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I modded my Aphex 105 to have variable depth
Old 23rd September 2013
  #1
Gear Head
 

Thread Starter
I modded my Aphex 105 to have variable depth

I like that the Aphex 105 quad noise gate has the switch for 6dB/90dB of reduction, and I figured that switch's position in the schematic might clue me towards which components could provide an easy mod to make it have a little more reduction on the 6dB side. I needed something more like 12dB or 20dB or so.

Aphex Tech sent me a schematic (Thanks Aphex Tech!), and boy was I right about it being an easy mod! All you have to do is take the cover off (4 screws) and you're ready to apply the mod!

Each 6dB/90dB switch simply shorts out one particular resistor to get the 90dB, and by piggybacking more resistance (a resistor or a potentiometer), it's easy to alter the 6dB setting to whatever you want it to be. Even better, the switch that Aphex uses for the 6dB/90dB switch has contacts on both top and bottom, so you can get to the necessary contacts on the top part of the switch without even having to remove the PCB! I actually tested my mod with clip leads without having to solder anything.

The value of the resistor that the switch shorts out is 5.26k. I planned to snip one leg and put a series "lower limit" resistor in series with my pot so my range could reach down to around 3dB of reduction, but still go all the way to 90 as well. I decided not to bother with the series resistor, as the reduction at the 20k side of the pot's range (20k in parallel with 5.36k = 4.22k) was very close to the original 6dB and likely adequate for my needs. So all I really did was solder two legs of a potentiometer right across the switch contacts that are used to short the resistor. I bridged the wiper and unused leg of the pot for noise immunity (limits the max resistance to 20K during intermittent wiper contact during rotation).

I used 22 turn pots with values of 20k. This made a nice wide range but also wasn't touchy, due to the range being spread out over 22 turns. Obviously when the switch is pressed to the 90dB position, it shorts both resistances and provides 90dB as usual.

I found some great little Bournes pots at my local electronics store that use little screw adjustments rather than a shaft, so they hardly take up any room on the panel. Plus they are mounted by a threaded shaft, which I'd never seen on one of these shape pots. The store had a pretty full drawer of them, so if anyone else needs some like this, feel free to PM me and we can work out me picking some up and sending them to you. I presume they are unusual/rare since I'd never seen any like it before. They were $4.95 each, so $20 (plus shipping) gets you enough to do all 4 gates. They only had 20k 22 turn in this particular model.

Caution: Be careful drilling the hole through the panel. Put the drill bit deep into the chuck, so when the hole "lets go" and you ram the drill bit in to the hilt, you won't hit anything like the pots on the underside of the audio board in the back.

Here's some pics.


The knob on the panel:



Top view of the pot:



A little more to the side, to see the two switch contacts needed:



See how they all fit in there without having to remove anything except the lid?
Old 23rd September 2013
  #2
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mjrippe's Avatar
 

Wow, very nice work! Thanks for sharing. Too bad they didn't have something like a 10 turn though, 22 is long way to go!
Old 23rd September 2013
  #3
Gear Head
 

Thread Starter
Yeah, you have to wheel around for a few seconds to hear any change, but I'm OK with that. They had 10 turns and many variations and values, but only that one model that had that great threaded shaft that made it such simple mounting and took up almost no panel space.
Old 7th October 2013
  #4
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hymenoptera's Avatar
 

awesome mod! good work, looks real professional
Old 7th October 2013
  #5
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nice one. even though I hated those things because the gates had a tendency to lock up when you change mic/cords during a multi band thing
Old 7th October 2013
  #6
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hymenoptera's Avatar
 

Quote:
Originally Posted by drtechno View Post
nice one. even though I hated those things because the gates had a tendency to lock up when you change mic/cords during a multi band thing
maybe the next mod could be a "reset" switch
Old 10th October 2013
  #7
Gear Head
 

Thread Starter
Quote:
Originally Posted by hymenoptera View Post
maybe the next mod could be a "reset" switch
A momentary pushbutton (push to open, not push to close) on either side of the 24vac power line coming in would do that. You wouldn't even have to open the case for that one! It wouldn't be on the front panel though...
Old 13th October 2013
  #8
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hymenoptera's Avatar
 

Quote:
Originally Posted by kelstertx View Post
A momentary pushbutton (push to open, not push to close) on either side of the 24vac power line coming in would do that. You wouldn't even have to open the case for that one! It wouldn't be on the front panel though...
If you poked around you could probably determine the cause of the "lock up", maybe a cap not discharging, for instance, and use a (NO) momentary to short that cap to ground via resistor.

I wonder, does the entire unit "lock up", or just that one channel? I don't own one of these.
Old 14th March 2016
  #9
Gear Head
 

Thread Starter
Quote:
Originally Posted by drtechno View Post
nice one. even though I hated those things because the gates had a tendency to lock up when you change mic/cords during a multi band thing
Forgot to mention that mine is in a pre-wired Gator box I take to each depo. That has never happened to me.
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