[jsteiger]

Hey folks

I have  finally just released my 2 new rotary graphic equalizer kits, the LC25 and the LC40.

Details and automated checkout can be had here:
http://capi-gear.com/catalog/index.php?cPath=22_117_119_212

I have changed the way the support docs and build pics are presented. Instead of cluttering up this thread with a zillion pics, I have them posted at my site along with detailed instructions. Chunger has just become too busy so he graciously advised me on photography equipment and technique so the pics are by yours truly. They will never compare but hopefully will be good enough! The build pictorial can be found here:
http://capi-gear.com/catalog/Build_LC25-40_Rev_A.php

Since this is the official support thread, please post all questions, components and/or build problems here. I will do my best to help you get things sorted.

And heres a pic of the lovelies:


Cheers, Jeff

[brewbacca]

Yay! They're out!

[geardude]

Awesome looking  eq's congrats Jeff!

Well I suppose I'll kick this beast off. Took my time installing and upon firing up ( with a red dot op amp) I'm getting a loud  humming. Passing audio, no pk led lighting however, it appears as though the Eq filter's seems to function as I adjust frequency control with the knobs.

Puzzled, I turned it off shortly there after as to no damage anything.

Taking it back apart- I've double checked to make sure no leads are touching eachother or the metal on both the switch PCB and the main Pcb.

EDIT: TURNS OUT IT WAS THE 3 SLOT SNACK BOX.

[jsteiger]

.....I have  noticed a discrepancy in the photo layout of the BTo5 photo guide as the arrows for the diodes go in the opposite directions, however it looks like  that's a different "prototype" pcb as the silkscreen shows it going that way too.

Not sure what this means exactly. The DTO5 board shown in the photos is a Rev B and that is what is shipped with the kits. These have been used for sometime in the LC53A kits and are not proto's. The diodes must be installed the way the silk on the board shows. The DTO5 boards are still Rev B and no changes have been made.

None of the boards shown in the pics are proto's but the same production boards that are shipped with the kits.

I would try it with the switch PCB plugged into the main PCB but NOT assembled into the L-bracket. In the pics it appears that some of the bent R's on the switch PCB are high and may be shorting to the L-bracket.

[kante1603]

Well I've doubled through, cleaned up the boards a little bit, .....

Hello,


doesn't look cleaned,a lot of solder flux on at least the main board.Also several leads are not cut propperly.
Maybe just cosmetic,but who knows.....


I second Jeff's comment on the leads of the bent resistors,some of them look like they have a full contact to the metal.


Best regards,


Udo.

[kante1603]

If this is all good then could it be the hum is created by the wiring outside the box?
I mean is there a patchbay and other gear the signal runs through?
Do you have other modules working propperly in your lunchbox?
Any unbalanced gear or cables in between?

Can you explain your listening chain?


Best regards,


Udo.

[Johnkenn]

Evening, gents. So...finished the build on a LC25...passes audio but no EQ works. Someone mentioned the relays? I'm nubistic, so be gentle...that's the blue Panasonic thingy's right? Maybe I'l try and touch up solder...Could it be the bypass?

[geardude]

Evening, gents. So...finished the build on a LC25...passes audio but no EQ works. Someone mentioned the relays? I'm nubistic, so be gentle...that's the blue Panasonic thingy's right? Maybe I'l try and touch up solder...Could it be the bypass?

Bummer John, looks like we're both having problems!!! Yes those are the relays,I initially suspected a shotty solder job on two particular relay contacts myself... touched em up but I'm still having issues, hopefully yours gets sorted out as well! I hate not being able to see the solder job from the top but so is life depending on the components haha. Why not upload some pics if that doesn't sort it out and we can compare!

[Johnkenn]

Thanks man...I knew what I was getting into...this math and all. But it's part of the experience. We shall overcome.

