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Projects => Build Reports => Topic started by: culturejam on May 21, 2013, 01:31:48 AM

Title: Duo-Vibe: a prototype --- DEMO ADDED
Post by: culturejam on May 21, 2013, 01:31:48 AM
I worked up this circuit as a possible commercial product. Still not sure what the fate of it will be, but at least I got this one cool pedal out of it, if nothing else. I'll post the schematic eventually.

Started working on the design back in February but just now got around to testing the proto boards. Everything works as is and it is dead quiet (no ticking whatsoever).

The downside is that the physical layout of the hardware was pretty bad on my part. So I had to manually wire some stuff that should have been board mounted. And of course, one of the pots was wired backward.  :lol: I do that every damn time.  

I've already revamped the layout to  make it a lot smaller, fix the layout issues, and I ditched one of the pots in favor of a switch (it makes a lot more sense that way).

Okay, so it's a two-stage vibe-phaser thing using LDRs as the variable resistance element. You may recall that I've played around with this general concept quite a bit. So far, this one is my favorite, as it hits the perfect mix between complexity and functionality.

There is a phase mode and a vibe mode. The phase mode sound like the vibe mode with with no pitch shift at all (just filter-like oscillations) and a bit sharper vowel sound. It actually sounds good both slow and fast. Backing off the depth a bit smooths out the triangle LFO into more like a sine wave, which helps on slow speeds.  The pot I ditched in the new design is a wave shape control, but you can really only hear the differences at the extremes. Slow square wave sounds weird, but it sounds great at higher speeds (and passable if the depth is backed off at slow speeds). It doesn't do sea-sick pitch bends, but you can definitely hear it in the vibe mode.

I'll get a demo clip posted in the next couple days. Finish is alcohol inks sealed up with Mod Podge, which also adds a nice texture.

DEMO ADDED:
[soundcloud]https://soundcloud.com/effdub/duovibe-demo[/soundcloud]
It's a little quiet, so you may want to turn up your speakers a bit. Goofed up on the recording level setting.


(http://i257.photobucket.com/albums/hh218/reverse_engineer/duovibe-1_zps0325d4a3.jpg)



(http://i257.photobucket.com/albums/hh218/reverse_engineer/duovibe-2_zps4b344992.jpg)
Title: Re: Duo-Vibe: a prototype
Post by: gingataff on May 21, 2013, 01:39:05 AM
Sounds like a cool pedal.
And that finish is gorgeous
Title: Re: Duo-Vibe: a prototype
Post by: das234 on May 21, 2013, 01:44:23 AM
The finish is great.  Curious how you get that marble finish to look like that, and can't wait to hear it.
Title: Re: Duo-Vibe: a prototype
Post by: spaceboss on May 21, 2013, 01:47:50 AM
Looks righteous!

Where to you obtain these here 'alcohol inks'? I've been flirting with the idea of incorporating some darker ones with a reverse etch.

Looking forward to hearing it.
Title: Re: Duo-Vibe: a prototype
Post by: nzCdog on May 21, 2013, 02:13:26 AM
Quote from: spaceboss on May 21, 2013, 01:47:50 AM
Looks righteous!
This!^
QuoteLooking forward to hearing it.
and this!!^

Gorgeous finishing... bring the demo!  8)
Title: Re: Duo-Vibe: a prototype
Post by: mjcyates on May 21, 2013, 02:27:35 AM
Love the finish. Looks great!
Title: Re: Duo-Vibe: a prototype
Post by: culturejam on May 21, 2013, 02:36:03 AM
Quote from: spaceboss on May 21, 2013, 01:47:50 AM
Where to you obtain these here 'alcohol inks'?

I get mine from Michaels. But they can be had on ebay or other venues. I use a cotton-pad stamper to apply the ink. Other folks like to drip it on or whatever, but I like the pattern of the stamp.
Title: Re: Duo-Vibe: a prototype
Post by: billstein on May 21, 2013, 03:21:53 AM
I have got to try alcohol inks. Do you put those on a bare box? How do you prep it?
Title: Re: Duo-Vibe: a prototype
Post by: ch1naski on May 21, 2013, 06:25:56 AM
Two things:

1 - Great finish.
2 - Let's hear the damn thing.
3 - I dont need to hear it,  I want a board.

