[BUILD] CAPI FC526~500 Series~FET Limiter Kit~Official Support Thread

Yes. Sorry but I cheat and use an Audio Precision so its easy for me.

yes I understand... no pb... I try to find this kind of oscillo!

But for now, I test the FC526, Great great great!!!!! about the sound! I like a lot, for sure!!!

But another question:

I have build 2 compressor, The LED Gain Reduction Meter doesn't react exactly the same, on the same sound... What can I have done wrong? because I would like to use this 2 compressor on a stereo signal?

is it possible, a sort of link?

There is no link function. Dual mono is the only solution.

Hi guys!

Finished my first of two builds.

Having some calibration issues. Pre calibration and Bypass signals are normal.

When circuit is activated:

TP 1-2-3 are fine but I can't get past 11dBu at the output (should be around +14).

Where should I look?

TP9 is -9.98 VDC. That cool?

Thanks!

Nevermind! Had metering issues... ALL (BUTTONS IN) IS GOOD!

Hi Jeff, i'm on the end with the making and my transfo has no blue green and brown wires. Instead it has a grey a pink and a purple. Could you enlighten me?
Cheers.
Lud.

Lud said:

Hi Jeff, i'm on the end with the making and my transfo has no blue green and brown wires. Instead it has a grey a pink and a purple. Could you enlighten me?
Cheers.
Lud.

Click to expand...

I'm not Jeff, but it seems you've ordered the kit with the Litz wire transformer (instead of the standard EA2623). Check your order to confirm, then follow the table on the datasheet found via a link on the product page for, or here: http://www.capi-gear.com/catalog/images/gallery/2623/2623-1-L-specs.pdf

I'm not Jeff, but it seems you've ordered the kit with the Litz wire transformer (instead of the standard EA2623). Check your order to confirm, then follow the table on the datasheet found via a link on the product page for, or here: http://www.capi-gear.com/catalog/images/gallery/2623/2623-1-L-specs.pdf
[/quote]

Thanks for your help!

I've tested the opamps, one does not work, one woks but makes lots of noises/cracks  and one works.

I' tested the 526 with the 2520 in receiver and my two red dot as preamp and output.
when the Lb is switch on all lights are illuminated exept the red and the 20orange. The 20orange, when once i pushed a little bit the modul in its fram, get iluminated for a second.
Nothing works exepted when i turn the ratio (which is really really hard to turn) on ABI and everythink turns off. When i turn again the ration on what seems to be 20 the leds turn on from the green to the 10orange and stay iluminated what ever i do.

Any help and suggestions will be awesome.

Have you tested the audio path and other test points per the docs? I would not worry about trying it with a bad opamp installed.

jsteiger said:

Have you tested the audio path and other test points per the docs? I would not worry about trying it with a bad opamp installed.

Click to expand...

No i did not... Sorry for that.

The 2520 kit that seems to work well when tried in a vp25 placed at the output gives me around 3mv when the reddot gives me around 1.7/1.8mv.
tp1 and tp3 give me nothing.
On my sound analyser the input & output knobs react well as the BYP switch.
Actually only the tp3 gives a value.

TP1 is right after the receiver stage. The rest of the audio path does not matter if signal is not getting past the receiver amp. The most likely cause will be the receiver opamp or something wrong with the relay circuit and signal is not even coming into the receiver opamp.

Ok, so i've made other tests and here is what i have noticed :

tp1 : is still at zero.
tp2 : still at zero
tp3 : 2.3mV DC
tp4 : 0.012V AC
tp5 : 2.08V DC
tp6 : 2.08V DC
tp7 : ?
tp8 : 1.84V DC
tp9 : 10.01V DC
tp10 : ?
tp11 : ?
All the points on the meter board are right.

I run some OH in it and things seemed right exept for the ratio that i don't noticed the changes and so the HPF switch.
The differents attack times seem pretty discreet while the release time is obvious.

Have you got ideas of what to check?

Thanks
Lud.

Lud, maybe you are misunderstanding the tests. TP1 is just after the balanced receiver stage. If you have signal applied to the input and this TP has no reading, the input stage is not passing audio. If the input stage is not passing audio, there will not be any audio getting to the rest of the circuit. Maybe you are measuring here for DC? If you are using a DMM, you can only measure audio in ACV mode.

jsteiger said:

Lud, maybe you are misunderstanding the tests. TP1 is just after the balanced receiver stage. If you have signal applied to the input and this TP has no reading, the input stage is not passing audio. If the input stage is not passing audio, there will not be any audio getting to the rest of the circuit. Maybe you are measuring here for DC? If you are using a DMM, you can only measure audio in ACV mode.

