[BUILD] CAPI LC53A~500 Series~Love Child EQ Kit~Official Support Thread

[chunger]

Quick question. . . I'm at the point where I have the main PCB and CB PCB built and passing signal.  I'm feeding it 1K sine @ 1.23V (4dBu) and the unit outputs 1.62V (6.4dBu).  Is this normal or should I be concerned?  Swapping op-amps results in the same behavior.

 

[kante1603]

Quick question. . . I'm at the point where I have the main PCB and CB PCB built and passing signal.  I'm feeding it 1K sine @ 1.23V (4dBu) and the unit outputs 1.62V (6.4dBu).  Is this normal or should I be concerned?  Swapping op-amps results in the same behavior.

Hi,
When I built mine I had just a small difference,about 0,1 dB or so,I used gar2520s.
Jumpers in correct position?
Did you have a a load on the output?
Maybe you can strap a 10 or 20k resistor over the output temporarily for giving it a load,your measuring equipment normally has an input impedance that is too high.

Udo.

 

[chunger]

thanks Udo, I was just probing with my scope so I guess there was no load.  I connected to my cheap spectrum analyzer's balanced input and everything looks good.  0.0dBu in --> 0.0dBu out.  All is well.

 

[kante1603]

thanks Udo, I was just probing with my scope so I guess there was no load.  I connected to my cheap spectrum analyzer's balanced input and everything looks good.  0.0dBu in --> 0.0dBu out.  All is well.

Good to hear,go chunger!

Have fun,

Udo.

 

[chunger]

Wheh!  Build photo-documentation complete. 

Please look through and let me know if there are any glaring errors in the build or the text.  The assembly aid as well as other documents were very thorough, and this project was a real treat to put together.  All aspects of the kit were really well thought out and executed.  I am very happy to be able to do my little part to showcase this build in detail.  Hopefully some fence-sitters will decide to take the plunge on a truly top-tier kit.

Now, let's see if this thing works when I fire it up!

 

[gar381]

Hey chunger

HOLY CRAP... Just checked out your  new photo-doc!!!

This is by far your VERY BEST WORK !!!!

congrats .. you are a very advanced DIY guy !!

NICE !!!

GARY

 

[wolfgang]

HOLY CRAP... Just checked out your  new photo-doc!!!

This is by far your VERY BEST WORK !!!!

congrats .. you are a very advanced DIY guy !!

NICE !!!

GARY

+1 
regards,
wolfgang

 

[kante1603]

HOLY CRAP... Just checked out your  new photo-doc!!!

This is by far your VERY BEST WORK !!!!

congrats .. you are a very advanced DIY guy !!

NICE !!!

GARY

+1 
regards,
wolfgang

Same here!

Very well done  chunger,

Udo.

 

[chunger]

Hey guys,

Hold the congratulations for a bit.  Jsteiger discovered L2 inductor labelled "L:7.0 H" is installed backwards on the photo thread.  I was able to fix it without issue w/ a Hakko 808 de-soldering tool, but I need to backtrack the photos and re-shoot a few of the LC-EP PCB sections.  . . all of the ones that show the L2 inductor that is    Luckily I have 2 kits on hand and can re-trace my steps.

These are the sort of errors you expect when you employ the services of a Chinese Labor Camp!  ;D

 

[chunger]

Effected photos have all been re-shot.  All photos showing L2 are now in proper orientation.  To my knowledge, the photo thread is now all correct again.  If you happen to be browsing through the thread for entertainment and find another error.  Please let me know ASAP.  I really don't want to mess anyone up.

 

[john12ax7]

Wow, what a nice photo build documentary, really well done.

 

[jsteiger]

Unity unit fully assembled, tested in bypass.  Hot unit lacking LC-EP board.  Feeding them 1k at +4dBu:

1st reading: negative side of C2 on the Main PCB.  - both 0.592 VAC
2nd reading: output pin of A1, DF on CB PCB  - both 0.591 VAC
3rd reading: output pin of A2, DF on CB PCB  - both 0.586 VAC
4th reading: output pin of A4, DTO5 on CB PCB  - both 0.4 VAC
5th reading: output pin of A3, DTO5 on CB PCB  - both 0.402 VAC
6th reading: neg side of C12 on the Main PCB - unity unit 0.402 VAC, hot unit 0.74 VAC

So we have a winner around the output amp. 
Compared resistances on main board again, all seem to match.

Tried and tested the following with no change:
Retouched all joints on main and J1-1 points
Swapped A1 and A2 positions

Wish I'd held off on fully assembling the good unit for comparative purposes.

Next idea?

Sorry Doug. I did not see your post before now. I have not been getting my notifications for this thread...for some reason.

Well, good as you have narrowed some stuff down. I will have to get a schematic done for this guy I think. It will make life easier in the future.

For now, besides the obvious components on the the main PCB, check the following as I assume the problem lies here. These are on the CB-PCB. R11, R12, R17, R18 and R19.

R17 is a series R to the non-inverting input of the Main PCB's A2.
R18 is in parallel with R17 when the J4 shunt is in "Lo-Z". (Check for possible short on the header?)

R11 is a shunt to gnd on the inverting input of the Main PCB's A2.
R12 is in parallel with R11 when the J3 shunt is in "Lo-Z". (Check for possible short on the header?)

R19 is just across the inverting and non-inverting inputs of the Main PCB's A2.

If everything around A2 on the Main-PCB is clean, the issue must be in the above.

Keep us posted.

 

[emrr]

OK, I apparently can't see decimal places on my meter.  R17 was 1K rather than 10K.  I checked it 3 times previously!

 

[jsteiger]

Well, shite happens. At least you got it sorted.

 

[emrr]

They sound cool, and different from Brian's TB550A.  They focus in different ways, for lack of a better descriptive.  Seems like more phasey whistle at extremes while sweeping, as inductors seem to bring out.  You can only really compare them apples to apples at +6 since they deviate in the extreme steps. 

 

[kante1603]

Hello Doug,

Glad you got that issue sorted.
May I ask which DOAs you used,I have gar2520 s in mine and wonder if I should do some experiments with swapping them to different ones in different combinations.

Thank you in advance,

Udo.

 

[emrr]

Gar2520.  I don't have anything else to try.  I have some early API and Melcor op amps, but they are a shorter solder pin that won't work here. 

 

[kante1603]

Thank you Doug,

Next time I order from Jeff I should take some of the orther types too.

Have a nice weekend,

Udo.

 

[jsteiger]

FWIW, I have many old 2520's that I have desoldered from my desk and what not. While the pins are short, they seem to work just fine in the sockets I use. Give them a try and see what ya think.

 

[chunger]

After testing these in the studio, we ended up settling in on the GAR2520's.  I our particular setup and use, the 2520 gave a bit more bite and definition in the treble that we were looking for.  One of our primary uses for this is drums, so we are actually looking for a little bit of punch out of the analog EQ's.

On vocals, the 2520 allowed for a tremendous amount of boost in the high end as while remaining smooth and not getting "spitty" and sibilant Amazing actually to be able to grab 10K and crank it up 8dB and have the vocal come forward in the mix without any nastiness.  With the 2520 behaving so well, I felt it gave more range than the 1731.  BTW, our console and D/A converters are a bit on the darker side so in another studio, the mellower 1731 is probably very sweet.