PCB Guitar Mania Active EQ Problem

[joelo]

At any rate, you can forget about making this circuit work on its own as it is, unfortunatly. I was trying to help you do that and I wasted your time, I am sorry !

No apologies needed! I thank you and everyone else who has posted here to help me with this!

As for what to do next, my simple brain needs to think for a minute 

[eh la bas ma]

I would try S. Kah's  idea :

Soldado schematics :


With your multimeter on continuity mode, you can make sure which R23's pad is connected to C19. That's where you connect your EQ' IN. And EQ's OUT on Level pot's pad 3, connected to C19.

In a first attempt you can leave the extra cap and resistor you added. Then remove them to see if there is any difference.

[joelo]

I would try S. Kah's  idea :

Soldado schematics :


With your multimeter on continuity mode, you can make sure which R23's pad is connected to C19. That's where you connect your EQ' IN. And EQ's OUT on Level pot's pad 3, connected to C19.

In a first attempt you can leave the extra cap and resistor you added. Then remove them to see if there is any difference.

If I understand this correctly, this is what I should do for this idea (diagram attached)?

Reading the part of the Facebook thread that deals with combining the Active EQ with the Soldado, this should do an "awesome job! 😍." Except for the fact that "The Character-pot now does nothing" which if this would work, I wouldn't care about. I was just about to give up on this to be honest before I went back and shared the Facebook post.

[eh la bas ma]

Your diagram looks correct, you need to find the right R23 pad, though. I don't think the Ground connection between the 2 boards is necessary, but it shouldn't be a problem in any case.

Edit : "Never give up" as our great Charles used to say....

[joelo]

I have it wired up as above (except for the ground between the 2 PBCBs) and there is signal in bypass but nothing when engaged. Turning pots & trimmers doesn't do anything. Should I remove the added cap & resistor?

[eh la bas ma]

Yes, it's the first thing to try if everything else is ok.

But maybe it's something else.

It might be a problem with the jacks : make sure the tips aren't touching anything when a cable is plugged in.
Or it could be the wiring.

Some picture showing inside the enclosure, with everything in place, will help to have a better idea about what could cause this issue.

Edit : Also, finding the right R23 pad and the right lug on the volume pot is essential. A continuity test will comfirm that. Both Volume and R23 are connected to ground, so if you are using the wrong pads to connect the EQ, it will kill the signal. See reply #41.

[joelo]

Yes, it's the first thing to try if everything else is ok.

But maybe it's something else.

It might be a problem with the jacks : make sure the tips aren't touching anything when a cable is plugged in.
Or it could be the wiring.

Some picture showing inside the enclosure, with everything in place, will help to have a better idea about what could cause this issue.

Edit : Also, finding the right R23 pad and the right lug on the volume pot is essential. A continuity test will comfirm that. Both Volume and R23 are connected to ground, so if you are using the wrong pads to connect the EQ, it will kill the signal. See reply #41.

Pretty sure I got the right pad of R23. There was continuity only with one R23 pad with one C19 pad when trying all the different combinations.

Removed the cap and resistor and still no signal. I have attached photos.

[eh la bas ma]

Is the Soldado Out pad empty, near D2 ? It should be connected to the 3PDT fx out.

Make sure there isn't any short between the 6 little pads on the 3pdt footswitch.

The smallest piece of hair can create a short circuit if it gets on a pcb. It's important to build it on a clean table, or somewhere clean. An old dry toothbrush will help you to clean your boards, if necessary.

Edit : oh, and the soldado board isn't connected to DC power jack ground, I just noticed it's not on your diagram, so I was wrong to say that the GRND connection between the 2 boards wasn't necessary. Both circuits need to be fully powered (+9v and Ground connected to DC power jack on both boards).

