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ChromaTalk Archives: January 2014

Chroma 21010172 back to live

Daniel Rickenbach [21010172] · Fri, 3 Jan 2014 03:21:00 +0100

Hi

just before end of last year, my Chroma #21010172 comes back to live. Due to the battery leakage which has destroyed a lot, it was a huge work, but I'm happy to have it now fully working. More Details and Fotos will follow

Daniel

David Hobson [21030506] · Thu, 2 Jan 2014 21:36:18 -0500

Great news Daniel, I have one that I am in the process of restoring. Glad to hear yours has come to life.

WTB: tapper and assembly

Philippe [21010227] · Fri, 3 Jan 2014 20:37:21 +0100

Hi all,

I'm looking for a tapper with assembly preferably with its 2 screws. Please contact me off list if you have one you don't need anymore.

Thanks,
Phil

David Hobson [21030506] · Fri, 3 Jan 2014 21:44:34 -0500

Hello again Phil, I happen to have a tapper assembly. You may contact me directly.

Regards

Getting a Chroma Working Again (21030767)

Chris Yakopcic [21030767] · Sat, 4 Jan 2014 14:02:23 -0500

Hi,

I have a Chroma that is not working at the moment and my suspicion (and hope) is that the main reason for my troubles is that I need to replace the power supply. I am writing this message to see if I could get a second opinion before I tried to place an order for the power supply unit replacement kit that Luca [21010226] and Sandro [21010294] are offering (assuming they are still being constructed).

Sorry if I am posting redundant information, I was unsure if I had the ability to search the backlogs of the archives without looking at each post individually. I would be happy to look at any previous posts if there are any similar descriptions of these issues.

The rest of this message provides details on the current operation of the instrument:

About 10 years ago with the help of this mailing list I was able to get this Chroma partially working. Two of the voice boards had to be removed and some keys had to be gradually unstuck. At that point I didn’t have a way to load the cassette tape, but it seemed like I could shape the sound myself and the instrument was operating correctly although it would easily go out of tune. I played around with it for a bit in this state for maybe a few months.

Occasionally I would have some trouble turning on the instrument where it wouldn’t fully power up upon switching it on, and I would just hear the low rumble of the tapper repeatedly. If I turned it off and waited a minute it might power up the next time I turned it on. Then the ability to power on decayed until I could no longer power it on successfully.

Then I got busy with school and grad school and kind of forgot about this instrument, but I wanted to get it out last week and see if I could get it working again.

Now the same kind of thing happens where I cannot power the instrument on successfully. Upon switching the instrument on, I hear a quiet rumble of the tapper and all of the lights flash between bright and dim and I see random lighting in the data readout. If I have an audio output (the xlr studio output) connected I get very harsh tones that sound kind of like data noise to me.

I’m sure it’s not great to be powering up the instrument in its current state but I figured I would try one more time to see if I could give you a few videos of what’s going on.

Here is a longer video with no audio connected that shows the lights when power is turned on. You will see me pressing keys because I forgot the PA system was off. The flashing between bright and dim on the LEDs I mentioned is faint and can’t really be seen in the video.

Here is a shorter video where you can hear what happens when the audio output is connected. I only turn it on for a second.

I have a strong background in EE and I would be happy to take any voltage measurements that you need with a decent handheld multimeter, although I don’t have access to an oscilloscope right now.

The next logical step in my mind would be to replace the power supply and see what happens, so I thought I would just check if anyone on the list also thought that was a good starting point.

Thanks for all of your help.

--Chris

John Leimseider [21030434++] · Sat, 4 Jan 2014 19:50:39 +0000

I would first replace the big filter cap and the 2 1 ohm resistors. I use 5 watt resistors there instead of the original 2 watt ones... It's also worth replacing the 2 electrolytics in the reset circuitry... That might be enough to get it going to check everything else.

Paul DeRocco [21030230] · Sat, 4 Jan 2014 18:46:12 -0800

What's happening is that the CPU is crashing, and erroneously landing on the magic 6809 op-code which puts it into test mode. In that mode, it reads every address in an infinite loop. Since the CPU runs at 2MHz, and there are 65536 addresses, it accesses each location, including the one that fires the tapper, about 30 times per second.

