Happy new year!
I am not sure if this is the right place to ask for help with this but here it goes.
I have built the Active EQ from PCB Guitar Mania. I had it combined with their Soldado preamp. the Level pot on the Soldado and the Treble pot on the EQ were having issues. I have since separated the 2 and just by doing that the Soldado works fine (sounds good!). But the Active EQ has the same problem.
With the Bass, Middle & Treble pots, and the 3 trimmers at noon, there is no sound. Turning up the Charakter trimmer the Treble pot is acting like a volume control with a loud/rough part toward the end of the rotation. I currently have a 9v and 2 1/4' jack wired to the board so plugging it in it is "on."
I have been receiving help from great people on the PedalPCB forum for a while but it was suggested I come here. I can post a link to that thread.
Here is the Active EQ:
https://pcbguitarmania.com/product/active-eq/
(https://i.postimg.cc/GT2VSQ54/IMG-5904.jpg) (https://postimg.cc/GT2VSQ54)
(https://i.postimg.cc/PpK04c2G/IMG-5905.jpg) (https://postimg.cc/PpK04c2G)
Hi Joelo,
Can you post voltages around the op-amps please? That'd give a us a good clue.
Ta!
Hi, I think this is the perfect place to ask questions about your builds.
If you are stuck with issues on circuits, it's always a good idea to post here, in my experience.
I am not sure i understand the issue : The EQ worked when it was coupled with the soldado, there was a signal both in bypass and with the circuit powered on. Bass and Mids were fine, there was only a problem with Treble. And now that the EQ board is separated from the soldado preamp board, there is no sound, both in bypass and active? Did i get it right ?
Did you check that both tl072 receive 9V on pin 8 ?
Soldering looks fine but, from what i can see on pics, there are some pads with (maybe) not enough solder.
The pcb is small, few components, so i would reflow every pads just to make sure it isn't a bad contact.
Edit : If you lost the signal after taking the board out of the first enclosure, it might be a wiring issue. Can you give the link to your pedalpcb forum post, please ?
Quote from: ElectricDruid on January 03, 2022, 05:08:56 PM
Hi Joelo,
Can you post voltages around the op-amps please? That'd give a us a good clue.
Ta!
I measured the Active EQ pins when the Soldado and EQ were world up together. I can give you those, or, I'm assuming I soul re-measure now that the EQ is a stand alone unit.
Quote from: eh la bas ma on January 03, 2022, 05:23:02 PM
I am not sure i understand the issue : The EQ worked when it was coupled with the soldado, there was a signal both in bypass and with the circuit powered on. Bass and Mids were fine, there was only a problem with Treble. And now that the EQ board is separated from the soldado preamp board, there is no sound, both in bypass and active? Did i get it right ?
Yes, however when it was complied with the Soldado the EQ board did have the Charakter trimmer pampered and the LED diodes omittted, with a 1M resistor in D1. I was advised of this early on (let's not get into that). However since then the Active EQ board is with all the parts from the build documents.
And, there is sound if I turn up the Charakter trimmer. And, the Soldado's Level control had a problem when combines, but by itself, it's fine.
Quote from: eh la bas ma on January 03, 2022, 05:23:02 PM
Did you check that both tl072 receive 9V on pin 8 ?
Edit : If you lost the signal after taking the board out of the first enclosure, it might be a wiring issue. Can you give the link to your pedalpcb forum post, please ?
I will check.
Here is the thread from PedalPCB:
https://forum.pedalpcb.com/threads/soldado-active-eq-from-pcb-guitar-mania.9570/
(https://i.postimg.cc/R3LyGGPN/tl072.webp) (https://postimg.cc/R3LyGGPN)
Here is TL072 pin out. Just to make sure there will be no confusion with pin numbers when you will post your readings.
Edit : You got a full kit or did you get the pcb and the components separatly ? Are you sure about the Character trimmer value ?
On the pedalpcb thread, I think there is something suspicious around reply #25, about led1 and 2. You suddenly lost the signal by adding them on the board. They might not be in opposite direction on your build as they are supposed to be. You made a signal probe, following the schematics you can check if the signal passes before and after these leds ?
