question concerning LFO

[pfeuh]

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]

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]

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

[pfeuh]

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

[lickspittle]

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.

[pfeuh]

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?

[Whelm]

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.

[pfeuh]

Thanks, it's done, now.

[KSS]

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.

[pfeuh]

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