One thing that can cause this is if the EPROMs are fading, and one or more bits sometimes (or always) read incorrectly. The solution is to reprogram the EPROMs. (You don't need to buy new ones.) The hex files containing the code can be found on the site. This is basically free, if you've got a programmer or can borrow one.

Nicholas Vining [21030777] · Sat, 04 Jan 2014 19:01:01 -0800

On 1/4/2014 6:46 PM, Paul D. DeRocco wrote:

What's happening is that the CPU is crashing, and erroneously landing on the magic 6809 op-code which puts it into test mode. In that mode, it reads every address in an infinite loop. Since the CPU runs at 2MHz, and there are 65536 addresses, it accesses each location, including the one that fires the tapper, about 30 times per second.

A random question, because I'm a huge coding nerd: is the erroneous landing on the 6809 opcode a feature of the platform (i.e. how you're supposed to tell that your CPU crashed, as you did) or simply a random behaviour?

Nicholas Vining [21030777] · Sat, 04 Jan 2014 19:09:14 -0800

Never mind, I answered my own question:

Halt and Catch Fire (Wikipedia)

You learn something new every day!

Paul DeRocco [21030230] · Sat, 4 Jan 2014 19:12:33 -0800

From: Nicholas Vining

A random question, because I'm a huge coding nerd: is the erroneous landing on the 6809 opcode a feature of the platform (i.e. how you're supposed to tell that your CPU crashed, as you did) or simply a random behaviour?

Unavoidable behavior. In the course of development, I'd occasionally see it, so I know that sound.

Trivia: this op-code made it very difficult for microcomputer manufacturers to build a secure system based on the 6809, because any code that executed this op-code would freeze the system until a hard reset. I believe some people building OS-9 systems actually went to the trouble of putting some logic on the outside to filter out this byte during a program fetch.

Chris Yakopcic [21030767] · Sun, 5 Jan 2014 20:56:10 -0500

Thanks for all of your help and your quick responses.

I think I am going to look into the new power supply approach (instead of replacing components on the old one) because I know I am eventually going to want to upgrade it anyway.

Then I will see if I can locate an EPROM programmer and see what happens when I try reprogramming them.

I'll will keep you updated when I start to get these things together.

Thanks again,

--Chris

Ratata on the Chroma

Jesper Ödemark [21010135] · Sat, 04 Jan 2014 20:50:56 +0100

Hi List!

This might be too obscure for most of you, but interesting for the discography and the fact that the Chroma is still with the same musician. It's a swedish documentary on the band Ratata (Hi Johan, are you on the list?).

Musik special - Ratata genom åttiotalet | SVT Play

Ratata was much part of the swedish 80's. The documentary is in swedish but around 34 minutes Johan talks about the album "Paradis" and mentions the Chroma as having been left in the Polar Studio by 10CC's producer. It was the first polyphonic synth he laid hands on and it shaped the sound of the album "Paradis" along with the Linn Drum etc.

Looking in the instrument registry Johan (21030017) has two more Chromas. I think he needs to get back with the details on those... :)

David Hobson [21030506] · Sat, 4 Jan 2014 17:35:26 -0500

Cool. I looked around a little and found this video on youtube which shows a Chroma at @ 7 seconds:

Thanks for the post.

Regards

Rhodes Chroma Keyboard For Sale (US/CAN)

Dryden Chambers · Mon, 20 Jan 2014 12:56:59 -0500

This well loved Rhodes Chroma keyboard is in very good condition. Unit is clean, well maintained and pampered in smokeless home studio. All keys work great. Wood has been cleaned up and refinished by professional local carpenter. Usual small marks, scratches , dings on body (wood and metal) due to age, nothing major. CC+ was added a few years back. Power supply is original, but large caps were replaced a couple years back and functions great with no issues. Comes with original pedals and parameter chart. 7 of the 8 voices are working perfectly, one voice board (0) has a Err, but was functioning fine recently so should be a easy repair. Pickup highly Preferred seeing there is no case. US/CAN only. No paypal, Located in upstate New York or near Toronto Canada. Would like to see this unit go a list member-good home before posting elsewhere, Asking $3000 US or best offer. First come, first serve. Please email privately for more details, questions, & photo's. SERIOUS ONLY PLEASE!. Thank you.

