Help finding spot on DOD Stereo Phaser based on Ross Phaser Ropez schematic

[Dreverb]

Hello, thanks in advance and sorry if my english is not as good as i would like...
Trying to mod a DOD stereo phaser FX20B to Vibe phaser.
Looking at the schemes seems similar to the ross phaser. 4 stages phaser.

I would love to know if is there any point similar in the DOD like the ross phaser 27k resisistor used to switch between vibrato and phaser in the other one...



and here is the DOD



Thanks anyway

[PRR]

[Dreverb]

Thanks so much! Ill try that.
Any other suggestion to make it sound more like a univibe is truly welcome

[ElectricDruid]

The key feature of the Univibe is that it uses different cap values for the different stages, so you could experiment by changing a couple of the caps. Or you could find a schematic for the univibe and have a look to see what values it has. You probably don't want identical values (since the rest of the circuit probably isn't the same) but if you kept the same *ratio* between the different caps, you'd get a very similar effect.

HTH,
Tom

[Dreverb]

Thanks again!
Another thing if possible...  please, Could it be possible to find this ones?


thanks so much, really

[ElectricDruid]

Perdonme, pero no te he entendido. ¿Que quieres, exactamente?

Estos dos componentes están conectados al LM13700, y tienes los números del pines donde conectan. Por lo tanto debe ser possible encontrarlos. ¿O esta no era la pregunta?

¡También mi Español no es tan bueno como quisiera, pero no tengo muchos oportunidades por practicar! 

T.

[Dreverb]

Muchas gracias! Disculpa, no me explique bien.
Estoy intentando modificar un DOD FX20B a partir de las mods que se usan para el Ross phaser, ya que son bastante similares. pero hay cosas que se me escapan...

Lo que me "falta" , si es posible, es identificar éstos dos ultimos componentes marcados aqui:


... saber cuales hacen su misma funcion o semejante en éste circuito:


Tu español es casi perfecto.
[b]¡Tampoco [/b]mi español no es tan bueno como quisiera, pero no tengo muchas oportunidades para practicar! 

[ElectricDruid]

Ah, ok, I get it now. You're trying to find the equivalent part on the other schematic.

No wonder you're having problems - the two LFO designs are quite different. The DOD one looks like it is based on the LM13600 or LM13700 OTA chip. The Ross one is a simpler op-amp design, more what you typically see.

However, the function of the two parts isn't too difficult. The 270K resistor sets the gain (ok, "transconductance", but let's not go into that) of that stage. In an op-amp, that's just done with the resistors, so you don't need it.
The 3.3uF cap is the main frequency-setting cap for the LFO and will determine how fast/slow it goes overall. I'd guess that the 10u C16 in the Ross diagram does the same job (the other caps in that part of the circuit look too small for LFO frequencies).

Since the two LFOs are so different, it might well give a similar frequency range despite being a different value. Sometimes the user instructions or the service manual (if you can find them online) have the LFO ranges, but often they don't.

¡Espero que esta te ayude!

Tom

[Dreverb]

Muchas gracias!