The signal goes first in a Presence trim. I would probe the tip of the In jack, to check the normal volume (coming from your instrument or a looper, etc), and then on R1, after the Presence trim, to make sure the trim is set to let the signal pass at approximatly the same volume as on the IN jack.
Quote from: joelo on January 03, 2022, 06:02:54 PM
Quote from: ElectricDruid on January 03, 2022, 05:08:56 PM
Hi Joelo,
Can you post voltages around the op-amps please? That'd give a us a good clue.
Ta!
I measured the Active EQ pins when the Soldado and EQ were world up together. I can give you those, or, I'm assuming I soul re-measure now that the EQ is a stand alone unit.
Re-measure please. Just take the voltage from ground to each pin on the TL072 in order CCW round the chip.
Thanks.
the circuit i found on the website of PCBmania is really really sketchy.
i mean, there is DC continuity to the input, from the Vb... basically making one diode always conduct. next to that, the Vb point must first overcome a diode before it charges the capacitors and makes the part of the circuit biased the way it should be.
(https://i.postimg.cc/3yzp9CVy/how-to-not-design-an-input.jpg) (https://postimg.cc/3yzp9CVy)
try a 100n capacitor between the input jack and the board, and a 1M resistor parallel to the 2 clipping diodes.
cheers
Quote from: ElectricDruid on January 03, 2022, 05:08:56 PM
Hi Joelo,
Can you post voltages around the op-amps please? That'd give a us a good clue.
Ta!
Here's what I'm getting:
IC1
1 4.38
2 4.38
3 4.31
4 0
5 2.79
6 3.79
7 3.78
8 9.14
IC2
1 1.43
2 1.23
3 1.19
4 0
5 4.73
6 4.79
7 4.79
8 9.14
Quote from: eh la bas ma on January 03, 2022, 05:23:02 PM
Did you check that both tl072 receive 9V on pin 8 ?
Those are reading 9.14 on both #8 pins, so that looks good, no?
Quote from: eh la bas ma on January 03, 2022, 06:33:11 PM
(https://i.postimg.cc/R3LyGGPN/tl072.webp) (https://postimg.cc/R3LyGGPN)
Here is TL072 pin out. Just to make sure there will be no confusion with pin numbers when you will post your readings.
Edit : You got a full kit or did you get the pcb and the components separatly ? Are you sure about the Character trimmer value ?
On the pedalpcb thread, I think there is something suspicious around reply #25, about led1 and 2. You suddenly lost the signal by adding them on the board. They might not be in opposite direction on your build as they are supposed to be. You made a signal probe, following the schematics you can check if the signal passes before and after these leds ?
The signal goes first in a Presence trim. I would probe the tip of the In jack, to check the normal volume (coming from your instrument or a looper, etc), and then on R1, after the Presence trim, to make sure the trim is set to let the signal pass at approximatly the same volume as on the IN jack.
The photo you posted doesn't show up for me but I think I got it correct. #1 is the upper left, then counting going down, across the bottom to #5, then up the right side to #8.
It was not a kit and I think the trimmer is the correct value. If it is wrong, then one off the others are wrong. Is there a way to check once they are soldered to the pcbs? I do know that I have the short lead in the square pad for both LEDs.
Turning the Presence trimmer all the way up seems about the same volume, all the way down is slightly quieter. Signal is hitting the Treble pot lugs which is after the LEDs if I am reading the schematic correctly.
However I don't get any signal from any of the LED leads. And when it is plugged in to power, LED 2 visibly lights up, but not LED 1. Not sure of those things mean anything.
Quote from: iainpunk on January 04, 2022, 10:04:34 AM
the circuit i found on the website of PCBmania is really really sketchy.
i mean, there is DC continuity to the input, from the Vb... basically making one diode always conduct. next to that, the Vb point must first overcome a diode before it charges the capacitors and makes the part of the circuit biased the way it should be.
(https://i.postimg.cc/3yzp9CVy/how-to-not-design-an-input.jpg) (https://postimg.cc/3yzp9CVy)
try a 100n capacitor between the input jack and the board, and a 1M resistor parallel to the 2 clipping diodes.
cheers
Haha, if you say so! This is the first schematic I've studied and I am just starting to see how it works.
