Audio & Design Gemini - head scratcher...

[mutterd]

Hey guys,

I have an ADR Gemini Easy Rider - its a 1 RU stereo FET compressor...

Its a great sounding little machine - easy to use, goes from smooth to pretty crunchy, super fast attack times... and its got some mojo for sure...

anyway, I am having a pretty weird problem - wanted to see if anyone around here has had anything similar...

the symptoms:

If I run a signal in, say a room mic on the drums, and set the compression for 10db's of reduction in the meter, at some point in between peaks, the meter will drop off...

There is still some compression present, even though it doesn't show any gain reduction on the meter...

At this point, it will rumble/crackle a bit, which will build up until it peaks, which sets off the compressor and then come back in on some successive drum beat...

If I crank up the input gain it will also peak out and sort of reset, work for a bit and then do the same thing all over...

my first thoughts were that it was a leaky cap letting some bad DC thru somewhere, just because of the rumbling/crackling kind of sounds likes a bad coupling cap in a tube circuit...

I had a bunch of the Vishays kicking around, so I swapped all the electrolytics...

There were a few I didn't have on hand, a pair of polystyrene caps and a few film caps - but I noticed the problem a few days before leaving so I didn't have time to get them in...

Then after that I thought it was maybe a bad pot because of how I could sort of pop the compression back in by turning the input and attack knobs...

But I cleaned all the pots and switches as best I could... It has 2 switched pots in each channel - on the ratio knob - you can click it in to 1:1 and use it as a line amp, and on the release knob for an "auto" setting...

After that I thought it might be a badly biased FET, but only because in my 1176's when the FET's aren't set up they just do the weirdest things...

A cold solder does kind if makes sense too... They were genius - the bottom panel comes off so you can access the whole board without removing it from the chassis...

Another odd thing:

If I have it in stereo mode - the meter just mimics channel 1 on the channel 2 led indicator - BUT - channel 1's knobs do not control channel 2 - channel 2's knobs still work...

Not sure if it's related, but it's a bit wired none the less...

I'll attach a copy of the schematic...

I am talking to some ADR gurus on both sides of the pond - but I just wanted to toss it out here too...

thanks guys.
Tim

 

[JohnRoberts]

Sounds like bad solder connection...

JR

 

[SSLtech]

We mixed the New Order Album 'Brotherhood' through several of these, along with a crossover/recombiner, as a multiband limiter... Hard. Core.

I've also used dozens of them over the years, and I wouldn't rule out a dodgy connection, whether solder, or moving contact (PCB to pot or wiper-to-track, for example).

While they were indeed often 'a little bit off', they -like the vocal stressors and compexes did have a habit of becoming cranky when disturbed, as they aged.

"leaky cap" sounds more like a guess rather than a likely problem. -A leaky cap doesn't suddenly fix itself, then start misbehaving, then fix itself... you get the drift.

A fun little unit, but I still love Compexes uber alles.

 

[mutterd]

We mixed the New Order Album 'Brotherhood' through several of these, along with a crossover/recombiner, as a multiband limiter... Hard. Core.

wow - thats amazing…

Brotherhood is such a crazy sounding record - I've always felt like there was such a crazy disconnect between the band and the vocals on that record - the band is so crunchy and mean and awesome sounding - and i love that it was a few gemini's to help get it there - but the vocals just never quite get there for me - but I have always been more of a Joy Division man… but Peter Hook - that guy has something special - I would love to hear how you got that bass sound...

Anyway - so I've got the Gemini working pretty well now - the rumbling and cracking was most certainly a bad solder - I hit most of the joints when i recapped it, but it was still there - and the rest after posting here…

as for the other things - the weird stuff that was corroborated by GDIYguy - which is the weird peaking while turning thru the ratio's was fixed by a thorough calibration.

at this point - she's running like a champ - albeit not as stereo matched as I'd like it to be - but since it was never intended to do any sort of buss duties - it doesn't bother me too much…

I really do love the way these old ADR's sound, there is just nothing like it - sure, the Compex wins, but this has got some excitement in it as well. Its great on violins, great on OH's - it good on things that you don't want to get too mean sounding…

I also just recently got one of those Express Limiters and holy smokes - those things are AMAZING - put that across the drum buss, or on the room mics and the toms leap up in the most amazing way!!!

thanks fella's
T.

 

[groupdiyguy]

just an update for the group...me and mutterd have been trading pm's about our geminis operational & control quirks, which much ADR gear seems to have, most of which cleared up after calibration, and some not, like the meter jumping when turning the ratio control on mine, but its really a non issue...I just turn the ratio slower and it doesnt do it, have no other issues, and it sounds great. Nice FET comp similar to compex in response for less cost, & with added benefit of being stereo.