Liberation into FreqBox

[tokenwelshman]

Hi

Newbie poster here, so be kind!

I've had a Liberation for a while. My dream keytar! Nice sound, but lacking a little grit for me. I've just got hold of a FreqBox, with the aim of getting the Liberation to talk to it and create a more monstrous sound.

I've got:
Liberation audio out - FreqBox audio in
Liberation CV out - FreqBox Freq in
Freqbox audio out - amp

With the Liberation CV Out and Trigger Out switched off, the FreqBox behaves as you'd expect with any other audio input. Switch Sync on and I get some lovely growly stuff. Mix set to about 50% and I get the pure Liberation ouput mixed with the FreqBox output - really nice.

However - with CV / Trig Out switched on at the Liberation controller, I don't get the behaviour I expected. The FreqBox VCO doesn't seem to track at all to the Liberation. The Scale and Range dials on the Liberation seem to have no effect on the FreqBox VCO pitch. The FreqBox VCO is outputting an incredibly high pitch, which doesn't seem to alter regardless of the key played on the Liberation. The FreqBox does seem to recognise the envelope of the sound the Liberation is playing, though, although I guess that's because the audio output from the Liberation is still being recognised.

Has anybody had any success getting the Liberation to control the FreqBox's VCO? Am I trying to achieve something that isn't possible with these two lovely bits of kit? Any advice will be gratefully accepted!

[JimF]

Hi Tokenwelshman,

it sounds like the freq cv input of the FreqBox could be faulty.

Check this by removing all connections to the FreqBox and connecting its Osc. output (not main out) to a mixer etc. Set it so that you can hear something from the FreqBox's internal VCO. Check that moving the FreqBox's VCO freq. knob changes the pitch.

If so, then so far so good. Now you need to give the FreqBox freq cv in a known good source of positive voltage, up to a couple of volts. This could come from other modular gear. Or: a quick-and-dirty way would be to take an AA or AAA cell, put it in an appropriate battery holder, solder a 6.5mm plug to the battery holder, sleeve to negative, tip to positive. (Best to use a stereo/TRS plug, leave ring without connection.) Check with multimeter: this should give about +1.5V at the plug.

Plugging this in to the FreqBox freq CV in (directly next to audio in) should cause the pitch to jump by somewhat more than an octave. If so, the FreqBox is probably ok (may need calibration), and you need to seek the problem in the cabling between Liberation and FreqBox, or in the Liberation itself.

If the pitch doesn't change, then it sounds like the FreqBox may need to go to the doctor.

If you're uncomfortable about the soldering etc, check if someone in your circle of friends has the necessary skills.

When the FreqBox and Liberation are both working and connected properly, the FreqBox will open a new sonic world, including something close to 2-operator FM sounds. (I use the combination FreqBox and Etherwave Pro theremin, magic!) I hope you can solve it, and enjoy!

Cheers,

JimF

[tokenwelshman]

Hi JimF

Thank you for the brilliant and quick reply!

The good news is my FreqBox is fine. I have a few modular bits and pieces, and connecting the output of a VCO into the FreqBox Freq In caused the pitch of the FreqBox Osc Out to vary nicely.

Which leaves us with cabling between the Liberation and the FreqBox, or the Liberation CV output. The cabling might be the most straightforward to investigate. Do you know what type of cable the CV output is expecting? My first test was using 1/4" TRS. Based on my latest test using using the modular signal, the FreqBox is happy with TRS input. Might the Liberation prefer something else eg TS rather than TRS?

And then testing the Liberation CV output... I assume I could pass it into the CV Input of the VCO in my modular - it isn't Moog, but I guess voltage is voltage and it should do something recognisable - does that sound sensible?

Thanks for your help again, really appreciate it.

tokenwelshman

[JimF]

Hi tokenwelshman,

sorry about the delayed reply, I was travelling (actually had a small amount of work in these troubled times!).

Caveat: I've never physically seen a Liberation, only photos, so I don't know exactly what it's outputs/connections etc are.

I assume, though, that it has a 1/4" (6.5.mm) socket for pitch cv out, probably TS, and that it's 1V/octave. (This is also what the FreqBox expects, assuming it's calibration is ok.)

The freq cv input on the FreqBox is TRS, earth to sleeve (of course), the cv that should control pitch goes to tip. The ring gives a constant +5V, for use with an expression pedal to control the pitch. The ring is supposed to be isolated/short-circuit protected, according to the documentation, so using a TS cable shouldn't hurt anything or stop anything else from working. But just to be safe, I use a TRS cable going into it (from my theremin's pitch cv out), with nothing connected to the ring.

So probably the first step should be to check that a pitch cv is actually coming from the Liberation. Easiest to check this using the actual cable that you will use to go to the FreqBox. With the cable connected to the Liberation pitch cv out, and pressing any (low) key on the keyboard, you should see some (probably positive) voltage between sleeve and tip of the TRS plug that will go to the FreqBox. If you see 0, then the cable is possibly faulty, or the Liberation has a problem. If not 0: then you can press a key on the Liberation one octave higher; the voltage should jump by 1V (assuming the Liberation works to 1V/octave standard). If that works, then the FreqBox's VCO should change pitch when you plug that cable in and play different keys.

