Dim C

[Uncle Krunkus]

After Christmas I'm going to build a clone of the Dim C, and thought some others here might want to follow along, and hopefully, contribute. I'll be doing a stripboard layout, thinking about different options, and acquiring parts etc. I've already had a bit of a chat to Scott about it, (no doubt he'll chime in soon) as he's already done one, and has a number of option ideas.
The first question (which is primarily directed at Mr Stites) is, should I keep all the original switching JFETS for the bypass, or should I replace them with a more mechanical solution? and, of course, why?

[Scott Stites]

Hey Uncle K,

Nice choice of projects! I truly love my Dim C.

I used the FET switching. Some people do have a bit of heartburn with using FET switching on anything because of 'Tone Sucking' - IE, even bypassed, running through the device will color the tone a bit. For me, it just hasn't been an issue - perhaps it's more of an issue with guitar than synth?

The advantage for me is that one can remotely switch the Dim C in and out with an electrical pulse rather than with a switch. My Dim C is configured to switch on a 0 to +V trigger pulse. I suppose if one used relays, it could be done with mechanical switching, but.....nah.

Cheerio,
Scott

[Pehr]

What is a "Dim C"?

[seraph]

[The Alison Project]

I will be one of the followers.

[fonik]

[Uncle Krunkus]

That's the one.
I was going to ask Scott all about his incarnation, then I realised he's already documented the whole thing very well on his site.
So the first thing I'll be doing is deciding on a front panel design for mine. That will dictate what I need to layout on stripboard.
Hey Scott!
If there were one thing on yours that you think you could do without, what would it be? and why?

[Scott Stites]

[mikeb]

I just wanted to say that the enclosure on:

http://mypeoplepc.com/members/scottnoanh/birthofasynth/id12.html

is very very slick. Very professional job... Some of the work people do will never cease to amaze me.

[Uncle Krunkus]

Yeah, I'll second that.
That's the shot which inspired me to do one.
And that's the quality I'm aspiring to.
Part of the reason I thought I'd start this thread is so others can see how you go about doing something like that. I mean, Scott's site shows how it's done, but everyone can check in on mine as it's happening.

[Gregg Hermetech]

i want one but am unable to use a soldering iron

anyone want to build me one?

[frijitz]

[Uncle Krunkus]

From what I've heard, it's the best sounding BBD chorus you can get.

[mono-poly]

A pcb run would be cool!

[Peake]

The Dimension C was a stompbox, yes? Wasn't the Dimension D the "best" BBD chorus one could get, in regard to subtle and non-cyclic sounding stereo FX (in comparison to the deep, swirly, ensemble effect of the Solina)?

I've never played with one. Are there any soundbites to bring me over to the dark side?

And that is an excellent case/setup!

[Scott Stites]

Ian,

The Dim C is an adaptation of the Boss DC-2 Chorus, which was the "little brother" to the original Dimension D. Both of the "Dimensions" were dual delay line chorus devices - the main "trick" was the that delay lines were modulated antiphase, which resulted in cancellation of the feeling of lopsided motion one gets with a one-delay-line chorus, and yet differs from the "motionless" chorus of the triple delay line "Solina" type choruses, which generally, but not always, are operated from a couple of triphase LFOs.

The dual delay line was the main modus operandi, but wasn't the only trick up the dimension's collective sleeve. After the delay lines, there is a fair amount of interesting signal equalization, inversion and crossmixing, without which the effect just isn't the same. Above all, they are a triumph of noise reduction. The use both pre/de-emphasis and companding to eliminate the hetereodyning one would expect from two BBD clocks cyclically "crossing paths". A friend of mine, who has an original DC-2, says that things almost seem quieter when he unbypasses it .

Each of the Dimension products operate in four modes - in other words, originally there were no adjustment pots - just four switches that select modes 1 through 4, and on the DC-2, they range from nearly subliminal to more noticeable. As I understand it, the DC-2 is much more "noticeable" in mode 4 (and I think I know why). It's the kind of effect that you can forget you are using until you unbypass it - then you realize it's been doing its thing and you immediately want to re-engage it, in most cases.