[kante1603]

@geardude,


this was to rule out wether the hum issue is coming from the outside or the module itself,the way you describe it it looks like a ground loop.
Or is it the 60 Hz plus noise on top?
The signal chain looks good so far,although I don´t know your chinese box.In case all cables are balanced it should be o.k.
I have similar chains here (VP28s/Lovechild eqs/FF800),all good.
Listening to the vp28 without the eq added works correct,yes?(vp28 output directly patched to a ff802 line input).
You monitor directly the output of the ff802?
Does the box have grounding options like switches ,jumpers or solder pads?
Just questions to finally rule out things,but since you say the issue is there with the eq active and not in bypass then it looks like a module related thing.Best will be Jeff answers from now on because I don´t know these modules (yet).


Best,


Udo.

[jsteiger]

I would confirm that all of the IC opamps are located/orientated properly especially the TL081 since its a single and the rest are duals. My next thing was to ask about the DT05.

I just yesterday got back my 2 built units from Paul Wolff that he had for AES. I am also in the midst of building a pair of LC25's for an engineer buddy who is tracking Joe Walsh tomorrow at House Of Blues here in Nashville. My back is a bit against the wall to get these done but can hopefully get the Test Points doc together to help pinpoint where things go south for you.

Is your bypass working properly?

[maq3396]

Hi Jeff,

Excuse the lack of knowledge here but I have not come across an explanation...

The frequencies of the two were obviously chosen for a reason.

What applications would you say each one is best suited for?

Thanks
Mac

[jsteiger]

Well, I just finished this pair of LC25's and they are working perfectly. I will collect some Test Point data to try and narrow down where your build goes south. It can be tricky trying to troubleshoot an odd problem that I have not encountered hands-on.

Something tells me its an opamp issue. If A6 and A7 are correct and A9 has been confirmed elsewhere, I would suspect A8 the DTO5. This can be confirmed by passing signal and measuring at the Test Points. Tips coming soon.

You can pass signal without the switch PCB inserted. This will put the relays into active mode and can remove possible issues on the switch PCB from the equation.

[jsteiger]

Its not the official document but the results are the same.

I injected a 400Hz sine wave @ 0dBu with a HiZ load following the LC25.

TP1. -9.49dBu, 260mV AC
TP2. -9.5dBu, 259.7mV AC
TP3. -9.53dBu, 259mV AC
TP4. -9.53dBu, 259mV AC
Module's output, +0.03dBu

TP1 is after the DTO5 and before the 1st half of A6 (LME49720).
TP2 is between the two halves of A6 (LME49720)
TP3 is after A6 and before A9 (2520 style output amp)
TP4 is after A9 and before the 2503.

If you have the means, you can monitor or "listen" at any of the Test Points.

[jsteiger]

I am not a DAW guy but know you can generate sine waves from the PC.

[jsteiger]

The module needs to be powered up to run signal thru it.

[jsteiger]

Alright sounds good thanks, I'll try my best and give it a go in the tight quarters. The module needs to be in active mode for this measurement I presume

Yes it does. Bypass is hard wire that simply connects the module's input directly to its output.

[Johnkenn]

So I had some of the diodes - first - in the wrong place. Got those switched to the right place. Still no luck. Found out I had the CR1 diode backwards. Got that fixed and the relays finally started working. But then started hearing crapping out which Jeff mentioned was probably a cold solder somewhere. So I touched up the entire switch pcb and boom - it's working. But - I do hear a drop in volume when it's in active mode. And it seems to change the tone a good bit even with EQ points zero'd out. Makes me wonder if I've futzed something else up.  I'm missing a small Allen tool (of course the one time I need it, it's the only one missing) so I haven't been able to really twist the knobs to see how it's effecting the sound...but painfully twisting the shafts seems to do what they're supposed to. I might try and touch up the main pcb tonight. Maybe that will cure my volume issue.

[jsteiger]

By HiZ load, I mean the device following the LC EQ is not 600Ω but something much higher as in greater than 10kΩ. I would imagine most converters are 10kΩ or higher.

What level did you send out?

You may need to "listen" to the signal at those test points to find out where the buzzing is introduced.

[jsteiger]

I sent out a 400hz sine at oDB where 0dbu=0dbfs

Again, I am no DAW guy but I know that 0dBfs will be more like +16dBu depending on how your rig is cal'ed. If you want to send a 0dBu tone your output level would be more like -16dBfs.