Just for my knowledge, what would the cap and resistor do? My goal is to combine this with their Soldado (link below) so if I was to try what you are suggesting, would that work when combined?
https://pcbguitarmania.com/product/soldado/
Schematic:
(https://i.postimg.cc/D8r4JhJ7/Soldado-shematic.png) (https://postimg.cc/D8r4JhJ7)
Quote#1 is the upper left, then counting going down, across the bottom to #5, then up the right side to #8
That's right.
QuoteIs there a way to check once they are soldered to the pcbs?
Probably not with a multimeter, because the components around are connected to it. They will prevent you from reading the resistance accurately. Values are usually written on the side of the trimmer, hard to read : you might need a good light to look at it (I always wear an headlamp for this kind of things). Hopefully, you can manage to read at least two of them.
If you remember paying attention to the trimmers values when you built the circuit, you should be ok.
QuoteI do know that I have the short lead in the square pad for both LEDs.
Ok, that's right. Led orientation's case closed...
QuoteMy goal is to combine this with their Soldado (link below) so if I was to try what you are suggesting, would that work when combined?
Yes, it will. We are trying first to get the EQ fully working . Once this is done, there won't be any trouble to put it back with the preamp circuit (good idea by the way, I was curious about this soldado preamp, seen it on musikding...but I am cautious with pcbguitarmania, I built 2 effects and they're not my best, by far ). Be that as it may, I guess IainPunk ' s suggestion is your best shot so far...
Did you try to reflow the pads ? Integrated Circuits like TL072 are sensitive to heat, so you might want to take them off the board before re-heating pads around them.
Looks can be deceiving... On my last build my soldering seems as good as yours, but one cap's leg wasn't allright (I knew it thanks to the signal probe). I reflowed it and the connection was restored, to my greatest surprise.
i suggest this simple mod. it just solidifies the biasing of the opamp. more reliable
(https://i.postimg.cc/rDDc461G/how-to-not-design-an-input.jpg) (https://postimg.cc/rDDc461G)
cheers
Quote from: eh la bas ma on January 04, 2022, 03:48:39 PMDid you try to reflow the pads ? Integrated Circuits like TL072 are sensitive to heat, so you might want to take them off the board before re-heating pads around them.
Looks can be deceiving... On my last build my soldering seems as good as yours, but one cap's leg wasn't allright (I knew it thanks to the signal probe). I reflowed it and the connection was restored, to my greatest surprise.
Got it, I didn't reflow yet.
Quote from: iainpunk on January 04, 2022, 07:13:44 PM
i suggest this simple mod. it just solidifies the biasing of the opamp. more reliable
(https://i.postimg.cc/rDDc461G/how-to-not-design-an-input.jpg) (https://postimg.cc/rDDc461G)
cheers
Are you suggesting this in addition to what you suggested earlier ("try a 100n capacitor between the input jack and the board, and a 1M resistor parallel to the 2 clipping diodes")?
EDIT: I now see by your diagram that the answer is "yes."
Also, how would I add a 1M resistor parallel to the 2 clipping diodes, and a 10uf where you say? Sorry for what may be to most of you a basic question, but I'm not far past noob
Quotehow would I add a 1M resistor parallel to the 2 clipping diodes, and a 10uf where you say?
1M resistor : one leg goes to Treble pot's pin 3, other leg to LED2 negative side (the pad wich isn't connected to the Character trimmer). You might need to use your multimeter on continuity test and have a look on the schematics to find the right locations .
10 uF cap : It's polarized, so the positive side goes to the Character trimmer's middle pin. Negative side goes to C1's pad, the one that is connected to R1.
For your curiosity, here is a pic to illustrate the difference between "in series" and "in parallel" :
(https://i.postimg.cc/HJM9qxfc/8400c81c0eced157cf64f4d5d9f584c48b38d8ad.jpg) (https://postimg.cc/HJM9qxfc)
i hope you can see it...
"VB", in case you were wondering and as far as i understand, is an internal network, each point marked VB should be connected together. Could also mean something like "Voltage Biasing"...
