Dual Tremolo

[yobleduwop]

Hey guys i was thinking of making a tremolo pedal and going for the approach of most boutique builders and making a tremolo pedal with two separate speed and depthj settings, so you have a on/off switch and a one/two speedoutput, is this as simple as just making two tremolos in one box and just have the second switch change between each of the pedals?
Does anyone have a schematic to a boutique pedal out there similar to this, i was thinking of using the tremulus lune on both sides,
Thanks Joel

[Mark Hammer]

If you look at a variety of modulation pedals that use the standard 2 op-amp LFO, you'll see that there are two frequent subvarieties.  Both will use a stage where there is naught but a cap (or back-to-back pair) in the feedback loop.  The "speed" control will either consist of a variable series resistance going to the input of the op-amp, or a voltage-divider (like a volume pot configuration).  You want the first one not the second.  The speed of the LFO is partially set by how long it takes to charge up the cap/s in the feedback loop of that op-amp.  As the input resistance of that stage gets smaller, the cap/s charge up faster and another triangle peak is produced.  Usually, there is a fixed resistor in series with the variable one to set the minimum chargeup time (i.e., fastest speed).

Why am I telling you this?  Because going from slower to faster speed is merely a matter of tacking a second variable resistance in parallel with the first.  So, if I had a 500k "speed" pot set to, say, 387k (a slower speed within the range of that circuit), slapping a second variable resistance set to, say 243k, would net me a parallel resistance of 149k, for a noticeably faster (but not fastest) speed.

The nice part of this is that nothing is disconnected or reconnected in such a manner to produce a pop.  It doesn't require a whole lot of parts, scores you a preset second speed, and only really takes up panel space (not board space).  The down side (you don't get something for nothing!) is that the two speeds share a common depth setting, and the two pots will interact such that where you set the one will depend on where you set the other. 

Note that value of the "add-on" pot used for the second speed will depend on how substantial a contrast you want between speed 1 and 2.  If you really and truly wanted one for slow and one for much faster speeds, then a second pot the same value as the first is probably fine.  If you wanted to be able to swap between two slower speeds, then the added pot should probably be double the value of the first so as to produce smaller changes in combined parallel resistance when added in.

[Pushtone]

I just build a dual chorus pedal or to be more accurate "a single chorus with dual controls"
I got the idea from a comment Mark Hammer made about how one could insert
a second LFO (with a second set of controls attached) and switch between LFOs.
Here is link to that build report with links back to Marks original comment.
http://www.diystompboxes.com/smfforum/index.php?topic=52149.0

It works great, as long as you don't mind having a second LFO board, or a larger main board.
Or you could design a dual LFO with a quad opamp to keep the redundant parts down.
I haven't looked at other schems, but this approach could be done with the EATremolo.

Since this great idea cam from Mark, and he has provided another solution above, it might be hard to decide on an approach.


There is also the Dragonfly speed mod in his gallery called "mod zone" .
A simple footswitch to add a resistor in series with the "speed" pot.
I did this simple mod on my EATremolo and it works OK in a limited way.

Surely the simplest but most expensive and time consuming way would be to just put two circuits in one box and be done with it.



Something I observed after the dual chorus build was that I alway position the
first set of controls the same each time I use the pedal.
The second set of controls gets fiddled with a lot, but not the first.

If I were to build a pedal now with dual controls I think I would make one set of pots internal, on trimmers.
Sort of like a "preset" sound or "auto mode". It could, however, be changed by opening up the enclosure.

If there were a lot of pots I would make some trimmers and other pots fixed resistors to produce an "preset" sound I liked.
Step on a footswitch and you would go to "manual mode" with full controls. This would allow you to keep the same size enclosure as
a pedal with one set of controls.

I also spent a short time looking for dual concentric (SPELLING??) pots but could not find any like B*SS uses.
Concentric pots would be a cool way to do it too.

Good luck

[$uperpuma]

check out the 4ms tremulus panneur (dual panneur) it may do some of what you are looking to do... www.commonsound.org

[Barcode80]

if you are interested, mouser sells that concentric pot i think

[Paul Perry (Frostwave)]

On the question of 'dual' trems, has anyone made one with two separate LFOs that go to a blend conrol, so you can have one or the other  or any blend between (eg a slow swell with a little fast trem action superimposed).

[oldschoolanalog]

If you can get your hands on Boscorellis' "Stompbox Cookbook"; he has the exact circuit in there that you're looking for. He describes the sound as "dueling tremolos".

[$uperpuma]

getting our hands on that book has become QUITE the joint mission.... we would LOVE to but it seems unobtainable under $200, if at all

[Dragonfly]

Hey guys i was thinking of making a tremolo pedal and going for the approach of most boutique builders and making a tremolo pedal with two separate speed and depthj settings, so you have a on/off switch and a one/two speedoutput, is this as simple as just making two tremolos in one box and just have the second switch change between each of the pedals?

i built a modified EA trem that had dual rates and dual depths...its easy to rig up a footswitch for swapping rates and depths...

http://aronnelson.com/gallery/The-Mod-Zone-%21/DUAL_VOLUME

or also...

http://aronnelson.com/gallery/The-Mod-Zone-%21/EA_TREM_DUAL_RATE_MOD?full=1

you can use either of the above drawings, and if done as footswitches, gives you TONS of options...

hi speed /hi depth
hi speed/ low depth
low speed / hi septh
low speed / low depth

or anywhere in between...

