Help me understand the Micro Vibe

[duck_arse]

that antonis, he's too hard.

jlo, observe the non-invert in of U2-2 [2 small for my eyes] - there is a 100k resistor to bias. this sets the stage input impedance. now there is two other 100k resistors feeding signal into that (+)in - so, what happens [to those original signals] when you have a 100k series feeding a 100k-to-ground [what the input impedance looks like]?

[antonis]

U2-3 if you use magnifier tool..

[jlo]

that antonis, he's too hard.

jlo, observe the non-invert in of U2-2 [2 small for my eyes] - there is a 100k resistor to bias. this sets the stage input impedance. now there is two other 100k resistors feeding signal into that (+)in - so, what happens [to those original signals] when you have a 100k series feeding a 100k-to-ground [what the input impedance looks like]?

You mean U3-2?

[duck_arse]

I have no idea.

you can quote me.

[jlo]

(R18 + R9 + R8) is in parallel with R20?   So the net resistance is 66.6k.   So the voltage coming out of U3-1 is 0.398 of its input? 

[antonis]

(R18 + R9 + R8) is in parallel with R20? 

Who knows.. 
(Hard enough, Stephen..??)

[jlo]

Im clearly confused.  Is the input signal divided into wet and dry paths and then mixed at the end like the Univibe?  If so I can't see where the two separate paths are.  I thought the signal split at U1-1 output.  Wet going through the various phasing stages and the dry was going through R18 going L to R on the schematic and then mixed into the + input of U3-2 along with the output of U3-1. 

[antonis]

Im clearly confused.

You're not the only one.. 

Last attempt: Are we talking about dry/wet mix or about R22 right leg signal attenuation..??

[jlo]

In the univibe circuit, the input signal is split.  The wet path undergoes phase shifting and is mixed in with the dry signal in chorus mode.  In vibrato mode, the dry signal is not mixed in.  Micro Vibe only has chorus.  So does it have the same architecture of splitting the signal and mixing the two at the output? 

[ElectricDruid]

In the univibe circuit, the input signal is split.  The wet path undergoes phase shifting and is mixed in with the dry signal in chorus mode.  In vibrato mode, the dry signal is not mixed in.  Micro Vibe only has chorus.  So does it have the same architecture of splitting the signal and mixing the two at the output? 

If it has chorus, then yes definitely it splits and mixes. The difference between "chorus" and "vibrato" modes is whether the dry signal is mixed in. If it is, then you have chorus (dry signal + modulated "wet" signal") or if not vibrato (just the modulated "wet" signal).

[jlo]

In the univibe circuit, the input signal is split.  The wet path undergoes phase shifting and is mixed in with the dry signal in chorus mode.  In vibrato mode, the dry signal is not mixed in.  Micro Vibe only has chorus.  So does it have the same architecture of splitting the signal and mixing the two at the output? 

If it has chorus, then yes definitely it splits and mixes. The difference between "chorus" and "vibrato" modes is whether the dry signal is mixed in. If it is, then you have chorus (dry signal + modulated "wet" signal") or if not vibrato (just the modulated "wet" signal).

Right so then where is the dry signal path?  I thought it was from U1-1 output across R18 and then mixing just after R22 into +input of U3-2?

[ElectricDruid]

If you're talking about this schematic:

https://postlmg.cc/N5BSZtvx

Yes, you're right. R18 takes the output from the input buffer U1-1 to the output mixer U3-2. Interestingly, it's a passive mixer into a non-inverting op-amp, instead of the (perhaps more common) inverting active mixer. Not that it makes a huge amount of difference when this is a phase shifter circuit - phase is going to get scrambled either way.

[jlo]

If you're talking about this schematic:

https://postlmg.cc/N5BSZtvx

Yes, you're right. R18 takes the output from the input buffer U1-1 to the output mixer U3-2. Interestingly, it's a passive mixer into a non-inverting op-amp, instead of the (perhaps more common) inverting active mixer. Not that it makes a huge amount of difference when this is a phase shifter circuit - phase is going to get scrambled either way.

So thats a different path that Antonis is describing. 

(R18 + R9 + R8) is in parallel with R20? 

Who knows.. 
(Hard enough, Stephen..??)

[PRR]

Right so then where is the dry signal path?

That's what I see too.

[antonis]

Making things clear now you can see that both signals (Wet & Dry) are divided on R18/R20/R22 junction..

[jlo]

Making things clear now you can see that both signals (Wet & Dry) are divided on R18/R20/R22 junction..

Ok so now revisiting the gain structure.  Are both wet and dry signals halved and then combined before tge U3-2 input? 

[antonis]

It depends on paricular point of view..

What's your documented viewpoint..??

[jlo]

It depends on paricular point of view..

What's your documented viewpoint..??

Can you please clarify your question?  Im having trouble understanding

[duck_arse]

Making things clear now you can see that both signals (Wet & Dry) are divided on R18/R20/R22 junction..

thanks antonis - this was the point I was trying to drive at.

[ElectricDruid]

Making things clear now you can see that both signals (Wet & Dry) are divided on R18/R20/R22 junction..

Ok so now revisiting the gain structure.  Are both wet and dry signals halved and then combined before tge U3-2 input? 

Yes. For both wet and dry, you've got a 100K/100K divider, so the level is halved. And then the amp provides some make-up gain. 150K and 118K (118K?!? Seriously? I don't believe it) gives 150/118+1 = x2.27, so there's a very slight boost overall.