Quote from: iainpunk on January 04, 2022, 10:04:34 AM
the circuit i found on the website of PCBmania is really really sketchy.
cheers
can anyone see an explicit mention on the schematic of IC2A for the build in question? it's possible/probable those voltage measures are wrong, but without some idea of how it is wired, we can't tell.
possibly, if you pull the IC's from their sockets, repower the circuit and then measure the voltages on the empty socket pins, we might see something. possibly.
your C7 - why mount underside, space reasons? wrong or bad connection there will cut all signal flow to the following stages.
Quote from: duck_arse on January 05, 2022, 08:44:53 AM
Quote from: iainpunk on January 04, 2022, 10:04:34 AM
the circuit i found on the website of PCBmania is really really sketchy.
cheers
can anyone see an explicit mention on the schematic of IC2A for the build in question? it's possible/probable those voltage measures are wrong, but without some idea of how it is wired, we can't tell.
possibly, if you pull the IC's from their sockets, repower the circuit and then measure the voltages on the empty socket pins, we might see something. possibly.
your C7 - why mount underside, space reasons? wrong or bad connection there will cut all signal flow to the following stages.
Yeah the underside mount was because of not planning ahead, I got to C7 and it didn't fit.
The IC2 measurements look weird?
I've attached the entire schematic.
(https://i.postimg.cc/tZF3MLnd/ACTIVE-EQ-schematic.png) (https://postimg.cc/tZF3MLnd)
indeed yes you have attached the schem I was also looking at. those opamps are both duals, but the circuit diagram only shows three opamps. without knowing how the fouth opamp is connected, we can't say what correct voltages on that half of the IC should be.
the part marked IC1_B on your schem also looks to me to be wrong voltages, as it is being biased by the part marked IC2_B, which shows about half supply volts. we'd be expecting IC1B to be close to that same voltage.
but without a complete, accurate circuit, it's all guesswork.
QuoteAnd, there is sound if I turn up the Charakter trimmer
Sorry if this is redundant but just to be clear, there is no sound when the circuit is switched off, and there is when it's powered on, if you turn this trimmer ? That would suggest that the signal can go all the way through the signal path on the pcb.
Maybe some more experienced forum member could show you the signal path on schematics. Then you would be able to audio probe this path to see where the signal stops when the circuit is switched off.
About these voltage readings, did you try Iain's idea with the extra cap and resistor ? If so, maybe you should do the test again to see if something's changed.
Edit : i tried to find the signal path, correct me if i'm wrong :
(https://i.postimg.cc/zVjY6ZP5/Screenshot-2022-01-06-at-18-17-57-EQ-Development-tool-building-docs-pdf.png) (https://postimg.cc/zVjY6ZP5)
Quotecan anyone see an explicit mention on the schematic of IC2A for the build in question? it's possible/probable those voltage measures are wrong, but without some idea of how it is wired, we can't tell.
Is it what you're looking for ? Looks like it mentions IC1 and IC2 pin 4 and 8.
(https://i.postimg.cc/JHCt6VYZ/Screenshot-2022-01-06-at-18-26-42-EQ-Development-tool-building-docs-pdf.png) (https://postimg.cc/JHCt6VYZ)
Edit : i guess i'm wrong. We need pin 1,2,3...
Quote from: eh la bas ma on January 06, 2022, 12:01:53 PM
Edit : i tried to find the signal path, correct me if i'm wrong :
(https://i.postimg.cc/zVjY6ZP5/Screenshot-2022-01-06-at-18-17-57-EQ-Development-tool-building-docs-pdf.png) (https://postimg.cc/zVjY6ZP5)
That looks like it to me! :icon_biggrin:
One thing I am seeing (and maybe understanding after reading the blurb at the seller's site), is that the active EQ is not designed to be a stand-alone circuit...thus the absence of a DC blocking cap on the input. Adding one would maybe help keeping that first opamp biased when you plug in a guitar (or pedal that has a volume control leading to the output.)
The docs do reccommend boxing the EQ (and a group of other add-on eq tools) as separate pedals, but say things like
Quote...you should be able to read schematics and spot which is the best part to place them and which parts of the original circuit you should remove...
So there is the provision of leaving the volume control out and patching your circuit in there.
Further info:
QuoteActive EQ: Based on the Freeman BE-OD and the Dirty Shirley EQ section. We consider this EQ the best fit for Preamp emulator projects and high gain pedals.
