Boss Dimension C chorus

[SeanCostello]

Whilst I can't argue with anything you've said there, none of it will help me to achieve a stereo output! In practical terms it's not really a big issue, but I want my pads to be lush and mellow

Yeah, the Dimension-D would help make a mono signal stereo. You might also want to look into a Boss SE-50, since they have a Dimension-style chorus in there (although it might be 3-phase instead of the antiphase Dimension chorus). The batteries on the SE-50 go after awhile, but you only lose the user programs, while the factory patches stay. The price can be pretty reasonable, around $100 or so.

For super nice pads, run the DX-27 through a Moog filter clone, THEN through your stereo chorus. The DX-27 can be set up to be stridently bright, and the Moog filter will give you all the mellow you need.

Sean Costello

[Jaicen_solo]

Haha, you guys think i'm made of money?!
The fact that I'm buying a DX27, not a DX7 should have given the game away

[Dave_B]

They are pretty reasonable, for the simple reason that after a few years, the internal battery fails. This results in a complete loss of all the internal programs, both factory and user presets. Effectively rendering them useless.

  I'm not sure about that.  I've always understood that you just need to replace the battery and restore your custom presets. 

[DiyFreaque]

Square   I don't think so. Have to check again.

Actually the LFO is trianglish, but the response of the clock circuit to the LFO creates a response that makes it seem like softly slewed square wave modulation rather than triangle wave modulation. 

In my rack-mount Dim C knockoff, I created a stereo input using the spare ME570 section as a compressor, and running the 'right' path individually.  I normalled the right input so that the Left/Mono input would send the mono signal down that path when a plug was not inserted into the right stereo input.

This left the opportunity to make the Dim C sound absolutely horrible if one did not observe the proper input connection - IE, if a signal is inserted only into the right input, and the left/mono output is used for the output, then only the 'right' delay line makes it to the output - no crossmixing, nothing.  This provides an opportunity to listen to what a single delay line in the Dim C actually does.

So, tonight I made a quick recording of the effect (it can be accessed at the following link - 867 KB):

http://mypeoplepc.com/members/scottnoanh/sitebuildercontent/sitebuilderfiles/dimc_delay_compare.mp3

I patched my Korg DW6000 through the Dim C into my Sidekick amp.  From the amp, I patched line out straight to the recorder.

00:00 - 00:17  Just the synth - the Dim C is bypassed.  Mono.
00:18 - 00:35  The Dim C is unbypassed and is in mode 4, with both delay lines (normal use).  Mono
00:36 - 00:55  The DW6000 is plugged into the right input, using mono out, so that only the 'right' delay line can be heard.  Nasty*. Mono nasty.

BTW, I can modulate the Dim C with external CV's.  With an external triangle LFO used as the CV, the effect is exactly the same.

If the sample can't be accessed from the above link, it's clear at the bottom of this page under the link "Dim C One Hand Clapping":

http://mypeoplepc.com/members/scottnoanh/birthofasynth/id9.html

Cheers,
Scott

*Not a good nasty, either.

[bwanasonic]

Scott-

I like the clips. Nice *Eno-esque* stuff.

Kerry M

[DiyFreaque]

Thanks, Kerry.  The Dim C certainly goes a long way to making someone sound better than they really are.  I recall when I first showed my brother the Dim C and what it did, he pretty much indicated that it was like 'cheating'

Take care,
Scott

[Jaicen_solo]

That LFO does indeed sound nasty on it's own! Definitely a hint of squareness about it. Sounds lovely and lush with both lines though!!
I can't tell you how much I want one of these now! I'm going to look at the layouts of FP's CE-2 tomorrow and see if I can cobble together something similar using an inverted LFO from just one board to drive the second.

[DiyFreaque]

Sounds like a pretty good idea to me. I figure with hetereodyning cut out, it will sound pretty nice and ought to bring you that stereo chorusing you're after.   I'd sure be interested in hearing how it comes out! 

My DW6000 has 'stereo' chorus built into it.  It's a single delay chorus (MN3009 based), and actually, in stereo, one side is chorused and the other is not.  As simple as that is, it's actually quite effective.  I prefer that method of deriving stereo from an essentially mono effect over inverting the wet signal in the opposite channel, which kills the effect if a stereo recording is played in mono.  Having few modulation options and simple wavetable DCO's, the DW6000  desperately need chorusing.  With the Dim C around, though, I rarely use the on-board chorus. 

Take care,
Scott

[Jaicen_solo]

Actually the LFO is trianglish

DIYFREAQUE, Is that a bit like spanglish??

edit: Ooops, forgot the reason for this post!
Ok, I just looked at the schematic of the CE-2. and it seems to me that it would be a relatively easy job to take a feed from the collector of Q4, and use that as an inverted clock signal to drive a second LFO.
It might require a small amount of buffering but it seems fairly easy to do. On the second chorus side, the clock IC and associated parts can then be ommitted.   

