Refurbish of the PAiA Gator

[dan5150]

Hey guys,

I am now at a place where I am getting stumped, and could use some input from most of you that are smarter than me. :-)

I started this conversation in this thread (http://www.diystompboxes.com/smfforum/index.php?topic=79508.0) a few days ago. However, I realized the inital topic was about a vero layout, and not about the original product itself, therefore rather than hijack the old one, I am starting a new one....

I pulled out my oringal build of the PAiA Gator Noise gate from my "parts box", threw it on the bench in an effort to get it working again.

The good news is that it works. However not quite as good as I would like.

The main issues I am having are:

Threshold isn't really useable. Basically all the way to "zero" still cuts the signal too agressively.
Noticeable "boom" when gate kicks in.
Sucks a TON of gain from my signal! (Although not much volume)-  When engaged, it basically turns my dirty channel of the amp into an almost clean channel.

The very minor mods I have done are:

Remove "Ext. Trigger Jack".
Wire in a true byapss stomp switch.
Install a standard DC power jack.
Replace Threshold POT to a 25k (instead of 250k)

At this point, I am out of ideas. Could the "Gain suck" have to do with the Op amp buffer? All of the IC's are socketed, so I can replace them easily...


Any pointers/tips would be sweet!

[petemoore]

The main issues I am having are:

Threshold isn't really useable. Basically all the way to "zero" still cuts the signal too agressively.
Noticeable "boom" when gate kicks in.
Sucks a TON of gain from my signal! (Although not much volume)-  When engaged, it basically turns my dirty channel of the amp into an almost clean channel.
  Hmm, all the things noise gates promise to not do.
The very minor mods I have done are:
Remove "Ext. Trigger Jack".
Wire in a true byapss stomp switch.
Install a standard DC power jack.
  As long as it works...
Replace Threshold POT to a 25k (instead of 250k)
  This is something that could be enough to limit seriously the range of threshold, do you have a 500k pot handy ?

[dan5150]

Thanks Pete!

I did swap out to a 500k pot for the threshold and the difference is minimal. (I gues I am still a little confused in that I thought reducing the value of the pot would let more signal (due to less resistance) in.)

I could continue to increase the resistance by adding more fixed resistors in series with the pot to see if that helps....

Any ideas on the "gain suck" and the very noticeable noise when the gate closes?

[petemoore]

  Any ideas on the "gain suck" and the very noticeable noise when the gate closes?
  From what I understand the Piaa designs are worthy.
  The behaviour you describe is all things a noise gate shouldn't be known for.
  I would work more on determining if it is actually functioning properly to begin with, testing, searching and debugging.

[Cliff Schecht]

You can try increasing R8 and decreasing (or even eliminating) R7 for your gain problems and maybe even getting rid of the 100 pF cap in the feedback loop. Or instead you could try adding some gain to the first op amp stage, this would boost the levels feeding the gate circuit and increase output when signal is being passed.

This is looking at the Gaussmarkov schematic btw!

[Marcvv]

Ok, I will give an ellaborate response as this is something I have been dealing with.
I worked on an original kit by Paia. Please buy that to support them (if it is still available).

I received quit some help of Scott Lee of Paia and I am here posting part of his reply. I hope he does not mind. If so then please someone should let me know and I will remove this.



As the Gator is a noise gate and it is designed to be further down the line in your pedal chain.
Therefore it is not designed to handle the guitar signal. You have to make an adjustment to do that.

This is what Scott Lee suggested and that worked for me:

"A simple mod that makes the gate circuit more sensitive to the
input signal is to add some resistance from the R12/R13 junction to
V+.  When I've tried this before, I found that about 6.1M did the trick,
but you'll have to select some parallel or series combinations of
resistors to get this, or, use a trim or pot that is nearly this value with a
fixed resistor in series for an adjustment.  Then with the Threshold
control set for the most sensitivity, adjust so the inherent noise in the effect
or the guitar connected but not being played opens the gate.  Then, higher
settings should shut it again and you can set it for the perfect
balance of guitar decay, noise, or not."


