Pete Cornish - OC-1 Optical Compressor  [traced]

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

Pete Cornish - OC-1 Optical Compressor  [traced]

Postby aionios » 15 Nov 2019, 22:21

All right, the legendary Mystery Pedal™ is finally done!

I traced the Cornish OC-1 Optical Compressor over the summer and today I'm ready to share it.

Pete claims this is an all-original circuit design, and fortunately I can confirm that it's not quite like anything I've seen before. The audio path is pretty simple, but the sidechain has a few unfamiliar tricks, perhaps taken from an obscure op-amp application note someplace.

In any case, though, it sounds great!

Schematic:
cornish-oc1-trace-schematic.png


The unit traced was from 2014. There are no known circuit revisions since that time.

Full tracing journal here:
https://aionelectronics.com/blog/tracin ... ompressor/

Imgur gallery with 50+ photos including X-rays:
https://imgur.com/a/sjtezCB

PCB available here:
https://aionelectronics.com/project/oce ... ompressor/
You do not have the required permissions to view the files attached to this post.
Aion Electronics - DIY PCB projects for classic and obscure circuits

For this message the author aionios has received thanks: 15
guiddruid (16 Nov 2019, 11:04), Intripped (16 Nov 2019, 09:43), lietuvis (17 Nov 2019, 12:45), lohstah (16 Nov 2019, 18:35), Manfred (15 Nov 2019, 23:30), marmaliser (18 Nov 2019, 10:38), modman (28 Nov 2019, 08:57), mr coffee (01 Jan 2020, 00:50), roseblood11 (03 Dec 2019, 02:50), Zokk (16 Nov 2019, 13:44) and 5 more users
aionios
Breadboard Brother
 
Posts: 105
Joined: 22 Mar 2012, 01:12
Location: Des Moines, IA
Has thanked: 7 times
Have thanks: 148 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby guiddruid » 16 Nov 2019, 11:03

IC3A/IC3B looks like the "precision full wave rectifier" circuit from Horowitz & Hill (don't have my copy to hand, but IIRC this is it; https://en.wikipedia.org/wiki/Precision_rectifier), but with D2 connected on a separate op-amp. Seems to me this should be functionally equivalent. Not sure what (if any) advantages this would bring. [edit] Sorry, D2 is also backwards compared to that circuit, and the signal is going into inverting input of IC3B. Not sure if that's then achieving the same result. [edit yet again] Nope. I don't understand how IC3B functions at all with pin 5 connected to GND. If it were connected to Vb, I think it would work as a "perfect" diode, preventing that node from dropping below Vb & would also bias that node in the circuit.

IC4B/Q2/Z1/R37 looks like an opamp current source, converting the voltage at IC4B + to a current through the LED. Again, I'm pretty sure this is in Horowitz & Hill; https://en.wikipedia.org/wiki/Current_s ... nt_sources
guiddruid
Breadboard Brother
 
Posts: 88
Joined: 14 Aug 2009, 13:18
Has thanked: 9 times
Have thanks: 4 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby bmxguitarsbmx » 18 Nov 2019, 20:27

Yeah, I agree. The circuit around IC3b almost makes sense to make a FWR... But, then makes no sense. Anybody have an explanation for that part?
bmxguitarsbmx
Solder Soldier
 
Posts: 189
Joined: 25 Mar 2010, 22:15
Has thanked: 296 times
Have thanks: 94 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby bajaman » 18 Nov 2019, 21:25

Don't forget - the LM358 is a single supply optimised dual op amp and does not require a half bias voltage to function in this application :wink:
cheers
bajaman
be kind to all animals - especially human beings

For this message the author bajaman has received thanks:
bmxguitarsbmx (19 Nov 2019, 03:02)
User avatar
bajaman
Old Solderhand
 
Posts: 4372
Joined: 26 Jun 2007, 22:18
Location: New Brighton, Christchurch, NZ
Has thanked: 465 times
Have thanks: 1632 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby guiddruid » 18 Nov 2019, 21:58

