gates sta level pops

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rove

Well-known member
Joined
Jul 14, 2005
Messages
83
Location
KY
Hey everybody, this is my first post, been lurking for a little while, excellent and informative forum!
I recently bought a heavily modded Gates Sta-level compressor (attack, release, threshold controls added). It sounds pretty good, but it occasionally makes some relatively low level pop and sometimes fizzing sounds. Otherwise it is pretty quiet. I have replaced all the tubes and get no difference in the noises, it is intermittent and rare enough that I almost feel I can use the compressor for something real, but then in a quiet section there is a "pop". I am thinking I may even have some sort of problem with my AC coming into the house, but that will have to wait till the electrician can come by...
Anyways if there is any more information I can add to try to troubleshoot this, let me know. Otherwise, suggestions? I have the schematic/manual.
thanks for the time. It appears the unit was re-capped at some point.
 
welcome to the Lab!

I´m not familiar with that special thingy but when you say pops then a bell rings and it reminds me on dying electrolytic capacitors. Recapping them might be a solution. Have you ever treated the tube sockets with any chemicals (don´t know the real english name - contactspray???)? If so throw the sockets away and put new ones in.
You can try a search here, maybe someone posted something related before. If nothing else helps throw that box away and tell me where you left it. :green:

beware of DIY, it´s an addiction :mad:
:sam:
Jens
 
do the pops cause the compressor to act? that could be telling.

I had some pops on my am864 and i grounded the chassis and it went away, you could try that.



ps: good luck with the whole CIA agent leak investigation..... not! ;)
 
ha ha did not even think of the name and our "times" when I registered.
Thanks for the tip on the bad caps, that is what I am hoping it will NOT be, but could be. As far as grounding, I think that may have something to do with it as there is a bit of what sounds to me like 60 cycles coming through at low level. and sometimes it just lets out a little noise that I am not sure how to describe, let me think on it. The noises don't show on the meter as the meter only shows gain reduction and the noises are not loud enough to cause it to compress.
thanks for the replies so far.
 
Hey Rove,

I think grounding would be a good place to start before ripping out the caps... What you described was symptomatic of a grounding issue I had with a pair of pairs and an EQ. I would also get a low, faint. hum and the EQ would pop, crackle and sound distorted at times. Since star grounding everything the box is as quite as a mouse and the EQ has not a single audible noise and no hum at all.

Cheers

Matt
 
Thanks again for the suggestions.
I am going to take the Compressor over to a friend's who has a much better working knowledge of how to go about grounding it. This will also give me an opportunity to see if it just a "ghost" in the studio or something. So far the frustrating thing about DIY is that I don't already know everything, I keep telling myself to just be patient and keep practicing and learning.
Anybody here have first hand experience with grounding a Sta-Level?
 
let us know when you know everything. You´ll be the first!
Most of us are fishing in ink - at least I do. Deep black ink.
It´s about learning. I do something, make mistakes and then I learn and so on...
:thumb:
Jens
 
maybe I should have said "anything" and not everything...
I'll let you all know when I have at least figured out this compressor problem!
 
Hi Rove;

My STA isn't grounded from the power outlet either, In other words theres no 3rd Prong.. which is really whacky. Is your Gates Power connected to Screw terminals? what I have done was get a new Plug with a ground connection and connected the ground to the ground terminal (the same place you connect ground of your output XLR). After doing that my unit quieted down.

Another thing you should check is your Power Caps (C7 and C12 I think?)
20-20 mfd. and 15-15-10 Mfd. When I took a signal tracer to my unit those Caps were dry and leaky .. which created a motor-boat (popping) tremolo sound. Which would increase/decrease according to adjusting the input/output.

the Schematic - very essential.
 
Back when those were made, three pronged chords were pretty rare.

You have a vintage piece of tube equipment. These things make noise. All kinds of different noises. So it's hard to troubleshoot over the net, as noise is sound, something which can't be put into words easily, like a voltage or resistance. So it is very frustrating for us to try and help you. What would take two seconds if we were at your house, can take days on the forum.