Alternatively, use a suitable adaptor and connect the Liberation pitch cv out to any modular element (best: VCO) that will respond to a cv, and check it there. As you say, voltage is voltage, and even if the VCO you're testing with isn't 1V/octave, something should change. But it's best to use that actual cable that will go to the FreqBox (with adaptor if necessary), to verify that the cable is ok.

If these steps have checked out, and the FreqBox still doesn't respond to the pitch cv from the Liberation, then I'm a bit stuck. If all the cables are ok, and the Liberation is definitely sending a pitch cv, then maybe the FreqBox has a fault after all.

Hope you can sort it!

Cheers,

JimF

[tokenwelshman]

Hi JimF,

No problem at all - I assume being out and about with work is a good thing in these very strange times!

I found some useful information about the Liberation's CV output in a copy of the Taurus 2 manual, bizarrely! There's a section on connections into the Taurus which suggests the Liberation as a controller keyboard. I've added a screen grab. As you say the Liberation output is a 1/4" socket. The Taurus manual specifies that the cable from the Liberation CV out to the Taurus keyboard in must be a stereo cable, and also notes "In On Ring" on the output from the Liberation in the diagram. (Whereas it says "In On Tip" for the Trigger Out connection from the Liberation which I'm not using.) Does this suggest that the CV from the Liberation is on the ring of the cable whereas the FreqBox is expecting CV on the tip?

I don't have an oscilloscope so I can't directly measure the output from the Liberation. Plugging it into the FreqBox using a TRS cable gives the behaviour I first described - the VCO of the FreqBox shoots up to a high but audible pitch, and does not vary when the keys are pressed. (The Liberation itself is behaving fine, so the keyboard is generating CV internally.)

I plugged the Liberation CV output into my Eurorack modular, which I think operates on the same 1V/Oct system. The Eurorack takes 1/8" cables so there's a further adaptor required between the 1/4" TRS and the Eurorack. This time, the CV output from the Moog seems to have no impact at all on the VCO on the modular - it doesn't shoot up high as it does on the FreqBox. The CV socket on the modular's VCO is working fine with other inputs. This makes me wonder whether the connection into the modular is true. The 1/4" to 1/8" adaptor is TRS so in theory it should be okay.

Hmm. I'm hoping the answer is the ring / tip issue, as I assume it's easy enough to solve this with a TRS cable that flips the ring and tip signals...

Cheers

tokenwelshman

[JimF]

Hi Tokenwelshman,

a bit difficult to get clear info from the diagram. But reading it one way, it _could_ mean that the Liberation pitch cv out is on the ring of a TRS socket. So it might be worth trying to make a cable:

T - R
R- T
S - S

ie a crossover cable between ring and tip, and seeing if that helps. Assuming that the other connection (tip?) in the Liberation may have simply +5V on it, that could explain the sudden jump to a high, constant pitch. Using a crossover cable should be ok, if it's only +5V at the other end.

Hope this works. Otherwise, I'm not sure what to suggest.

Good luck!

JimF

[tokenwelshman]

Hi JimF

Brilliant, thank you for this suggestion. It sounds a lot cheaper than getting my Liberation's control box repaired, so it's got to be worth a try!

I'll let you know how I get on...

Cheers

Aaron

[JimF]

Hi Aaron,

just another quick thought:

In making the crossover cable, it might be best to leave the ring unconnected at the FreqBox end, to prevent +5V going somewhere it shouldn't. It really shouldn't be a problem; I assume that the various circuits are buffered/protected, but you never know...

On the basis of suspicion that the Liberation cv out tip carries +5V, and that the actual pitch cv is on the ring:

(Liberation) T - (FreqBox) unconnected
(Liberation) R - (FreqBox) T
(Liberation) S - (FreqBox) S

ie no ring connection at FreqBox end.

You may simply have to try all variants, to see if one of them works.

Btw, I'd highly recommend buying a simple, cheap digital multimeter (not oscilloscope), to make it easier to check what voltage is where. Costs about 10-20 of whatever your local currency is (if you're in Europe, USA, Australia etc - $, €, £ etc) at any electronics shop or chain. A worthwhile investment.

Cheers,

Jim

[tokenwelshman]

Hi Jim

Sorry for the delay in responding, I was away all last week.

Thanks for the suggestions. I wouldn't know where to start in making a cable (perhaps I should learn!!) so I ordered a TRS crossover cable. I've just tested it and the FreqBox VCO is still not responding to the Liberation CV out.

I noticed that when inserting the TRS cable into the FreqBox, with nothing plugged into the other end, I still got the frequency "jump" when the cable was part-way in. Probably nothing to do with the voltage at the Liberation's tip after all.

I guess the next step is to get hold of a voltmeter and check if anything is actually coming from the Liberation. I can see all this leading inevitably to a trip to the synth repair shop!

Cheers

Aaron

[JimF]

Hi Aaron,

assuming that the Liberation and FreqBox are working ok, I would have expected some combination of cables as discussed, including (perhaps) TRS crossover, to have worked. So it really is sounding like a problem in one of the 2 instruments. Sorry I can‘t be more helpful...

Good luck!

Jim