Certainly the most complex of the pack. Includes an internal Presence control, followed by Character trimpot that regulates how a set of LEDs compress the signal. Then we jump into a passive treble control, followed by an Active Bass section. Now's when you have to choose if you want to have a volume control of the overall circuit inserted here from your main PCB board (Tube screamer, Plexi, etc) or to place just an internal trimmer as an additional control. After this volume section it comes the active mids control.
One of the characteristic that makes this board the best solution for preamps and high output circuits it's the Power output option, this works the best for those high output preamps to go and feed directly into a power amp, and the regular output will be tamed into a more pedal friendly volume. If you are using this board with a pedal that's not famous for his big output (Klon centaur for example) you should use the power output.
Being a member of the pcb guitar mania group on facebook, I tried to ask about IC2A.
https://www.facebook.com/groups/1066092703545364/posts/2104453826375908/?comment_id=2104626933025264¬if_id=1641518406738909¬if_t=group_comment&ref=notif
If you can't or won't go on Fb, here the answer that an other member kindly gave me :
"Took a quick look, the input to that first op amp isn't biased properly on the schematic. possibly before the input, there needs to be a decoupling cap & a biasing resistor (in that order).
In the original circuit (BEOD), the input comes from an opamp's output, so it's already bias'd and has low output impedance when it gets to the presence control.
BTW, I always considered that 470k biasing resistor after the volume control to be unnecessary and was mistakenly left in."
I also asked for voltage readings from people who built the same EQ, to have some exemples, but no luck so far...
Quote from: eh la bas ma on January 06, 2022, 10:01:56 PM
Being a member of the pcb guitar mania group on facebook, I tried to ask about IC2A.
https://www.facebook.com/groups/1066092703545364/posts/2104453826375908/?comment_id=2104626933025264¬if_id=1641518406738909¬if_t=group_comment&ref=notif
If you can't or won't go on Fb, here the answer that an other member kindly gave me :
"Took a quick look, the input to that first op amp isn't biased properly on the schematic. possibly before the input, there needs to be a decoupling cap & a biasing resistor (in that order).
In the original circuit (BEOD), the input comes from an opamp's output, so it's already bias'd and has low output impedance when it gets to the presence control.
BTW, I always considered that 470k biasing resistor after the volume control to be unnecessary and was mistakenly left in."
I also asked for voltage readings from people who built the same EQ, to have some exemples, but no luck so far...
mmmmmm, yes, nice work eh la bas ma, but really, the build docs? isn't that the place to put all the information a builder will need? here's our new pre monster tone amp drive over board, we're not going to tell you how to build it tho, you need to search out a geezer on fakebook, he knows a guy has seen a pencil copy of the circuit diagram, might point you to someone who can guess at the board designators .......
Quote from: duck_arse on January 05, 2022, 08:44:53 AM
possibly, if you pull the IC's from their sockets, repower the circuit and then measure the voltages on the empty socket pins, we might see something. possibly.
I've been too busy to do anything with this for a few days but I see the latest posts, so thanks for all the continued interest!
I pulled the ICs and here's what I'm getting:
IC1
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 9.14
IC2
1 0
2 0
3 0
4 0
5 4.73
6 0
7 0
8 9.14
Quote from: eh la bas ma on January 06, 2022, 12:01:53 PM
Sorry if this is redundant but just to be clear, there is no sound when the circuit is switched off, and there is when it's powered on, if you turn this trimmer ? That would suggest that the signal can go all the way through the signal path on the pcb.
No problem, I currently have it wired directly to the jacks, no footswitch, so when I plug it in it's on. There is no sound with all pots and trimmers at noon. Turning up the Charakter trimmer lets sound through.
(https://i.postimg.cc/GH3FHYWT/Active-EQ-Only-Wiring-No-Switch.png) (https://postimg.cc/GH3FHYWT)
Quote from: idy on January 06, 2022, 02:05:43 PM
One thing I am seeing (and maybe understanding after reading the blurb at the seller's site), is that the active EQ is not designed to be a stand-alone circuit...thus the absence of a DC blocking cap on the input. Adding one would maybe help keeping that first opamp biased when you plug in a guitar (or pedal that has a volume control leading to the output.)
