Square Wave Guitar Pedal - Page 1
Forum section: electronics / beginners

author: Legal_Planet
author_rank: Newbie
timestamp: March 16, 2018, 11:11:24 pm
content: I'll jump to the case to avoid wasting too much of the readers' time. But I'll note I've done some rather hideous armature circuits to attempt this before asking people who're far more experienced.So the question is what'd be the best way to achieve a square wave from a guitar signal?I'd measure the voltage from the pickups but have no tools to do so. But the internet gods are saying 35mV to 1v is average. So I'm thinking boosting the voltage and using an op-amp (in my case a LM324) as a comparator would somehow work? I've tried to do so with no luck. But again I'm quite the nooby here.

author: Wimberleytech
author_rank: Super Contributor
timestamp: March 16, 2018, 11:20:49 pm
content: Quote from: Legal_Planet on March 16, 2018, 11:11:24 pmYou probably did not bias and ac couple it correctly. Search "op amp guitar preamp schematic" and there are many ideas to choose from. Take the output of the preamp and drive into another 324 properly biased acting as a comparator.

author: Legal_Planet
author_rank: Newbie
timestamp: March 16, 2018, 11:27:18 pm
content: Thanks! Will give a look and a try.

author: Zero999
author_rank: Super Contributor
timestamp: March 17, 2018, 12:16:33 am
content: Why not use a proper IC designed to be a comparator, such as the LM393 or LM339? The LM324 is designed to be a linear amplifier, not a comparator. It can be used as a comparator but very poorly, compared to a proper comparator IC.

author: Dumpsterholic
author_rank: Regular Contributor
timestamp: March 17, 2018, 02:05:54 am
content: Craig Anderton's book is a little dated. but inside it you'll find a couple of fuzz circuits which sound pretty good with electric guitars. If I remember correctly, he has a circuit built around a CD4049 hex inverter that'll give you a nasty square-wave sound.https://www.barnesandnoble.com/p/electronic-projects-for-musicians-with-soundsheet-craig-anderton/1000130023/2679416112164?st=PLA&sid=BNB_DRS_New+Marketplace+Shopping+Textbooks_00000000&2sid=Google_&sourceId=PLGoP164984&gclid=EAIaIQobChMI6u_azKHy2QIVTLnACh0TAAgsEAQYASABEgL8RPD_BwE

author: Audioguru
author_rank: Super Contributor
timestamp: March 17, 2018, 03:25:54 am
content: A raspy squarewave sounds awful on good speakers by a person having good hearing. It sounds fine on a cheap guitar speaker that has bad high frequency response by a person who is deaf.I turn off my hearing aids when I hear electric guitar fuzz or bagpipes.

author: Wimberleytech
author_rank: Super Contributor
timestamp: March 17, 2018, 04:03:42 am
content: Quote from: Audioguru on March 17, 2018, 03:25:54 amWell...it is Friday night.

author: Legal_Planet
author_rank: Newbie
timestamp: March 17, 2018, 04:05:19 am
content: I found a pdf of the book online and have been reading through it from start for the past 30 minutes. Wanted to stop real quick to say thanks and that it's a perfect starting place. And the square wave isn't meant to be ear candy but rather a building block. No plans to destroy people's ears or my own!

author: Bassman59
author_rank: Super Contributor
timestamp: March 17, 2018, 05:25:17 am
content: Quote from: Audioguru on March 17, 2018, 03:25:54 amAn electric guitar tone necessarily involves the speakers in the cabinet and especially the low-pass response of those speakers. It’s all part of the signal chain.A Rat fuzztone into a direct box into a mic preamp sounds awful. Into my ‘62 Bandmaster which drives a 2x12” cabinet, it sounds pretty great.

author: Bassman59
author_rank: Super Contributor
timestamp: March 17, 2018, 05:27:26 am
content: Quote from: Legal_Planet on March 16, 2018, 11:11:24 pmDon’t use a comparator. An op-amp with back-to-back diodes in the feedback loop is a good starting point. Seehere, for example.

author: mgraves235
author_rank: Newbie
timestamp: March 27, 2018, 03:32:06 am
content: a purely square wave audio signal will sound horrible, plus running DC current into a speaker is a great way to destroy it.

author: iampoor
author_rank: Frequent Contributor
timestamp: March 27, 2018, 03:41:42 am
content: Guitar square waves sound pretty good. Good in a "raw" sort of way (Yeah its an acquired taste!). Depends on the effect. I like Tim Escobedos square wave shaper, but its pretty intense!http://www.diale.org/escobedo.htmlQuote from: Audioguru on March 17, 2018, 03:25:54 amMost guitar speakers roll off past 7khz...many GOOD amps do too. Sounds like you just dont like fuzz tones. Reasonable enough.Quote from: mgraves235 on March 27, 2018, 03:32:06 amExcept it is a common effect....A "Fuzz box" basically is a square wave generator, and sounds far from horrible. We have beenusing them for a good 50 years now. :-)

author: Nerull
author_rank: Frequent Contributor
timestamp: March 27, 2018, 07:48:03 pm
content: Square waves were common in synths for a while too.The NES sound chip's two primary channels are square waves, as was the 8-bit Atari line.