Digital Chroma

Paul DeRocco [21030230] · Wed, 22 Jan 2014 22:15:55 -0800

If anyone's going to be at NAMM, and would like to try out the Digital Chroma, contact me off-list. I'm going to have it in a room at the Hilton.

Dave Bradley [16330135] · Thu, 23 Jan 2014 09:24:27 -0600

!!!!

pictures please!!!!

Dave

Bruce Sklar [21030660] · Thu, 23 Jan 2014 16:31:17 -0500

What is that you're talking about !! Pictures?

Chris Ryan [21030691] · Thu, 23 Jan 2014 13:35:18 -0800

See NAMM anyone?, January 2013.

Paul DeRocco [21030230] · Thu, 23 Jan 2014 14:27:13 -0800

Digital Chroma pix

Here are some pictures, including the interior.

Ian Hamilton [21010150] · Fri, 24 Jan 2014 09:34:49 +1100

Having problems viewing the images. :(

Chris Ryan [21030691] · Thu, 23 Jan 2014 14:35:46 -0800

I'll try to post them to the archives tonight.

Christian Kleine [21030210] · Thu, 23 Jan 2014 23:35:27 +0100

Re: Digital Chroma pix

that is quite amazing. is there more info about this somewhere?

Ciao,

Christian

Dave Bradley [16330135] · Thu, 23 Jan 2014 16:47:52 -0600

Re: Digital Chroma pix

Are the preset buttons still active? I don't see a board behind them.

David Clarke [21030085++] · Thu, 23 Jan 2014 19:45:16 -0400

Re: Digital Chroma pix

Here are some pictures, including the interior.

Unless there's a specific reason not to (e.g., perhaps a commercial venture to come), it might be nice to have a 'Digital Chroma' page (or two) on the main Chroma site (capturing the info discussed from last year + pics, etc.)

Ditto, it'd be nice if there were some audio samples to perhaps compare the sound of typical patches on the digital Chroma vs. the original Chroma.

Paul DeRocco [21030230] · Thu, 23 Jan 2014 16:08:29 -0800

Re: Digital Chroma pix

I've been busy with other things, but I do intend to do a web site for the project soon. It'll have sound samples and perhaps links to videos.

Dryden Chambers · Thu, 23 Jan 2014 19:25:45 -0500

Re: Digital Chroma pix

will it be available as a standalone application, plugin, or will you need a gutted or newly manufactured Chroma ?

Paul DeRocco [21030230] · Thu, 23 Jan 2014 17:28:06 -0800

Re: Digital Chroma pix

For now, I'm just doing an upgrade kit for Chromas. But lots of people want a plug-in, so I may well do that too. But that won't happen in the very near future.

Paul DeRocco [21030230] · Thu, 23 Jan 2014 17:28:49 -0800

Re: Digital Chroma pix

From: Dave Bradley

Are the preset buttons still active? I don't see a board behind them.

Everything works. Even the cassette switches access a USB flash drive.

Jeff Bova [21030407++] · Thu, 23 Jan 2014 18:42:30 -0800

Re: Digital Chroma pix

I just met Paul and saw the digital chroma, I'm very excited about it well Done Paul!

Dave Bradley [16330135] · Thu, 23 Jan 2014 22:51:10 -0600

Re: Digital Chroma pix

How close to a Chroma does it sound? (Eying my busted Chroma)

Jeff Bova [21030407++] · Thu, 23 Jan 2014 21:13:55 -0800

Re: Digital Chroma pix

I thought it sounded remarkably close, but without anyway to A/B them and to be fair, I couldn't give it a close enough critical listen. Having the familiar interface was great. Big voice count, a much more detailed display, Stereo etc. I'm sure Paul will post more of the details.

Chris Ryan [21030691] · Fri, 24 Jan 2014 00:57:52 -0800

Re: Digital Chroma pix

On 2014-01-23, at 2:35 PM, Chris Ryan wrote:

I'll try to post them to the archives tonight.

The pictures are now available at the site: see Digital Chroma pix.

