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

[jsteiger]

I just added another 50pc batch of these to the store.

 

[PeteJE]

Can anybody comment on these sonically when it comes to clarity / transparency in a light ratio (2:1) on clean vocal?  As something more like a mastering touch on a vocal?  Hoping to get depth and clarity and fullness in a light mode without too much harmonic or fuzzy coloration.  Clearly these are fantastic for color and  crushing parallel compression hugeness (I listened to the drum examples on realgear online - awesome), but wonder about a less colored use.  For some reference have been using massey CT5 in plug in world and the JLM LA 500 in the analogue and have used just about all different models of the analogue classics over the years.

 

[jsteiger]

Can anybody comment on these sonically when it comes to clarity / transparency in a light ratio (2:1) on clean vocal?  As something more like a mastering touch on a vocal?  Hoping to get depth and clarity and fullness in a light mode without too much harmonic or fuzzy coloration.  Clearly these are fantastic for color and  crushing parallel compression hugeness (I listened to the drum examples on realgear online - awesome), but wonder about a less colored use.  For some reference have been using massey CT5 in plug in world and the JLM LA 500 in the analogue and have used just about all different models of the analogue classics over the years.

Hi Pete, I would suggest posting over at RGO and tagging John Kennedy. He has one of the first 8 units that I built up. I know many folks are working on them but I don't think anyone has made it to the finish line yet. If John is not super busy, he may be able to post some clips. FYI, Rob Schnapf had a demo for a few weeks. He tried it on everything. I could probably get him to reply if you post your question on the FC526 thread at RGO.

 

[stribor1]

One unit up and running, did the 3x1731 myself, everything fired up right from the bench. Just finished the calibration, quick soundcheck, works great on drums!!! I'm ordering a second one.
Anyhow, any instructions on the THD N measurement? Don't have any analyzers just my DAW (Windows, Cubase, RME HDSPe AES32, Mytek 8x192)can someone recoment an plug-in or easy to use app?

 

[jsteiger]

One unit up and running, did the 3x1731 myself, everything fired up right from the bench. Just finished the calibration, quick soundcheck, works great on drums!!! I'm ordering a second one.
Anyhow, any instructions on the THD N measurement? Don't have any analyzers just my DAW (Windows, Cubase, RME HDSPe AES32, Mytek 8x192)can someone recoment an plug-in or easy to use app?

I am far from a DAW guy but did some googling and found this for a Windows machine. I found the link in a SoundOnSound article http://www.sillanumsoft.org

 

[PeteJE]

On main PCB parts, can anyone id the two loose glass diodes on the BOM for me?  I id the 9 (on tape), the two small black are the FDH333 I believe, the two larger black are the 1N4004 I believe, but don't know what the two loose other ones are (look like the 9 on tape)....  thanks.  (chunger!! I'm scared without the pics, ha)

 

[jsteiger]

On main PCB parts, can anyone id the two loose glass diodes on the BOM for me?  I id the 9 (on tape), the two small black are the FDH333 I believe, the two larger black are the 1N4004 I believe, but don't know what the two loose other ones are (look like the 9 on tape)....  thanks.  (chunger!! I'm scared without the pics, ha)

One will be the 13V zener. The markings on the side with be :
24
3B

The other will be the 4.3V zener and will be marked 4V3.

You will need some sort of magnification to read these labels.

 

[PeteJE]

On main PCB parts, can anyone id the two loose glass diodes on the BOM for me?  I id the 9 (on tape), the two small black are the FDH333 I believe, the two larger black are the 1N4004 I believe, but don't know what the two loose other ones are (look like the 9 on tape)....  thanks.  (chunger!! I'm scared without the pics, ha)

One will be the 13V zener. The markings on the side with be :
24
3B

The other will be the 4.3V zener and will be marked 4V3.

You will need some sort of magnification to read these labels.

Thanks Jeff, I just got it - my table mag + glasses barely made it lolol......

 

[JeromeMason]

Having an issue here, when the comp is engaged getting a very thin sound, almost like a HPF as been rolled up to 400hz. Could this be in the Q-bias setup? I've always turned my trim pots CCW before I adjust, did you have this preset or anything?

