question concerning LFO

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Kent, luketeaford, Joe.

Post Reply
User avatar
pfeuh
Learning to Wiggle
Posts: 6
Joined: Thu Feb 20, 2020 10:44 am

question concerning LFO

Post by pfeuh » Tue Mar 30, 2021 6:26 am

Hello,

hello, as I have a small modular polyphonic 4 voices, I've searched for a 4 x LFO with common adjustment for delay, waveform and frequency, 4 trigger inputs and 4 outputs. As I have found nothing, I'm building one.

I've spied 2 commercial modules, Doepfer A-147-2 and Behringer 150 (a copy of the vintage Roland Modular). The oscilloscope tells me that:

Code: Select all

            A-147-2 150
Sinus       AC      AC
Triangle    AC      AC
Square      AD      DC
Saw         DC      DC
As a musician I suppose that square waves should be DC, because when you use a LFO/square on the pitch, it's for adding one or two semitone. any idea on why it's not the same on these 2 blend? Ease of production, not done by musician, something else?

A vibrato on classic guitar can't decrease the pitch under the note, the fret fixes the low limit, So same question for all the waves, why AC instead of DC?

jorg
Ultra Wiggler
Posts: 896
Joined: Fri Apr 03, 2015 9:38 am
Location: East Coast USA

Re: question concerning LFO

Post by jorg » Tue Mar 30, 2021 12:47 pm

Generally, I'd prefer that an LFO output AC (i.e. centered at zero). Some do that; some put the bottom of the waveform at zero. It's really a matter of preference (designer and buyer).

nigel
Ultra Wiggler
Posts: 786
Joined: Wed Jan 16, 2013 6:49 am
Location: Melbourne, Australia

Re: question concerning LFO

Post by nigel » Tue Mar 30, 2021 3:48 pm

Because a modular synth isn't a guitar? Because an LFO is used for much more than vibrato?

User avatar
pfeuh
Learning to Wiggle
Posts: 6
Joined: Thu Feb 20, 2020 10:44 am

Re: question concerning LFO

Post by pfeuh » Tue Mar 30, 2021 4:48 pm

Thanks for your answers. No compromise, I'm going to implement the 2 ways.

lickspittle
Learning to Wiggle
Posts: 49
Joined: Fri Feb 07, 2020 5:40 pm

Re: question concerning LFO

Post by lickspittle » Tue Mar 30, 2021 4:58 pm

If I understand you correctly (apologies if not), you may want to take a look at Electric Druid's Stomp LFO chip... https://electricdruid.net/product/stomplfo/

Bipolar, unipolar in each direction and everything in between.

User avatar
pfeuh
Learning to Wiggle
Posts: 6
Joined: Thu Feb 20, 2020 10:44 am

Re: question concerning LFO

Post by pfeuh » Wed Mar 31, 2021 12:40 am

The specs seem awesome and it's very cheap! I would have gladly exchanged the tap tempo pin for a reset/delay start pin. Thanks a lot, I'm going to buy some of them for tests.

EDIT

Unfortunately, I don't want a paypal account. It's writen Pay via PayPal; you can pay with your credit card if you don't have a PayPal account.... But how can I pay with my credit card? :bang:

User avatar
Whelm
Veteran Wiggler
Posts: 589
Joined: Fri Sep 11, 2015 7:27 pm
Location: West Coast Ish

Re: question concerning LFO

Post by Whelm » Wed Mar 31, 2021 9:30 pm

You can pay via your credit card through PayPal's platform, you just enter your information the way you would on any other site. You don't need to make an account AFAIK.

User avatar
pfeuh
Learning to Wiggle
Posts: 6
Joined: Thu Feb 20, 2020 10:44 am

Re: question concerning LFO

Post by pfeuh » Wed Mar 31, 2021 11:11 pm

Thanks, it's done, now.

User avatar
KSS
Super Deluxe Wiggler
Posts: 5290
Joined: Mon Jan 25, 2016 7:28 am

Re: question concerning LFO

Post by KSS » Sun Apr 04, 2021 7:55 pm

The best LFOs will have an offset ability. This way you can put the bottom or top of its waveforms where ever you want or need them to be musically. Having utiliites like mixers and dedicated level-offset tools allow the same thing throughout your patch, including LFOs set up the 'wrong' way. ;)

A variable bias or offset ability is *much* more important than having only one or the other or both of unipolar and bipolar output of waveforms.
Treat utility modules as stars instead of backup singers.
Treat power supplies like Rockstars instead of roadies!
Chase magic sound, not magic parts.

User avatar
pfeuh
Learning to Wiggle
Posts: 6
Joined: Thu Feb 20, 2020 10:44 am

Re: question concerning LFO

Post by pfeuh » Mon Apr 05, 2021 12:51 am

Thanks for this tip. I came to the same conclusion, but it's good to have a confirmation.

Post Reply

Return to “Music Tech DIY”