Click to expand...

Hi Jeff, yes i do understand.
Just to be clear about the opamps : I have bought three gar2520 kits and i already had 2 red dot perfectly working in my couple of VP25. One kit is working, one makes noises, and one is not working. I have tested the 526 with the opamps working.
Today i've mixed some drums like i would do with any of my comps and everything was working (i did not noticed yet the impact of the HPF though). I'm not used with the input/threshold pot but i'm pretty pleased with the results so far! Thats my first FET gear.
So obviously i should have something at TP1. I must do something wrong. I do the measures with my poor DMM so that could be the issue. I'll ask some help with people who knows about electronics and who could give me access to an oscilloscope and could help me for all the tests and calibration. Those guys could also help me with fixing the opamps.

I'll keep you informed.
Cheers.

I am about to order a LC53A and a FC526 to complete an amazing channel strip along my VP28 in a custom enclosure. What is the difference between All Discrete, +1 and +2 for the FC526?

Thanks,
G

Golgoth said:

What is the difference between All Discrete, +1 and +2 for the FC526?

Click to expand...

The all discrete will need 3 discrete opamp kits with it.

The "+1" comes with one IC adapter opamp kit so two discrete amps will be needed.

The "+2" comes with two IC opamp kits so only one discrete amp is needed.

Oh okay! Tough choice...

I thought I would share some info I recently discovered. It relates to folks having calibration trouble and the symptom of "running out of room on the RV8 trimmer" when trying to calibrate the meter.

I shipped a pair of kits to a TapeOp magazine reviewer. He said one kit cal'ed up just fine but was having trouble with the other. He described the above symptom and that the RV8 trimmer would "bottom out" before he could achieve the proper meter voltage at TP10. I would normally not do this but under the circumstance (magazine review) I thought it would be a good chance to see what the deal was since a handful of people have experienced a similar phenomenon so I asked him to ship it to me.

I wanted to start at the beginning so when I got the unit in, the first thing I did was bottom out both RV1 and RV8. I did this by turning in one direction unit I could hear them acoustically "click". I then count 12 turns back in the opposite direction. Since they are 25 turn trimmers, this puts them very near their factory set mid position.

Next I wanted to adjust the VVR FET safely out of conductive range so I could dbl check the audio path. I set the unit the 20:1 and followed the steps in the guide. That is when I discovered that the VVR FET was NOT set properly and actually not conducting at all.

The audio path was perfectly fine so I adjusted the VVR FET for the stated 0.5dB of loss.

It took me 3-4 turns of the RV1 and RV8 trimmers to get the meter voltage set just right. Absolutely no trouble at all.

In conclusion, if you are having trouble cal'ing the meter, make sure the VVR FET is properly biased. If not, you will never get the meter set right. Also you must be set to 20:1 (not ABI). You should also check the bias voltage of the FET at TP7. If this reading matches what was marked on the pink FET baggie, (and there are no build blunders), you should be able to cal in the meter spot on with no trouble.

Hope this helps!
Best, Jeff

i am trying to calibrate my FC526. Made a bit of mistake. I somehow 'touched' something on the meter PCB. I smelled a little bit of a burning but it was like, really temporary. And the unit still seemed to be working. Anyway, went ahead with testing/calibration.

Three known good opamps on board
When I try and calibrate, my meter JUMPS from 2.24v straight up to 2.5v (not able to 'tune' the voltage to 2.487 on the front panel RV1 without it shooting straight up).

When I try and use the compressor, it compresses but I can't really tell if the attack/release are working correctly because the Led literally 'switches on' (up to 7) and off. In fact it seems like the compressor is only working in an On/Off fashion, if I increase the input level up to a certain level. Its like the compressor 'kicks in' rather than smoothly comes in

I've calibrated one FC526 successfully already. Anyone got any ideas what might have got fucked during this final stage, that might be causing this?

Matt

Jeff, can you advise if there are any voltages I should be reading to tell me where the problem may lie?

Matt

Matt

I would check all of the TP voltages in the doc's as well as the meter PCB voltages that are published. There are many. You can also verify how much compression you are getting by noting the level with and without the GR switch engaged. It should be easy to verify smaller amounts.

You can also pull the meter PCB from your good working unit and try it on the unit in question. That may tell you if the issue in fact resides on the meter PCB. There will be no adjustments needed to swap the boards. Do not change anything except  unplug one meter PCB and plug in the other.