But, there are some things you could try. Get some chopsticks or a #2B pencil. It has to be a #2B. #2 won't work. :razz: Then bang the non metalic end on the tubes and components, listening for noise. With something that old, the first thing you will notice is that when you tap on the tubes, all kinds of noise will be generated. This can be from the tube socket/vacuum tube pins connection, or microphony (noise) from the tubes themselves. You can either replace all the tube sockets (ugh!), or clean them with some type of cleaner (everyone at this forum has their own special favorite brand) and retension them with a dental pic or small screwdriver. Take the tubes out and try to work the gap close on the semi-circular portions of the socket that hold the tube pins.

Next, get a big filter cap, say 40 uf at 450 volts, and bridge it across the high voltage caps in the power supply. Use alligator leads so you don't fry any bacon off your back. See if you notice a reduction in 120 cycle hum. I have never heard a filter cap make popping noises, but there is a first time for everything I guess.

Try a seperate ground wire if you like, but don't expect any miracles. If the power coming into your house is that dirty, then a ground wire might not fix it completely. (talking like a laywer here).

Compressors can make a thumping noise when they are compressing. This is due to a dc hitting the transformer due to tube and transformer imbalance. This is normal for compressors of this type. It is what inspired engineers to invent other designs. You can probably get rid of most of it by balancing the tubes in the push-pull compressor circuit, and maybe setting a balance pot if you have one on that circuit. You may be able to insert resistors into the leads of the transformer to cut down on thumping also.
Look at different rev schematics for that thing if you can find them.

Oh crap. Here comes the UPS truck!
I'm out.
 
Well I took the sta level over to a friends and we tried a few things, turns out there was a loose solder connection, but fixing it did not change anything. So the next thing we tried was grounding the power with a 3-prong cable, attaching the ground wire to the ground terminal screw as suggested. The result... the unit stopped making the strange noises... for about 20 minutes, then started again. well at this point we decided to just run some stuff through it and see how it sounded and while it did occasionally pop, it seems a bit better behaved than before, and for the last hour or so I didn't hear any popping, so it seems to have helped something. Then we tried to figure out how the mods (threshold knob, attack knob, release knob with 3 position switch and fine tune pot) were done and where they would be in the original schematic which was quite interesting.
thanks again for the suggestions here, I think I can live with this thing the way it is now, at least until I get more experience under my belt and try to add my own mods, etc.
 
I would be really inteersted in knowing more about this mods. I´m getting a original unit for restoration in two months or so. It´s coming by surface from USA, and it can take a looong time to arrive, so would you take your time and make a drawing of the mods in the original schem?

Anyone likes this unit as it is?

Looking at the original schematic, I really think there is too much going on there for it to sound good as a studio tracking/mastering limiter... I´m thinking of cleaning it up, to a more standard compressor schem, like collins 356E-1...
 
Clean the sta level is not!
I think the mods (despite the troubles I am having with the unit) make the compressor far more versatile, the only original control was a single/double time constant switch. And the cool thing is that all the mods I described on mine can be done with out taking a drill to the chassis as all the holes already exist. As far as drawing you out a schematic, I can attempt something, but I haven't drawn a schematic since school (7 or 8 years) so don't expect much! I would be happy to send you pix too, just PM me.
I'll probably continue with some of the other troubleshooting suggested here as the comp is still kinda fussy, in the meantime if anybody thinks of any other suggestions I am listening!
thanks.
 
Don´t you want to pst the pics and schems herre?. There might be some more interest
good point! I am going to take some new pix and get them up as soon as I can. stay tuned...
 
just store them on a site and post the link, with the image file name after the link, like

www.lab.com/picture.jpg

or you can add the cute little "img" tags at the top of the editing windows, but it's not necessary, and actually un-wanted if the files are in the 500k 1 mb range.

'cj

holy cow, I picked a working link by accident! igore that .
 

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