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

[jsteiger]

Jeff! Thanks so much for responding. Aside from a snafu on a vp28, this is the first module that’s given me an issue out of the 10 I’ve built(6 vp28s, 3 bt50s and all op amps)

When I first built the unit, it was passing audio in bypass mode, and was passing audio and trying to compress when activated. Meters were working too.
I wasn’t sure how to cal it back then, just wanted to make sure it powered on without smoking. No smoke.…then when I got it on the test jig, it started acting weird. Long story short, i powered on lots of times to try and figure it out and there was no smoke. Then one day, when plugged into my APi rack, it started smoking.

For starters, I realized I had one connector on my test job backwards. So I’ll remedy that.

PR3 seems fine, but PR4 is slightly burnt. They both still read 10r. Should I replace them anyways?

D1 and D2 are installed correctly

As for DT05, R5 and R6 smoke immediately as soon as power hits it…..I’ll triple check the DT05 for build fails. I’ll try and add a pic when I get home

You probably have some misplaced transistors on the DTO5. The OCD in me would replace the discolored 10R.

 

[Kpaas]

You probably have some misplaced transistors on the DTO5. The OCD in me would replace the discolored 10R.

I’ll replace that this week, and check the resistors on the DT05. Thanks Jeff! Can’t wait to hear this thing.

KP

 

[Kpaas]

I replaced the DT05 yesterday, and put a working op-amp in. Fired it up, and no smoke. Passes audio in bypass with a sine wave, and I'm getting 10v at Tp9. When I engage the compressor, I get an Audio spike for a second or two, then it drops down to a few db more than the incoming signsl...nowhere near +7.75dbu....also, the Q-Bias trim pot doesn't seem to be doing anything...any ideas??

KP

 

[jsteiger]

I replaced the DT05 yesterday, and put a working op-amp in. Fired it up, and no smoke. Passes audio in bypass with a sine wave, and I'm getting 10v at Tp9. When I engage the compressor, I get an Audio spike for a second or two, then it drops down to a few db more than the incoming signsl...nowhere near +7.75dbu....also, the Q-Bias trim pot doesn't seem to be doing anything...any ideas??

KP

Gosh that's hard to try and pinpoint. I'd for sure start looking for multiple misplaced resistors.

 

[Kpaas]

Ha.

Gosh that's hard to try and pinpoint. I'd for sure start looking for multiple misplaced resistors.

alright. I’ll start there. I’m assuming it’s something in the audio path, could it be the DTO5?

 

[RandyBeast321]

Hello,

I'm working on a bunch of Limiter Builds. I want to ensure I'm calibrating correctly using Pro Tools and my Signal generator.

I created an Aux track and added a signal generator with a 1K sine wave. I output that to one of my physical outputs and use a DMM to measure the AC coming out. 24.5 mV = -30dbu

To measure, I put black on pin 3 and red on pin 2.

Once I verified the voltage, I plug that into the capi 511 where the compressor is connected, then I take the output of that channel, and while the compressor is in bypass, I confirm "what I get in, is what I get out" still using DMM.

from there, I just use the output cable to verify the rest.

so my question is when I'm verifying 7dB of gain reduction:

**Gain Reduction Meter Calibration**
1. The goal for the next procedure is to get 7dB of gain reduction happening.
2. Start by flipping the GR toggle to off.
3. Apply a 1kHz sine wave @ +7dBu to the input.
4. Turn the input pot up to approximately 1:00.
5. Adjust the output pot so that your device monitoring the output level reads +7dBu.
6. Engage the GR toggle. Take note of the output level.
7. Disengage Gain Reduction.
8. Adjust the input pot up or down by the level amount noted in step #7 above. For example,
my reading in step #7 was +0.4dBu so I will adjust my input pot up so that the level at the
output is +7.4dBu. Then adjust the output pot to yield a +7dBu output level.
9. Engage the GR toggle to verify that you have 7dB of gain reduction. If not, adjust the
input an output pots as needed.
10. Once that has been verified, turn the GR toggle off.

What Number am I looking for to know 7dB of gain reduction is happening with DMM? I can adjust the input and output all day long to ensure 7dbu of output. but when I flip GR on, am I looking for 2.24V RMS? (7dBV = 2.24V RMS)

There are no videos anywhere on how to do this. So, if this is correct, I will work on a YouTube tutorial to help out anyone confused.

