CV Patchbay between LP/SP's and CP-251's

The Moog Forum Moog Music General Topics Forum
1

Hey there,

I have an LP St.II (with CV Output Mod), midichained with two SP’s and I also have two CP-251’s.
The SP’s and CP-251’s are to be rack mounted behind my LP, however I wish to make all the LP/SP CV&Gate inputs (+ outputs from LP CV Out Mod) more accessible to the CP-251’s by adding a patchbay below the CP-251’s. If possible, I would also like to route the audio ins/outs and headphone outs from the LP/SP’s, though the same patchbay.

I have read and tried to understand patchbay configurations from different threads - both on moog forums and other various forums, but I cannot seem to understand how my setup would work with any of them.

I don’t wish to setup/temporarily break any common connections etc. as all the recording studio examples on the web state, I’m just simply trying to bring the rear panel of the SP’s (and side panels of the LP) to a more accessible/patchable location close to my CP-251’s.

Some Questions:

  • Is there a way to configure patchbays so that each rear jack simply sends the signal to the front jack? i.e. top front jack 1 goes straight to top rear jack 1, bottom rear jack 1 goes straight to bottom rear jack 1, with no connection between top jack 1 and bottom jack 1?

  • Can I have signals running in different directions through any jack in the patchbay?

  • Can a single patchbay jack accept and pass-along a stereo headphone signal?

  • I am aware that gate signals may cause a problem, as with a cable constantly plugged into the LP/SP’s, they will constantly sound. How would I work around this issue?

  • I use EP-2 Expression pedals and would like to be able to plug them straight into the patchbay. Do I need to use TRS for all CV/Gate connections?

  • Are there any issues with audio, gates, CV’s, and headphone signals running though the same patchbay (without me patching the paths together at all)?

  • Do I need to think about grounding issues or anything like that?

  • Are DBX PB-48 Patchbays any good/would it work for my application?

Sorry about all the questions, I just don’t understand it all after reading various articles etc. that mainly concentrate on audio routing in studios.
Any help would be greatly appreciated!

Regards,
David Smyth
NZ

2

Hi David..

A bunch of us have done patch bays for moogerfoogers and I presume LPs on this forum and we should be able to get you started in the right direction.

The good news: A lot of the input/output jacks on the LP/SP will be usable with a patchbay with no modifications.
The bad news: Some of them will require tweaking (from an electronic circuit standpoint)

To answer a few of your questions. You should look for a balanced patchbay (TRS patchbay). These will enable you to utilize the +5V on the ring for the CV inputs (to allow an expression pedal to work with the patchbay), and the signal at the tip, in addition of allowing you to use a headphone output. The LP/SP CV outputs and audio outputs are mono and would work with a simple TS cable.

The patchbay that I use is the Samson SPatch Plus http://www.sweetwater.com/store/detail/SPatchPlus but there are others that you can use.

This patchbay has 3 modes, Normal, Half Normal, and Thru. For what you are looking to do, you would want to have it configured for thru (the other modes send signals from top to bottom and break connections when you plug stuff into the front as you’ve read about studio setups). This basically sends the signal from the input (on the rear of the bay) to the output (on the front of the bay) and isolates the top and bottom jacks. So this will work with the audio output, audio input, all the CV outputs (and gate), and i believe (but dont quote me) with the Filter and Volume CV inputs… You end up with issues with the pitch input (and the autotune feature) and as you mentioned, the gate input.

These jacks are different. I havent tried them with a patch bay yet (I can later today and tell you what happens), but i presume they wont work without modifications. However, if you have them midi chained together, i dont think you’ll use the volume CV input and Gate CV input often.

A good rule of thumb to keep things tidy and not to get confused is to keep all the inputs on the bottom and all the outputs on the top rows..

Audio and CV signals should be fine in the same patch bay (each patch ‘pair’ is isolated from each other). The only issue you would have to be careful would be putting CV outputs to an audio input. Some devices that you send that signal to (audio interface, amp, headphones, etc…) might not be able to handle slow electronic signals, and to top it off, the CV signals are a lot hotter (i.e. louder) than audio. So be careful, but shouldnt cause too much trouble. Audio signals going to a CV input should be fine, but remember audio is AC (going negative to positive voltage), and some CV jacks are only rated form 0-5V..

As for grounding, the only real issue i know of really pertains to patching a bunch of stuff together and creating ground loops. These just cause noise and maybe radio interference, but it shouldnt be damaging, just annoying if you are trying to record.

The DBX PB-48 that you reference should work. This one requires you to open up the bay to change configurations of the circuit board, but they call it “de-normalled for straight throughput”. So, not as easy as a switch on the front panel.

Hope that answers some of your questions.

Cheers,

Rob

3

Hi Rob,

Thanks for your response - it’s very informative and I now know what type and configuration of patch bay will suit my setup - TRS Balanced with a de-normalled (thru) configuration.

I would like to utilize the functionality of all the CV’s, so I’ll look into the workarounds (i.e. for gate and pitch) when I get a patchbay and start setting it up. I recall reading in threads in moog forums about soldering resistors into the patchbay - I assume I’ll need to do something like this to make the offending CV’s/Gates work.

Anyways, thanks again for your help!

Regards,
David Smyth
NZ

4

The resistors and soldering is true for some of the moogerfoogers, but im not sure about the LP gate/pitch CV inputs. I dont know if anyone actually figured that one out.

Cheers

5

Ohok, I guess I’ll just have to cross that bridge when I get there..

If you do end up trying some of these types of signals through a patchbay, I’d be keen to hear how it goes!

Thanks,
David Smyth
NZ