AC

[petemoore]

On the question of 'dual' trems, has anyone made one with two separate LFOs that go to a blend conrol, so you can have one or the other  or any blend between (eg a slow swell with a little fast trem action superimposed).
  Interesting approach^, one I've been sort of interested in, over my head though as to how to impliment.
  Another one I think is interesting is to put an LFO 'on' the LFO, controlling the speed of the sweep...ramping from fast to slow tremolo automatically..might not be the simplest solution, but replacing the 'Tremolo Speed' pot with LDR's/LED controlled, LED's driven by LFO.
  Of course I'd want even more controls...width between fastest and slowest 'secondary LFO/speed sweeper'...stuff like that...and no ticks...and would rather dream about it than prototype it....something that can sound more like an engine 'RPM revving" , less like a motor spinning @ 'x' RPM.
 

[yobleduwop]

Could i use the same theory as the switch between the speed pot on the ea trem to switch the speed fine and smoothness stage on the tremulus lune
Thanks Joel

[Processaurus]

On the question of 'dual' trems, has anyone made one with two separate LFOs that go to a blend conrol, so you can have one or the other  or any blend between (eg a slow swell with a little fast trem action superimposed).

Yessir  I sold that one but I have its twin in pieces in a box somewhere, you see I managed to put nearly every single transistor in backwards...  )Though I think if I did it now I would use your idea from a while ago of using a dual gang linear pot to alternately control the depth on each LFO (when one is up the other is down) instead of the opamp audio panning circuit I used to mix them together.  I liked the opamp buffering the mix because it could drive an LED with the composite waveform.

Using that pedal occasionally in a live setting though, makes me wish there was a second footswitch to short out the pan control to one side, for options like the original poster wanted.  That knob ended up getting fiddled with quite a bit.  Might actually be cool in a rocker pedal or something...

This is way more complicated than what yobleduwop originally was asking for, of course.   

[Mark Hammer]

Strategies for using two modulation sources:

1) Two modulation sources are used in either/or manner as modulation "presets".  They can be of the same modulation type or different.  E.g. LFO1 is triangle, LFO2 is some other waveform.  LFO or random voltage source.

2) Two modulation sources are used for "blending" rather than either/or, via a mix control.  Obtaining only source 1 or source 2 is still possible, but intermediate mixes are too.  This can produce anything from very periodic to reasonably aperiodic modulation.

3) One modulation source is used to control a second modulation source.  So, for example, LFO1 is a generally slow sinusoidal source that gradually alters the average speed of LFO2.  Since the "final" modulation source remains periodic, this arrangement never gets quite completely aperiodic, however it acquires a little more variety than a single LFO, and lends itself to interesting rhythmic uses since one can essentially predict when the changes to LFO2 will happen.

This is a very simple listing that doesn't even factor in use of multiple random sources, filtering of random source, envelope followers as modulation sources used to control a 2nd LFO or blend with it, and a whole host of other things.  We didn't even say much about waveform control, and said diddley squat about multiple modulation sources controlling separate parameters (e.g., one controlling amplitude and another controlling a lowpass filter).  We also said nothing about "morphing", foot-pedal blending, or ramp-up/ramp-down options.

I mention all of this stuff because whenever one decides that multiple modulation or selection between types/rates/forms of modulation is desirable, you need to ask yourself what it is that you want and need the created options to do for you.  For many, a simple speed1/speed2 choice is all that is needed.  For others, more exotic options are desirable for what they permit in terms of creative rhythmic effects, or creative atmosphere effects.  For yet others, the simple desire is to get rid of predictability, and that in turn could be an expression of a desire for surprises, or a desire to have the modulation be so aperiodic that it becomes part of the background "texture" rather than something that demands listener attention because of its obvious cyclical nature.

Bottom line: think about what you want before you commit to a circuit.

[oldschoolanalog]

getting our hands on that book has become QUITE the joint mission.... we would LOVE to but it seems unobtainable under $200, if at all

OK, heres what I'll do for y'all. I dont have a scanner, but if someone wants to post this Boscorelli trem, I can snail mail a copy. You MUST PROMISE to post these docs (3 pages) somewhere readily accessable. First person interested will get them. I am not sending out more than one copy. PM me if interested. Sorry, but thats the best I can do, hope it can be of some help...

[oldschoolanalog]

This just in. Go to moosapotamus and check out the issue of Stompboxology on trems. Tremolo-Matic #11. REALLY worth a look.

[loylo]

The tremulus lune project at commonsound already offers two solution to have a dual tremolo: add another board that acts as if there were two tremulus in series, or add another small board with a second lfo that modulates the main lfo. Check out, you don't have to reinvent everything.

I plan to mod my tremulus in order to have a dual-tremolo, but I don't know which solution I have to choose.
I'd like to have interesting rhythmic figures such as (II.II.II.II.I.I.II.II.II.II.I.I.) repeated like that:
http://perso.orange.fr/lmeiff/bi-tremolo.mp3
I presume that this result could be easily achieve with numeric technologies.
With two tremulus lune in series, the tremolo rate would have to be set very precisely and I think the specific rhythmic figure I've described couldn't be obtained.

From Mark Hammer comment, I wonder if I have to try solution 3:

3) One modulation source is used to control a second modulation source.  So, for example, LFO1 is a generally slow sinusoidal source that gradually alters the average speed of LFO2.  Since the "final" modulation source remains periodic, this arrangement never gets quite completely aperiodic, however it acquires a little more variety than a single LFO, and lends itself to interesting rhythmic uses since one can essentially predict when the changes to LFO2 will happen.