Thanks

 

[RandyBeast321]

I replaced the DT05 yesterday, and put a working op-amp in. Fired it up, and no smoke. Passes audio in bypass with a sine wave, and I'm getting 10v at Tp9. When I engage the compressor, I get an Audio spike for a second or two, then it drops down to a few db more than the incoming signsl...nowhere near +7.75dbu....also, the Q-Bias trim pot doesn't seem to be doing anything...any ideas??

KP

Hey man,

in my exp with building these things, when I get something way wonky like that, it's because something got put in backwards or in the wrong spot. Check all your diodes and caps, make sure they are correct and in the right direction. check your relays and chips, make sure they are correct. and last, check all the transistors and make sure they are all in the correct spots and facing the right way.

one time, I put one transistor in backwards and it screwed everything up....

 

[Deadly Mix]

Measured, and installed all of the resistors except for 2.
R28 & R52 are listed in the BOM as 470k, but my Fluke says they're 47k

 

[RandyBeast321]

Measured, and installed all of the resistors except for 2.
R28 & R52 are listed in the BOM as 470k, but my Fluke says they're 47k

the color codes would also agree with your fluke, do you have a stash of resistors? i have 100s of different values hanging on my wall to grab when I need em. Resistors are super cheap.

 

[jsteiger]

Measured, and installed all of the resistors except for 2.
R28 & R52 are listed in the BOM as 470k, but my Fluke says they're 47k

I would dbl check the installed R's that should be 470R and 47k. Once I had a local guy mix them all up. Nothing was in it's proper place.

 

[jsteiger]

Hello,

I'm working on a bunch of Limiter Builds. I want to ensure I'm calibrating correctly using Pro Tools and my Signal generator.

I created an Aux track and added a signal generator with a 1K sine wave. I output that to one of my physical outputs and use a DMM to measure the AC coming out. 24.5 mV = -30dbu

To measure, I put black on pin 3 and red on pin 2.

Once I verified the voltage, I plug that into the capi 511 where the compressor is connected, then I take the output of that channel, and while the compressor is in bypass, I confirm "what I get in, is what I get out" still using DMM.

from there, I just use the output cable to verify the rest.

so my question is when I'm verifying 7dB of gain reduction:

**Gain Reduction Meter Calibration**
1. The goal for the next procedure is to get 7dB of gain reduction happening.
2. Start by flipping the GR toggle to off.
3. Apply a 1kHz sine wave @ +7dBu to the input.
4. Turn the input pot up to approximately 1:00.
5. Adjust the output pot so that your device monitoring the output level reads +7dBu.
6. Engage the GR toggle. Take note of the output level.
7. Disengage Gain Reduction.
8. Adjust the input pot up or down by the level amount noted in step #7 above. For example,
my reading in step #7 was +0.4dBu so I will adjust my input pot up so that the level at the
output is +7.4dBu. Then adjust the output pot to yield a +7dBu output level.
9. Engage the GR toggle to verify that you have 7dB of gain reduction. If not, adjust the
input an output pots as needed.
10. Once that has been verified, turn the GR toggle off.

What Number am I looking for to know 7dB of gain reduction is happening with DMM? I can adjust the input and output all day long to ensure 7dbu of output. but when I flip GR on, am I looking for 2.24V RMS? (7dBV = 2.24V RMS)

There are no videos anywhere on how to do this. So, if this is correct, I will work on a YouTube tutorial to help out anyone confused.

Thanks

Hello,

I'm working on a bunch of Limiter Builds. I want to ensure I'm calibrating correctly using Pro Tools and my Signal generator.

I created an Aux track and added a signal generator with a 1K sine wave. I output that to one of my physical outputs and use a DMM to measure the AC coming out. 24.5 mV = -30dbu

To measure, I put black on pin 3 and red on pin 2.

Once I verified the voltage, I plug that into the capi 511 where the compressor is connected, then I take the output of that channel, and while the compressor is in bypass, I confirm "what I get in, is what I get out" still using DMM.

from there, I just use the output cable to verify the rest.

so my question is when I'm verifying 7dB of gain reduction:

**Gain Reduction Meter Calibration**
1. The goal for the next procedure is to get 7dB of gain reduction happening.
2. Start by flipping the GR toggle to off.
3. Apply a 1kHz sine wave @ +7dBu to the input.
4. Turn the input pot up to approximately 1:00.
5. Adjust the output pot so that your device monitoring the output level reads +7dBu.
6. Engage the GR toggle. Take note of the output level.
7. Disengage Gain Reduction.
8. Adjust the input pot up or down by the level amount noted in step #7 above. For example,
my reading in step #7 was +0.4dBu so I will adjust my input pot up so that the level at the
output is +7.4dBu. Then adjust the output pot to yield a +7dBu output level.
9. Engage the GR toggle to verify that you have 7dB of gain reduction. If not, adjust the
input an output pots as needed.
10. Once that has been verified, turn the GR toggle off.