(did i say "two things"?  ;) )
Title: Re: Duo-Vibe: a prototype
Post by: LaceSensor on May 21, 2013, 09:37:49 AM
would buy
Title: Re: Duo-Vibe: a prototype
Post by: midwayfair on May 21, 2013, 01:56:07 PM
Beautiful.

Is the vibe vs. phaser mode simply removing a stage, or a cap change? I guess I'll have to wait for the schematic. :)

... Enter it in the contest? :)
Title: Re: Duo-Vibe: a prototype
Post by: Scruffie on May 21, 2013, 02:03:07 PM
Quote from: midwayfair on May 21, 2013, 01:56:07 PM
Beautiful.

Is the vibe vs. phaser mode simply removing a stage, or a cap change? I guess I'll have to wait for the schematic. :)

... Enter it in the contest? :)
Well i'd guess as is standard he's removing the dry signal... with only 2 stages i'm guessing the caps may already be staggered to get a bit more out of the sound in vibe mode, possibly not though.

Unless he's going with the trem definition of vibe and then could be a stage removal.

So... FET buffer input in to 2 x darlington all-pass stages with a tremulust lune LFO with a few of the mods removed on it?
Title: Re: Duo-Vibe: a prototype
Post by: culturejam on May 21, 2013, 02:17:03 PM
Quote from: midwayfair on May 21, 2013, 01:56:07 PM
Is the vibe vs. phaser mode simply removing a stage, or a cap change? I guess I'll have to wait for the schematic. :)

It's a cap value change. The value has a huge impact on the sound, and I spent a couple  hours just playing around with value to find two that would make the pedal more versatile. But you could just tweak it for one sound and ditch the switch.

Quote from: midwayfair... Enter it in the contest? :)

I thought about it. But I'm not ready to release the schematic just yet, and I wouldn't feel right about entering a "secret" design. I promise I will make it public in the near future, though.


Quote from: Scruffie on May 21, 2013, 02:03:07 PM
Well i'd guess as is standard he's removing the dry signal...

Here's what's weird...there is always some dry passthrough. If you completely remove dry, the effect is greatly diminished. I have no idea why, but it works that way. It might be because feedback/feedforward seems to work oddly with only two stages. That's actually why I added the output buffer (to keep the feedback output isolated from the effect input and causing impedance issues). So basically the mode switch toggles between two caps (33n and 3n3, as I recall), and that filters the feedback. As I recall (it's been a while), the larger cap is more vibey (pitch bend).

The LFO started as the stock STM oscillator (which is itself a trimmed down Lune LFO). I tweaked it a bit to make it work better with the LED/LDR in the context of something that's not a tremolo.

So yeah, if you look at the Tourbillon schematic, it's like that but with two stages and a different LFO and different feedback setup.
Title: Re: Duo-Vibe: a prototype
Post by: Scruffie on May 21, 2013, 02:39:12 PM
Quote from: culturejam on May 21, 2013, 02:17:03 PM
Quote from: midwayfair on May 21, 2013, 01:56:07 PM
Is the vibe vs. phaser mode simply removing a stage, or a cap change? I guess I'll have to wait for the schematic. :)

It's a cap value change. The value has a huge impact on the sound, and I spent a couple  hours just playing around with value to find two that would make the pedal more versatile. But you could just tweak it for one sound and ditch the switch.

Quote from: midwayfair... Enter it in the contest? :)

I thought about it. But I'm not ready to release the schematic just yet, and I wouldn't feel right about entering a "secret" design. I promise I will make it public in the near future, though.


Quote from: Scruffie on May 21, 2013, 02:03:07 PM
Well i'd guess as is standard he's removing the dry signal...

Here's what's weird...there is always some dry passthrough. If you completely remove dry, the effect is greatly diminished. I have no idea why, but it works that way. It might be because feedback/feedforward seems to work oddly with only two stages. That's actually why I added the output buffer (to keep the feedback output isolated from the effect input and causing impedance issues). So basically the mode switch toggles between two caps (33n and 3n3, as I recall), and that filters the feedback. As I recall (it's been a while), the larger cap is more vibey (pitch bend).

