Pete Cornish - Bypass buffer  [traced]

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Starman
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Post by Starman »

Had anyone investigated the Cornish bypass buffer?

I'm wondering if there's something special about it. I wouldn't be too surprised if it's really the same buffer used in some of this BOSS/DOD/Ibanez pedals.

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super velcroboy
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Post by super velcroboy »

we need a pedal to reverse first :mrgreen:

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Post by soulsonic »

Someone should get an LD-1. It's pretty much the cheapest thing you can get from him and it would reveal what his buffers are all about.

I was researching different kinds of buffer circuits last night - there's literally dozens of different ways to do a buffer, and they all pretty much perform the same task; it's just that they have different strong points as far as what kinds of things work best on the inputs and what things work best on the outputs. Though I'm curious to see what kind of buffer he uses, I don't think we're going to see any surprises or anything that will challenge the general perception of how a buffer works.
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jrc4558
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Post by jrc4558 »

IMHO all the buffer needs to have is high headroom (+/-15VDC supply) and low output impedance with good current capability. I'm not mentionaning the bandwidth since buffers should not alter the EQ.
Anything that can get you there is good enough of a buffer. :)

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Post by Pedalpusher »

There was some discussion about buffers on TGP so I experimented with My VS RT66. I tried running strait into the amp and then through the RT66 with both effects off. There was a barely noticable difference. And I mean barely. If I had more effects The RT66 would come after a wah and fuzz which seems like a good place for a buffer. I just saved over $300.00 by not having to buy a Cornish buffer! :applause:

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super velcroboy
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Post by super velcroboy »

to be honest, tgp doesn't really discuss anything

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Post by Pedalpusher »

super velcroboy wrote:to be honest, tgp doesn't really discuss anything
LOL

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Post by monkeyxx »

super velcroboy wrote:to be honest, tgp doesn't really discuss anything
sorry that was too good not to bump.


I would like to ask if anyone's messed with Cornish buffers since then up to now. I just built the G2 buffer from dirk hendrik schematic. It adds a significant amount of brightness, which sounds good on some amps and pedals, and not so good on others. It made my ram's head big muff circuit unuseable, which I thought was ironic. It really added sparkle and life to my really warm/thick/dark sounding amps, and added a lot of kick to my strat's bridge pickup. Unless I'm missing something was that buffer designed specifically for the G2 pedal only, or is this the same buffer he puts in all his stuff? Do we even know this?

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Post by lolbou »

It's the same buffer indeed in both units.
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Post by monkeyxx »

I noticed in the G2 there is also, on the output, a 91 ohm resistor in series with the circuit there, and a 50K resistor from signal to ground. in the gut shots these two are soldered to the output jack. Is this a part of the buffer circuit that should be included always when using this buffer? I notice none of the DIY layouts include it. I was wondering because the G2 buffer seems to drive some of my pedals too hard, and this seemed like a pad of some sort

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Post by gilmour_pugliese »

monkeyxx wrote:I noticed in the G2 there is also, on the output, a 91 ohm resistor in series with the circuit there, and a 50K resistor from signal to ground. in the gut shots these two are soldered to the output jack. Is this a part of the buffer circuit that should be included always when using this buffer? I notice none of the DIY layouts include it. I was wondering because the G2 buffer seems to drive some of my pedals too hard, and this seemed like a pad of some sort
In my layout I've removed those two resistors... Because I'm thinking that they are used (and placed) in conjunction with the whole G2 circuit, and should be removed in a standalone buffer use :hmmm:

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Post by Oliphaunt »

Here is the schematic I used and the verified vero I created from it. My experience with this buffer is that is has a nice natural "feel" compared to some others I have tried such as the simple IC buffer and other one transistor types. I think the input impedance may be a little low for general use. It sounds perfect with my Carr Rambler but darkens the tone a little bit with my Blackface Fenders.
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Cornish G2 Input Buffer - vero 02 tighter.jpg
Cornish G2 Input Buffer - vero 02 tighter.jpg (39.89 KiB) Viewed 6309 times
Cornish G2 Input Buffer.gif
Cornish G2 Input Buffer.gif (18.14 KiB) Viewed 6309 times

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Post by monkeyxx »

oh I'm a dummy I did use a schematic like that. is there any advantage if using this in an effect build of separating the output padding resistor pair from the main buffer and putting them on the output jack AFTER the effect? I wonder what difference that would make

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Post by Taller76 »

Oliphaunt wrote:Here is the schematic I used and the verified vero I created from it. My experience with this buffer is that is has a nice natural "feel" compared to some others I have tried such as the simple IC buffer and other one transistor types. I think the input impedance may be a little low for general use. It sounds perfect with my Carr Rambler but darkens the tone a little bit with my Blackface Fenders.
Somewhat of a zombie thread, my apologies...
In the attached vero build (thanks!) R10 is spec'd to be a 50K
After looking at the G2 Input buffer it appears to be listed as "51E" (I assume a fat-fingered "R" was supposed to go there instead) and the Madbean Darkside shows R8 (part of the input buffer) to be a 51R...If I had to guess this should be a 51R, correct? What purpose does this component serve in this circuit?
Sorry for resurrecting the dead....