Four modes may sound limiting - I thought that and put on manual freq and depth controls. I wouldn't do that again if I were building it today - I don't know how they did (probably a lot of debate and work) both those Roland/Boss engineers found the exact sweet spots for the modes. I've never made it sound better than the preset modes (which I also included on the Dim C). I did put in an external CV control, which is great for making it do things it wasn't designed to do, and I would keep if I were building it again. The TZF output was an opportunistic through zero tap I put on it. I never use it. I wouldn't do that again, either. I put on switches to slow the internal LFO down - that does sound nice, and I would do that again as well.

You may have heard a Dimension D - JH built a clone of it, and, IIRC, didn't you pay him a visit a few years back? If I were he, I would have had it front and center when I was shoing off my synths. Of course, JH has so much cool stuff, it probably has a lot of competition.

Mike:

Not having heard one, I would still say the Dimension D was probably the superior model between the two. It had balanced inputs, and more headroom. It used the MN3007/MN3101 chipset, whereas the Dimension C uses the MN3207/MN3102 chipset. I've always intended to build a Dimension D, but the real unobtainium in the thing are the RIAA amps they used in it - if you can find them, they're hideously expensive. I'd have to find a suitable substitute. A few of the transistors used are very hard to find on this side of the pond as well.

As I mentioned before, I believe Mode 4 is implemented differently between the two devices. The Modes basically set both frequency and depth of modulation of the delay lines. In the Dim C, Mode 4 is an additional set of frequency/depth of modulation settings. IIRC, the Dim D's mode four differs from Mode 3 only in that it allows more of the wet signal through, unless I don't IIRC

Also, IIRC, the Dimension D was strictly stereo out, and also accepted mono or stereo inputs. The original Dimenstion C takes a plain mono signal and renders it in mind bending, spacy stereo as well. It, however, can render a very beautiful mono signal (that path is absent in the Dimension D). My Dim C has been modified to accept and process stereo signals, yet retains the original mono input/outpu functionality as well. If you look at the schematic, you'll see that's quite easy to do. One section of the compressors is unused and waiting for that path.

In any event, don't let the "Stompbox" status of the Dim C fool you. The effect is nothing short of miraculous, IMO. It has grown to be one of the most sought-after stompboxes in the world. When I racked it, I buffered the input, put in a variable attenuator and converted the input impedance to 100K. This makes it quite usable with keyboards, though a lot of people use it with boards in its native form.

I've got some samples here:

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

To me, the most amazing sample is of how the delay lines actually are modulated. You'd think it would be a smooth triangle/sine motion up and down, right? It's not! The modulation is more trapezoidal. If you listen to just one delay line "wet" the thing sounds sick - and not the good "sick" the whippersnappers use today as a term, but bad sick. If you kick in the second delay line, the transformation is utterly amazing. I've got a sample that demonstrates that here (it's the "One hand clapping" sample on the page linked above).

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

It starts out with my DW6000 through the Dim C with effect off. The middle part is Mode 4. The last part is with only one of the delay lines operating. You can hear the wobbly motion of the delay line in that section.

Oh, yes, the Dim C is the purtiest thing I got. The late, great Jeff Pontius designed the panel in FPD. We teamed up on it - I did the electronics, and Jeff did the enclosure and final mounting of the parts. His Dim C is identical to mine.

Cheers,
Scott

[Peake]

Thank you for all of the information!

I love Mode Zero as well. The very first Dim C example sold me immediately:

http://www.modezero.com/sounds0000/dx7bells-dimensionc-1.mp3

And yours are very nice as well, and very, very thorough. Much appreciated!

It seems that the C is less subtle than the D. I once had a D and the first setting was very mild, and IIRC, the fourth not as thick as your last setting example (DW synth). This is both good and bad...but for those who want a C, it's great!

I'd certainly want to build one, for what it is (but would still want another D to use alongside it). The D was wonderful for entire mixes, where you can't be too thick.

And I'd never noticed an RIAA setup in the D schematics (never really looked that hard either). It brings up something that's been knocking around in my head for a while, to use its pre-emp and post decode curve as a set-and-forget enhancer. Looks like Roland figured that out years ago! (I recently put a vinyl record against its CD version, and the vinyl kicked its ass all over town and then underground. Then again. The bass, especially the midbass and "chesty" area, were soooo much better on the record, and the CD just sat there, and was uncompelling, to say the least. I know that people use different EQ and mastering for each format, but come on... I hope that this is not universal, but if it is, there is a solution).

