Cornish P-2 guts

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Re: Cornish P-2 guts

Postby JimiB » 24 Mar 2010, 15:51

I feel as though a diversion has happened and the gent with the P2 to degoop was driven away.
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Re: Cornish P-2 guts

Postby Greg » 24 Mar 2010, 22:46

JimiB wrote:I feel as though a diversion has happened and the gent with the P2 to degoop was driven away.


Yes it does.
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Re: Cornish P-2 guts

Postby devastator » 24 Mar 2010, 22:50

what is this "French product" you guys are speaking of :?:


you talk about , maybe, ROADRUNNER ?

that's the only one "boutique" french builder with "heavy" box . They made a fuzz, enveloppe filter/distortion and a tremolo. .
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Re: Cornish P-2 guts

Postby soulsonic » 25 Mar 2010, 02:59

Greg_G wrote:
JimiB wrote:I feel as though a diversion has happened and the gent with the P2 to degoop was driven away.


Yes it does.

I agree. :?
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Re: Cornish P-2 guts

Postby flood » 30 Mar 2010, 06:53

ryanuk wrote:
DougH wrote:I was always under the impression that the appeal of the Cornish stuff was low noise, consistency, and ruggedness. It was intended for a clientele that was dealing with a completely different set of problems than most- people who play big stadiums and arenas. Now the "ruggedness" aspect may be a false premise, based on mictester's comments. But I never thought that it was intended to appeal to the average bedroom or bar gig musician based on mojo or fancy paint jobs, or even "tone". I thought it was always understood that they were existing circuits rehoused and integrated with his buffer circuitry and/or his custom pedal boards. It doesn't seem like the kind of thing that is going to be appealing to most people who hang out here (or even places like the gear page).

Not sure why Cornish threads always stir up such controversy. If you think they are overpriced and not that interesting, you're probably right- and you certainly don't need one. But if you play regular 50,000+ gigs and are vitally concerned about equipment not crapping out mid-song, it's probably worth it to you to pay the price. Doesn't seem like a big deal either way to me.


Doug_H - exactly what I was trying to say, execpt I think you put it better!

ryanuk wrote: Clearly these units are aimed at touring musicians who demand a more rugged unit with a classic sound. If you arent a pro, and you arent touring 300 days a year, then a regular Big Muff (vintage or otherwise) should be fine. Take the Edge for example - hes got a regular BMP sitting on top of his racks.


It seems that main argument against Mr Cornish is ruggedisation - the pedals are nothing special in terms of design but they are supposed to be flawless in terms of longevity.

Looking at the pics of the P-2, I cant see how anyone can claim that its not carefully wired. I know that some examples of failures have been referenced but can we really expect EVERY SINGLE pedal to be completely flawless. Mr and Mrs Cornish are human after all.

With regard to the coloursound references - I assume you mean that these have been rehoused and sold with the pots "stuck" literally. I can only presume that it was a certain sound that the customer would have wanted, no?

I still dont think we can bash Mr Cornish - he's selling to a niche market. If I were touring constantly, I know I would prefer one of his units or a rehoused/rewired stock BMP compared with a stock BMP thats been wired by god knows who...

Edit: That's my 2p and I stick to it whilst begridging no-one who disagrees. The spirit of debate rules!! Vairety is the spice of life :thumbsup


i agree 2000%. PC's been delivering to the most demanding users who tour under the most demanding conditions and he's done it consistently; i think the average user doesn't really NEED the kind of stuff he makes.

i'm amazed the bashing has gone on this long - last time i visited and posted here was 6 months ago i think.
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Re: Cornish P-2 guts

Postby Greg » 30 Mar 2010, 07:31

Personally I agree that Cornish makes a good rugged pedal for professional use... and I see no reason to bash him.
Fair comment and discussion of his build techniques, etc is OK... and what this site is all about.

There doesn't seem to be a lot of originality in his designs which is a little disappointing given his reputation.
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Re: Cornish P-2 guts

Postby lolbou » 30 Mar 2010, 20:26

biffa wrote:Has he ever claimed to have made an original guitar effect?


He wrote that he build the Deacy Amp for May...

