How to use the full range of the cp251 with a Sub Phatty?

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radioland
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How to use the full range of the cp251 with a Sub Phatty?

Post by radioland » Wed Nov 20, 2013 5:33 am

Hey folks

I posted this problem in an other thread where it didn`t really fit in, so I give it a new try here.

I tried out the cp-251s triangle LFO out into the Sub Phattys pitch in, and I only got the top half of the waveform. In addition, the pitch change was only minimal (compared to what happens when you do the same with the frequency input of a FreqBox). How can I fix that? Putting the LFO out through an attenuator (+5) or through the mixer (offset and master at the maximum) didn`t help much.

First question: How can I use the full range of the cp251 (-5V to +5V) with my Sub Phatty (0V to +5V)? Is this possible with only the cp251?

Second question: Why is the depth of the modulation so much greater (about 5 octaves) with a FreqBox "Freq in" than with the Sub Phatty "Freq in" (less than an octave)?

Thanks for your help,

radioland
Sub Phatty, MF-101, MF-103, MF-104M, MF-107 (3), MF-108M, CP-251 (2), EP-2, Gibson Les Paul Studio 60s Tribute, Fender 50s Precision Bass, EBS Valve Drive, Lehle Sunday Driver, EHX Big Muff Pi, EHX Stereo Pulsar, TC Electronic Trinity Reverb, Logic Pro X

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Portamental
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by Portamental » Wed Nov 20, 2013 8:02 pm

As you witnessed, you get only the top half of the wave on an LFO modulation wave because CV input is 0 to +5v only on the SubP

The CP-251 LFO wave is -2.5 to +2.5v. Running through an attenuator can only attenuate that... that's what it's is made for.

You can patch the CP-251's to the mult, from the mult, 2 patch cables to two jacks of the mixer. This way you can boost the LFO wave to -5 to +5 volts. The SubP will still get only the positive part.

Both the Minitaur and SubP are sub-standard Moogs as far as pitch and filter CV inputs are concerned.

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bichuelo
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by bichuelo » Wed Nov 20, 2013 9:15 pm

Portamental wrote:As you witnessed, you get only the top half of the wave on an LFO modulation wave because CV input is 0 to +5v only on the SubP

The CP-251 LFO wave is -2.5 to +2.5v. Running through an attenuator can only attenuate that... that's what it's is made for.

You can patch the CP-251's to the mult, from the mult, 2 patch cables to two jacks of the mixer. This way you can boost the LFO wave to -5 to +5 volts. The SubP will still get only the positive part.

Both the Minitaur and SubP are sub-standard Moogs as far as pitch and filter CV inputs are concerned.


Do the Taurus and Little/Slim Phatty work better in this regard?
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Portamental
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by Portamental » Thu Nov 21, 2013 12:06 am

bichuelo wrote:Do the Taurus and Little/Slim Phatty work better in this regard?


The LP I know for sure is fine. The Slim is fine too, according to literature. Taurus 3 manual states only 0 to +5 volts for pitch and filter CV input, so that would be a no.

radioland
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by radioland » Tue Nov 26, 2013 9:43 am

Shouldn`t it be possible to raise the +/- 2.5V of the LFO to 0 - 5V with the offset knob? In the manual it says that the offset knob can raise or lower a mix by +/- 5V. I don`t really understand why I didn`t manage to achieve that with the cp251 and the Sub Phatty.

Has anybody technical background information about this?
Sub Phatty, MF-101, MF-103, MF-104M, MF-107 (3), MF-108M, CP-251 (2), EP-2, Gibson Les Paul Studio 60s Tribute, Fender 50s Precision Bass, EBS Valve Drive, Lehle Sunday Driver, EHX Big Muff Pi, EHX Stereo Pulsar, TC Electronic Trinity Reverb, Logic Pro X

Amos
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by Amos » Tue Nov 26, 2013 10:37 am

You can add +2.5V of offset to the LFO signal using the CP-251 mixer... patch from LFO out to one of the cv mixer inputs, then adjust the mixer Offset knob to about 3 o'clock (knob indicator pointing to the right)... then patch from the +out of the mixer to the pitch input of the Sub Phatty. This should give you the entire LFO signal sweeping from 0V to +5V. (make sure the mixer input and Master knobs are at maximum also.)
The CV input is calibrated to 1V per octave, so you should hear a 5-octave change in pitch as you sweep the pitch CV input signal from 0V to 5V. In the case of the Freqbox, it is not calibrated to 1V/Octave, so it may well have a more extreme response to the same pitch-CV sweep.