[Steben]

That LFO does indeed sound nasty on it's own! Definitely a hint of squareness about it. Sounds lovely and lush with both lines though!!
I can't tell you how much I want one of these now! I'm going to look at the layouts of FP's CE-2 tomorrow and see if I can cobble together something similar using an inverted LFO from just one board to drive the second.

Aha! I was thinking of the Small Clone. Of course the CE-2 has 3207 and 3102 as the Dim C does...
I was thinking of adding a 3rd ""mixing" board with PCB-mounted Jacks and in/out companders.

[A.S.P.]

Actually the LFO is trianglish

DIYFREAQUE, Is that a bit like spanglish??

perhaps trapezoid ?

like in fig.3, here: http://www.pat2pdf.org/patents/pat3489843.pdf

[stm]

perhaps trapezoid ?
like in fig.3, here: http://www.pat2pdf.org/patents/pat3489843.pdf

Holy Mackerel! an elecro-mechanical implementation of the DC-2   

Has puretube seen this

[Steben]

Isn't it a leslie-box without speaker?
Looks like Hammer's idea of inverted phasing.

[A.S.P.]

Holy Mackerel! an elecro-mechanical implementation of the DC-2  :icon_exclaim: 

Has puretube seen this

has Sebastian missed this:
http://www.diystompboxes.com/smfforum/index.php?topic=30258.20 ?

[Steben]

Actually the LFO is trianglish, but the response of the clock circuit to the LFO creates a response that makes it seem like softly slewed square wave modulation rather than triangle wave modulation. 

Hey I looked closer to the original schem. Just after the LFO the signal goes to an inverting amp with gain of 47/33 ~= 1,5. This means a fourth of the triangle gets clipped, resulting in a subtle trapezoid.

[stm]

Hey I looked closer to the original schem. Just after the LFO the signal goes to an inverting amp with gain of 47/33 ~= 1,5. This means a fourth of the triangle gets clipped, resulting in a subtle trapezoid.

That's not correct:

The LFO opamps are fed with 7V according to the schematic. The output of these opamps can swing typically within 1.5V from the supplies, so output can actually range from 1.5V up to 5.5V.  Now if you take into account the clipping voltages and the 100k and 33k resistors that define the triangle voltage sweep range, you obtain a triangle waveform that swings between 2.8 and 4.2 V (centered around 3.5V). Now let's apply the gain of 1.42 (47/33) around the 3.5 reference voltage, and we get a sweep between 2.5 and 4.5 V, which is still within the linear range of the opamps.

Mhhh, one would say I didn't really did the 1.4 amplification properly. Let's do a check: (4.5 - 2.5) / (4.2 - 2.8 ) = 2.0 / 1.4 = 1.42

[Steben]

mmm, didn't know enough about triangle LFO's. I guessed they went to max (1.5 to 5.5).
Do you mean changing the supply voltage or swapping with a rail-to-rail doesn't change the triangle?

[stm]

mmm, didn't know enough about triangle LFO's. I guessed they went to max (1.5 to 5.5).
Do you mean changing the supply voltage or swapping with a rail-to-rail doesn't change the triangle?

Au contraire mon ami, supply changes and rail-to-rail v/s non r2r op-amps DO affect frequency and amplitude in that kind of LFO.
This design is sensistive to almost everything! But it works in practice because deviations are small enough to be tolerated or unnoticed.

[puretube]

X-mas riddle:

which commercial product is being described here ?

(btw: fig. 2(2), 2(3), 2(4) and 2(5) show the painful endeavour (sic!) how to overcome transitional problems in time-domain circuits,
similar to the problem in the latest looper thread ).

[SeanCostello]

X-mas riddle:
which commercial product is being described here ?

Wow, was this actually used in a product from Roland in the 1970's? It basically sounds like using a dual pitch shifter, where one voice is slightly shifted up, and the other voice is shifted down. Each voice is an overlap/add pitch shifter. I wouldn't be surprised if Eventide and other high-end audio companies use similar algorithms for their "Detune" presets today.

EDIT: OK, I was wrong about Eventide using this: http://www.pat2pdf.org/patents/pat4369336.pdf is an Eventide patent that illustrates a digital technique very similar to the Roland Dimension D algorithm. The patent details a very specific digital implementation, but the underlying concept is the same.

OK, if I have to field a guess, it would be the Roland RS-505 Paraphonic. I have never heard one of these, but the ensemble used four BBD chips, which fits in with the patent.

Sean Costello