Pete Cornish wrote:
THE RECORDING AMPLIFIER:

Although I cannot be sure of the date (possibly 1973/4), during my tenure as Chief Engineer at the Sound City group of companies, I was asked to build a small, battery powered amplifier to be used with the treble boost for recording. I built this amp from parts obtained locally in Soho - Lisle Street was a very good source of electronic components in the early 70's - but sadly all details of this amp were lost when the Cities Group closed in July 1975.

In October 1976 I was asked, by Brian May's then Tech, Richie Anderson, to build a low power amplifier that could be used with my Treble Boost for recording. I utilized a small bookshelf loudspeaker cabinet and added a battery powered amp module that I modified to have the same frequency response as the Vox AC30 “normal” channel (see photo Recording Amp X 2). Richie explained that the technique used to record this tiny amp was by placing it face down on a pillow and setting up the microphone very near the back panel.


Here's the source...

He should have called it a "Corny" amp then... :popcorn:
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Re: Cornish P-2 guts

Postby Greg » 30 Mar 2010, 23:59

AFAIK he's never stated what his pedals were based on or that they weren't original...
Other's made that assessment.
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Re: Cornish P-2 guts

Postby JimiB » 31 Mar 2010, 05:18

they are just really good sounding versions of what they are. This is assuming that they are used as intended. Played into a clean amp with lots of headroom. This at least goes for the SS-3 and G2. Absolutley glorious into a Hiwatt.
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Re: Cornish P-2 guts

Postby phibes » 31 Mar 2010, 16:30

Anything sounds good with a HiWatt! :lol:
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Re: Cornish P-2 guts

Postby Alex Frias » 31 Mar 2010, 19:10

I can't agree more...
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Re: Cornish P-2 guts

Postby Cub » 18 Jan 2019, 17:25

The blokes over at effectslayout have done the P-2 and have included the buffer.
http://effectslayouts.blogspot.com/2018/12/cornish-p2-probably.html

Two components are different from the schematic posted earlier in this thread. The collector resistor in the recovery stage (12k instead of 10k) and the cap on the high pass filter side of the tone pot (.1µF instead of .01µF).

The 91 ohm resistor between the wiper of the volume pot and the output puzzles me, as does the 50k resistor between the output and ground.
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Re: Pete Cornish P-2

Postby Cub » 19 Jan 2019, 10:04

I see the schematic posted by Ulysse.Gaunarol is no longer on ImageShack, so I attached it. Mind you, the .0010 cap on the high pass filter on the tone pot is a typo, this should be .01µF instead.
Also attached is a schematic posted by Brian the Mad Bean himself on the MBP forum. Brian says he can't recall where he got the values from, but it's almost identical to the one posted by Ulysse.Gaunarol. The only differences are the diodes are now labelled (guessed?) to be 1N914 and Brian added his own power filtering.
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Re: Cornish P-2 guts

Postby andy-h-h » 19 Jan 2019, 12:10

I'm not quite sure what to make of the schematics - the board below is a de-gooped Pete Cornish G2 from elsewhere on this site. You can see it also says P2, so same layout, different values / parts.

The G2 does not have a BMP tone-stack, just a basic capacitor to ground filter, where the schematics are a more of a BMP. You can't do both on the same board. Thoughts? Maybe the schematic above is a P-1???
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Re: Pete Cornish P-2

Postby Cub » 19 Jan 2019, 14:02

Hi Andy,

All I had as a source is this quote from page 3 of this thread that goes with the first schematic.
Ulysse.Gaunarol wrote:Paul Garrison gave it to me. He works in L.A at Truetone Music in Santa Monica
He did the rehousing of the Ted Witcher's P-2:
http://www.thegearpage.net/board/showth ... 9&page=257
This schematic does not include the buffer part


Then there's this quote from DIYSB, which supports the schematic, Brian's redrawing and the layout on effectslayout. No idea from where they got their information, though.
https://www.diystompboxes.com/smfforum/index.php?topic=33137.msg264668#msg264668
I read once that Pete Cornish would have hardly no changes to the BM to his P2. Well, due to my experience with the BM I rather think he did a full remake with flawless parts and added a impedance converter as well.


But all that is just speculation and, apparently, all incorrect. You're right, you can't build a Muff with the regular tone control on the same board as a G-2.

