Dimension C Build Report

[DiyFreaque]

Construction hasn't actually started yet - I'm still ironing out some details, but I thought I'd start this thread and update it as things progress.

Weekend before last, I went over to Jeff Pontius' house, did the usual drooling over his Wall'O'Synth, and demonstrated the Dim C breadboard.  Prophet 5 through the Dim C is really, really nice, BTW.

We're each going to build a rack mount unit - Jeff's designed a really nice front panel for it using Schaeffer's Front Panel Designer, and we're going to have the front panels made by Schaeffer.  They'll be blue and have the logo "Dim C / TZF".  Normally, I like to credit the main source of the design, but we were hesitant to put 'Boss' on the front panel.  I have no plans to market anything I build, but I do plan to feature this on my website, and didn't really know if Boss would appreciate their corporate name on something that was not built by them, should they chance across and see it.

The controls and features we decided on are as follows:

Signal input attenuator control (dual ganged for stereo input)

Three mode switches.  These will be two position toggle switches.  Note that mode 1 will be active when all toggle switches are off.

Mode select switch and frequency and depth controls.  The mode select switch will select between the frequency and depth being set by the original Dim C mode switch operation or the frequency and depth controls (pots).

Internal LFO range switch - this will be a three position switch that will select between the normal LFO range of the original Dim C, a low range, and a very low range.  This for the benefit of both the TZF output and the Dim C (I find the Dim C to have a pleasing, though very different character at slower LFO frequencies).

A three position Internal/CV/Manual toggle switch, Manual/CV attenuator control, and CV input jack.  Position one will allow control of the Dim C by the internal LFO.  Position 2 will allow manual/external control of one of the delay lines, and position 3 will allow manual/external control of both of the delay lines.

The manual/CV attenuator control will be dual purpose and works in conjunction with the CV input jack.  If no plug is inserted into the CV jack, then this control will allow manual control of either one or both of the delay lines (inversely when both delay lines are selected).  In other words, it will set the delay lines for a static delay time.  Setting only one of the delay lines static is handy for nice TZF effects.  Setting both allows the Dim C to act as a sort of comb filter tone control.

If a plug is inserted into the CV input jack, then either one or both delay lines can be controlled by an external bipolar CV input (again, inversely when both delay lines are selected).  The jack used will be a stereo jack with a NC signal switch for passing the internal DC manual control bias when no plug is inserted.  Inserting a plug will open the NC switch and pass the external CV through, and also ground the base of an internal transistor allowing a bias to be inserted for bipolar operation.  Interestingly, even uni-polar signals (such as an EG) have a very cool effect on the Dim C in this mode, and for good reason if you think about it.  In this mode, the manual/CV attenuator control acts as an attenuator for the external CV input.

Momementary Bypass switch and external active bypass jack.  The active bypass jack will toggle bypass with a 5V positive pulse.

Power switch (toggle or pushbutton, haven't decided yet)

TZF output (a cool idea from Mike Irwin).

Left/Mono input
Right stereo input

Left/Mono output
Right stereo output

We're hoping to put the PCB into a rack enclosure, and mount a power input jack on the enclosure and powering the thing from a +12VDC wall wart, with internal regulation.

That's it! (for now).

Cheers,
Scott

[Mark Hammer]

That's, uh, quite the far cry from 4 push buttons, isn't it?  There are some of us for whom things like this unit beg for so many bells and whistles and optins, that equipping it with 4 buttons, as Boss did, is tantamount to getting a guitar with one string and 3 frets.  Sure, they might sound dependably great, but there is so much more that can be achieved.

I really wish that companies like E-H and MXR had opted for a parallel "adventurer" series of pedals that shadowed their main line.  In some respects, they did do this with a few things, like the Little Big Muff compared to BMP, or the MXR Micro flanger and Micro chorus.  But wouldn't it have been swell to be able to plunk down an extra $20 for the "deluxe" version of the pedal, where more controls were installed rather than presets, and board-mounted trimpots were brought to the surface?  Obviously it would have been a true headache for the companies involved, but it would have been wonderful for the consumers.

[DiyFreaque]

I agree.  

Still Boss did an admirable job of making something totally usuable with a minimum of fuss, which is a nice feature in itself of the original Dim C (and Dim D, too).   The nature of these effects are less of an in your face type of effect than other effects, so using them becomes almost a subliminal experience - until you hit the bypass, anyway.  One reviewer of the Dim C said it was more of an effect when it was turned off, since he used it all the time.  So, I think it was easier for Roland/Boss to get away with four modes of an effect that provides less coloration than, say, a Mutron Phaser or an A/DA flanger.  Four modes on something more intense like that would quickly become more obvious and tiring during use, I think.

My main use for it is with a synthesizer, but its very nature seemed to cry for post-processing application rather than as a building block in sound generation, which meant (to Jeff and me) that a rack mount format would serve the purpose better than as a synth module.

Putting it in rack mount left us with a lot of unused real estate, which inflamed my feature creep tendencies, and this final configuration is actually a trimmed feature set from my more extravagent notions.  Our main goal was to preserve the original no-fuss functionality and tone of the Dim C, yet add some more functionality/tonality to it at the same time.  The front panel is rigged so that if all of the 'extra' switches (not the mode switches themselves) are in the up position, you are in original Dim C country, so you can get there in a hurry.  That's the main purpose of even having a selector between mode switch operation and use of freq and depth pots.  That, and mode 1 would always be a bit out of reach (technically) because the pots would never be open like the original mode 1 switch, which was just a vestige of the original four switches (whether on or off, the mode 1 switches were always open).

BTW, one really cool thing for a Dim C would be an envelope follower setting.  I found that manually sweeping the delay lines, or using an EG just gave it such a nice character - individual notes or chords just 'ring' in such a different manner, if you know what I mean.

