Easy Vibe Question

[Barcode80]

I'm whipping up an easy vibe for a friend, and I'm curious about the chorus/vibrato switch. I just need to know which mode is chorus and which is vibrato? I'm thinking when you switch in the extra resistor that's chorus mode. Am I right?

[OwenF]

Whilst im not familiar with that specific circuit, I know from other vibes/phasers that vibrato is simply the phase shifted signal, whereas the chorus or phaser effect is achieved by mixing the phase shifted signal with the dry signal to achieve notches.
Looking at this schematic: http://www.hollis.co.uk/john/easyvibe.jpg I am going to have to say that the top 'lug' of the vib/chorus switch is vibrato as it is just completing the circuit for the phase shift stages. The bottom 'lug' I would imagine is chorus as it taps dry signal from the first buffer stage to mix with the wet signal.

In case your not aware, the bottom part of the schematic is the LFO and the top section is the phase shift stages with the amount of shift set (amongst other things) by the capacitors at the non-inverting inputs. A good way to learn about vibe circuits would be to read the technology of the univibe at geofex. Helped me and i'm still learning

Hope that helps.

[Barcode80]

Yeah, to be honest, modulation and phase shift are definitely my weak points. I understand them, but not their practical implementation. Thanks, I knew the "easy" implementation of vibrato is simply the phase shifted signal without the clean mixed in, but for some reason I was having a mental block. Probably from staring too Long at John's hand written schems!

[R.G.]

Technology of Phasers and Flangers, http://www.geofex.com

[Barcode80]

I should have been more specific RG

I completely understand the concept of phasing, but when it comes to applying the electronics to do so, that's where I falter. I often have trouble discerning what specific sections of schematics do, but mainly I only have this issue in modulation type schematics, where by their very nature the circuits are more complex. I have a hard time discerning, for example, that "x" opamp stage is serving "y" purpose, while "a" opamp stage is acting as a "b" in this circuit. Make sense?

[Barcode80]

Okay, now I'm pissed!:)

I built up the circuit, just like last time, and... nothing. Well, not nothing, but it wouldn't vibe. I could get the clean buffered signal when I switched to chorus mode, but in either mode the modulated signal wasn't there. I then found I had one of my LEDs attached to the LDRs in backward, so I fixed that.

The vibe comes to life.... sorta. It works, but there was a lot of distortion, half volume, and not much effect.  So I went and found a few cold joints, etc, and tried again. I had the LFO working now, but only in the last 1/4 of the rate pot. Anything below that wouldn't oscillate, almost like it was locked up. Also, the LFO was making a tick so loud it would be more accurate to say it was thumping, and it was doing more tremolo than anything else.

So I did some research and read somewhere that NE5532 (the Dual Opamp I have a ton of) is a bad opamp to use for LFO, and that it can be hard to get it to work right.

This was the one time I had ever direct soldered opamps in, so I just trashed the board and started fresh. I re-populated the board, and once again, no effect. The LEDs (the ones not in the LDR package) are lit solid. It appears I have no LFO again. SO, if power is all good (I'm assuming from the LEDs) and opamps are 4558, what could the problem be?