The docs do reccommend boxing the EQ (and a group of other add-on eq tools) as separate pedals, but say things like Quote...you should be able to read schematics and spot which is the best part to place them and which parts of the original circuit you should remove...
So there is the provision of leaving the volume control out and patching your circuit in there.
Further info:
QuoteActive EQ: Based on the Freeman BE-OD and the Dirty Shirley EQ section. We consider this EQ the best fit for Preamp emulator projects and high gain pedals.
Certainly the most complex of the pack. Includes an internal Presence control, followed by Character trimpot that regulates how a set of LEDs compress the signal. Then we jump into a passive treble control, followed by an Active Bass section. Now's when you have to choose if you want to have a volume control of the overall circuit inserted here from your main PCB board (Tube screamer, Plexi, etc) or to place just an internal trimmer as an additional control. After this volume section it comes the active mids control.
One of the characteristic that makes this board the best solution for preamps and high output circuits it's the Power output option, this works the best for those high output preamps to go and feed directly into a power amp, and the regular output will be tamed into a more pedal friendly volume. If you are using this board with a pedal that's not famous for his big output (Klon centaur for example) you should use the power output.
That seems confusing then. Would it be better to pair this back up with the Soldado then? Since we know that works on it's own?
I don't think so. Friedmann BE-OD and your Soldado don't have the same design. It'll be easier to make it work first.
Edit : Besides, you already tried both together and it didn't work it only prevented the Soldado from working correctly.
In your position, I would fully wire the circuit (3pdt switch), untill it works, even if i have to take it off later.
I did a similar project (OD + EQ) and both circuit have their own footswitch, with an order switch (spdt). I can engage both or just one circuit, and decide in wich position they are, OD before or after EQ. I found the wiring method on this forum ( looking for "order switch"), I can find it again if you need it.
I strongly suggest that you try Iain's idea with the extra cap and resistor, and if it still doesn't work, to take some fresh voltage measurements of both TL072 with this modification, and post them.
Edit 2 quick recap : It has been established that one op amp can't work correctly, the board on its own doesn't work properly, it needs the Friedmann amplifier to do so (replies #24 and 25). The build doc gives a warning about being a complex project that needs you, the builder, to know how to make it work (!). The seller never did the necessary arrangements neither to adapt this circuit for stand-alone use, nor even for average hobbyists, wich is rather uncommon. Fortunatly, a solution has been suggested to overcome this issue (reply #14).
Quote from: joelo on January 07, 2022, 03:10:07 PM
Quote from: duck_arse on January 05, 2022, 08:44:53 AM
possibly, if you pull the IC's from their sockets, repower the circuit and then measure the voltages on the empty socket pins, we might see something. possibly.
I've been too busy to do anything with this for a few days but I see the latest posts, so thanks for all the continued interest!
I pulled the ICs and here's what I'm getting:
IC1
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 9.14
IC2
1 0
2 0
3 0
4 0
5 4.73
6 0
7 0
8 9.14
much as i hate to say it, those voltages look right, according to the schematic. the 4V73 at IC2B is buffered and fed to IC1 a and b as bias but as the opamp is not fitted, the buffering and feeding isn't being done, so everything is nought.
Quote from: eh la bas ma on January 07, 2022, 04:16:10 PM
In your position, I would fully wire the circuit (3pdt switch), untill it works, even if i have to take it off later.
I did a similar project (OD + EQ) and both circuit have their own footswitch, with an order switch (spdt). I can engage both or just one circuit, and decide in wich position they are, OD before or after EQ. I found the wiring method on this forum ( looking for "order switch"), I can find it again if you need it.
I strongly suggest that you try Iain's idea with the extra cap and resistor, and if it still doesn't work, to take some fresh voltage measurements of both TL072 with this modification, and post them.
Edit 2 quick recap : It has been established that one op amp can't work correctly, the board on its own doesn't work properly, it needs the Friedmann amplifier to do so (replies #24 and 25). The build doc gives a warning about being a complex project that needs you, the builder, to know how to make it work (!). The seller never did the necessary arrangements neither to adapt this circuit for stand-alone use, nor even for average hobbyists, wich is rather uncommon. Fortunatly, a solution has been suggested to overcome this issue (reply #14).