Philippe [21010227] · Fri, 24 Jan 2014 10:21:17 +0100

Re: Digital Chroma pix

I'd be curious to know exactly what you mean by :

On Fri, Jan 24, 2014 at 2:28 AM, Paul D. DeRocco wrote:

For now, I'm just doing an upgrade kit for Chromas.

Would that be an addition to existing Chromas ?

Paul DeRocco [21030230] · Fri, 24 Jan 2014 09:41:20 -0800

Re: Digital Chroma pix

Exactly. Rip out all the old electronics (except the keyswitch boards, and optional pressure sensors), and put in new boards.

Roel D. [21010092] · Fri, 24 Jan 2014 18:53:06 +0100

Re: Digital Chroma pix

I suppose you could easily make a midi-expander starting from this digital board? Would be a great way to take a Chroma on the road!

(And nice to meet you all. When I get the time to start repairing the Chroma I dug up from under piles of dust, you'll get to know me better for sure.)

Roel

Chris Smalt [21010280+] · Fri, 24 Jan 2014 22:28:24 +0100

Re: Digital Chroma pix

Here are some pictures, including the interior.

Awesome

min.struct · DATE

an additional display for the Chroma

Hello list, during january, it's wishes time, and Paul D. DeRocco with its DigitalChroma seems to have drawn the road for my display whish ;)

this is exactly what i would dream of for an original Chroma with CC+

digitalchroma1thumb

By any chance, is there any arduino or raspberry Pi genius, reading this message, who could interface the CC+ with those two oled displays ?

Frank Hettlich [21030041+] · Sat, 25 Jan 2014 01:07:08 +0100

Digital Chroma expander/knob box

Hi Paul,

as probably most other Chroma users I was always asking myself which kind of potential buyers you are aiming at (software guys, "desperate" Chroma owners who can´t fix their Chromas, new Chroma admirers, unhappy Chroma users without an expander)?

Personally I would like to see a digital Chroma box (kind of digital expander) with lots of knobs and the same color scheme. Would be nice to put one (or two) on top of a Chroma.

Good luck

Frank

Bruce Sklar [21030660] · Fri, 24 Jan 2014 21:02:14 -0500

I beg the gods- a Chroma digital expander please- so i don't have to rip my chroma apart!

Doug Terrebonne [21030114] · Sat, 25 Jan 2014 03:52:24 -0800

Re: Digital Chroma pix

Exactly. Rip out all the old electronics (except the keyswitch boards, and optional pressure sensors), and put in new boards.

The horror... :). Now stuffing one into a rack or desktop case would be kinda neat....

Brian McCully [21030361] · Sat, 25 Jan 2014 06:53:08 -0800

Re: Digital Chroma pix

Is it all done, Paul? v1.0? or are you in alpha, beta...? Is this upgrade for sale? Turn-around time? I have an ornery Chroma that could be made available.

Frank Hettlich [21030041+] · Sat, 25 Jan 2014 19:56:26 +0100

Re: Digital Chroma expander/knob box

To further elaborate my idea/wish I might add that this Chroma knob box/digital expander might offer the capablity to select a "Chroma ID" that chooses between different Chromas connected by MIDI and the digital one "on board".

So the Chroma knob box/digital expander would serve 2 purposes and/or kind of potential customers:

  • existing Chroma owners that are able to comfortably edit their Chromas AND get the new digital version
  • new users who wish to get the Chroma experience without having to pay a premium

I own the now defunct/obsolete "Touchdigitalcontrollers" impOSCar hardware controller that sold for around 1000 Euros and it is one of the finest hardware device I ever put my hand on. So it definitely IS possible to make a valuable Chroma controller for under 1000 ($,Euro, GBP). Adding the digital Chroma hard- and software might be another 1000 or slightly more.

I see a (big?) market for such a device. A project like this could be financed by early adaptors who might benefit from a rebate by paying in advance.

All the best and good luck with the Digital Chroma

Frank

David Hobson [21030506] · Sat, 25 Jan 2014 15:03:05 -0500

Re: Digital Chroma expander/knob box

Hello,

I am currently creating a software emulation of the Chroma and am thinking about an interface. At the current rate it will take approximately 1 1/2 to 2 years. Just wanted to throw that out there.

