simple phase shifter

gabbagabi

hi

i´m searching for quite simple phase shifting circuits

i try this one
http://experimentalistsanonymous.com/diy/Schematics/Phasers/Single%20Phase%20Stage.gif

but i have no phase shift at the Output, whit sine or tri in the input

the intention is to have a adjustable phase shiftet LFO signal

thanks for links or ideas!
ahoi
gabbagabi

blue hell · Posted: Mon Mar 16, 2009 4:11 pm Post subject:

The phase shift you are getting will likely be very small with this circuit for LFO rate signals. The idea of it is that it gives the stated phase shift at a certain frequency, and with the component values used that would in the audio range. To get it down to LFO rates would likely (without doing calculations that is Rolling Eyes

) need very large capacitors in the circuit. So probably this is not the most suitable way to get phase control over LFOs, you'd want an LFO that has phase control built into it's core design I think ... and I googled a bit but couldn't readily find something suitable ... maybe one of the gurus here will have an idea or two ...

jnuaury · Posted: Mon Mar 16, 2009 4:16 pm Post subject:

I have been eyeing up this schematic

http://www.uni-bonn.de/~uzs159/triphase.html

haven't tried it yet but seems like a nice simple way to get a multiphase vc-lfo

Tim Servo

Yo Gabbagabi,

The Mankato VCF can be used as a wide range VCLFO (0.016Hz to 20kHz), and has eight outputs each with a 45 degree phase difference (0 degrees, 45 degrees, 90 degrees, 135 degrees, etc.). It also make a pretty nifty VCF. Wink

With this, you'll have a wide variety of phases available, but there is no provision for a variable phase output. The disadvantage to using a VCF as an oscillator is that you only get sine waves for outputs (that usually isn't a problem for most LFO duty).

HOWEVER, I'm also working on a new VCLFO that does have VC adjustable phase. It has two sets of outputs, and the phase of the second set is adjustable from 0 to 180 degrees under voltage control. This design also has all of the "standard" output waveforms (tri, square, saw, pulse, maybe VC tri to square and stepped saw). Actually, I call this my VCPO (Voltage Controlled Phase Oscillator). While it doesn't have the range of the Mankato, it does cover an 18,000:1 span. In LFO mode, it will cover 0.0078Hz (about 2 minutes/cycle) up to 150Hz. It should also make an interesting VCO in the audio range.

My schedule varies quite a bit, but I'm hoping to get a PCB of the VCPO available in the next 3 to 6 months. Sorry, but I can't nail down a date any better than that right now. Still, just wanted everyone to know that some stuff is cooking at Magic Smoke Labs. Wink

I can post some sound samples of the VCPO doing LFO work and as an audio oscillator if anyone is interested.

Tim (and his cat, Igor) Servo

gabbagabi · Posted: Tue Mar 17, 2009 2:56 am Post subject:

next i will try to raise Cap values , thx Blue Hell

gabbagabi · Posted: Tue Mar 17, 2009 8:26 am Post subject:

got it
THX for final tip Blue Hell

blue hell · Posted: Tue Mar 17, 2009 3:01 pm Post subject:

ian-s · Posted: Tue Mar 17, 2009 4:20 pm Post subject:

I'm guessing you would need to adjust the phase control whenever the lfo frequency changes.

Also, a non sine wave would have it's shape distorted due to different phase shifts on the harmonics?

These may not be a problem for your purposes. Smile

gabbagabi · Posted: Wed Mar 18, 2009 1:14 am Post subject:

yes all other then sine are distorted!

i´am always open for a better Idea

.

ian-s · Posted: Wed Mar 18, 2009 1:34 am Post subject:

gabbagabi · Posted: Wed Mar 18, 2009 4:29 am Post subject:

thanks for this link, looks very interesting

if this Saw Phase shifter works like i imagine,
i will belive in Magic, maybee
Shocked

gabbagabi · Posted: Wed Mar 18, 2009 11:01 am Post subject:

dosent work, no magic Wink

Scott Stites · Posted: Fri Mar 20, 2009 3:15 pm Post subject:

I've been working on a similar concept, only at audio range.

You can phase shift a sawtooth, feed the sawtooth into an ideal diode rectifier to get a triangle. You could then distort the triangle into a sine wave. Thomas Henry has a marvelous circuit for that function which does not waste an OTA. The TH circuit can be found on my site under the "MultiPhase" page (the one with the schematics).

For the sawtooth phase shifter, check out Scott Bernardi's Obesifier or any other sawtooth animinator. You'll want a trim to connect the dots on the output sawtooth. Google the Digisound Sawtooth Chorus unit - it will show you where to put the trim.

You will also want a fairly fine adjust on the phase control, due to the nature of the circuit.

This stuff does work; I have a fuzzy breadboard to prove it Very Happy

frijitz · Posted: Fri Mar 20, 2009 6:27 pm Post subject:

blue hell · Posted: Fri Mar 20, 2009 6:30 pm Post subject:

synthmonger · Posted: Sat Mar 21, 2009 6:21 pm Post subject:

This peaked my interest. I'm going to shoot for an all cmos phase shifter, or at least a hybrid with my new friend the 4007 as vc control. I'm thinking a panel with multiple manual phase shift elements and a master phase shift control. This way you could gang them together and have dual 6 stage or tripple 3 stage or one 12 stage, sorta deal.