But the only way to forward-bias D2 is for pin 6 to go below GND. Even if that were possible, with the supply rails on IC3 being +Vc/GND, I don't see how the input circuitry in the opamp can work.
guiddruid
Breadboard Brother
 
Posts: 88
Joined: 14 Aug 2009, 13:18
Has thanked: 9 times
Have thanks: 4 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby Ben N » 21 Nov 2019, 10:33

How about a roll-your-own vactrol--will that work?
Ben N
Resistor Ronker
 
Posts: 333
Joined: 12 Dec 2008, 04:34
Location: Israel
Has thanked: 24 times
Have thanks: 14 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby Agent86 » 22 Nov 2019, 22:35


For this message the author Agent86 has received thanks:
Satch12879 (25 Nov 2019, 15:09)
Agent86
 
Posts: 9
Joined: 22 Dec 2008, 14:37
Has thanked: 0 time
Have thanks: 1 time

Re: Pete Cornish - OC-1 Optical Compressor

Postby andy-h-h » 28 Nov 2019, 10:24

Finished a vero layout for this, will give it a run on the weekend and post if it goes well. I'm pretty happy with my bajaman optical limiter, so see how it compares.
andy-h-h
 
Posts: 45
Joined: 22 Jul 2017, 04:54
Has thanked: 10 times
Have thanks: 15 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby tubegeek » 09 Dec 2019, 04:39

andy-h-h wrote:Finished a vero layout for this, will ... post if it goes well.


Didn't go well? Curious about this one. Thanks!
tubegeek
 
Posts: 1
Joined: 15 Dec 2011, 04:37
Has thanked: 2 times
Have thanks: 0 time

Re: Pete Cornish - OC-1 Optical Compressor

Postby andy-h-h » 09 Dec 2019, 08:09

tubegeek wrote:
andy-h-h wrote:Finished a vero layout for this, will ... post if it goes well.


Didn't go well? Curious about this one. Thanks!


Yes it did go well - just waiting on an NSL-32 to confirm 100% (should arrive this week). It sounds good, I was using a different vactrol, which was working, but not quite right (compressing, but not enough).

This is the layout I used.
You do not have the required permissions to view the files attached to this post.

For this message the author andy-h-h has received thanks: 3
Cigla tel. (31 Dec 2019, 14:39), Manfred (09 Dec 2019, 10:34), tubegeek (12 Dec 2019, 18:12)
andy-h-h
 
Posts: 45
Joined: 22 Jul 2017, 04:54
Has thanked: 10 times
Have thanks: 15 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby stefanogueli92 » 29 Dec 2019, 11:27

Hello friends... Thanks to all the people who works on this project I'm a doctor and that's the first time i see x ray applied on guitar pedal... I want to ask you if anyone has the ready to print pcb layout... Thank you in advance
stefanogueli92
 
Posts: 11
Joined: 28 Jan 2019, 14:20
Has thanked: 6 times
Have thanks: 1 time

Re: Pete Cornish - OC-1 Optical Compressor

Postby Whoismarykelly » 31 Dec 2019, 04:22

stefanogueli92 wrote:Hello friends... Thanks to all the people who works on this project I'm a doctor and that's the first time i see x ray applied on guitar pedal... I want to ask you if anyone has the ready to print pcb layout... Thank you in advance


Aion Electronics sells a top notch PCB that fits a 125B.
Whoismarykelly
Resistor Ronker
 
Posts: 380
Joined: 22 Oct 2007, 19:26
Has thanked: 2 times
Have thanks: 7 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby Cigla tel. » 31 Dec 2019, 10:41

Whoismarykelly wrote:Aion Electronics sells a top notch PCB that fits a 125B.

I can't believe what this forum has turned into? The motherboard sales ads?

From the former place where enthusiasts selflessly shared PCB designs, their knowledge, and assisted those who were unable to buy pedals, to the place where we pull naive forum members to buy PCB from other forum members who realized that they could make money on this way?