Also, for most folks they'll be using their DAW's to monitor the levels being sent and monitored, I don't have any elaborate metering that will tell me dbu or vu, everything is just db that I can reference to -18dbfs. Is there some formula to be able to use so we can translate dbu into db? For instance, none of my metering will even go to +15.5dbu.

On THD+N I'm guessing the best way is to read the output with a spectrum analyzer and adjust until most of the noise is gone? That's how I did it but, maybe that's where this roll off is happening, maybe it's run too soft?

I think my problem is in the calibration, and my scope is being borrowed right now so I'm trying to do this in my DAW like a lot of folks will, it'll be good to go ahead and get this in the build thread.

Thanks!

 

[pachi2007]

http://www.cranesong.com/Volts%20to%20dBu%20to%20VU%20Comparison.pdf

You can send a tone from the secuencer and measure volts across pin 2 and 3.
I guess you can move the fader till you get the needed volts/dBu.

There´s a video at Hairball about calibrating very useful.

Also useful:

http://www.sengpielaudio.com/calculator-db-volt.htm

Hope it helps

 

[jsteiger]

First off, it would be helpful to know if the opamps are new builds and/or if they have been tested in something else. Starting up with 3 freshly built opamps in a freshly built FC526 is a definite no-no! So please, anyone posting for help, let us know those details first.

Having an issue here, when the comp is engaged getting a very thin sound, almost like a HPF as been rolled up to 400hz. Could this be in the Q-bias setup? I've always turned my trim pots CCW before I adjust, did you have this preset or anything?

None of the trim pots should be turned before it is specified in the calibration doc. They are all in their factory set position which is somewhere near 50%. Turning them all CCW is for sure not a good way to start especially if you look at step 14 of the calibration doc which states that the Q-Bias trimmer should be turned CW. I also have it bold and underlined in the doc. 

I would recommend to turn GR off, monitor the output level, turn the Q-Bias trimmer CW until the level stops increasing. This will take the VVR FET out of its conductive range. At this point, measure the freq response to see if it is high passed still. If so, you have a problem with the audio path somewhere. We'll go down that path if and when we need to.

PSA, when adjusting the Q-Bias trimmer, turning it CW will let the signal level increase. Turning it CCW will essentially turn the signal level down. Kinda reacts like turning a volume knob, in a logical fashion. Hope that makes sense. It's opposite of an 1176 so keep that in mind, or just follow my calibration doc to the letter and you'll be fine.

 

[rabe]

I just finished building my first FC526, my 7th kit from CAPI, thank you Jeff for such addicting products. 
When applying the 1khz sine wave and flipping the toggle to ACT I still get a .775 vac reading on my meter.
All 3 of the op amps are taken from existing working preamps.
I have check for solder bridges and didn't find any.
I would be grateful for any suggestions on where i should start trouble shooting.
Thanks,
Rob

 

[jsteiger]

Are you saying the hard bypass relays are not flipping?

 

[rabe]

The switch seems to be working; when in the BYP position there is continuity between to outside 2 back pins and when it is in the ACT position there is no continuity. 

 

[jsteiger]

When in hard bypass the following gold fingers should be connected;

Finger #2 to #10

Finger #4 to #8

When in ACTive mode, there should be no continuity between the above gold fingers.

 

[rabe]

Thanks for the quick response!!
There is continuity between the #2 to #10 fingers
and the #4 to #8 fingers in both BYPass and ACtive modes. 
Should I replace the switch?  I have another from a second FC526 kit that i haven't started yet.

 

[jsteiger]

Thanks for the quick response!!
There is continuity between the #2 to #10 fingers
and the #4 to #8 fingers in both BYPass and ACtive modes. 
Should I replace the switch?  I have another from a second FC526 kit that i haven't started yet.

Hmm, I would check continuity on the switch pins before removing it. The chances of a bad switch are pretty slim.

What is your test jig apparatus? Did you have the 10R in between the #5 and #13 gold fingers?

 

[rabe]

I do not have the 10R in between the # 5 & #13 fingers. 
I am using a Lindell 506 lunch box and the EXT test jig from you.
I pulled the 526 out of the jig to test the fingers.
I am using an Wavetek Meterman DMM to test with
The switch seems to be good.  I must have made a mistake somewhere.

 

[jsteiger]

Install the 10R and try it again 

 

[rabe]

Adding the 10R resister didn't work