The LFO started as the stock STM oscillator (which is itself a trimmed down Lune LFO). I tweaked it a bit to make it work better with the LED/LDR in the context of something that's not a tremolo.

So yeah, if you look at the Tourbillon schematic, it's like that but with two stages and a different LFO and different feedback setup.
Ahhh that ol' chestnut, the volume drop can be gotten around but it isn't always necessary to completely remove the dry for something pleasing. Sounds like the cap swap does the job you want anyway.

I just went with Lune LFO as lots of people seem to favour it  ;) yeah that could be a bit hard on off for vibe... can't see the parts you'd have used in the shot but did you go with something sinusoidal?
Title: Re: Duo-Vibe: a prototype
Post by: culturejam on May 21, 2013, 02:59:34 PM
Quote from: Scruffie on May 21, 2013, 02:39:12 PM
Ahhh that ol' chestnut, the volume drop can be gotten around but it isn't always necessary to completely remove the dry for something pleasing. Sounds like the cap swap does the job you want anyway.

It's not just a volume drop. It really sounds like the effect "depth" is gutted if dry is killed completely. I can't explain it, but that's what my ears hear.

Quote from: ScruffieI just went with Lune LFO as lots of people seem to favour it  ;) yeah that could be a bit hard on off for vibe... can't see the parts you'd have used in the shot but did you go with something sinusoidal?

It's still somewhat choppy, even when on the "smoothest" setting. It's a bit lopsided, as is usual with LED/LDR. The LDRs just don't turn on/off linearly. But I tweaked the Depth control a bit to help smooth out the wave a little on less deep settings. It's got some trem-like character, for sure.
Title: Re: Duo-Vibe: a prototype
Post by: Scruffie on May 21, 2013, 03:19:19 PM
Quote from: culturejam on May 21, 2013, 02:59:34 PM
Quote from: Scruffie on May 21, 2013, 02:39:12 PM
Ahhh that ol' chestnut, the volume drop can be gotten around but it isn't always necessary to completely remove the dry for something pleasing. Sounds like the cap swap does the job you want anyway.

It's not just a volume drop. It really sounds like the effect "depth" is gutted if dry is killed completely. I can't explain it, but that's what my ears hear.

Quote from: ScruffieI just went with Lune LFO as lots of people seem to favour it  ;) yeah that could be a bit hard on off for vibe... can't see the parts you'd have used in the shot but did you go with something sinusoidal?

It's still somewhat choppy, even when on the "smoothest" setting. It's a bit lopsided, as is usual with LED/LDR. The LDRs just don't turn on/off linearly. But I tweaked the Depth control a bit to help smooth out the wave a little on less deep settings. It's got some trem-like character, for sure.
Have a think about why it might sound like depth is going with dry signal removed... just your wet path...

Have you tried 'clipping' the wave? And adding some extra capacitance at the output to smooth the wave? I don't know if you want it overly smooth though, that choppyness is probably a bit of the charm with just 2 stages.
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: culturejam on May 22, 2013, 01:53:21 AM
Added a demo clip to the first post.
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: nzCdog on May 22, 2013, 02:31:25 AM
It's certainly got some great sounds man, nice work. 8)
Title: Re:
Post by: ch1naski on May 22, 2013, 02:56:12 AM
I got queasy at the 1:30 mark.;D I like that it's very present in the slower speeds.....I could almost hear the opening notes to "shine on you crazy diamond"......

Sent from my Nexus 7 using Tapatalk HD
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: Guitarmageddon on May 22, 2013, 06:50:30 AM
That's really cool Forrest. Of course it looks beautiful, but I've been waiting on the clip.
I really like the square wave sound and especially the phased trem effect at about 2:37
Sweet!
Title: Re: Duo-Vibe: a prototype
Post by: culturejam on May 22, 2013, 05:10:53 PM
Thanks for the kind words, guys.  :)

Quote from: Scruffie on May 21, 2013, 03:19:19 PM
Have a think about why it might sound like depth is going with dry signal removed... just your wet path...

