MESA Dr + Tone TwEQ active EQ: How to use send and return pads ?

[eh la bas ma]

Hello,

I am trying to wire these two boards together. I 'd like to get the EQ "inside" the Mesa thanks to Send & Return pads,with a "Dual effect with master Bypass" configuration as shown here page 6 : https://pcbguitarmania.com/wp-content/uploads/2019/03/Pedal-Wiring-Guide-1.pdf

But I don't know if it's even possible,or if it's a good idea, and can't find any clear instructions about how to proceed.

I am working with this, but there is no mention of Send & Return in these exemples :

https://wiki.pedalpcb.com/wiki/2-in-1_Pedal_Wiring

https://guitarpcb.com/wp-content/uploads/2018/07/BD_Tone-TwEQ.pdf

https://pcbguitarmania.com/wp-content/uploads/2019/08/Mesa-DR-Building-doc.pdf

"We have included‘Return’and ‘Send’pads so you can hook up any EQ section you want"

I understand i can use a single DC power jack for both. My question is : Should I only connect EQ's "board IN" and "board OUT" pads to Mesa's "Send" and "Return" ? And leave EQ's "jack IN" and "jack out" empty ?

Here is 3 pictures :

[garcho]

Should I only connect EQ's "board IN" and "board OUT" pads to Mesa's "Send" and "Return" ? And leave EQ's "jack IN" and "jack out" empty

Presumably, the only thing connecting "jack IN" and "jack OUT" to "board IN" and "board OUT", is wire. They're separated so you can use a switch for bypass/engage. So, yes, you leave the jack in and out unconnected.

[eh la bas ma]

I did the Wilkie1's alternate wiring scheme, "allowing to punch-in" the EQ into the other circuit :

https://guitarpcb.com/.../upl.../2018/07/BD_Tone-TwEQ.pdf...

So I jumpered Send & Return (these are located at the end of the Mesa Rectifier's circuit, so i don't see the point to use them : I thought they were located before the preamp or between two sections of the circuit). I have a good response from High and Mids, but Bass is quite weak. Now i'm considering to add a third "order-switch" as shown here : https://www.madbeanpedals.com/forum/index.php?topic=2879.0

because I presume the Bass's pot's response will increase if I wire the EQ before the Rectifier OD ?
Could it be possible to connect the EQ at some more interesting location in the Mesa Rectifier 's circuit than before or after it ?

In my wild dreams i imagine a blend pot in the OD, from which i could fine-tune the EQ's presence. But from what i am reading here, it can't be easily done, or it depends on the Mesa's Rectifier's circuit configuration : https://www.diystompboxes.com/smfforum/index.php?topic=104293.0

[iainpunk]

i recommend building a stand alone bass control in front of the Rectifier overdrive, this has control over the character of the drive, while after the drive, it just controls the amount of low end.
for the mid and treble, after the OD is a good place to have them.

cheers, Iain

[eh la bas ma]

i recommend building a stand alone bass control in front of the Rectifier overdrive, this has control over the character of the drive, while after the drive, it just controls the amount of low end.


cheers, Iain

I just tried a combination w/ a Boss Ge-7 (100, 200 Hz fully slided up, 400 Hz at 75 percent) before the OD.
The Ge-7 thicken the signal a bit but not as much as I would expect with these settings. I tried with a different OD (DOD250 clone set on 1N4148's clipping ) and it's almost the same. Ge-7 is more noticeable with germanium clipping, so I presume the 1N4148's Rectifier's clipping stage  is eating at the bass frequencies ? Are 1N4148 diodes Bass frequencies killers ?

[iainpunk]

not really, both circuits just have a lot of bass cut. the 250 less than the rectifier, but still, more than the GE7 can make up for.
with a lower threshold or higher gain, you'll get more perceived bass.
id you have a totally flat frequency response and you clip the living daylight out of it, you'll get a fuzz, which sounds bass heavy even with thin single coils, but turning down guitar volume til its clean leaves you with a fairly flat response back.
this translates to: if you lower the clipping threshold by half, or double the gain, you'll get double the bass, while the rest stays the same, because its already clipped.

you can change some caps in the rectefier to make it respond better to the bass control, or have a 2 capacitor blend, which is a bass control.
C5 and/or C6 are there to cut bass before the distortion. i would put a 100n and a 100k pot in series, and put that pair parallel to both those capacitors

cheers, Iain

[eh la bas ma]

you can change some caps in the rectefier to make it respond better to the bass control, or have a 2 capacitor blend, which is a bass control.
C5 and/or C6 are there to cut bass before the distortion. i would put a 100n and a 100k pot in series, and put that pair parallel to both those capacitors

Thanks! I am going to try your idea. I found some old and usefull threads about it.

