Some Cornish pedal questions.... and build questions..

[msurdin]

Hey Everyone.

I was recently looking over the pete cornish site and ran over a few things I was intrested in and wondered if there is any way to build "something" like it.
The first this is his "LD-1"
http://petecornish.co.uk/SAELD-1.html
From what i understand it takes your guitars low impedence, and makes it a high impedence signal and puts it into a line driver.
(Can someone explain the differenc eto me between a line driver and buffer?)
Is it possible to make something "Like" this?

The second this was his A/B/C box.
http://petecornish.co.uk/SAEABCBox.html
I am only intrested in a ABY box. But his has some intresting information. It prevents hum, and drives your long cables and keeps the high impedence from all your effects...
It also has your normal channel that does not go out of phase. And the other channel apparently has a 50% chance of going out of phase when using 2 amps, so it has a phase reversal switch. Is this build-able also?

Thank you for you time!

Matt

[slacker]

The LD is a buffer there's loads of decent DIY ones, for example the ggg ones. A line driver just means it can drive a low impedance, so you can connect a long cable to it and you won't get any signal loss, which is what any of the DIY buffers are designed to do.

For a hum free ABY check out this http://www.geofex.com/FX_images/oaspltr.gif that does everything you want except the phase reverse. I think you could add this by putting a switchable inverting buffer in between the switches and output A.

[msurdin]

So using the GGG IC buffer would be doing the same thing?
I was told its the same buffer as the amz buffer? True?

How would I do the switchable inverting buffer?


Thanks guys!

[slacker]

So using the GGG IC buffer would be doing the same thing?

Yes

How would I do the switchable inverting buffer?

If you look at the inverting opamp buffer here http://www.muzique.com/lab/buffers.htm take that and put it between the switch and the output and add a bypass switch.

[msurdin]

So that buffer is going to have its own bypass switch to bring it in and out of the a channel on the aby?

[slacker]

That's right, bypass it and both channels are in phase, switch it in and they're out of phase. To be honest I don't think you need it, if you've got 2 amps then just moving around in front of them will change the phase of the signal that hits your ears, so I don't think it matters what the phase is that comes out of the speakers. Same if you're micing them up if you just move the mics around you can get them in or out of phase.

[msurdin]

I guess its why he uses that just for a 3 out...

[Mark Hammer]

Keep in mind who Cornish's clients tend to be: people who play on very large stages.  As such, there is a modest-to-big difference between the sort of buffer that simply matches impedance between stages, and the sort of higher-current stage that successfully delivers a signal over a 100ft cable to the sound guy seated in the middle of the festival crowd.  Jack Orman has a nice high-current buffer project on his AMZ site that you might want to take a look at.  Not complicated.

[Ben N]

Just adding to Mark's note: The IC you choose also makes a dffference if you are looking for high current drive for long cable runs. AFAIK, among common opamps the 5532 (and kin) is the king for this sort of thing, especially if you parallel up the two opamp stages in the chip, although it does not have a particularly high input impedance.

Phase correction is probably important only if you are running two channels of the same amp that are out of phase with each other, like a black  or silver face Fender. Check out RG's Adjusticator here:
http://www.geofex.com/circuits/circuit_sweepings.htm

Ben

[slacker]

Anyone ever tried using an LM386 to make a buffer/line driver, I'm thinking if it can drive an 8ohm speaker a long cable run should be no problem. You could have an opamp or a high impedance discrete buffer as a front end and then an LM286 set up for unity gain. You could even switch between the 2 inputs to give you a reverse phase option. Is there likely to be any mileage in this idea? 

[msurdin]

now my rig is pretty much like this

Guitar 8 foot cable

13 pedals...

aby out

If the ic buffer is alright for this should I make 2 for each in on the aby, or just after the aby?

And on the output of the board should I buffer that also? Alot of my effects have been buffered with that ic buffer

[Dragonfly]

Keep in mind who Cornish's clients tend to be: people who play on very large stages.  As such, there is a modest-to-big difference between the sort of buffer that simply matches impedance between stages, and the sort of higher-current stage that successfully delivers a signal over a 100ft cable to the sound guy seated in the middle of the festival crowd.  Jack Orman has a nice high-current buffer project on his AMZ site that you might want to take a look at.  Not complicated.

Absolutely 100% correct.

From what i've seen, Pete Cornish's pedals aren't anything mindblowingly complicated...just well thought out, and constructed like little tanks !

Jacks buffer should work very well for 99.99999% of the people out there....

[Mark Hammer]

now my rig is pretty much like this

Guitar 8 foot cable

13 pedals...

aby out

If the ic buffer is alright for this should I make 2 for each in on the aby, or just after the aby?

And on the output of the board should I buffer that also? Alot of my effects have been buffered with that ic buffer

1) That's a short distance, though you haven't specified the distance from the last pedal to the amp.

2) How many of these are true bypass and how many come with an onboard buffer?

3) Ultimately, you simply want to be certain that the first pedal in line doesn't have to contend with anything having too high an output impedance, and that the amp doesn't have to contend with the same.

[msurdin]

The first effect i am going to have there is a wah. The budda bud wah.
I'm not really sure but i think the tube driver might have one...
I know one of my compressors does (boss cs2)


From effects to the 2 amps it could be from 7 to 15 feet.
Would that be a problem?

[Mark Hammer]

No need for anything fancy under the circumstances you describe.  As long as there is at least one buffer somewhere that is always in circuit, you'll be fine.  So, if you had one buffered pedal on somewhere at any point you have the requisite buffering.  Alternatively, if you have a buffer at the very front end of your pedal chain, then no matter what you have on or off, there will be a low-to-high impedance buffer between the guitar and amp.  You're home free.

[Ben N]

You're home free.

... assuming the wah is not last in your chain.

[msurdin]

my wah is first in line, after the aby.

For the first buffer, should i have it like aby>buffer>effects. Or buffer on A, and B and then let it just go to effects...

For the out aby should I put a buffer there?

DO I need buffers on send and return pedals? I might have 10 foot cables going and coming back..

thanks