Sub Phatty KB Gate Input

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Joined: Sun Nov 12, 2017 4:43 pm

Sub Phatty KB Gate Input

Post by Speedball » Tue Dec 18, 2018 11:58 am


Can someone please explain how to use the Sub Phatty KB Gate input port?
The manual says "The KB GATE input accepts a +5 volt signal, which causes the Sub Phatty’s envelopes to trigger." , but the gate opens permanently as soon as I plug something in so how should I use this port?
I was hoping that I could use my Matrixbrute Gate CV Out to trigger the Phatty envelopes but that doesn't seem possible?

/ Andreas

Posts: 5
Joined: Thu Aug 25, 2016 10:56 am

Re: Sub Phatty KB Gate Input

Post by OneLittleFonzie » Thu Jan 03, 2019 7:25 am

Moog Tech Support wrote:

In response to your questions:

1. You are correct: When you insert a dummy cable (not connected to
anything) into the LP KB Gate input, the tip/sleeve connection is broken
and the Gate goes high through a 10k pull-up resistor. The Gate is open
and you hear sound. When you short tip/sleeve together (as is the
default configuration of the Moog footswitch), tip shorts to sleeve
which is ground (O Volts, low) and the Gate is closed. No sound from
the LP.
2. Yes, the sleeve of the KB Gate is connected to ground.
3. The manual specs are correct. Applying a +5 Volt signal will open
the gate. Zero volts or a grounded signal turns the Gate off.

It's worth noting that the +5 Volt signal must be "driven" enough to
pull-up the LP's Gate. This may be your problem. The CV products that
we make (such as the CP-251 and VX-351) have buffered outputs from
opamps that have sufficient power to do this. If your +5 Volt signal
isn't turning the Gate on, it may need a little more "juice." Measure
the signal with a voltmeter and make sure it's +5V. If it still isn't
turning on the LP, try sending it through a standard opamp buffer. If
it can pull current from a standard power rail (with at least +5 volts)
it should be good to go.

Hope this helps.

Posts: 7
Joined: Sun Nov 12, 2017 4:43 pm

Re: Sub Phatty KB Gate Input

Post by Speedball » Sat Jan 05, 2019 5:41 am

Thanks for the reply!

The Sub Phattys gate stays open even when I connect the Matrixbrute Gate Out to the phatty KB Gate Input.
My Matrixbrute outputs +4.94V (on tip) when it's gate is open, maybe that's not enough "juice" then? I don't have any other equipment to test it.

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