Tech note: On both the Sub Phatty and the Minitaur, the filter CV input is purely-analog, it is not scanned by the processor and it is not limited to the range 0-5V. You can apply a bipolar CV such as the CP-251 LFO to the filter CV input and you will hear the full LFO cycle modulating the filter.

radioland
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by radioland » Wed Nov 27, 2013 3:11 am

Wow, thank you Amos that you care to help an insignificant Swiss greenhorn! I greatly appreciate that and I am astonished how such a small company can produce so many great things AND care so much for their customers.
Glad to hear that I can use the cp251 the way I thought I could, and thanks for the info about the filter CV in. I hope to be able to apply your information this evening and thus learn more about synthesis and CV. Sometimes I feel like a synthesis apprentice with no idea, but I have to admit it`s getting better :D .
Just out of curiosity: Does the volume CV in range from 0 to +5V or does it also accept negative voltage? I guess I wouldn`t have found that out by myself because the manual says that the pitch, filter and volume CV ins ranged from 0 to +5V.

Thanks again,

radioland
Sub Phatty, MF-101, MF-103, MF-104M, MF-107 (3), MF-108M, CP-251 (2), EP-2, Gibson Les Paul Studio 60s Tribute, Fender 50s Precision Bass, EBS Valve Drive, Lehle Sunday Driver, EHX Big Muff Pi, EHX Stereo Pulsar, TC Electronic Trinity Reverb, Logic Pro X

Amos
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by Amos » Wed Nov 27, 2013 2:19 pm

radioland wrote:Just out of curiosity: Does the volume CV in range from 0 to +5V or does it also accept negative voltage?


Volume CV is indeed 0V to +5V.

unfiltered37
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by unfiltered37 » Wed Nov 27, 2013 6:53 pm

Is there any specific reason for unipolar vs bipolar CV inputs?

nathanscribe
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by nathanscribe » Sun Jan 26, 2014 2:33 pm

Just want to bump this for some clarity on the specs - rather than risk damaging anything.

I know the LP manual states 0-5V for all the CV/Gate inputs. But what happens if a voltage outside this range is applied? What protection is used at these inputs, are these figures nominal only? Most of my analogue kit puts our 15V gates. I'm not sure I'd want to plug that in without knowing I won't blow something on the LP.

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furiousgreencloud
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by furiousgreencloud » Mon Apr 28, 2014 9:02 pm

For all my kwetching about the crappy CV on the sub phatty, I actually tried it, at lease with Filter CV, today and was very pleasantly surprised. Although the Filter CV is 0-5V it is not unipolar, (as amos explains above), so positive and negative modulations are possible. And I didn't even have to buy any more gear! Really would be nice if the specs were clear in the manual. I got the hint when I saw the triangle wave was modulating the wave/filter & pitch in a bipolar fashion. Strangely (or maybe not for reasons i don't know) the other wave shapes are only positive modulations.

I used my DC coupled MOTU UltraLite Mk3, to get any shape of positive and negative modulation, with the -4.14 to +4.16V it produces, very happy! This at least for the filter this allows one any number of modulations with any shapes at digital audio rates. I'll post some Ableton Max4Live patches when done.

I don't think I'll be able to ring mod with the CV Vol in. But maybe I can FM with the the PitchCV if was I think these are bipolar. The Pitch CV is not linear (it's 1V/Oct) but i was thinking I could reverse the math to trick the Pitch CV to have a Linear Effect. It *should* work if it's zero crossing/bipolar. Not that I have a way of producing negative voltage CV anyway, but if it's normalized to 2.5V I could do it! Metallic Gongs/Bell Tones here we come! The only other way I've got anything metallic is, (a) is using a external digital ring modulator, which works rather well. (Not was good as real FM) and (b) creating inharmonics using audio rate filter frequency modulations (whines) and then jumping into them using a fast filter attack and decay. Give a nice impact, but not the complex warbling of bells.

Maybe I should give up and just keep digital for FM. I hear is was hard to do back in the day.

- furiousgreencloud (still no bell tones without external ring mod)

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furiousgreencloud
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Re: How to use the full range of the cp251 with a Sub Phatty

Post by furiousgreencloud » Tue Apr 29, 2014 7:06 pm

The quest for metallic/inharmonc tones continues...

Ok so i tried modulating the Pitch and Amp/Vol with negative amounts and NO GO.

Details:
- Vol is really just volume scaler, not a modulation from the current VCA level. Zero is Off. +5 is Current Level. So no ring modulation.
- Pitch is only an offset 0-5V you can only pitch up, so you're always modulating sharp. This is very strange because the internal LFO, can do it bipolar (but only for the triangle & S&H waves) and even at (constant) audio rates. It's alway an exponential scale (1V/OCT), it's not really useful for new timbres. Or is it? What do you all use it for? Analog Arpeggios, with a lag processor might be fun? But then a we have glide and midi.

Does anyone use even use any modulation except EG and Triangle, the others are so harsh/sirenish?

I guess I'll have to try with the Slim Phatty........ Or get something without presets, which is why i think/thought the the phattys are rad. I thought I could like play them in a band (http://thetherapy.bandcamp.com/), without asking for everyone to wait while I dial in my settings for pieces of paper.

Alternatives: Verona Lancet Filter Sounds Great, Intellijel Atlantis Does Linear FM. Basically go modular from the start. You'll never be disappointed with a lack of INs and OUTs, and (but?) you'll never get the same sound twice.

- fgc

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