How to add more mids to this circuit?

[ToneRangerAudio]

Howdy!

I really want to add some more mids into this circuit that the legendary Analogguru assembled back in 2008. The circuit is pretty scooped sounding, so having some more midrange/body content would be amazing. Anyone have any ideas on what component(s) I can swap out to make that happen?

Thanks!

[ToneRangerAudio]

Bump

[FiveseveN]

There's nothing scooping the mids in the part of the circuit you've shown us.

[ToneRangerAudio]

There's nothing scooping the mids in the part of the circuit you've shown us.

I don't think there's necessarily something being scooped, rather the highs are being accentuated created a scooped feel.

[antonis]

Make C4 ten times bigger (100pF or so)..

P.S.(irrelevant to highs accentuation)
I'd place a 47 to 100 Ohms resistor between U21.A output and C10..

[ElectricDruid]

There's nothing scooping the mids in the part of the circuit you've shown us.

Agreed. Makes you want to see what's off to the RHS where the tone controls would go, doesn't it?!?

[ToneRangerAudio]

Make C4 ten times bigger (100pF or so)..

P.S.(irrelevant to highs accentuation)
I'd place a 47 to 100 Ohms resistor between U21.A output and C10..

Tried this and it didn't do anything unfortunately!

[Matthew Sanford]

This thing got me digging for some reason, seems Analogguru's site is now defunct (?), but he mentioned the Korg thing it's based on and Aion has this scheme, so here is the end part - of course that is for +/- 15v and he did for 9v battery. Seems that final part is an active bandpass if I understand it correctly, with an extreme range well beyond audible frequency, but... ToneRangerAudio, are you certain you used the correct value parts? I know making mistakes like that is my go to....

[idy]

+1 there is nothing there that has any real eq shaping. Suspect an error somewhere.

[ToneRangerAudio]

This thing got me digging for some reason, seems Analogguru's site is now defunct (?), but he mentioned the Korg thing it's based on and Aion has this scheme, so here is the end part - of course that is for +/- 15v and he did for 9v battery. Seems that final part is an active bandpass if I understand it correctly, with an extreme range well beyond audible frequency, but... ToneRangerAudio, are you certain you used the correct value parts? I know making mistakes like that is my go to....

Yep! I've actually built around 100 of this circuit on veroboard!

[antonis]

C6 comes into game, now..
(it's actually set there to prevent IC2B high frequency oscillation and NOT for audio frequencies LPF, toghether with R8..)

47pF (with upward trend) should be a reasonable starting point for highs attenuation..

[bluelagoon]

Here's one Dirk Hendrick prepared earlier -
Korg SDD 3000 Preamp

[bluelagoon]

Here are some more related links to same Korg SDD3000 Preamp

Trabantland SDD3000

Analogguru - SDD-preamp

[antonis]

Here's one Dirk Hendrick prepared earlier -
Korg SDD 3000 Preamp

Out of curiosity..

1. Is there any need for D1/D2 clamping diodes..??
2. If yes, aren't D3/D4 redundant..??
(unless, of course, D3/D4 dynamic resistances involve in U1.A gain branch..)

[ElectricDruid]

Out of curiosity..

1. Is there any need for D1/D2 clamping diodes..??

Good question. "They're in the original" is probably the answer.

2. If yes, aren't D3/D4 redundant..??

I was wondering about this too. They're connected to a virtual ground point at IC1A pin2, so I don't really see how the forward voltage could *ever* be exceeded.

(unless, of course, D3/D4 dynamic resistances involve in U1.A gain branch..)

I don't see how that's possible.

[ToneRangerAudio]

Here's one Dirk Hendrick prepared earlier -
Korg SDD 3000 Preamp

Out of curiosity..

1. Is there any need for D1/D2 clamping diodes..??
2. If yes, aren't D3/D4 redundant..??
(unless, of course, D3/D4 dynamic resistances involve in U1.A gain branch..)

To be completely honest with ya'll, I'm still new to a lot of this stuff, so I'll try to keep up!

I removed D3 and D4 yesterday and absolutely nothing changed in the sound. I was trying to find some ways to change the clipping and putting things in those spots did nothing!

[antonis]

I removed D3 and D4 yesterday and absolutely nothing changed in the sound. I was trying to find some ways to change the clipping and putting things in those spots did nothing!

Try to remove D1 and D2..
Then you'll be able to play with D3/D4 clipping threshold..

Or use a lower forward voltage drop diode pair in place of D3/D4..
(Schottky or Ge..)

Or move D3/D4 after U1.A..
(between C7 and R118..)

You see, D1/D2 forward voltage drop sets the upper limit of input signal to U1.B, which is wired as unity gain buffer (voltage follower) so its output can't be higher than its input..
(actually, it's a bit lower on D3/D4 junction due both to U1.B output impedance / R4 voltage divider and voltage drop across R6..)
So, for identical D1/D2 and D3/D4 pairs, no extra clipping can occur..