How good is the Pigtronix EP-2 at imitating the sound of a vibe pedal? [demos]

[Cortexturizer]

I've had the EP2 for a couple of months now, and let me tell you the learning curve with this pedal has been as steep as it can go, very powerful pedal but also very hard to dial in. I've had the desire to build a Harbinger lately so I wanted to try and see how close can the EP2 come to the sound of a univibe. After all it's photocell based (there's like 5-6 vactrols in there, maybe more) and it's 18V.
I've included 4 tracks, each representing a certain setting, first with the speed set to trower-ish speed, then the other half of the clip starts with a very slow speed and then I manually set it to fast and play like that.
The LFO smooth switch sets the resonance to zero, so when it's ON, the resonance is zero.
With the resonance anywhere higher than zero, you start to hear the phasing, and above 35%, for example, it starts to be aphaser through and through. EP2 can go to ridiculous depths and it is really a bomb of a pedal. Ridiculously funky as well.
The Invert switch shifts the tonal center more to the bass or to the higher end of things. All in all, I think it sounds pretty good at doing the univibe thing, what do you guys think and which sound do you like best of the 4 sounds?

[soundcloud]https://soundcloud.com/kuato-design-stompboxes/invert-minus-lfo-smooth-is-1?in=kuato-design-stompboxes/sets/ep2-as-a-vibe[/soundcloud]

[soundcloud]https://soundcloud.com/kuato-design-stompboxes/invert-minus-lfo-smooth-is?in=kuato-design-stompboxes/sets/ep2-as-a-vibe[/soundcloud]

[soundcloud]https://soundcloud.com/kuato-design-stompboxes/invert-plus-lfo-smooth-is-on-1?in=kuato-design-stompboxes/sets/ep2-as-a-vibe[/soundcloud]

[soundcloud]https://soundcloud.com/kuato-design-stompboxes/invert-plus-lfo-smooth-is?in=kuato-design-stompboxes/sets/ep2-as-a-vibe[/soundcloud]

Oh, and I don't know how to play the bridge of sighs, I was playing out of memory of the song haha, I suck at it, lol.

I shoudl probably write this as well - on every clip the first half is the neck pickup, the second half is both pickups engaged. The overdrive is the Sunking, and the reverb you hear is the subdecay spring theory that is placed before the overdrive. The EP2 is also placed before.

[Cortexturizer]

nobody? come on guys, I know there's some serious vibe aficionados out there

[LaceSensor]

On the whole Id say it clearly sounds like a phaser with the uni vibe caps
Its nice but to me it lacks the true assymetric warble of a vibe.

If you like this kind of phase/vibe cross over, you should try the Lovetone Doppelganger or the various clones.
To me it can cop a real nice vibey tone, as well as having the less obviously phase-y vibrato mode
Plus, you can run two LFOs at once.

[Cortexturizer]

Cool I was just wondering. I decided to order the harbinger board nevertheless a while ago :-) 
The doppelganger always sounded fantastic to me and there's a test on yputube where the guy test out four pedals dpoing the univibe thing, the fulltone deja, line 6 fm4, effectrode, and the doppelganger and the lovetone was by far the best sounding to me :-)
I've been watching the clones here closely and a lot of guys had done em great, at some point I will certainly jump on the wagon as well

[RobA]

Hmm, your embedded sound cloud links come up blank for me. I've probably got some issues with out-of-date flash or something similar. I was able to get them to play by going to your sound cloud page though.

Some of the samples sound pretty close to some Univibe things to me -- but it does sound different to me. I'd tend to agree that it's in the LFO.

The simplest vib-ie thing that has the right kind of feel to me is the Tri-Vibe and I think it's the LFO design in that one that makes it work. That reminds me, I'm supposed to do something with that circuit -- it would also be a pretty easy one to put the LFO rate under expression pedal control. 

[kothoma]

[...] I'd tend to agree that it's in the LFO. [...]

Well, that's one thing that makes me think from time to time. Shouldn't it be possible to start with either a JFET or a LED/LDR or a OTA four stage design with the appropriate capacitors in each stage and emulate the right LFO with a small microcontroller circuit (incorporating lamp lag etc. and all)?

Edit. Forgot to mention the switched capacitor design...

[RobA]

[...] I'd tend to agree that it's in the LFO. [...]

Well, that's one thing that makes me think from time to time. Shouldn't it be possible to start with either a JFET or a LED/LDR or a OTA four stage design with the appropriate capacitors in each stage and emulate the right LFO with a small microcontroller circuit (incorporating lamp lag etc. and all)?

Edit. Forgot to mention the switched capacitor design...

Well ... that's pretty much what I was supposed to do with the Tri-Vibe circuit. It's two Tri-vibes using two LFO's controlled by one MCU. There are two ways to arrange the two Tri-Vibe circuits, stereo or split frequency. I've tested both ways and I like them both.

[kothoma]

[...] I'd tend to agree that it's in the LFO. [...]

Well, that's one thing that makes me think from time to time. Shouldn't it be possible to start with either a JFET or a LED/LDR or a OTA four stage design with the appropriate capacitors in each stage and emulate the right LFO with a small microcontroller circuit (incorporating lamp lag etc. and all)?

Edit. Forgot to mention the switched capacitor design...

Well ... that's pretty much what I was supposed to do with the Tri-Vibe circuit. It's two Tri-vibes using two LFO's controlled by one MCU. There are two ways to arrange the two Tri-Vibe circuits, stereo or split frequency. I've tested both ways and I like them both.

Are you experimenting with different curves? I guess you need something between a triangle, a sine, or a trepezoid wave with a bit of asymmetry?

[RobA]

[...]
Are you experimenting with different curves? I guess you need something between a triangle, a sine, or a trepezoid wave with a bit of asymmetry?

