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VX-351 outputs -5V

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VX-351 outputs -5V

Postby stevehunt » Thu Oct 25, 2018 6:00 am

As per the manual, my VX-351 sends -5 to +5V on its vel, pressure and mod wheel outputs, among others. This seems a bit odd and non-standard. The modular gear I'm connecting to expects 0-5V. Do I need to build a set of level shifters, is there a secret hidden switch to change the levels or am I missing something obvious here? Thanks
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Re: VX-351 outputs -5V

Postby stevehunt » Thu Oct 25, 2018 7:56 am

ps I'm an electronics engineer and I think my preference here is to modify the VX internally. Is there a schematic anywhere? Thanks
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Re: VX-351 outputs -5V

Postby Markyboard » Sun Nov 04, 2018 11:29 am

Why do you want to do this? Are you trying to get the full sweep of the knob to operate between 0 and 5 V? That's more involved then a simple blocking diode. The voltage of these signals is generated from the Voyager, not the VX-351. If you're planning on modding the VX-351 which is a passive device you'd probably need some kind of power supply for active components needed to level shift the signals.

You never anticipate having external modules that need -5V to +5V? Are you aware that most of the the Voyager CV inputs operate between -5V and +5V?

Btw schematics for Moog products are not made available.
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Re: VX-351 outputs -5V

Postby stevehunt » Tue Nov 06, 2018 6:06 am

Why? I said: The modular gear I'm connecting to expects 0-5V. I want zero aftertouch to give zero CV modulation.

The VX-351 DOES receive +/-15V from the accessory port so I could add active circuitry if I wanted.

Moog do not make schematics publicly available but someone somewhere does have some and maybe they are available unofficially somewhere...

I have added four level shifters in the back of my modular rather than inside the VX where space is more limited.
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Re: VX-351 outputs -5V

Postby MC » Tue Nov 06, 2018 10:38 am

This is precisely why MIDI was invented: there has never been an industry standard on CV ranges and trigger voltage/polarity.

Like everyone else since the 1970s, you had to build converters to get synthesizers to talk to each other.
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Re: VX-351 outputs -5V

Postby Markyboard » Tue Nov 06, 2018 11:14 am

stevehunt wrote:Why? I said: The modular gear I'm connecting to expects 0-5V. I want zero aftertouch to give zero CV modulation.

The VX-351 DOES receive +/-15V from the accessory port so I could add active circuitry if I wanted.

I have added four level shifters in the back of my modular rather than inside the VX where space is more limited.


Ah ok - makes sense. I was thinking more about the "among others" . I typically run these VC signals into VCAs for level shifting/bias but understand not everyone wants to spend the money or take up space on these type modules.

Didnt know about the +/-15V on the acc. port - tnx.
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