Treadle vibe/phaser

[duck_arse]

plug the speakers, unplug the speakers. plug the speakers, V8, V9, V4. unplug the speakers. where'd the other two stages go? still 2 oscs? no treadley?

sounds like it's chewing something, Wavey Davey. tweet tweet.

[Kipper4]

See my last post, schematic included
2 stages, no treadle. no fuss.
It's chewing Phase friends. Eat it and weep.
Whatya think of the clean/phaser/vibe pot?
I thought it worked well.
Don't unplug your speakers there will be another right along soon.
Another wheel to reinvent. 

Edit. It works even better now the clean pot has its own 10k to op amp input.
That cleared up the noise issue. Thanks SteveO. Still some clean ups to do.
Keep those speakers pegged.

[ElectricDruid]

Edit. It works even better now the clean pot has its own 10k to op amp input.
That cleared up the noise issue. Thanks SteveO. Still some clean ups to do.

Yeah, I was going to mention that too. With that inverting amp on the output, it makes sense to use it as a proper inverting mixer. Did you get rid of one of the caps in the clean path too? You had a 100nF DC blocker at one end, and a 1uF at the other - don't need 'em both. I'd also use the "clean" pot as a level control with the bottom of the pot grounded and the wiper taken to your mixer resistor, but perhaps your "variable gain" method is preferred, dunno. Do you really need x22 gain to boost the level at the output? Seems like the signal must have suffered on the way through if so. I'd want to boost it a bit on the way in to improve the signal/noise ratio, rather than boosting it (and any noise) after the effect. Finally, you could put a little tiny cap across that 220K feedback resistor in the output amp, just to limit the frequency response and stop any crazy RF oscillations the op-amp might wonder about getting into on its bad days. That can help keep noise down too. 22pF would give you a 32KHz roll-off.

Good luck from here on!

Tom

[Kipper4]

Still some work to do here. Planned for the upcoming week.
Thanks guys.

[Kipper4]

A little updated schematic and demo.
You guys have to be getting bored with this one already but I'd appreciate your eyes and knowledge to see if anything can be further improved or if theres still any bits I could remove.

The blend works ok but I think I might try a different taper. Suggestions on this please.

[ElectricDruid]

The blend pot is a audio level control, so the theory says a log pot should be best - we hear in decibels and all that. What have you got?

Tom

[ElectricDruid]

Oh, and shouldn't that 220nF (B2) be the other side of the pot?

The pot is grounded, but the amplifier is biased to the midpoint. I'd have thought that means the cap needs to separate them. Whereas the Q5 stage is grounded the same as the pot.

Alternatively, you could take the bottom of the pot to the Vb I suppose, but I don't like it. Dunno why exactly, but it doesn't feel right.

HTH,
Tom

[samhay]

Sounds good Rich.

Can I ask a big picture question? Do you really need a depth and a mix and a volume control? I can understand 2 out of three. Maybe. As it is, you can't get a wet-only signal...

Also, you are not asking much of VB here, so why not use the IC4A as the input buffer?
And, have you considered staggering the caps in Magnavibe-ish stages to make it a little more Univibe-ish?

[Kipper4]

"Also, you are not asking much of VB here, so why not use the IC4A as the input buffer?
And, have you considered staggering the caps in Magnavibe-ish stages to make it a little more Univibe-ish?"

I tried the other half of the op amp as the input buffer (inverting set up)
It sounded much less hifi. It works but sounds nothing like as good.
However using a non inverting input op amp buffer is fine.
Thanks thats a few less parts and space.

I have changed the second lyman cap (L) to a 47nf. Should i try some different values. If so which?


Thanks Tom
I made a few other changes thanks to your suggestions.
Schematic coming up.

[Kipper4]

I ditched the 100pf caps they were choking the phase pretty much.
Thanks Guys and Thanks D.A.
Further suggestions always welcome.


Eratta
resistor 27 should be 33k not 47k

[Kipper4]

Heres a similar version with an alternate p90 style lfo shown.
And some differing vactrols. that suit more common parts for stompboxers.
Also note the resistor for the dry path at the op amp input (3) value has changed to 24k. 22k will work also as well.
I'm reserving judgement on using the volume pedal as a speed control hooked up via a switched 1/4" jack. (LFO1 only)

[Fender3D]

I'd lower R26 (1M) to 47K~100K and use IC3's pin 3 as an alternate (switched) input for R38.
You may taste in phase or out of phase... phasing

[Kipper4]

Great Idea Thanks Fender3D.
Now I have a dilema. The phase mode is lower output than the Antiphase.IIRC
How do I compensate for this?
Volume pot at output? This probably wont work as one mode is below unity.
different gain resistors (Rin,Rf)?
pot in the place of R27?
It sounds amazing.

[Kipper4]

Hold the posts.
I think I have it.
When switching vibe inputs I have to switch the dry input too.
So DPDT. Snippet coming up.

[Kipper4]

[Fender3D]

In a differential amplifier you'd use R2=R38, R3 and R27=R26
If all the resistors are all of the same ohmic value, that is: R3, R38 = R2 = R27 = R26 then the circuit will become a Unity Gain Differential Amplifier and the voltage gain of the amplifier will be exactly one or unity.

[Kipper4]

Brilliant thanks Fender.

[Kipper4]

I found if i make R4 less than 10k it oscillates.

[ElectricDruid]

Is that what you wanted? That switches the phase of both signals, so it's equivalent to leaving it how it was, but inverting the whole output.

I thought you were aiming to just invert the phased path, in which case the dry path could switch input resistors to keep the levels similar, but doesn't need to move to the other op-amp input.

Have I got the stick by the wrong end?

Tom

[Kipper4]

Yer your spot on Tom.It was a quirk of the breadboard making me think otherwise.
I need to change a few values but otherwise its done.