True bypass technique article.

darron · April 11, 2007, 05:20:52 AM

Following on from this thread link, I decided to write up a quick article on true bypassing. There's nothing revolutionary in there but it should be good for beginners. Suggestions are welcomed (:

Here it is: link

John Lyons · April 11, 2007, 12:27:04 PM

That's a nice little article there darron! Thanks for posting that. I think it will help people undertand what's going on.

John

MartyMart · April 11, 2007, 12:28:38 PM

Nice work darron, good images and easy to understand .
MM

ezanker · April 11, 2007, 02:17:23 PM

Thanks for the nice article, I'm sure a lot of people will really appreciate it!

Quick correction:
On figure A. of the 3PDT switch you need to change one of the 2 LED labels to Ground.
EZ

darron · April 12, 2007, 04:46:33 AM

thanks for all of the positive feedback guys (:

Quote from: ezanker on April 11, 2007, 02:17:23 PM
Thanks for the nice article, I'm sure a lot of people will really appreciate it!

Quick correction:
On figure A. of the 3PDT switch you need to change one of the 2 LED labels to Ground.
EZ

i intentionally didn't write ground because someone may want to switch the positive (if negative grounded) line to switch the led. you are right though that it is a bit inconsistent with figure b. any suggestions for a re-labling?

thanks again (:

markm · April 12, 2007, 07:01:53 AM

Fantastic Job Darron!!
I saved the PDF file!
Thanks for that bit of info.

darron · April 12, 2007, 07:05:39 AM

Quote from: markm on April 12, 2007, 07:01:53 AM
Fantastic Job Darron!!
I saved the PDF file!
Thanks for that bit of info.

thanks MarkM... but why would YOU need to save that info? I bet you could lecture it!

i'm glad that we could exchange lessons (:

ezanker · April 12, 2007, 10:06:39 AM

Quote from: darron on April 12, 2007, 04:46:33 AM
i intentionally didn't write ground because someone may want to switch the positive (if negative grounded) line to switch the led. you are right though that it is a bit inconsistent with figure b. any suggestions for a re-labling?

It is fine as is. You could label the top one LED- (minus) and the bottom one Ground and just state in the text that this assumes you are disconnecting the LED from ground to turn it off. I guess the idea of the article is to use figure b anyway, so probably just leave it

EZ

audioguy · April 12, 2007, 12:03:55 PM

Nice work! I've saved a copy as well.

lautmaschine · April 13, 2007, 01:20:59 AM

Darron, thanks for this.

the effect input to ground makes sense, and is something i'll have to try. I don't think I quite understand the advantage of of connecting lugs 8 and 9 though. could you elaborate?

darron · April 13, 2007, 01:29:33 AM

Quote from: lautmaschine on April 13, 2007, 01:20:59 AM
I don't think I quite understand the advantage of of connecting lugs 8 and 9 though. could you elaborate?

yeah (:

normally in bypass mode a signal would enter the switch, return out, go through a jumper, enter the switch again, and then come out as the output. the switch just before the output is not really necessary. by jumping lugs 8 and 9, in bypass mode the signal only has to be switched by a single switch at the input, as though it was a SPDT, then it goes straight to the output. this sounds more reliable to me. this jumper does not effect the signal when the effect is toggled ON though, it's just an extra bit of wiring/coper that goes nowhere in that case.

i hope that helped, maybe i didn't explain it very well. you could use the same principal on a DPDT switch also with no LED.

alderbody · April 13, 2007, 03:17:10 AM

useful stuff, darron

great job!

thanks!

sjaltenb · April 13, 2007, 03:21:10 AM

hey darron thanks for that. when you say use a 1m resistor from the effect input etc etc...can you explain this in a little more detail... i dont understand where the resistor is connected to...Thanks!

darron · April 13, 2007, 03:34:18 AM

Quote from: sjaltenb on April 13, 2007, 03:21:10 AM
hey darron thanks for that. when you say use a 1m resistor from the effect input etc etc...can you explain this in a little more detail... i dont understand where the resistor is connected to...Thanks!

hi sjaltenb. sometimes when you toggle a foot switch to activate an effect you can hear a bit of a pop or click noise in the audio signal. this is usually caused by a little bit of static electricity that has built up which is discharged into your audio signal and heard. a good way to get rid of that noise is to use a 1m or a 2m2 resistor going from the effect input and output to ground (usually negative). this will discharge the static to ground so that when you toggle the switch it doesn't make that horrible noise. it could also help to protect your electronics if you have sensitive components.

any time that you connect your signal to ground it effectively mutes the signal. if you connect your signal to ground with a resistor, it will only mute a part of it. that's how a guitar's volume control works. volume knobs in effects are often a 500k potentiometer, 1m (1,000k) is large enough so that you can't hear any volume loss, but small enough so that static will pass through it.

i use 1m rather than 2m2 because its easier to find 1m in 1% metal films compared to carbon composite. i think blue resistors look prettier than brown

i hope that helps. if anyone has something to add/improve on this matter i'd be interested to hear it.

alderbody · April 13, 2007, 03:57:28 AM

i think it's the charge from the input/output caps of the circuit that causes the pops when True Bypassed.

darron · April 13, 2007, 04:05:18 AM

Quote from: alderbody on April 13, 2007, 03:57:28 AM
i think it's the charge from the input/output caps of the circuit that causes the pops when True Bypassed.

there's that too, and maybe that is more important. good call. i've noticed sometimes carpet for bedroom gigging seems to make a difference. if you make a true bypass box and loop it around an effect sometimes the pops seem to occur at random times. maybe i'm imagining this? with a grounded input you shouldn't need a pull-down resistor at the front of the signal anyway. otherwise with a DPDT it's a very good idea to put those resistors in there.

sjaltenb · April 13, 2007, 05:53:11 AM

im sorry for being a "newbie" but im about to build a huge Pete Cornish style board that will use about a dozen 3pdt true bypass circuits so i want to make sure i do everything to the best specs to reduce any and all noise!...so i want to make sure i understand this correctly..

i should put a 1m resistor inline between the "fx send" on the 3pdt and the "input" on the board, and between the "output" on the board and the "fx return" on the 3pdt?

Im still learning and reseraching but im learning very quickly! however...all these grounds etc kind of confuse me

Anyways, again sorry for being slow

Thanks Darron

ChrisPtacek · April 13, 2007, 01:56:43 PM

Article's not displaying for me. I get the PDF to open, and there's a couple sentences at the bottom, but the rest is all blank. I will try it from another machine a little later, and see if it's just my PC... probably is.

puretube · April 13, 2007, 02:07:06 PM

it`s >1Mb, might take a while to load...

QSQCaito · April 13, 2007, 05:15:03 PM

Very good indeed.

I'd like to make a suggestion. But It wouldn't be about the essentials of true bypass. Just better ways of wiring the DPDT. As Rg posted.. Or I can't really remember who. By this way Input is sent to ground when effect bypassed:

Green: Guitar Input
Violet: Effect Input
Brown: Guitar Output
Orange/pinky: Effect Output.
Black: Ground

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True bypass technique article.