OK, recap (mostly for me) on what I am going to do next:
I am going to wire it to a footswitch
Add a 100n capacitor between the input jack and the board (reply #8)
Add a 1M resistor parallel to the 2 clipping diodes (reply #8)
Add a 10 uF capacitor between Charakter trimmer & C1 (reply #14)
I have added a diagrams of what I think is the correct wiring. Look ok?
As far as the order switch, I like that idea but I already have an enclosure drilled for the combination of these 2.
(https://i.postimg.cc/SnPQvtV8/Active-EQ-Only-Wiring.png) (https://postimg.cc/SnPQvtV8)
I am not sure you still need the 100n cap. I have a feeling that it was a first idea, and that Iain would have add it on the diagram, reply #14, if it was still necessary.
Your wiring looks ok to me, I would have used the ground pad on the pcb, to connect to the switch ground, but I don't think it makes any difference.
If all this still doesn't work, you can also try to connect the switch "fx out" to the "power out" pad, instead of "out", just in case... Power out should be louder, with more volume.
You said you have a signal when the character trimmer is in a certain position, does the EQ works too ? Bass, Mids, Treble ?
I have added the 1M resister and the 10 uf cap. Still the same situation. Bypass works. When on, with Charakter trim all the way CCW (this works backwards I'm assuming), Volume trimmer all the way up, Charakter at noon, and all 3 pots at noon, there is no sound. Turning up the Treble pot CW there starts to be scratch sound at about 2 o'clock, clean strong signal at about 3 o'clock and scratchy signal past that. Bass & Middle pots seem to do what they are supposed to when there is a signal. Turning the Charakter trimmer CW the signal disappears pretty quickly. Turning the Presence trimmer CCW the signal gets quieter and scratchy (to the point of no sound) and turning it CW it gets louder and scratchy. I have included a photo of the added components.
Shouldn't the Charakter and Presence trimmers not have a volume effect, just EQ?
(https://i.postimg.cc/H8M96zWp/IMG-6003.jpg) (https://postimg.cc/H8M96zWp)
I think Presence should interact with the signal volume, because it adds some resistance to the signal. Character should add some compression to the signal with leds, so it could interact with the volume too.
Can you please confirm that :
_ Every pads have been reflown.
_ All parts values and orientations are double checked, trimmers and leds first (you can download something like "Atlence resistor viewer " to check the resistors values without taking them out of the board). I know I insist a lot on these leds, but if there is something wrong with the character trimmer, it's the first place to look...
If everything seems allright, you can try to find where the scratches come from, or where the signal behaves suspiciously, with an audio probe, following the signal path, with the circuit powered on, (see path reply #21) until you notice something. Then you can focus on that part of the circuit.
Here is an audio probe tutorial in case you never had to use one before :
https://diy-fever.com/misc/audio-probe/?fbclid=IwAR1hzfEJN-ErFMBhlLGe9pyGj1KKzid53vWKblD6U4e-glaxIuFiJuPVork
Always connect the ground first, and at a safe location, like IN or OUT 's ground lug.
Edit : ...and you don't have to waste a good cable to build a probe, an input jack will do the trick. You can connect a cable from your amp to the probe's input.
Quote from: eh la bas ma on January 14, 2022, 12:57:14 AM
I think Presence should interact with the signal volume, because it adds some resistance to the signal. Character should add some compression to the signal with leds, so it could interact with the volume too.
Can you please confirm that :
_ Every pads have been reflown.
_ All parts values and orientations are double checked, trimmers and leds first (you can download something like "Atlence resistor viewer " to check the resistors values without taking them out of the board). I know I insist a lot on these leds, but if there is something wrong with the character trimmer, it's the first place to look...
If everything seems allright, you can try to find where the scratches come from, or where the signal behaves suspiciously, with an audio probe, following the signal path, with the circuit powered on, (see path reply #21) until you notice something. Then you can focus on that part of the circuit.
Here is an audio probe tutorial in case you never had to use one before :
https://diy-fever.com/misc/audio-probe/?fbclid=IwAR1hzfEJN-ErFMBhlLGe9pyGj1KKzid53vWKblD6U4e-glaxIuFiJuPVork
Always connect the ground first, and at a safe location, like IN or OUT 's ground lug.