What is this forum now, "Amazon" or maybe "Aliexpress", or just a place where we can find PCB design to make FREE STOMBOXES?

We all know that PRE MADE PCBs can no longer be corrected as PCBs circulating freely "on the paper" in the forum.

Unbelievably! :cry:

For this message the author Cigla tel. has received thanks:
stefanogueli92 (02 Jan 2020, 03:13)
Cigla tel.
 
Posts: 15
Joined: 06 Apr 2016, 14:34
Has thanked: 4 times
Have thanks: 5 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby plush » 31 Dec 2019, 12:00

Cigla tel. wrote:
Whoismarykelly wrote:Aion Electronics sells a top notch PCB that fits a 125B.

I can't believe what this forum has turned into? The motherboard sales ads?

From the former place where enthusiasts selflessly shared PCB designs, their knowledge, and assisted those who were unable to buy pedals, to the place where we pull naive forum members to buy PCB from other forum members who realized that they could make money on this way?

What is this forum now, "Amazon" or maybe "Aliexpress", or just a place where we can find PCB design to make FREE STOMBOXES?

We all know that PRE MADE PCBs can no longer be corrected as PCBs circulating freely "on the paper" in the forum.

Unbelievably! :cry:



I see nothing wrong here, as long as PCB seller openly publishes his schematics.
User avatar
plush
Resistor Ronker
 
Posts: 328
Joined: 08 Dec 2015, 10:29
Location: Moscow, Evil Russia
Has thanked: 31 times
Have thanks: 85 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby Cigla tel. » 31 Dec 2019, 14:34

plush wrote:I see nothing wrong here, as long as PCB seller openly publishes his schematics.

You may not see it, but I see that someone is consciously making money through this OPEN site which was not the practice before. :applause:
Lately, members who making schematics from "traced" stompboxes just come here trying to charge their efforty. :shock: :shock: :shock:

Where that selfless spirit disappeared when comes to sharing of PCB etching images on this so called FREESTOMPBOXES forum? How they can bee free if we must buy PIRATED PCB?

Than, maybe i should pay for real pedal?!? If i should buy suspicious PCB, pedal enclosure, and all the components, spend time making it, ... and at the end, who will guarantee that i will get exact the same sound? Who can tell that this " aionios" schematics are 100% correct?

I opened dozens of usual pedals and beside other mistakes, for example, i found that there were many more components in the clipping sections than the gentleman had typed in his free published "schemes" and PRE MADE PCB for sale?
That means that schematics are incorrect?!?
And we should BUY PRE MADE PCB made from incorrect schematics?

I have been disappointed with the behavior of the members of this forum lately. Everything was shared earlier, that's why we came here. Now we are doomed to BUY suspicious pirated PCB from forum members just because they don't want to share anymore PCB etching templates. Fuck that! :evil:
Cigla tel.
 
Posts: 15
Joined: 06 Apr 2016, 14:34
Has thanked: 4 times
Have thanks: 5 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby plush » 31 Dec 2019, 14:40

Cigla tel. wrote:
plush wrote:I see nothing wrong here, as long as PCB seller openly publishes his schematics.

You may not see it, but I see that someone is consciously making money through this OPEN site which was not the practice before. :applause:
Lately, members who making schematics from "traced" stompboxes just come here trying to charge their efforty. :shock: :shock: :shock:

Where that selfless spirit disappeared when comes to sharing of PCB etching images on this so called FREESTOMPBOXES forum? How they can bee free if we must buy PIRATED PCB?

Than, maybe i should pay for real pedal?!? If i should buy suspicious PCB, pedal enclosure, and all the components, spend time making it, ... and at the end, who will guarantee that i will get exact the same sound? Who can tell that this " aionios" schematics are 100% correct?

I opened dozens of usual pedals and beside other mistakes, for example, i found that there were many more components in the clipping sections than the gentleman had typed in his free published "schemes" and PRE MADE PCB for sale?
That means that schematics are incorrect?!?
And we should BUY PRE MADE PCB made from incorrect schematics?