I'm gonna make an assumption: that since the human ear hears in a logarithmic fashion, blending the signals this way will seem more natural and each increment of rotation of the pot will give you an "approximately equal" sensation of blend, rather than an abrupt and hard to control situation that a linear pot may produce.

IOW, you may get very little going on in the 1st half of rotation of a linear pot (or last half), and then the action occurs from 1/2 to full.   A log pot will correct that.  It's not about absolute signal level, but how we perceive it as humans.

so it should be A100k ? this forumite seems to differ :

I use a larger pot, 250k or 500k to decrease the residual effect of the bigger cap.
As the pot goes bigger it gets closer to a rotary switch with >5 input caps.

In my RM I have a 4.7n, and a 10n + 250kb pot. It goes from treble to full boost.

I don't know what "RM" means (Range Master maybe ?), but from what i can understand here, I guess I will have to try various pots.

Basically you send the signal through a small cap and when the resistance is high on the pot the signal is limited through the
larger cap, not all but mostly...compared to the small cap which is getting full signal current.
When the resistance is low or none, the large capacitor is parallel with the small cap which is add both capacitances.
So, small cap = small sound (less bass). Large parallel capacitance + full sound, more bass.

and use this methode ? He said it's "parallel" . If I read this correctly, two A100k terminals are connected to the 47 pf/470pf caps.
According to this short thread : https://www.diystompboxes.com/smfforum/index.php?topic=20902.0 even the VR wiring is a whole matter itself, with hard, meaningful choices...

[iainpunk]

you did some good diggin' there, yes, RM means Range Master here!

that schematic you posted, the ''extra small cap'' is both C5 and C6, so you can just jump them both with the pot+cap combo. i think a 100k and 100n goes a long way, at least, as a starting point, you should experiment with the values to get your perfect bass response and cut depth.

cheers, Iain

[POTL]

Hello do I understand correctly that you want to use this equalizer in the effects loop of the rectifier? this is not a good idea.
1) Rectifier is fatter than the Mark series of amplifiers. High-pass filters pass much more low frequencies, the Mark series amplifiers have stronger filtering and a more toned sound at the beginning of the chain, the equalizer returns them after the preamp.
2) The Mark series does not know how to post an equalizer, only a pre-equalizer, a graphic equalizer is located after the preamp, like a tone stack at a rectifier.
3) The rectifier already has a midrange cut in its tone stack, the graphic equalizer will duplicate its work, with some differences, but it's the same.
I see no reason to use this equalizer. if you are interested in changing the sound, then try modifying the amplifier.

[iainpunk]

Hello do I understand correctly that you want to use this equalizer in the effects loop of the rectifier? this is not a good idea.
1) Rectifier is fatter than the Mark series of amplifiers. High-pass filters pass much more low frequencies, the Mark series amplifiers have stronger filtering and a more toned sound at the beginning of the chain, the equalizer returns them after the preamp.
2) The Mark series does not know how to post an equalizer, only a pre-equalizer, a graphic equalizer is located after the preamp, like a tone stack at a rectifier.
3) The rectifier already has a midrange cut in its tone stack, the graphic equalizer will duplicate its work, with some differences, but it's the same.
I see no reason to use this equalizer. if you are interested in changing the sound, then try modifying the amplifier.

its a preamp pedal, using opamps, and has a bunch of changes. its not an amp were talking about here.

cheers

[eh la bas ma]

POTL thanks anyway, I wish I could listen to the real amplifier one day, not to mention play with it (cost around 3000 euros...).


I did the bass Knob with A100K wired as variable resistor, but i can't notice any obvious change when i turn the pot CW or CCW.

I figure C6 pad is OUT and C5 is IN, I left empty the two pads that ring together with the multimeter on continuity mode.

One A100K's outer terminal is free.

Did i make a mistake in the wiring, or should I try a bigger cap than 100n ?

[iainpunk]

that wiring looks wrong. the original caps should be left in their original places, and the 100n and 100k would be connected to the outer pads


cheers, Iain

[eh la bas ma]

ayaaah !

Bass frequencies are flowing through the speakers, it's impressive !

I unintentionally swaped C5 22n with 220n, I liked it, I think I might try even higher.

Thank you very much for your help Iain.

I learned a lot and I will use this Bass pot mod on other overdrives !

Just in case, it looks like this :


Edit : I put back the 22n of course, to have a good range.

[iainpunk]

that looks good, you can go even higher with the bass cap, like 220n or maybe even 1u if you have non-polarised 1u's. but the law of diminishing returns comes peaking its head around when the values get to large.

i'm glad you like it and even more glad you learned something!

cheers