[BUILD] CAPI 553F~500 Series~LC Equalizer~Official Support Thread

[Mishegas]

TIS97*
*my girlfreind's minimoog is FULL of 'em! 

Slaughtering a minimoog..........you sir are a monster....

Udo,

I was just joking about my girlfriend's minimoog...

.....the truth is; I don't have a girlfriend.

 

[kante1603]

Udo,

I was just joking about my girlfriend's minimoog...

.....the truth is; I don't have a girlfriend.

;D

 

[Mishegas]

Just did the calibration and the test points....

It would appear that I'm in the ballpark?...I believe my 400Hz signal is a wee bit hot. -602mV at the card edge connector-so.....

........Jeff's.......................................Mine               
-------------------------------------------------------
#1, 600mV (after A1 receiver)...........602mV
#2, 600mV (after HPF PCB)...............602mV
#3, 596mV (after A3 follower)...........599mV
#4, 594mV (after LPF PCB)...............595mV
#5, 591mV (after A4 follower)...........592mV
#6, 243mV (before A2)....................243.2mV
#7, 413mV (after A2).......................413.7mV

considering the slightly hotter signal, do these look proportionally ok?

Thanks everybody for all the help and kind attention!

 

[jsteiger]

Yes those seem fine.

 

[MPCNYC]

Hey Jeff,

Just finished the first of two 55F kits and all went well.....my usual process of having to fiddle a bit with the metal work to get things to line up, but that wasn't bad at all. Thanks again for a wonderful product! Insanely cool tone shaping EQ. I've built upwards of 25 of you kits to date and they are all running just perfect. The mid band is super sweet sounding!

I'd love to hear from you or anyone else with experience with 553F with regard to opamps. I had some GAR1731's around so that's what I put in the unit. Just wondering what people's preferences were and what the character of the Liebers, GAR2520, etc, imparts on the the sound of the 553F!?

Thanks again!

Michael

 

[pitol678]

Super stoked! finished this build today and it was my first unit that I had to calibrate which I had been so intimidated by. However, I got the Extension jig from CAPI and it simple and everything worked right out of the gate. Thanks Jeff, cant wait to start using this!

 

[Matt D]

I finished a pair of these recently and have been using them for tracking EQ's.  The bands are nicely voiced so if I'm thinking "I'd like a little more high end out of that acoustic guitar" and I bump the HF knob up a little bit and it sounds like what hear in my head only better. Same goes for the bass and mids. Easy build and great documentation.

 

[turk sanchez]

...hey guys, just starting a build here (doing a pair of these 553f EQ's) ~ just finished the high pass filters, low pass filters and discrete followers. Just thought I'd share a pic. Build is a breeze and having fun so far

 

[turk sanchez]

...another pic. I just have to do final assembly on the other one and then calibrate them. Really nice kit.

I had a little trouble getting a few of the sockets for the DOA's to heat up and flow, so per Jeff's advice, I turned up the heat to over 800 (I went to 850) and that helped. Some of the pads are pretty small (especially on the discrete followers) but there is a good deal of room between pads so it was actually pretty smooth. Really excellent BOM (printed in "stuffing order"). I can't wait to hear this.

 

[turk sanchez]

I LOVE 'em!!! Just finished. They sound incredible. THANK YOU, Jeff! Amazing kits.

 

[Flukes]

Hi guys,

At the first stage of calibrating this bad boy, the unit is passing signal but it's super quiet.

Where would you suggest to start with troubleshooting?

Best.
Mat

 

[jsteiger]

So is the CMRR trimmer calibrated or not? The first stage is a -6dB receiver so under normal (not CMRR test/cal) conditions, whatever balanced signal is applied to the input, at the output of the first opamp should be appx 6dB lower.

As always, what opamps are you using and who built them? Possible bad opamp builds are the FIRST thing to rule out.

 

[Flukes]

Hey Jeff,

I'm using pre-built red dots bought from you so I've ruled those out.

Could you explain the CMRR trimmer calibration further?

I should also mention I'm using one of your 51 test jigs for the calibration.

Best.
Mat

 

[jsteiger]

Basically you are inject the exact same signal into the inverting and non-inverting inputs of the receiver opamp. Because they are of opposite polarities, in a perfect scenario they would cancel out fully within the opamp and the output of the opamp would be nothing. Since perfect is not achievable we look for the lowest possible output from the opamp. The trimmer is on the input side of the amp and ever so slightly adjusting the signal going to the non-inverting input for as close to possible perfect null within the opamp.

Once this adjustment has been made, you can disengage the CMRR test switch on the Extension Jig. The level measured at the output of the opamp (same spot we monitor for CMRR) should be approximately 6.1dB lower than the signal level at the card's input.

 

[Flukes]

Hi Jeff,

Are you talking about the tiny knob at position RV1? Adjusting this knob is doing zero to the output level.

The output is reduced by 20dB when fed through the 553F.

Also, I've used your extension jig with a DIY RE Colour and the output only changes slightly.

What else would you suggest?

 

[jsteiger]

Hi Jeff,

Are you talking about the tiny knob at position RV1? Adjusting this knob is doing zero to the output level.

Yes but they will not change the output level of the entire module by very much when in standard operating mode. The RV1 trimmer is ONLY turned when you are adjusting for CMRR as described on the side of the Extension Jig.

The output is reduced by 20dB when fed through the 553F.

What else would you suggest?

Swap opamps around first. If they are pre-built they should be fine. It could be an issue with one of the discrete followers. You could also have some R's swapped around and in the wrong places. Cold solder joints are also a likely cause.

 

[Flukes]

Cheers Jeff,

Before I get stuck into checking all of the components, I just double checked the pre-flight measurements and for both A1 and A2 (between  +V/-V and C) the resistance is less than 100k.

Also, interestingly the resistance of A2 (between O and C) is 55k but A1 is less than 100k.

Does this ring any alarm bells for you?

Best.

 

[jsteiger]

No bells. These are all fine. We are basically looking for direct shorts when checking the voltage rails.

 

[Flukes]

Ok good, how do I do that?

 

[jsteiger]

Ok good, how do I do that?

Sounds like you did it above by measuring DCR between the opamp V pins and ground.