And this is why I have those MN3007s... They were for the D, just in case.

Thanks for bringing this project, and for your excellent site and copious notes. If I made a C, I'd want to add the Korg "crossover" effect of having a highpass on the input to the delay, for a choice of having the bass swim or not. Try that out; it's really nice to have the upper freqs shimmer but the bass not moving along with it, as an option.

[Scott Stites]

Hey Mike,

[Scott Stites]

BTW, did you get a load of that DC-2 PCB on Modezero? That layout engineer must have thought the marketing guys were nuts. "You want me to fit what into a stompbox?"

[Uncle Krunkus]

Hey Scott,
just letting you know that (especially since I recieved your parcel) the Dim C is still firmly in my sights for my upcoming "effects" stage. Once I get the Klee singing along with the ASM-2, I'll be looking at doing at least two stereo BBD devices. (one will be "like" a Dim C, the other will be "like" two cross regenerated phase flipping D-2s) Due to copyright concerns though, I'm looking at going back to my beloved stripboard and doing one offs.

[Peake]

All this, -and- I'm a hypocrite... I sent the spring reverb guy to Google, and I didn't do the same thing for myself when confronted with "Dimension C".

Give me room to grow, I'm working on it.

And Scott, I agree, the C appears to be something to make individual instruments glisten. (The D is great on guitar, BTW.) I noted, as you've evidently done, that the C has "it", the euphoria we're all after, when something is just right and it's obvious.

This is the sort of thing I go on and on about. Be careful, you stand a chance of understanding me more fully. The Manley Variable-mu has "it", certain LA2As have "it", the Moog Modular has "it"... I just try to shout about "it" when I find it. Cousin It notwithstanding.

Now I'm torn between projects. How awful to have too many great things to choose from!

Regards.

[kokoon]

i'd be interested in following this as well!

[Scott Stites]

I'd love to hear a 'D live. I still haven't let go of the dream of building one. I bet some decent modern op amps could replace those HA's. I even found a place to get one of those switch assembly's! And, like you, I've got some MN3007s waiting in the wings.

[dave_b]

For those who don't hang out on the stompbox side of things very much, there is a verified PCB layout for the DC-2 at the Topopiccione site. It's got an s-load of jumpers, but it's something to see.

[germaniac]

After having marveled over the sound of the Stites-O-Phonic Dim C for a long while, I finally scared up the bucks for an original stompbox-version DC-2. (I can't guess why the guy sold it to me, other than he was extremely hard-up for rent that month. If I were him, I think I might have entertained the thought of sleeping on a bus bench if it meant I could keep my Dim C. )

I use the box with a 9V wall-wart, but it would be nice to have a rack version--stripboard, PCB, or whatever. No problem running line-level signals through it, though it will overdrive (albeit in a musically pleasing way) if you're not attentive to the source level. But Scott's inclusion of an input attenuator addresses this perfectly.

As for the big daddy Dim D, I haven't heard one in person either, and I lost all romantic notions of owning one when I found that the going prices in my neighborhood were in the $900 range (as of about a year ago). My Roland XP60 keyboard includes an effect called "Space D" which digitally simulates a dual antiphase chorus, but it holds none of the enchantment of the little lavender stompbox at all, nor of the Stites-O-Phonic implementation. In fact, I spent most of my time twiddling parameters in the XP60 trying to duplicate the sound of the DC-2, with rather blah results. What it needs (among other things) is four simple presets like original--good proof of what's been said about the original's sweet spots. I'd imagine the Dim D, with it's extra headroom and so forth, would just be more of a good thing (like a dash of Tapatio on your chorizo and eggs), but I can't say the Dim C is even slightly disappointing.

To reiterate what's been said around here before: even a leaf/snow-blower would sound good running through this thing. Another way I like to think of it is, it's the best effect you never knew you were hearing. Either way, once I had one, it was hard to imagine how I got along without it. IMHO, pretty much a must have for any electronic music tool box.

Regards,
Joe