Author Topic: Jet Phaser: noise gate or soft switching???  (Read 2563 times)

armdnrdy

Jet Phaser: noise gate or soft switching???
« on: December 28, 2011, 03:38:00 PM »
Hi all,

I'm working on redesigning a Roland AP-7 Jet Phaser board and can use a bit of help identifying a part of the circuit. It looks to me that the "Gate" board that was added after the initial design consists of an input buffer ( I've read posts that the first version of the AP-7 had a signal drop when the effect was engaged) and FET switching.

 I have seen a post by a very respected member calling this a noise gate. Can someone please look at the schematic to verify this?

Sorry about the whole service package! Hit download document (under first and previous) to open the PDF. The gate board schematic is on page 6. I tried to upload just the Gate Board to the gallery but had problems logging in.  

http://www.aronnelson.com/gallery/main.php/v/MrHuge/album102/album79/AP_7.PDF.html



Thanks,
Larry
« Last Edit: December 28, 2011, 04:10:37 PM by armdnrdy »
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Mark Hammer

Re: Jet Phaser: noise gate or soft switching???
« Reply #1 on: December 28, 2011, 04:46:36 PM »
As near as I can tell, the only sort of noise control on the AP-7 would appear to occur in the form of a diode just before the Resonance control.  I gather the idea is that unless the feedback signal is above the forward voltage of the diode (which, presumably, residual hiss will not be) it won't make it through.  The residual hiss will be included with the phase-shift signal that gets passively mixed at the output, but it won't be inadvertently boosted by the feedback path in the absence of signal to mask it.

There IS a gate on the CE-1, but as near as I can tell, none of the early large-chassis phasers used a gate.

PRR

Re: Jet Phaser: noise gate or soft switching???
« Reply #2 on: December 28, 2011, 11:40:43 PM »
> Sorry about the whole service package! ... The gate board schematic is on page 6



Not a noise gate. Buffer before effect, two "gates" to select direct or effected.
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armdnrdy

Re: Jet Phaser: noise gate or soft switching???
« Reply #3 on: December 29, 2011, 01:05:05 AM »
Thanks PRR for uploading the schematic. I was having some issues today in the gallery.

I'm not an electronics guru but that's what it looked like to me. Thanks for confirming. I'll keep the input buffer and ace the switching on the new board.
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)