I guess phrased it wrong. I'm not really completely wiping out dry. It's impossible to do so in this circuit. When the LED is dark, the signal is going through is basically dry. When the LED is lit, the signal is out of phase with the input. In between those extremes is where things sound interesting, as there is a mix of in-phase and out-of-phase sounds as they cross over. Adding the cap-coupled feedback path (or is it feedforward?) essentially gives a constant in-phase signal path from input to output, which makes the phase oscillation sound more pronounced at certain points in the sweep. At least I think that's what's happening.  ;D
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: midwayfair on May 22, 2013, 05:40:53 PM
Sounds awesome. The vibrato mode is really much better than the magnavibe by itself, and I really like the mild phaser sound on this.

I note from looking at the layout that the switch is a SPST. If you really wanted to get fancy, a DPDT on-off-on could make a third vibe mode, one without pitch shifting but also without the "wah"-ish sound of the phaser mode. It'll sound really watery. All you do is take two resistors of the same value as the emitter resistors and put them in parallel with the fixed emitter resistors to ground. When you switch them in, they half the value of the emitter resistors and you get very little pitch shift. (This is the voicing I used in the blue warbler.) You only need one pole because they're both connecting to ground. Plus it would be really easy to just use a cheaper SPST still, by only using one side of the switch pads ...

or you could build a third effect on the same board and have an extra product but tell everyone it's a completely different amp and totally NOT the same pedal they've already bought twice :D ...
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: culturejam on May 22, 2013, 07:00:48 PM
Quote from: midwayfair on May 22, 2013, 05:40:53 PM
I note from looking at the layout that the switch is a SPST. If you really wanted to get fancy, a DPDT on-off-on could make a third vibe mode, one without pitch shifting but also without the "wah"-ish sound of the phaser mode. It'll sound really watery. All you do is take two resistors of the same value as the emitter resistors and put them in parallel with the fixed emitter resistors to ground. When you switch them in, they half the value of the emitter resistors and you get very little pitch shift. (This is the voicing I used in the blue warbler.)

I'll have to check that out. Sounds like a neat bit of bias trickery you've outlined. Does halving the emitter resistance cause a volume bump? Seems like it would, at least for the in-phase collector output signal.
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: midwayfair on May 22, 2013, 07:32:50 PM
Quote from: culturejam on May 22, 2013, 07:00:48 PMDoes halving the emitter resistance cause a volume bump? Seems like it would, at least for the in-phase collector output signal.

Well, without deciphering your emitter/collector values on the board, you're probably at 10K on both the emitter and collector, right? What's the actual volume difference in a transistor stage when you go from 10K to 4.7K? It's almost imperceptible -- it might be a couple decibels at most on the treble side of the wave swing only. Whereas the emitter will always be at unity volume unless the biasing is just wrong or the emitter resistor becomes much smaller, like <1K.

I find that I'm less sensitive to small volume changes than many people, though, so obviously: YMMV.
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: neiloler on May 22, 2013, 09:51:03 PM
Very cool finish, and I dig the sounds. Even in the extreme setting, I still felt like it maintained its musicality.
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: culturejam on May 22, 2013, 11:47:37 PM
Quote from: midwayfair on May 22, 2013, 07:32:50 PM
Well, without deciphering your emitter/collector values on the board, you're probably at 10K on both the emitter and collector, right? What's the actual volume difference in a transistor stage when you go from 10K to 4.7K? It's almost imperceptible -- it might be a couple decibels at most on the treble side of the wave swing only. Whereas the emitter will always be at unity volume unless the biasing is just wrong or the emitter resistor becomes much smaller, like <1K.

Good point.  ;D
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: culturejam on May 23, 2013, 12:28:21 AM
Just tried this bad boy with some fuzz. Sounds pretty damn good *in front* of dirt. Not so much with a dirt box in front of the vibe. But like everything else tone related, some folks may like the dirt first.
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: TreeSlayer on February 24, 2015, 12:49:54 AM
hey, Bruh! PLEASE send me the docs on this!!! it's WAY cool!!!

Layton
Title: Re: Duo-Vibe: a prototype --- DEMO ADDED
Post by: culturejam on February 24, 2015, 02:05:39 AM
PM me your email and I'll get you the schematic and whatever else I have for that version of the board.