Help with adding true bypass to bass wah.

rosssurf · January 22, 2007, 07:45:59 PM

A friend has asked me to add a true bypass switch to his dunlop bass wah. I have found a few things on line that will assist me in doing so, Hopwever I can wire it with a input buffer or delete the input buffer. I admit I do not know what this is. What is a buffer why might I need one , or conversly remove it?
Thanks

jonathan perez · January 22, 2007, 07:48:53 PM

why do you need to true bypass it?

rosssurf · January 22, 2007, 07:55:25 PM

He says it is sucking his tone. He also wants a little more bass from it. $:-\$

jonathan perez · January 22, 2007, 07:58:53 PM

well, i can help you, if the wah looks the same as the rest of the dunlop wahs...which i think it does.

http://www.stinkfoot.se/andreas/diy/mods/dunlop.htm

can you post a gut shot? if the "bass/gain" resistor is at 470ohms, then something like, say...430 ohms will do the trick, in adding more bass.

monty.carlos · January 24, 2007, 09:33:38 AM

This isn't the white Dunlop bass wah, is it? The optical one?

rosssurf · January 24, 2007, 06:17:50 PM

it's aactually the black one. It's a gcb 95 or 100.

jonathan perez · January 24, 2007, 06:30:04 PM

i figured as much, post a gut shot so i can see the similarities.

rosssurf · January 24, 2007, 07:24:18 PM

Thanks battle , What exactly does a buffer do? and why is it no longer needed if I add a true bypass switch?
That link is a great help.

Paul Marossy · January 24, 2007, 10:50:49 PM

The GCB-100 (bass wah) is exactly like the GCB-95, but with a lower value for the sweep cap. That's the only difference between the two circuits.

R.G. · January 25, 2007, 12:34:37 AM

A buffer is a circuit that presents a very high input impedance to a signal source and outputs a replica of that signal with a low output impedance.

That is, it eats almost no current from the signal source, and therefore does not load it down, and it can supply lots of current out, so it can drive loads that would suck the original signal source dry.

A buffer is usually a gain of one, but the word is sometimes used with other modifiers to indicate a gain of minus one (inverting) or a gain other than one.

The original wahs had a low input impedance so they loaded down guitar signals and disproportionately cut treble, even when "bypassed". True bypass fixed that.

Later wahs had input buffers so they were nonloading, and did not suck treble. With a good enough buffer you do not need true bypass. The business about an input buffer causing tone problems is a little suspect, so I would be very hesitant to remove a buffer that's already there. And I doubt that a buffered wah is causing tone problems. Could be, but approach that with some skepticism.

You need to go read "The Technology of Bypasses" at GEO, http://www.geofex.com for more on buffers and bypassing.

jonathan perez · January 25, 2007, 01:03:15 AM

Quote from: R.G. on January 25, 2007, 12:34:37 AM
A buffer is a circuit that presents a very high input impedance to a signal source and outputs a replica of that signal with a low output impedance.

That is, it eats almost no current from the signal source, and therefore does not load it down, and it can supply lots of current out, so it can drive loads that would suck the original signal source dry.

A buffer is usually a gain of one, but the word is sometimes used with other modifiers to indicate a gain of minus one (inverting) or a gain other than one.

The original wahs had a low input impedance so they loaded down guitar signals and disproportionately cut treble, even when "bypassed". True bypass fixed that.

Later wahs had input buffers so they were nonloading, and did not suck treble. With a good enough buffer you do not need true bypass. The business about an input buffer causing tone problems is a little suspect, so I would be very hesitant to remove a buffer that's already there. And I doubt that a buffered wah is causing tone problems. Could be, but approach that with some skepticism.

You need to go read "The Technology of Bypasses" at GEO, http://www.geofex.com for more on buffers and bypassing.

+1!

but keep in mind, RG, were dealing with "tone connoisseurs"...

there isnt much tone going on in a bass, anyways...so i dont see why just leaving it alone would be fine. for the longest time i used a non-true-bypassed crybaby...i think i only changed 2 resistors...left the rest alone...truth is, NOONE could tell the difference...by noone, i mean audience/friends/cousins/dog.

true bypass isnt needed in every circuit, especially if a good buffer is in hand. and i really think too many 'BOOTEEKERS" are using true bypass to their advantage...for a fact, ill get up to 6 questions per auction i put up, with my builds, all asking "is it true bypassed?"

but if you really want to get dirty about it, check out the link i sent you, for sure.

MikeH · January 26, 2007, 09:02:08 PM

Quote from: Paul Marossy on January 24, 2007, 10:50:49 PM
The GCB-100 (bass wah) is exactly like the GCB-95, but with a lower value for the sweep cap. That's the only difference between the two circuits.

I heard this is the only difference between a 95 and a Hendrix wah too. Is that true?

jonathan perez · January 26, 2007, 09:02:49 PM

yes, and i think it has a couple extra caps parallel to the .22 caps, right?

southtown · January 26, 2007, 09:31:55 PM

Quote from: thebattleofmidway on January 25, 2007, 01:03:15 AM

there isnt much tone going on in a bass, anyways...

uhhhh what?

Paul Marossy · January 26, 2007, 09:38:34 PM

QuoteI heard this is the only difference between a 95 and a Hendrix wah too. Is that true?

MikeH-

Not sure about the sweep cap, but I believe that the Hendrix wah has a 470K pot instead of a 100K pot in it.

jonathan perez · January 26, 2007, 10:01:40 PM

Quote from: southtown on January 26, 2007, 09:31:55 PM
Quote from: thebattleofmidway on January 25, 2007, 01:03:15 AM
there isnt much tone going on in a bass, anyways...

uhhhh what?

compared to an overblown plexi

southtown · January 27, 2007, 05:52:42 AM

I'll bite my tongue. but lets just say theres reasons why people but new $10k foderas a clean sound is veeery important to a bassist

Laus · January 27, 2007, 10:26:58 AM

as a bass player I really needed the true bypass om my GCB-95. It didn't have an input buffer and sucked a lot of tone/highs. Most bass players think only in terms of bass, but forget about treble. And believe me, there's a lot to win there.

TS: you have to find out which revision of the pedal you have. I would change it to true bypass anyway, if your bassplayer uses cabinet with a tweeter, necessity drops a bit. But the LED indicator is helpful..

Meanderthal · January 27, 2007, 12:01:40 PM

Quotea clean sound is veeery important to a bassist

And people wonder how I could prefer a SS cheap Behringer head to my V4b...

Quotethere isnt much tone going on in a bass

Quotecompared to an overblown plexi

WTF? Sorry, but I strongly disagree. Unless ya mean a guitar is better suited than a bass for a guitar amp...

Fact is, there are as many rich variations in bass tone (whole universes of tone based on technique and gear combinations, strings, room size, it goes on and on)possible as there are for guitar, and from my perspective, probably more. It's all a matter of perception, but if you listen you will notice that any instrument in a band has a lot going on tonewise... if the music as a whole is done well... subtle variations in bass tone can cause goosebumps, adrenalin, or even yawns.

I could list endless examples of songs with great bass tone, all of them with different bass tone, but that would be overkill for something so easily 'proven'. Just listen to music in general... it's in there. Heh- there's a lot of music out there thats only redeeming social value is great bass tone.

Ok, I'll shut up now.

Except to add that I won't tolerate tone sucking pedals either...

Paul Marossy · January 27, 2007, 12:47:48 PM

I'm a quasi-bass player, and I can attest to what the other bass players have said.

News:

Help with adding true bypass to bass wah.