What Number am I looking for to know 7dB of gain reduction is happening with DMM? I can adjust the input and output all day long to ensure 7dbu of output. but when I flip GR on, am I looking for 2.24V RMS? (7dBV = 2.24V RMS)

There are no videos anywhere on how to do this. So, if this is correct, I will work on a YouTube tutorial to help out anyone confused.

Thanks

I would use a DAW to verify the AC level not a DMM. There is a post a bit back where someone goes thru the steps of calibrating with a DAW. We actually don't have a DAW in the shop. We have 2 AP's that we use for this.

 

[Deadly Mix]

I would dbl check the installed R's that should be 470R and 47k. Once I had a local guy mix them all up. Nothing was in it's proper place.

Thanks. That clears it up. I also zoomed in on the side image of your product page for it and see 47k resistors. So, the BOM is the typo. It says "470k" and is also in the wrong order for a 47k value.
It's where a 470k would be... Well, technically, it's 1 spot away from where 470k should be if that's what it actually was.
I'll attach a picture so you can see the value typo and where it's out of order.

 

[jsteiger]

Thanks. That clears it up. I also zoomed in on the side image of your product page for it and see 47k resistors. So, the BOM is the typo. It says "470k" and is also in the wrong order for a 47k value.
It's where a 470k would be... Well, technically, it's 1 spot away from where 470k should be if that's what it actually was.
I'll attach a picture so you can see the value typo and where it's out of order.

I can assure you the BOM is 100% correct and accurate. There is only one of these resistors in question visible in the side product shot and it is indeed a 470k. The 4th band might look red but it is orange.

 

[RandyBeast321]

I would use a DAW to verify the AC level not a DMM. There is a post a bit back where someone goes thru the steps of calibrating with a DAW. We actually don't have a DAW in the shop. We have 2 AP's that we use for this.

yes, I use the DAW to output the Signal and verify using the DMM.

it just clicked on me that we are looking for 0dBu when GR is engaged while verifying 7dBu of gain reduction. so when GR is engaged, DMM should show 0.775V when finished correct?

 

[jsteiger]

yes, I use the DAW to output the Signal and verify using the DMM.

it just clicked on me that we are looking for 0dBu when GR is engaged while verifying 7dBu of gain reduction. so when GR is engaged, DMM should show 0.775V when finished correct?

Yessir!

 

[Deadly Mix]

the color codes would also agree with your fluke, do you have a stash of resistors? i have 100s of different values hanging on my wall to grab when I need em. Resistors are super cheap.

Unfortunately not, I should probably stock up on random components considering all the projects I have planned.

 

[rlanter]

When building the FC526-XFMR, I have ended up with 3 extra parts. One is a 3.16K ohm bias resister to be used in the T84 circuit. Does anyone know what this is and what is the T84 circuit?
I also ended up with two, what appears to be diodes in a bag labeled #1. They do not have any markings on them. Does any one know what they are used for and where they go?
Thanks....

 

[jsteiger]

When building the FC526-XFMR, I have ended up with 3 extra parts. One is a 3.16K ohm bias resister to be used in the T84 circuit. Does anyone know what this is and what is the T84 circuit?
I also ended up with two, what appears to be diodes in a bag labeled #1. They do not have any markings on them. Does any one know what they are used for and where they go?
Thanks....

These parts are not from one of our kits.

 

[Deadly Mix]

My 10M (R5) and 3.9M (R20) are measuring below 2.8M and readings never seem to settle on a number when measuring with multimeter (Fluke 179).

I'm tempted to think the problem is the Fluke 179 approaching its max because it seems unlikely that the 2 highest resistors are the only ones not reading accurately, but I checked online and it said that the 179 goes up to 50M.

Should I buy a new one of each, or what?
I don't have any spare resistors to use in their places.

 

[Deadly Mix]

It gets worse... Mouser says both resistors are out of stock and discontinued. I'm building a pair of comps. So, I want them as identical as possible.