I have been disappointed with the behavior of the members of this forum lately. Everything was shared earlier, that's why we came here. Now we are doomed to BUY suspicious pirated PCB from forum members just because they don't want to share anymore PCB etching templates. Fuck that! :evil:


Quit your bullshit, no one makes you buy their stuff.
Guys are giving you free schematics and are asking for nothing in return.

So go and mind your own business, pal.
User avatar
plush
Resistor Ronker
 
Posts: 328
Joined: 08 Dec 2015, 10:29
Location: Moscow, Evil Russia
Has thanked: 31 times
Have thanks: 85 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby Cigla tel. » 31 Dec 2019, 14:46

plush wrote:
Cigla tel. wrote:
plush wrote:I see nothing wrong here, as long as PCB seller openly publishes his schematics.

You may not see it, but I see that someone is consciously making money through this OPEN site which was not the practice before. :applause:
Lately, members who making schematics from "traced" stompboxes just come here trying to charge their efforty. :shock: :shock: :shock:

Where that selfless spirit disappeared when comes to sharing of PCB etching images on this so called FREESTOMPBOXES forum? How they can bee free if we must buy PIRATED PCB?

Than, maybe i should pay for real pedal?!? If i should buy suspicious PCB, pedal enclosure, and all the components, spend time making it, ... and at the end, who will guarantee that i will get exact the same sound? Who can tell that this " aionios" schematics are 100% correct?

I opened dozens of usual pedals and beside other mistakes, for example, i found that there were many more components in the clipping sections than the gentleman had typed in his free published "schemes" and PRE MADE PCB for sale?
That means that schematics are incorrect?!?
And we should BUY PRE MADE PCB made from incorrect schematics?

I have been disappointed with the behavior of the members of this forum lately. Everything was shared earlier, that's why we came here. Now we are doomed to BUY suspicious pirated PCB from forum members just because they don't want to share anymore PCB etching templates. Fuck that! :evil:


Quit your bullshit, no one makes you buy their stuff.
Guys are giving you free schematics and are asking for nothing in return.

So go and mind your own business, pal.

Stuck that "free schematics" in your ass! Fucking idiot!
Cigla tel.
 
Posts: 15
Joined: 06 Apr 2016, 14:34
Has thanked: 4 times
Have thanks: 5 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby plush » 31 Dec 2019, 15:02

Cigla tel. wrote:Stuck that "free schematics" in your ass! Fucking idiot!


Alas, yer mighty internet boxing aint appreciated.
Facts are valued, your butthurt is not.

You've proven yourself enough tho.
User avatar
plush
Resistor Ronker
 
Posts: 328
Joined: 08 Dec 2015, 10:29
Location: Moscow, Evil Russia
Has thanked: 31 times
Have thanks: 85 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby Whoismarykelly » 06 Jan 2020, 23:41

I doubt very many people would choose to DIY etch a dense double-sided board rather than buy a professionally made one for a few bucks. You can certainly make your own PCB layout from the schematic and post it for others to use.

For this message the author Whoismarykelly has received thanks:
stefanogueli92 (07 Jan 2020, 15:02)
Whoismarykelly
Resistor Ronker
 
Posts: 380
Joined: 22 Oct 2007, 19:26
Has thanked: 2 times
Have thanks: 7 times

Re: Pete Cornish - OC-1 Optical Compressor

Postby stefanogueli92 » 07 Jan 2020, 15:06

i gently request it, because i have not knowledge to read schematic and perfectly trace a ready to print pcb... in this forum there a lot of good people, who like to share knowledge and happines.... so i'm waiting for you... have you a nice day friends
stefanogueli92
 
Posts: 11
Joined: 28 Jan 2019, 14:20
Has thanked: 6 times
Have thanks: 1 time

Next

Return to Boutique Stompboxes dissected...

Who is online

Users browsing this forum: jubz, sergedeep and 3 guests

cron