Oh well, perhaps it will be solved one day. Until then, there's plenty of other Muff pedals and other fuzzy little noise makers to build. :)
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Re: Cornish P-2 guts

Postby andy-h-h » 19 Jan 2019, 21:34

Hey Cub - who knows..... schematics may well be for a P1 minus the buffers, as these sound like they have a BMP tone control.

http://www.petecornish.co.uk/SAEP-1.html

The tone facility on the P-1™ has been designed to provide Treble Boost when set Clockwise and Bass Boost when set Counter Clockwise. Settings in-between CW and CCW will provide varying amounts of high and low frequency boosting: experiment to find your optimum setting.
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Re: Cornish P-2 guts

Postby Cub » 19 Jan 2019, 23:23

That description of the tone pot on the P-1 suits the schematic a lot better. Most peculiar!

On the other hand, I've done a little digging on TGP and found Ted Witcher posted photographs of his board before and after the P-2 was rehoused.
https://www.thegearpage.net/board/index.php?threads/show-your-cornish-in-your-pedalboard.433110/#post-4716018
Image
Image

And a close up shot from a different thread.
https://www.thegearpage.net/board/index.php?threads/show-us-your-re-housed-pedals.427719/page-3#post-6545529
Image
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Re: Pete Cornish P-2

Postby Ghandi » 05 Feb 2019, 13:32

Both are also really close to the Skreddy P19 which aims for the same sound.
The only differences are 10k/200ohm (P19) vs 12k/390ohm (P2) on the collector and emitter of the first three transistors...

Cub wrote:I see the schematic posted by Ulysse.Gaunarol is no longer on ImageShack, so I attached it. Mind you, the .0010 cap on the high pass filter on the tone pot is a typo, this should be .01µF instead.
Also attached is a schematic posted by Brian the Mad Bean himself on the MBP forum. Brian says he can't recall where he got the values from, but it's almost identical to the one posted by Ulysse.Gaunarol. The only differences are the diodes are now labelled (guessed?) to be 1N914 and Brian added his own power filtering.
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Re: Cornish P-2 guts

Postby Cub » 05 Feb 2019, 16:49

The schematics Ulysse.Gaunarol and Brian the Mad Bean have posted are nearly identical to Sovtek Muffs.
http://www.bigmuffpage.com/Big_Muff_Pi_versions_schematics_part3.html
Different transistors, of course. The feedback caps are 560pF instead of 430, 470 or 500pF and the cap on the HPF side of the tone control is .01µF instead of .0039µF.
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Re: Cornish P-2 guts

Postby JBJ » 16 Mar 2019, 00:55

analogguru wrote:Normally I have no intention to waste my time by responding to paranoid false accusations without any substrate. But since this is a theme of general interest I will respond in this special case.

The basic technology of the "mythical Cornish Buffer" is well known since the early 60´s an was already used in the germanium era as you can see here:

[ Image ]

The technology is called "bootstrapping" whereby a portion of the signal is fed back to the bias divider to increase the input impedance. The darlington configuration shown is only necessary with low-gain (hfe ~ 80) transistors as the 2N1309.

So where is the difference to the Roland AP-2 buffer I mentioned ? First, here is a redrawn version:

Analogguru AP-2-style Buffer schematic

So what is obvious is that the bias for the first stage is not taken from V+ instead it is taken from the collector of Q1 via R2. This leads to an additional (AC and DC) feedback resulting in more temperature stability, lower distortion/increased headroom and lower collector output impedance.

Then you can see that the signal is not taken from the emitter instead it is taken from the collector. You can ommit Q2 and R7 if you only want to drive "high impedance" stages.

Because the signal is taken from the collector, the first stage even has a (small) gain of 2 (6 db). The second transistor doesn´t amplify, it is only a buffer to lower the output impedance (< 100 Ohm). That´s important when driving long cables.

Overall it can be expected that the "AP-2-Buffer" has:

a higher input impedance,
a lower output impedance,
less noise,
less distortion,
and even a small gain

compared with the "mythical Cornish Buffer" - with only 2 additional components.

analogguru


Does anyone have the schematic of the AP-2 buffer redrawn by Analogguru?
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