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ChromaTalk Archives: May 2000

Hello, Seeking Chroma Info, and unit For Sale (not mine!)...

John B. Rotondi [21030185+]

Hi All!

I am new to this newsgroup, so I hope this message get to you...

My name is John, and I am the proud owner of 2 Chromas- one purchased from Chuck Wilde of 'Missing Persons', and the second from another private party. The Chroma was the main keyboard for my '80s original progressive rock band based in LA, 'Birds Of Fire'- we had one at our rehearsal studio, the other at my home- as I did the majority of the original programming and housekeeping of the library (I play bass). The first was purchased in it's heyday, and the second after MIDI caused the used prices to drop, making it affordable as a spare (and saved wear and tear on it and my back!)... I later purchased Ken Yparilla's Chromaface MIDI converters for both...

I am interested in links and sources for maintaining, updating, and otherwise supporting these units. I have some repairs to do to voice cards (I'm a tech, and have schematices, so should be able to get them going)... and would like to revitalize them for some upcoming projects I am doing- they still sound great...

Big beefs- both were in their cases for a while, and the foam has melted onto the wood! Yechhh! I will refinish the wood... but does anyone know about getting new (and non-melting) foam for the cases...

BTW, here is a recent listing for a until for sale in LA:

Arp Rhodes Chroma- $ 1350.00, comes with anvil case and pedals. Excellent condition. [e-mail address removed]

Regards to all,

John Rotondi
Woodland Hills, CA

Christopher Now

John Rotondi wrote:

Hi All!

Welcome, John!

Big beefs- both were in their cases for a while, and the foam has melted onto the wood! Yechhh! I will refinish the wood... but does anyone know about getting new (and non-melting) foam for the cases...

Welcome to the club. I don't believe anyone who left their Chroma in its case for more than a few months escaped this problem.

After I had mine refinished, I take an old 100% cotton bedsheet and place it on the bottom of the case before I put the Chroma inside. Before closing the lid, I wrap the sides and top of the Chroma with the remainder of the sheet such that it's "tucked in" and all the wood is protected. The sheet also keeps the foam dust from getting inside the unit.

This is a decidedly low-cost, low-effort solution, but it works very well for me. I just didn't want to spend any more time on the case than I had to. I think others have replaced the foam and I look forward to reading about their results.



I had a guy in LA redo the foam in mine. Can't find his darn number though His name is Dennis and he make's custom anvil cases as well...he made a super cool folding anvil case for my serge modular as well.

Re: Aftertouch and Velocity

Go to first message in thread (April 2000)

Chris Ryan [21030691]

At 4:36 PM -0700 2000/04/26, Christopher Now wrote:

Regarding the keyboard velocity and pressure sensor issues:

When I worked as a tech at a service center from 1982-1986, we routinely installed a factory-modified version of rev 14 firmware that improved the feel of the keyboard, (read: changed the velocity curve). Most Chroma owners really liked it, but to me it was a very subtle improvement as I never compared it to the older firmware - (since I've owned my Chroma, it never had the previous firmware, or even a stock rev 14) The "tweaked" version of the rev 14 firmware was 14a and only the last EPROM in the set got updated. I gave a copy of this to our fearless ChromaTalk moderator, Chris Ryan shortly before he moved back to Canada. I think that he perceived a difference, but I'm not sure if he had much time to spend using the keyboard. How's it going Chris?

I have just this past week actually got my Chroma set up again; it's not plugged in but should be later tonight. :) It's been six months since I played it (and then only briefly, as it was in the shop at CAE Sound), so it will be difficult for me to do an A/B comparison on the rev 14 versus 14a EPROMs at this point. Here is an excerpt from an e-mail I sent Chris after he'd helped me replace the chip last July:

"I can't say for sure whether I detect a difference, but it does feel good--yes, maybe there's a slight difference in the response. I also think that there's an improvement in the velocity response; perhaps it's a more uniform curve, where before it seemed biased towards higher velocities. But it's difficult to be completely sure."

In other words, it was pretty subtle. And since I tended to stand the Chroma against the wall and play it through my KX88 (until now--our new place has more room!), I didn't have extensive recent experience with the Chroma keyboard. And I have no experience with pre-rev 14, which my Chroma (a later model, which I bought in late 1983) shipped with.


Chroma Programmer posted

Jimmy Moyer [21030184]

Chris has posted the Chroma programmer I'd written about on his site. (Thanks Chris.)

It provides a synchronized display of all of the Chroma parameters and the ability to save and restore banks of named programs.

I can think this could be useful in two ways. It is an ancient DOS program that talks directly to a Roland MPU-401 (or fully compatible) MIDI interface and then to the Syntech interface. It will not run under Windows. I have an old 386 dedicated to just being a display for the Chroma. At least for me, this makes programming and organizing patches simple.