The pop you are talking about is something I struggled with as well.
It sound sounds exactly as when you would disconnect the battery.

Soott Suggested:

"Adding a 0.1uF capacitor to the points in the circuit for IC3 pins 1 and
3 will work to slow the gate change slightly and perhaps stop any click
or pop. "


That did not work for me so I asked his help again.

Scott replied:
"I thought the 0.1uF capacitor would take care
of the trouble.  Please double check to be sure it is a 0.1uF (sometimes
marked 104, or, 100nF) and that it has good connections with pins 1 and
3 of IC3 (parallel with R19).  Did you notice any improvement with the
addition of the capacitor?  It would work to slow the voltage transition
of this stage slightly.  Yes, it is like removing the battery and the
resulting voltage/no-voltage change.

There is another spot the transition can be delayed and that is from
Point N to the Attack Delay control R17.  Normally when the input signal
is sensed the two stages before the control work to make a dc level that
is delayed in it's transition from low to high by the control setting an
amount of resistance into the capacitor C8.  When the level falls back
low (to close the gate), the resistance of the control is bypassed
through diode D3 mounted on the pot.  If the wire from N to the control
is disconnected and a resistor used to connect it, this resistance will
work to delay the transition back to a low voltage.  I think a resistor
in the range of 1k or so would do here but you might have to go up to
10k or so.  The more resistance the slower the gate will shut.
Thanks again.  Sincerely,  Scott Lee"

It did not solve it either.

I called in some expert help of a friend of mine who stated that it is how it is designed.
We tried a lot of things and could not solve it.

Later I found out that it was solved using a powersupply instead of a battery.........It works well now.
Hence my reaction in another post on the Gator.

I still have a crackle on the gain pot. I am open to suggestions.


With many thanks to Scott Lee and Paia for great support.

Best,

Marc

[Mark Hammer]

And THAT is why they deserve your support and everyone else's too.  They have provided that level of help for over 30 years.

[Cliff Schecht]

It's always a pleasure talking to Scott, he's a really nice guy who knows the PAiA products like none other. His advice is always spot on and he's very down to earth to boot. I'm not even sure how he finds the time to do customer support on top of all of the other work he does.. He must be a superhuman or something .

[Strategy]

That's really interesting that you are working on the "old" Gator board, I recently came across one of those as well and had issues with it. My dad during a recent visit brought me a Gator he constructed back when it came out- in '80-something! (When I was a little kid, circa 1978-1983, he taught in a university electronic music lab that, due to short funding, required kit building of a lot of the equipment.)

It has the original goofy "electronic alligator" logo and everything, copper colored powder coat etc, obscure/obsolete parts, etc. and original construction manual.

It worked fine-ish (sort of erratic) but STOPPED WORKING when I tried to install a true bypass footswitch. I spent a few days on it bewildered that I could not get a new switch kludged in. He had omitted the switch entirely in order to have it "on all the time" - intended for use with synthesizers and PAIA modular synth kits.

I was pretty bummed mainly just because I felt like I destroyed my dad's almost 30-year-old DIY handiwork. Supposedly he has another Gator buried somewhere in my parents' basement. I'm keeping this one around in case I can get it sorted. Otherwise though I'll probably just build the version at www.gaussmarkov.net and install it in the vintage case!

I'll be interested to see your footswitch solution if you come up with one.

- Strategy

[the recluse]

This thread got me itching to pull my gator out and give it another shot as well.  I built one from the gaussmarkov layout about a year ago, and it worked intermittently and then stopped completely (I'm certain this was due to shoddy construction on my part).  So after some tinkering yesterday I got it fired up and working and, and I'm very happy with it.  I omitted the trigger jack, and removed the true bypass wiring I had originally used.  I was hoping that using the built in bypass would eliminate the severe popping the TB had, and it has.  It also seems like using the built in active bypass takes care of a level drop that would happen when engaging the effect.  I really prefer this circuit to the slow gear clone I built in that the swell function is easier to achieve and the available rise time is longer.  Also, like the slow gear, I have found that running a compressor in front of the gator evens out the threshold response.