One of my filters disappeared

[Control_Voltage]

Hi there,

Andy from Moog Tech Support here!

Please contact us directly for assistance with this issue, we will be happy to help you get it sorted out.

Andy Hughes, Service Manager
[email protected]
828-251-0090 xt 221

Nate Marino
[email protected]
xt. 204

Taylor Mott
[email protected]
xt. 217

Thanks,
Andy Hughes
Service Manager
Moog Music, Inc.

[deanolium]

Hi all,

I am experiencing the same problem. Both of my filters work from 1 to 3 poles, however, once in 4 pole mode both left and right signal is extremely attenuated and noisy. I am sure that I can handle replacing an IC chip, did the above advice fix the issue? I would consider sending my XL to NC, however, I have contacted Moog service twice and have been totally ignored.

Hi Paul,

The above IC was to replace a demultiplexer. This is basically a chip which takes in two inputs (which essentially holds a 2-bit number in binary, so 0-3) and has four outputs. Whatever number is on in the inputs makes that output turn on, whilst the other three outputs turn off. So if the inputs are 0 and 1, this refers to the number 1 in binary, and so output #1 turns on whilst outputs #0,#2,#3 turns off. Whilst is the inputs were 1 and 1, this refers to the number 3 in binary and so output #3 turns on, and so on.

This is probably used in the voyager to get which pole to use for a filter. The processor uses the two bit binary number since it saves bus lines; and this demultiplexer then turns a particular line on which then selects which poles to use. If this chip is faulty it could cause none of the lines to turn on if #3 is on which would mean when you select four poles you get silence.

However... that would be an all or nothing kind of thing. If you are getting noise, that could be something in the filter being off. Possibly the capacitor for the fourth pole. The multiplexer could still be broken if it's broken state is for that fourth line to flicker on and off, though I've no idea of the likelihood of that.

The best thing is to follow Andy's advice and contact them. They should be able to sort you out.

Good luck!