Edit : ...and you don't have to waste a good cable to build a probe, an input jack will do the trick. You can connect a cable from your amp to the probe's input.
Will do!
I did search the PCB Guitar Mania Facebook group and found this thread, don't know if it means anything helpful to where we are here:
https://www.facebook.com/groups/1066092703545364/posts/1861889947298965
Ah, that old thread at PCB GUITAR MANIA !
I had done some work in guiding Stephan Kah to get his EQs working in different configurations.
Quote from: Vivek on January 14, 2022, 03:20:31 PM
Ah, that old thread at PCB GUITAR MANIA !
I had done some work in guiding Stephan Kah to get his EQs working in different configurations.
So you are the same Vivek !
I always had some doubts...
QuoteI did search the PCB Guitar Mania Facebook group and found this thread, don't know if it means anything helpful to where we are here:
https://www.facebook.com/groups/1066092703545364/posts/1861889947298965
Looks like there is everything you need here.
S. Kah managed to make this EQ work with a Soldado and every steps are described.
On the other hand, it is a lot of work : you have to use IC2 pin 1, 2, 3 ... you need 2 extra resistors and 2 silicon diodes instead of leds (like 1N4148), in order to modify the first part of the circuit :
(https://i.postimg.cc/fVCsY36Q/243317179-4789945284359337-560658064299272386-n.jpg) (https://postimg.cc/fVCsY36Q)
...Or an easier way you can try is mentionned here : " I build the Soldado yesterday, connected the Active EQ at R23 (before volume and the last cap). There I have about 4-5V DC bias and it now does an awesome job!"
If it still doesn't work, in your situation, I would forget about this one and build an other EQ. I know this EQ from guitarpcb is more seriously designed and will work with every circuits without any overcomplicated mods :
https://www.musikding.de/Tone-TWEQ-active-EQ-kit
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 !
Quote from: eh la bas ma on January 14, 2022, 04:05:46 PM
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 :D
I would try S. Kah's idea :
Soldado schematics :
(https://i.postimg.cc/Yj2D4wV4/Screenshot-2022-01-15-at-03-06-09-Soldado-pdf.png) (https://postimg.cc/Yj2D4wV4)
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.
Quote from: eh la bas ma on January 14, 2022, 09:05:08 PM
I would try S. Kah's idea :
Soldado schematics :
(https://i.postimg.cc/Yj2D4wV4/Screenshot-2022-01-15-at-03-06-09-Soldado-pdf.png) (https://postimg.cc/Yj2D4wV4)
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.
(https://i.postimg.cc/mcPL6SV2/SOLDADO-Active-EQ-Wiring-NEW.png) (https://postimg.cc/mcPL6SV2)
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....
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?
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.
Quote from: eh la bas ma on January 18, 2022, 03:56:22 PM
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.
(https://i.postimg.cc/XBB6TCz7/IMG-6024.jpg) (https://postimg.cc/XBB6TCz7)
(https://i.postimg.cc/0rzv6TyR/IMG-6025.jpg) (https://postimg.cc/0rzv6TyR)
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.
Quote from: eh la bas ma on January 19, 2022, 03:15:17 AM
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.
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...
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.
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...
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.
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.
Quote from: eh la bas ma on January 20, 2022, 04:28:49 AM
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.
Quote from: eh la bas ma on January 20, 2022, 04:28:49 AM
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.
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.
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 :D
Thank you for all the help on this thread. I really appreciate it.
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!
It's ok to take them all. I am sure you will need them, soon or later...
Update for all who are interested. I got the Guitar PCB Tone TwEQ, populated it, and combined it with the Soldado and it works! For now I have omitted the Volume on the EQ circuit to see if I can live without it but after all the ups & downs I'm excited to have it working.
Congratulations !!!
I can bet you are already thinking about your next project. Keep us updated !!
Here is the final result. And yes, already building something else ;D
I ended up adding a trimmer instead of a pot for Volume on the EQ board.
Thanks again for all the help.
(https://i.postimg.cc/Jt5mmMn5/IMG-6081.jpg) (https://postimg.cc/Jt5mmMn5)
(https://i.postimg.cc/5jV1Z6xt/IMG-6082.jpg) (https://postimg.cc/5jV1Z6xt)