v1 rev1 circuit:



10µ only behaves slightly differently than 47µ or greater (which are almost identical), but much lower values would be significant.

So the question then becomes - if v2.1 adds caps between the clippers and Vbias, what values are they?

ggbb wrote: ↑14 Jan 2023, 11:06 Here's a graph of a sim comparing the AC response differences between 1µ, 10µ, 47µ, 100µ, and 220µ values for the bias filter cap in the OCD v1 rev1 circuit:

I apologize, I shouldn't have said "absolutely nothing"! Let me revise to say that a circuit with an appropriate level of power filtering, there should be no audible difference between using virtual ground or true ground. If the filter caps are low enough that the bass difference is noticeable, then they are also likely not doing enough filtering and it's unnecessarily noisy. If the tone response of the circuit truly and measurably changes when the filter caps are changed then I would call it poorly engineered.

I do have a v2.01 on the way and will post the details here once I have a chance to look at it.

i bet mike knew that cap can influence bass response, and either assumed it would add more bass or convinced himself that he heard more bass. that's some real old-school boutique builder behavior lol. probably didn't even simulate it...

mike's full quote from that thread:
"What's with the "new" OCDv2 and CS-OCD-Ge? The OCD is cool circuit because it clips to V-ref instead of ground....that’s the half-way point to ground, 4.5 volts to be exact...and is part of the reason that OCDs emulate the "sag" of a tube amp. A few years back ROHS laws started mandating that power supplies change to the noisy “switching type." Because of this, we had to increase the size of the filtering (electrolytic) cap for the “V-ref" section of the pedal's power supply, and there were some sonic repercussions. These larger caps allowed more LOW frequencies to swamp the clipping section of the circuit...taking away some of the articulation that many people loved about the v1 versions of the OCD...they became more "compressed sounding." A few weeks ago I was messing around and found a way to isolate the clipping via a smaller separate pair of caps and boom, I now could tune the amount off bass that passes by the clipping section without triggering it. Very...very cool. A Simple mod. All OCDs (bought direct from us) now ship with this mod, do yourself a favor and try a new one, and post a side-by-side video with any v1 you care to put it next to."

'A few years back ROHS laws started mandating that power supplies change to the noisy “switching type." '

That's a bunch of BS as far as I am concerned. ROH regulates the MATERIALS that can be used in the manufacture of a product. I find nothing that says ROH regulates the specific DESIGN of a product.

Here is the power supply used on my pedalboard, a Voodoo Labs ISO-5 which uses a toroidal transformer for its power supply. Note the ROH certification marking (CE):

https://media.sweetwater.com/api/i/q-82 ... .auto.webp

From my earlier post:

Ummm, the majority of pedalboard power supplies use transformers, usually toroidal, all of my home theater equipment use transformer power supplies, and most high end 2-channel stereo equipment use toroidal transformers. All are ROH compliant and sold world wide. Sounds like a pretty lame excuse for changing things.

https://www.rohsguide.com/rohs-faq.htm

Never the less, the OCD is a great pedal. It boosts many amps in ways that no other boost. So, it doesn't really matter. I do agree that switching power supplies are not all noisy. I'm running a DIY Neve preamp clone with nearly 70dB of gain off a very cheap LED SMPS and it is awesome. My "one spot" is a noisy little bastard though.

Do we understand what the new circuit is that bypasses bass?

Thirdly, the clipping stage is DC coupled, it is asymmetrical clipping clipping the negative side of the wave more than the positive side. Despite the Vbias being able to absorb sinusoidal steady state AC down to a very low frequency, the output impedance of Vbias is 5k - that is not low impedance. Combine 5k with the 2x10uF and you can calculate what types of bias shifts you get in the time domain, not the frequency domain. These resistive divider bias rails ARE low impedance to symmetrical, steady state AC signals only, but are high impedance to DC, asymmetrical signals, or asymmetrical clipping.

Sometimes I think we fall prey to "OCMD" Obsessive Compulsive Myth-buster Disorder where our bias lies in believing everything is bullshit. The bias shift due to grid current IS part of what tubes do and looking at the circuit, it is reasonable to conclude that a bias shift should be happening. I used to hound Bajaman about the bias shifts in his designs until I built them his way and realized they sounded better (My apologies Bajaman!). I've never opened my OCD up btw, so I don't know. Great pedal for the dual rectifier.

bluesky636 wrote: ↑15 Jan 2023, 14:01 'A few years back ROHS laws started mandating that power supplies change to the noisy “switching type." '

That's a bunch of BS as far as I am concerned. ROH regulates the MATERIALS that can be used in the manufacture of a product. I find nothing that says ROH regulates the specific DESIGN of a product.

Here is the power supply used on my pedalboard, a Voodoo Labs ISO-5 which uses a toroidal transformer for its power supply. Note the ROH certification marking (CE):

https://media.sweetwater.com/api/i/q-82 ... .auto.webp

From my earlier post:

Ummm, the majority of pedalboard power supplies use transformers, usually toroidal, all of my home theater equipment use transformer power supplies, and most high end 2-channel stereo equipment use toroidal transformers. All are ROH compliant and sold world wide. Sounds like a pretty lame excuse for changing things.

https://www.rohsguide.com/rohs-faq.htm

it's not entirely nonsense. there were some power supply efficiency laws passed in ~2010 that limited to the use of linear power supplies, because they aren't exactly efficient. for stuff like cell phone chargers it's all well and good. maybe mike tried running an OCD on one of those cell phone power supplies...

I don't know what any of that has to do with ROHS.

bluesky636 wrote: ↑15 Jan 2023, 23:15 I don't know what any of that has to do with ROHS.

i just said it wasn't entirely nonsense

RoHS has nothing to do with power supply efficiency laws.

RoHS, which is clear from the name, is about restricting the use of certain hazardous materials. For example, lead solder, cadmium plating, certain chromium additives for colorants:
https://en.wikipedia.org/wiki/Restricti ... _Directive

Efficiency laws are directly about not wasting energy and indirectly about greenhouse reduction. They are laws put in place to comply with larger government directives. The banning general incandescent lamps comes under a similar umbrella. There's also similar directives about losses in power distribution transformers, efficiency of motors used for consumer and industrial applications. Single-phase induction motors which meet the new efficiency laws are very difficult to design now.

https://www.digikey.com/en/articles/eff ... r-supplies
https://www.motioncontroltips.com/what- ... earmotors/

You can read about if you wish. Joe Average sitting at home in front of the TV is going to be totally oblivious to the increased demands placed on product manufacturers to meet new regulations.

The governing bodies that handle each of these laws varies from country to country.

Not to defend Fulltone, but I don't think it really matters here whether RoHS is to blame or not (it isn't). It's the proliferation of switching type power supplies that are the problem for him whether that's due to RoHS or, more likely, energy efficiency regulations from the EU, or something else. The worldwide market for power supplies has changed because of modern regulations and technical innovations and the race to make things inexpensive. Switching supplies are far more common now for pedals than they were ~20 years ago.

So clearly he doesn't have all his facts straight, but that doesn't change the fact that he felt he had to modify the power filtering in order to deal with noisier power supplies - which is perfectly plausible.