As a side note, I have uploaded music to Youtube (free music) that I have used my "real" Chroma in extensively. The other music may not be of interest, nor may be the music created with my Chroma:( Most of this music has only been live for about 3 months, and to find the compositions where I utilized the Chroma you may need to read the "about" fields under the "videos?"...here is a link to my "channel."

And here is a link to a Chroma song:

Paul DeRocco [21030230] · Wed, 29 Jan 2014 23:31:50 -0800

Digital Chroma status

Various people asked various questions about my intentions with respect to the Digital Chroma. I'll put all the answers together here.

The current status is this: the hardware design is finalized, and there are two hand-assembled units in existence which work nicely. I need to get a run of boards made, and source a few odds and ends like packaging for a kit. The firmware has a few bugs, and is missing the reverb and a couple of the more esoteric keyboard algorithms, so that's next on the to-do list. Fortunately, it is easy to upgrade the software from a flash drive or over a network. So realistically, it'll be out in a few months (since I have a day job).

How close does it sound to the original? I've written a converter that I ran the old factory presets through, and most sounds came out very close. There are still some flaws in the converter that make some of the more complicated sounds (e.g., Broken Glass) sound wrong, but the instrument is capable of making all those sounds. It's a cleaner sounding instrument, not surprisingly, but the oscillators do have enough intentional detuning to keep it from sounding dry. The filters are much better behaved at high resonance, or when self-oscillating. The main sound difference is an unequivocal improvement: it's stereo, and you can stack up multiple voices per key with detuning and stereo spread for a really spacious sound.

The market for the Digital Chroma is pros, or anyone with money to burn. I don't have a price, but it won't be cheap, because it has a very limited market, and a lot of work went into it. The Digital Chroma upgrade kit can fit into a Chroma Expander box, but because it includes the keyboard split capability, it still needs four link switches instead of two, so it would be necessary to punch a couple of LED holes in the Expander's panel. Fortunately, the Expander's panel actually has all four switches--only the graphics layer is different--so it would work fine, but some sort of stick-on label would be needed to show all four switches.

Frank Hettlich [21030041+] expressed a desire for a digital expander with lots of knobs. That's not something I think is practical, because the Digital Chroma has way more parameters than the old Chroma.

I may do a rack mount version, which of course could be sold to anyone, not just an existing Chroma owner, so that would have a larger potential market, and be a lot cheaper. My inclination would be to put it in a 1U chassis with a minimal user interface on its panel, and include a cheap Android tablet with a good touch-based editor. And of course it would respond to program changes from any decent MIDI keyboard controller.

I've also been asked about a VST plugin. That would involve a lot of rewriting, because plugins have to play nice with other plugins, for instance not using any CPU when not playing any notes; the Digital Chroma just runs all the voices continuously even when silent. Also, it's hard to prevent people from copying software, so it might not be a profitable venture.

I also have an idea of doing a Digital Polaris Upgrade Kit, with many more voices and a multi-track sequencer. There are a lot more Polarises out there, and I could leverage a lot of the Digital Chroma work (like the custom Linux version), so that could be a cheaper product. But that's just speculation at this point.

Bruce Sklar [21030660] · Thu, 30 Jan 2014 06:58:54 -0500

Re: Digital Chroma status

Paul- Bravo to you!! We are all excited I'm sure to see what transpires here.

David Gowin [21030611] · Thu, 30 Jan 2014 18:03:20 -0800

Re: Digital Chroma status

As a Chroma and a Polaris owner (2 Polaris's - Polari?) the idea of a Polaris upgrade kit has me quite interested. I hope you give it some thought!

See Digital Chroma & NAMM, January 2015.

case and pedals in the UK

Jesper Ödemark [21010135] · Mon, 27 Jan 2014 10:38:08 +0100

If someone in the UK is looking for an original case and/or pedals:

[Item 121260990258:]

[Item 121260992795:]

(Not my auction!)

Chris Ryan [21030691] · Thu, 30 Jan 2014 22:45:07 -0800

The case didn't sell, but the pedal sold for £15.00.