Yeah, the LFO curves are done using a table lookup type thing. So, you can precalculate pretty much anything you want. In line with what is done in the Tri-Vibe, an exponentiated sine LFO does a good job. It would be easy to add skew, lag or other sorts of distortion to that shape too.  Actually, there's probably enough computational power left over in the ATTiny84 to do some pseudo-randomization of the LFO lag if you wanted to too.

The test PCB's I've had made for the LFO controller are easy to program. So trying different things is straight forward to do. But, the current design is too big to use as a utility board in an effect. So, I need to redo it using SMD parts to get it down in size.

[kothoma]

[...]
Are you experimenting with different curves? I guess you need something between a triangle, a sine, or a trepezoid wave with a bit of asymmetry?

Yeah, the LFO curves are done using a table lookup type thing. So, you can precalculate pretty much anything you want. In line with what is done in the Tri-Vibe, an exponentiated sine LFO does a good job. It would be easy to add skew, lag or other sorts of distortion to that shape too.  Actually, there's probably enough computational power left over in the ATTiny84 to do some pseudo-randomization of the LFO lag if you wanted to too.

The test PCB's I've had made for the LFO controller are easy to program. So trying different things is straight forward to do. But, the current design is too big to use as a utility board in an effect. So, I need to redo it using SMD parts to get it down in size.

Right, the curve needs to be exponential. I understand the Tri-Vibe aims at a vibrato type of sound (like a chorus without the dry signal)? But what about the distinct (uni-)vibe variety of wobble?

Edit. Sorry, Cortexturizer. I really don't mean to hijack your thread. But this seems a great oportunity...

[RobA]

[...]
Right, the curve needs to be exponential. I understand the Tri-Vibe aims at a vibrato type of sound (like a chorus without the dry signal)? But what about the distinct (uni-)vibe variety of wobble?

Edit. Sorry, Cortexturizer. I really don't mean to hijack your thread. But this seems a great oportunity...

It should be doable, but I don't really know yet. I need to directly compare a UniVibe to the LFO's. But, I don't have a UniVibe. But that's really a situation to be in, so I believe an order for a Harbinger board and some associated parts is needed ASAP .

It's actually an effect I've wanted to build for some time now. I just haven't pushed myself into doing it because of the lamp and LDR's and shield ... But it really is silly of me not to have built one already. I even have a nice stop sign Hammond box waiting to put it in.

[kothoma]

[...]
Right, the curve needs to be exponential. I understand the Tri-Vibe aims at a vibrato type of sound (like a chorus without the dry signal)? But what about the distinct (uni-)vibe variety of wobble?

Edit. Sorry, Cortexturizer. I really don't mean to hijack your thread. But this seems a great oportunity...

It should be doable, but I don't really know yet. I need to directly compare a UniVibe to the LFO's. But, I don't have a UniVibe. But that's really a situation to be in, so I believe an order for a Harbinger board and some associated parts is needed ASAP .

It's actually an effect I've wanted to build for some time now. I just haven't pushed myself into doing it because of the lamp and LDR's and shield ... But it really is silly of me not to have built one already. I even have a nice stop sign Hammond box waiting to put it in.

I have a Harbinger One board somewhere... And I remember ordering a lamp/LDR set from banzaimusic (http://www.banzaimusic.com/Univibe-Upgrade-Kit.html, ouch). I just didn't find the time to make something out of it... (And that reminds me of all the parts for a Doppelganger, that must be somewhere in the chaos...)

[kothoma]

[...]
Right, the curve needs to be exponential. I understand the Tri-Vibe aims at a vibrato type of sound (like a chorus without the dry signal)? But what about the distinct (uni-)vibe variety of wobble?

Edit. Sorry, Cortexturizer. I really don't mean to hijack your thread. But this seems a great oportunity...

It should be doable, but I don't really know yet. I need to directly compare a UniVibe to the LFO's. But, I don't have a UniVibe. But that's really a situation to be in, so I believe an order for a Harbinger board and some associated parts is needed ASAP .

It's actually an effect I've wanted to build for some time now. I just haven't pushed myself into doing it because of the lamp and LDR's and shield ... But it really is silly of me not to have built one already. I even have a nice stop sign Hammond box waiting to put it in.

So the idea would be to make measurements at the LDRs of a working univibe pedal to get the exact control signal for the allpasses. These could then be perfectly replicated with µc controlled LED/LDRs. The result should exactly sound like the real thing as the audio path would be untouched. The build probably turns out smaller in the end: smaller voltage regulator, simpler LFO, smaller optical unit?

[RobA]

[...]
So the idea would be to make measurements at the LDRs of a working univibe pedal to get the exact control signal for the allpasses. These could then be perfectly replicated with µc controlled LED/LDRs. The result should exactly sound like the real thing as the audio path would be untouched. The build probably turns out smaller in the end: smaller voltage regulator, simpler LFO, smaller optical unit?

Yeah, that's pretty much the path for this particular application of the LFO board. When trying to adapt it to other phase-ie vibe-ie type circuits I'd guess that there would be a some further tuning that would be needed to get close to the right sound and feel.

I've tried it with a couple of Phase 45's on breadboard and you can get some interesting things there with different LFO shapes and having them in phase, out-of-phase, or in quadrature with each other.  I think that there's lots of potential in using small MCU's for LFO generation.

[kothoma]

I've tried it with a couple of Phase 45's on breadboard and you can get some interesting things there with different LFO shapes and having them in phase, out-of-phase, or in quadrature with each other.

That sounds like great fun! Did you feed the JFETs directly or did you replace them with CMOS switches (CD4066)?

I think that there's lots of potential in using small MCU's for LFO generation.

Totally agree.   Edit: just think of Leslie type spin-up/spin down...