Cheers!

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Post by monkeyxx »

Taller76 wrote:
Oliphaunt wrote:Here is the schematic I used and the verified vero I created from it. My experience with this buffer is that is has a nice natural "feel" compared to some others I have tried such as the simple IC buffer and other one transistor types. I think the input impedance may be a little low for general use. It sounds perfect with my Carr Rambler but darkens the tone a little bit with my Blackface Fenders.
Somewhat of a zombie thread, my apologies...
In the attached vero build (thanks!) R10 is spec'd to be a 50K
After looking at the G2 Input buffer it appears to be listed as "51E" (I assume a fat-fingered "R" was supposed to go there instead) and the Madbean Darkside shows R8 (part of the input buffer) to be a 51R...If I had to guess this should be a 51R, correct? What purpose does this component serve in this circuit?
Sorry for resurrecting the dead....

Cheers!
I would guess it controls impedance. I would also like to know if this is an error in fact? Before I go around using these buffers all over the place

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Post by monkeyxx »

I am crawling along in my electronics education, and I would love to know if these little parts of the circuit are being used to raise or lower the impedance of the signal at different points in the circuit, which would be why they are split across the jacks? And how it works, what theories I should study.

I would also love some insight to why Cornish would use two buffers in a row in a circuit like the G2, one for bypass, and one on the circuit input before the actual effect.

I messed with this a bit in a big muff I was designing and noticed a change in tone, for one thing.

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Post by marshmellow »

Leave it out completely, all it does is lower your level a tiny bit. If you have to use it for the sake of authenticity, 50R would be completely wrong, stressing the transistor way too much. Using that non-standard value instead of 47k doesn't make any sense either. Make it 47k-100k or something like that, it won't matter.

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Post by Taller76 »

marshmellow wrote:Leave it out completely, all it does is lower your level a tiny bit. If you have to use it for the sake of authenticity, 50R would be completely wrong, stressing the transistor way too much. Using that non-standard value instead of 47k doesn't make any sense either. Make it 47k-100k or something like that, it won't matter.
Thanks for your help!
In the G2 (and the Madbean Darkside) a 50R is spec'd for that position....out of curiosity what is the function of it once applied to the entire G2 circuit and why wouldn't it be a 47k-100k in that application?

I am basically borrowing the G2s input buffer and using it as a stand-alone....really wish there was a verified schematic of the LD-1 but some speculate that it is the same thing as the G2 input buffer....

Sorry for the n00bish questions, but I like to knows the hows and whys....Ill build it and see!

Cheers!
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Darkside_ver.2 rotated.pdf
(397.53 KiB) Downloaded 307 times
Cornish_G2 v.3.pdf
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Post by marshmellow »

I don't understand where you are getting the 50R from, because it's not in either of those schematics (we are talking about Darkside-R39 / G2-R40, right?). Anyway, you don't need the resistor, it does nothing but waste space. Why Mr. Cornish included it, I don't know.

And to repeat, a small value resistor (like 50R) in this position would load down the preceding stage way too much. So if you put it in, make it at least big enough it doesn't hurt anything (like 47k - ...). But it's a waste of two hard earned cents in my opinion.

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Post by Taller76 »

marshmellow wrote:I don't understand where you are getting the 50R from, because it's not in either of those schematics (we are talking about Darkside-R39 / G2-R40, right?). Anyway, you don't need the resistor, it does nothing but waste space. Why Mr. Cornish included it, I don't know.

And to repeat, a small value resistor (like 50R) in this position would load down the preceding stage way too much. So if you put it in, make it at least big enough it doesn't hurt anything (like 47k - ...). But it's a waste of two hard earned cents in my opinion.

OK...well just for the sake of illustration I have attached the portion of the schematics I'm referring to....there are 2 "buffers" a so called effects buffer and an input buffer so that might be where the confusion is. All I want to do is lop this buffer off and use it as a stand alone buffer à la the Cornish LD-1. Not even sure if the 2 are the same but like I said it seems to be assumed that they are (the g2 input buffer and the LD-1).
This is the input buffer from both schematics....thanks again for the info.
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G2_R6_51E_R.png
Darkside_R8_51R.png
Darkside_R8_51R.png (6.44 KiB) Viewed 5626 times

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