So : Soldado Ground near D1 connected to DC power jack's ground. And Soldado Out pad near D2 connected to 3PDT Fx Out

Edit 2 : just so you understand, your guitar signal goes first (from the jack IN and the footswitch IN and fx IN) in the soldado board IN, then all the way through the Soldado signal path until R23.
At R23 the signal goes to the EQ board IN, then all the way through the EQ signal path. From EQ board Out it returns into the Soldado at Level pot pin 3, and finally it goes from the Soldado board Out to the footswitch (fx Out), which send the signal to the jack Out.

[joelo]

Is the Soldado Out pad empty, near D2 ? It should be connected to the 3PDT fx out.

Make sure there isn't any short between the 6 little pads on the 3pdt footswitch.

The smallest piece of hair can create a short circuit if it gets on a pcb. It's important to build it on a clean table, or somewhere clean. An old dry toothbrush will help you to clean your boards, if necessary.

Edit : oh, and the soldado board isn't connected to DC power jack ground, I just noticed it's not on your diagram, so I was wrong to say that the GRND connection between the 2 boards wasn't necessary. Both circuits need to be fully powered (+9v and Ground connected to DC power jack on both boards).

So : Soldado Ground near D1 connected to DC power jack's ground. And Soldado Out pad near D2 connected to 3PDT Fx Out

Edit 2 : just so you understand, your guitar signal goes first (from the jack IN and the footswitch IN and fx IN) in the soldado board IN, then all the way through the Soldado signal path until R23.
At R23 the signal goes to the EQ board IN, then all the way through the EQ signal path. From EQ board Out it returns into the Soldado at Level pot pin 3, and finally it goes from the Soldado board Out to the footswitch (fx Out), which send the signal to the jack Out.

Yes, thank you, that is obvious to me now that you say all that. Sorry for not catching it before I posted.

I made those connections and, hurray, there is signal when engaged!

However the pots and trimmers on the EQ don't do anything. I have it on a loop and there is no change in the sound Turing any of them. The Soldado Level and Gain are working normal.

[eh la bas ma]

I would try to skip the last part of the Soldado circuit :

Don't return to the soldado board, just take the wire from the EQ OUT and connect it to your footswitch Fx Out instead of the Soldado volume pot. And leave the Soldado Out empty.

Alternatively, you could try to audio probe the EQ board to check if it does something to your signal (see reply #35). For exemple you can probe C7 or R10, after the Mids control to see if that works, or if the signal can even reach it.
You should set all trimmers at 12' when testing the EQ pots : you don't want to turn the volume off and kill the signal...

[joelo]

Connecting the EQ OUT to the Fx Out does send signal when engaged. The Bass, Miss, & Treble seem to do what they should. The Volume & Presence trimmers do what they should. Charakter doesn't do anything which is that the result from the Facebook thread said.

However, the Volume pot on the Soldado doesn't do anything and the Gain pot acts like a volume.

[eh la bas ma]

That's a success...

Soldado Volume won't work because the signal doesn't reach it anymore. I suggest to take out the volume trimmer on the EQ board and wire a pot instead ( mid pad on the pot's middle lug, etc.). You could take the Soldado volume pot to do that (since it's useless), or an A50k, A100k. This way you'll have a Volume control on your stompbox.

About the Character trimmer, I think i remember reading on the Fbook post that using silicon diodes (like 1N4148) instead of leds could provide some compression, and maybe revive this trimmer. But you have a whole preamp circuit, it can compress the signal very well on its own. In my opinion, compressing a signal with leds isn't the purpose of EQing...and it won't be half as good as what the Soldado can do...unless you'd like to turn this EQ into an overdrive ?

Looks like you're about to cross the finishing line...

Edit : I just noticed what you said about the Gain pot...i can't see why it wouldn't work...What happens if you boost the guitar signal, before the Soldado ?
You might need to audio probe the soldado board at R23 to see if there is some distortion. That would tell us if the EQ is the cause of this no-gain situation...

Edit 2 : Before audio probing, you could try to clean the board and box it. Maybe there is a short somewhere because the board and the pots aren't properly installed. Pots shouldn't be in contact with each other, and their bottom side should be isolated, with plastic tape or pieces of cardboard, from the pcb...Same goes for the jacks : any contact between the tips and the enclosure kills the signal, so you need to adjust them carefully in the enclosure to avoid that. There is also your R23's wire connection : make sure the tip of the wire soldered to the board isn't shorting anything...