Take care,
Scott

[puretube]

information lost...

[Mark Hammer]

Ton,

I am indeed heartened by that.  At the same time, I understand the difference between what guys like you and I think, and what the accountants say makes business sense.  I also understand the aversion that the tech support crew have towards giving some users enough rope to hang themselves.

Still, stuff like the release of the E-H Bi-Filter bodes very well for folks who want to have the controls to achieve something a little different.  I would also expect that the booming aftermarket industry (the Keeleys of the world) presents itself as an untapped niche.

[DiyFreaque]

Hi gang,

Here's an update of the Dimension C build (dubbed Dim C/TZF).

To begin with, I've been having problems with my ISP/Web site - I for some reason or other, cannot access my original Synth DIY site to edit it, and after a week, it still remains that way.  

I can however, create a new web site, so I've done that in the interim.  I have a page up with details of the Dim C/TZF, including schematics of the awful things I'm doing to the original Dimension C .

You can find the page at this URL:

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

Cheers,
Scott

[StephenGiles]

This is fascinating, look forward to seeing the finished product.
Stephen

[DiyFreaque]

Thanks, Stephen, I can't wait til it's finished also.  Right now we're still trying to figure out a rack enclosure that can be used with a Schaeffer panel.

I added a sample of the Dim C/TZF (on breadboard) processing my modular synth, with the Dim C being modulated with an external triangle wave LFO.  It's clear at the bottom of the page, or this link can be used to access it as well.  It's 1.44 MB.

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

Cheers,
Scott

[puretube]

WOW!


information lost...

[DiyFreaque]

Well, Jeff and I have finalized our selection of hardware - we're going to be using aluminium Bud rack enclosures - we'll have to use the faceplates for something else, as the faceplates will be made by Front Panel Express.

I started work on the boards last weekend.  The Dim C/TZF is going to consist of four separate boards - a large 'Main' board that will handle most of the audio functions, two smaller delay boards which will each house a BBD/Clock and LPF filters, and a small 'control' board, which will house the LFO, bypass logic/debouncing, and CV processing.

I've added a page with lurid photos covering the board construction phase here:

http://mypeoplepc.com/members/scottnoanh/birthofasynth/id11.html

Cheerio,
Scott

[puretube]

cheerio, and good luck!  

[DiyFreaque]

Thanks, I'll need it  

Forgot to mention, I'm powering the thing from a 12V wall wart.  I ordered two different one's to try out, one from Mouser and one from Electronic Goldmine.  I must say, I rather prefer the one from EG over the one from Mouser.  The Electronic Goldmine wart actually has a two prong cord that plugs into the outlet coming from one end of it while the other end is the 1/8" jack I chose to use for power input (which will be located on the back of the enclosure).  A wart like this is a bit handier, as it doesn't 'crowd out' a power strip.  Course, I don't know how noisy the thng is (I'm regulating it down to 9V on board) - prolly as crappy as any other cheap WW one would find.

Cheers,
Scott

[DiyFreaque]

Slowly but surely.....

All the boards have been soldered up, they can be seen here:

http://mypeoplepc.com/members/scottnoanh/birthofasynth/id11.html

I'm working on block diagrams of each board, and I'm debating with myself whether to post schematics of the entire project - I don't mind sharing anything one bit, but I fear the monolith that is Roland/Boss.

The Schaeffer panel's are being ordered this week.  As I understand it, those things have about a 2.5 week turn around.  That'll give me some time to test the boards out, which ought to be quite a chore, actually, considering the interconnections.  I can't finalize the interconnection wiring until the drilling/assembly party, because I haven't decided on the best board arrangement within the rack chassis - I haven't seen it yet, though I do have the dimensions.

I'm eager for this project (rechristened simply "Dim C" instead of "Dim C/TZF") to come to a conclusion for two reasons: (a) I can't wait to use it and (b) it's dominating my breadboards.  I am loathe to disassemble it from the breadboards until everything is tested out on the protoboards.

I've got many a project in the pipes, including one that involves (for me) the holy grail of BBD's: MN3011


Cheerio,
Scott

[Mark Hammer]

I've got many a project in the pipes, including one that involves (for me) the holy grail of BBD's: MN3011

Me, too, but it'll have to be a secret for a while, if only because there are SOOOO many options available with that blasted chip.

Nice work, incidentally.

[DiyFreaque]

Thanks. Mark!

I've PM'ed you on another matter, but one of the apps for the MN3011 that has always fascinated me is, of course, modulating it - flanging, chorusing, same old drill  

Whilst Googling MN3011, I ran across one oblique reference to an A/DA multi-tapped chorus device that uses the MN3011, but have found nothing else about it - did such a beast exist?

Cheers,
Scott

[Mark Hammer]

Whilst Googling MN3011, I ran across one oblique reference to an A/DA multi-tapped chorus device that uses the MN3011, but have found nothing else about it - did such a beast exist?

The full schematic for the STD-1 is available in a largish zip-file at www.adadepot.com

Sadly, there are no soundclips, but the user manual makes very provocative reading.

The product name is a funny one, and certainly nothing that would fly these days given the other meaning of "STD".  I am reminded of the difficulties the Rolls-Royce company had in marketing the "Silver Mist" to German millionaires.  Other can confirm or refute, but I was led to believe it essentially translates as "garbage".

[puretube]

information lost...

[Mark Hammer]

Excellent link!  Many thanks.  Looking forward to reading how he integrates the doubler and "reverb".  I assume there is something to learn here about the infamous heterodyning problem of multiple differentially-clocked BBDs.

[DiyFreaque]

You two have made my day!

Thanks Mucho,
Scott

[DiyFreaque]

Here's another, just dealing with the doubler/reverb:

US Patent 4489439

Cheers,
Scott