Harmonic Trem options

[Joncaster]

I'm boxing up my Hearthrob Trem, which is just a killer sounding trem, I like that it's simple and versatile and easy to build.

I think it would be great to have a companion trem, that sits between my univibe and the hearthrob in sonic territory.
That leads to Harmonic, Brownface type trems, which I love the sound of (never played through one, though).
There seems to be a few designs around from a few years ago,
Wanted to check what would be nice and simple, and get that kinda vibe across?

I have an eye on the RG Keen Ersatz Fender Pro Vibe
The twin peaks seems overkill for me.

Any other circuits that fit the bill?

Thank You

[bluebunny]

I quite like Jon Patton's Cardinal tremolo.  The thread is here, although the original pictures seem to have gone...  You can find v2 build docs at 1776.  (I built the v1 incarnation.)

v1: v2:

[Joncaster]

That does look cool, only problem is finding Vactorals here is a mission (well it was last time i tried)

[Joncaster]

Apparently finding 2n5952 or 2n5485's is a mission here as well.
Dammit this country.

Any substitutes for those if I went the Fender Pro Vibe / Vibra-tone route?

[Mark Hammer]

Rolling your own vactrols isn't that hard, really.  I would hope that finding LEDs, photocells, and shrink tubing isn't as hard as finding 2N5952s.

[Joncaster]

Rolling your own vactrols isn't that hard, really.  I would hope that finding LEDs, photocells, and shrink tubing isn't as hard as finding 2N5952s.

Hmm, that would be a pretty rad DIY feather in the cap.
Yeah photocells by the bucketload round here.

Thanks Mark.

[Mark Hammer]

I find a few hurdles to clear in making them:

1) A stable proximity between LED and LDR is important.  Some folks will use those thin flat LEDs, and lie the LDR on one side of the LED.  I use regular round LEDs, fille the top down flat so that it takes the shape of a soup can, and adhere the LDR to that now flattened surface.

2) Shrink tubing isn't quite as opaque as you might think.  Black is certainly better than grey, white or yellow for keeping external light out, but consider two layers of heat shrink for insurance.  Either way, do note that what you measure when the unit is sitting atop your work surface is going to be affected by ambient light from your workspace, which will NOT be there when the unit is installed inside a box.  Good to have some object handy that can block out most light from the unit when you go to measure it.

3) If you can, find out what light wavelength the LDR is most sensitive to, and make sure to use an LED colour that complements that.

4) LEDs can be gotten in different efficiencies.  It may be best to start out with higher-efficiency units and simply up the current-limiting resistance of whatever is driving the LED to get a suitable brightness, as opposed to using an under-illuminating LED and wondering why the LDR isn't showing much variation.

[Ben N]

I haven't had the opportunity to test this yet, but I think a double layer consisting of light-colored heat shrink (to concentrate maximum LED light to the photocell) with an outer layer of black might be the best.

[Joncaster]

Thanks Mark,
I'm a bit concerned about all the "absolutely need a VTL5C1 for the Cardinal" I've been reading, but I can see about matching those specs (plenty of LDR dark resistance variants I can choose from, above 30M), etc.

[Mark Hammer]

I haven't had the opportunity to test this yet, but I think a double layer consisting of light-colored heat shrink (to concentrate maximum LED light to the photocell) with an outer layer of black might be the best.

Or, I suppose a person could simply wrap the assembly in aluminum foil (shiny side in), and then encase that in heat shrink.  I'm going to have to try that out.

[Joncaster]

So far the Cardinal and the Vibra-Tone/Ersatz Fender both have caveats.

Are their any other options, before I start getting parts together?
I might end up placing an overseas order and add some cool stuff I can't get here, in the end...

[Elektrojänis]

Or, I suppose a person could simply wrap the assembly in aluminum foil (shiny side in), and then encase that in heat shrink.  I'm going to have to try that out.

Add an extra wire in there for grounding the foil and you will a bit have extra shielding for interference... Probably not really usefull, but guaranteed to confuse somebody who tries tracing/cloning your circuit.

[FlyingWild]

I've been wanting to build a harmonic tremolo too, and the Cardinal is atop my list, but I put it on hold due to the "VTL5C1" then the importance of matching Q2 and Q3. I can easily get SMD 2N5457's and have some 2N5458's which according to the documentation is a fine substitute, but the idea of trying to match SMD transistors isn't appealing.

Regarding the VTL5C1 has anyone tired the Xvive ones? I've seen some cheap on ebay, but recently got some VTL5C3 which have a coloured dot to represent the version (yellow in the case of the VTL5C3) which were more expensive, and don't look like the ones on ebay, and were purchased from a reputable synth supplier.

Joncaster you asked if there is another option: Catalinbread Pareidolia schematic is out there.

But I'd personally prefer to try and make the Cardinal, my stumbling blocks being the matching for SMD FETs and the VTL5C1 unless the Xvive VTL5C1 is a fine substitute.

[FlyingWild]

Curiously my VTL5C3 has different markings and the Xvive 'X' is different to that on their website which makes me wonder if I really have an Xvive!

http://www.xviveaudio.com/productInfo.asp?id=358

[Joncaster]

I'm still looking at the Jfet Vibratone, cause if I can just get a bunch of the right Jfets locally, it's easier than doing a smallbear order and shipping.

Currently wondering if NTE451's will work in place of the 2n5952/2n5485/2sk30?
Seems to have a similar Vgsoff... Not sure what else to look for.

[ElectricDruid]

Curiously my VTL5C3 has different markings and the Xvive 'X' is different to that on their website which makes me wonder if I really have an Xvive!

http://www.xviveaudio.com/productInfo.asp?id=358

That looks like the Xvive optos we've got here in the Druid workshop. We bought a thousand direct from Xvive in Singapore, so I know they're the real deal. If anyone's interested, I can put them up in the shop. At the moment we only sell them as part of the parts kit for the FilterFX pedal (discussed here in another thread somewhere).

[Mark Hammer]

I hadn't noticed the Filter FX previously.  Sounds nice, and the StompLFO certainly simplifies things.  If you had a suitable threshold detector, the One-Shot generator could be used to provide a triggered envelope sweep when repeats are minimized.  That's neither better or worse than a steady-state LFO, merely a different flavour.

I might also note that band-reject (notch) sounds nice when modulated/swept.  Anderton included that option in his EPFM Super Tone Control, which is also a state-variable filter.  The builder would need a 4-position rotary to imp0lement it, however.

[ElectricDruid]

Maybe I should knock up a quick StompLFO harmonic trem? Wouldn't be that hard to do. Would have quite a lot of options for quite a limited number of parts. Only trouble is two optos in anything doesn't make for the cheapest build. Still, it'd sound nice I'm sure.

That said, "quickly knocking something up" usually takes me several months. That's just how it goes. First design, then test, then PCB layout, then prototype, then revising the design, redoing the layout, ordering more PCBs, building them up, etc etc...takes a while, even if you get right on the case.

PS: Mark, I agree about the FilterFX and the Oneshot. Since the Oneshot and StompLFO chips are very similar, it is actually possible to stick the OneShot in the FilterFX hardware and trigger it using the (previously) "tap tempo" switch. It's a bit wacky, but there's a few good sounds to be had out of it.

[bluebunny]

I hadn't noticed the Filter FX either.  Looks interesting!

If anyone's interested, I can put them up in the shop.

Yes please, Tom. 

[FlyingWild]

I'd certainly be interested to see what you came up with ElectricDruid.

I'm putting together a Tremulous Lune at the moment which is what the VTL5C3 is for, but I'll probably be itching to play with a new tremolo by the time you're not quite done with the first design ;-)