[joelo]

Actually forget my last post.

The Gain pot does add distortion to the signal. Full CCW there is no sound but it gets louder and more distorted as it is turned CW. It was like that before when the EQ board didn't do anything - but I'm not sure if it was like that when the Soldado was on it's own. I seem to remember even with the Gain full CCW there was volume and a bit of distortion. Maybe this is because there is no Volume in the circuit?

Should I still try replacing the Volume trimmer with a pot? I will use the one from the Sodado board.

[eh la bas ma]

It's always useful to have a volume control on an high gain circuit. Every trimmer can be replaced by a pot of the same value, on every circuit.

Before you desolder, or cut the Soldado Volume pot, I suggest you try it one last time on its own to see how it behaves. This way you will be sure that everything is fine, no more doubts.

It's a matter of a few seconds to desolder both R23 wire going to the EQ board, and the wire from the EQ out pad going to Fx out. Just connect this last one to the Soldado Out pad (Soldado Out -> footswitch Fx Out).

I hope this unfortunate Active EQ experience didn't give you the wrong impression about building stompboxes. There are usually some issues, but this EQ required some advanced skills from the start : its input needs to be biased correctly by an other circuit.

[joelo]

It's always useful to have a volume control on an high gain circuit. Every trimmer can be replaced by a pot of the same value, on every circuit.

Before you desolder, or cut the Soldado Volume pot, I suggest you try it one last time on its own to see how it behaves. This way you will be sure that everything is fine, no more doubts.

It's a matter of a few seconds to desolder both R23 wire going to the EQ board, and the wire from the EQ out pad going to Fx out. Just connect this last one to the Soldado Out pad (Soldado Out -> footswitch Fx Out).

I think that is a good idea. In fact I am concerned that continuing with combining this EQ with the Soldado will alter the sound Soldado, and since that is what I was after to begin with, it might be better to, in spite of this 2 month journey, just box up the Soldado on its own. Or maybe try the one from GuitarPCB that you suggested, if that in fact is a simple combination of the two circuits.

[joelo]

I hope this unfortunate Active EQ experience didn't give you the wrong impression about building stompboxes. There are usually some issues, but this EQ required some advanced skills from the start : its input needs to be biased correctly by an other circuit.

No this has taught me some good knowledge in fact. After a few years and about 20 pedals, I have had some issues for sure, but this was one a bit of nativity on my part, and I think a bit of responsibility of PCB Guitar Mania. I mean in the EQ build documents it states:

For that purpose we even recommend to box the Eqs as if they were normal pedals so you can plug them and compare them easily.

That doesn't seem to be the case with the Active EQ at least.

[eh la bas ma]

I always like to be able to control the EQ on every overdrive, distortion or fuzz. In my opinion, it's a good idea to have one or two very good stand-alone EQ box. It's just easier to combine it with other effects. I like the GE-7, but it's classic. About Preamp circuits, I would expect that they do a better job after the other gain effects. In my mind it's the preamp that shapes the tone the most, so I may need an EQ, either before,  inside or after, but that's probably only because I often like to be cautious with mids. Especially when other instruments enter the scene.

[joelo]

I've been thinking about it and I'm pretty sure that I am going to try that Guitar PCB EQ with the Soldado. Most likely after the Soldado circuit. Seems like a simple connection. They are out of stock at the moment so it give me time to back out and box up the Soldado on its own too 

Thank you for all the help on this thread. I really appreciate it.

[joelo]

Actually one more thing. I have been removing parts form the EQ PCB partially for practice and partially in hopes to use them in the future. Is there any reason I shouldn't use anything from this board again? I was excited how easy the pots came off after sucking the solder!

[eh la bas ma]

It's ok to take them all. I am sure you will need them, soon or later...