Someone might want to make a similar Windows based program. I've included the source so the grunt work of translating a packed Chroma program into parameters wouldn't have to be done again.

-> Jimmy

Philip Dodds Interview

Go to first 'Philip Dodds Interview' thread (April 2000)

Chris Ryan [21030691]

I sent our questions to Philip Dodds last night. He responded, "This is a long list! It will take me some time to respond, but I will do so with pleasure - it will be fun." I look forward to reading his responses, and will post them as soon as I receive them. Thanks, everyone, for your contributions.


Dave Bradley [16330135]

Did you ask about the Intel/Motorola CPU controversy?

Chris Ryan [21030691]

Yes--I think I pretty much got everything covered. The questions are appended.


How did you first get involved in ARP and electronic musical instrument design?

What other instruments did you work on at ARP?

Your appearance in "Close Encounters of the Third Kind" made synthesizers more visible to a wide audience. Tell us more about your work on the film. Did you compose the famous alien tune?

What happened after you got the Chroma team set up again at CBS? How much work was left to be done?

How many people were on the Chroma team? Were there chief hardware and software engineers?

Apparently Sequential Circuits had a Chroma disassembled in their lab. Was there any awareness at CBS of the Prophet T8 design?

How did the single-slider programming model concept come about? Was it strictly a means to achieve cost savings, or was there an attempt to simplify programming or a feeling that most players were non-programmers? Was any user testing done?

Who was responsible for the visual design of the front panel?

What are the real differences between the first fifty Chromas (hand built) and later production models? What about models 2101 versus 2103--were they for different countries (the 2101s seem to be found in Europe), or are they indicative of other design changes?

As released, the Chroma Expander can really only be used to be a "linked" voice, rather than to increase polyphony. Why wasn't the hardware/firmware set up so that adding an Expander would actually double the number of voices available (since this would seem to have been the most intuitive purpose of the Expander)?

How was the Chroma launched? One article mentions a Peter Vetesse demo video, which none of us have seen. Any memories of reactions, notable events, etc.?

A few questions about architecture. Why was there only a single noise generator, and only seven levels of resonance?

A Keyboard magazine article claims that the Chroma was built around an Intel 80186, but a Motorola 6809 and Intel 8039 were actually used (the Polaris seems to use the '186). Was a change made at some point in development?

A weak point of the Chroma hardware design seems to be the power supply, which most of us owners seem to have had to deal with at some point. What is the story behind this?

The Chroma has the ability to read and write "subroutines" via the cassette interface. What was the actual intended purpose of this functionality? Were there ever any "subroutines" issued to the public, or was this strictly for internal use?

A number of current Chroma owners have a fair amount of technical knowledge, and have built or considered building modifications to the instrument. A few questions about customization:

Was the pressure sensor modification ever shipped? How difficult would it be to build such an upgrade today?

Would it be possible to speed up the software envelopes and make the LFOs go faster?

Would there be any way to obtain source code (hopefully commented!) for the ROMs? Any way to allow hackers to implement their own OS, or maybe play with some of the keyboard algorithm behaviors?

Were there any plans (besides the Polaris) for future designs? What about the rumoured 88-key version?

What was your involvement with, or knowledge of, the Polaris? Was it really a Chroma?

Why was the Chroma discontinued?

How many more Chromas could have been built? It seemed that there was a large surplus of parts in the years following its discontinuation.

What do you know about the sale to Roland? Did that company ever contemplate continuing the Chroma line?

What is your best and/or most humourous memory of the project?

Any tips or tricks you might recall?

Do you have any memorabilia or other information you could provide for the Chroma web site?

Do you have a Chroma now?

Do you still follow electronic musical instrument design? Any comments on "modern" virtual analog synthesizers like the Korg Z1? Anything that strikes you as interesting?

What are you doing now? Future plans?

Bill Lacey


Great job on assembling the questions. Can't wait till he gets back to you. Forgot to ask you to ask him who 'thunk' of the thumper. Probably best not to ask, since it may have been his idea and might hurt his feelings. Anyway, thank goodness you can turn it off. It really horrified me when I first got my Chroma to hear it whack away.

I added this question later; see Phil Dodds/Tony Williams Interview: thunker question for Tony Williams's response.

BTW, someone on the net is selling a Chroma with the Polyphonic Aftertouch. I'm trying to get some more info from the seller. I thought they were never shipped. It will be nice to get clarification from Phil.

See Poly Aftertouch below for responses.


Bill Lacey
Digital Sound & Picture, Inc.

Dave Bradley [16330135]

the dreaded thumper

Actually, I appreciated my thumper. It performed well for the job it was designed, which was giving tactile feedback in a loud live performance situation. I gigged regularly with a Chroma + Expander setup for years, and needed to feel that thump when using it live.

Dave Bradley
Principal Software Engineer
Engineering Animation, Inc.

Kurt Otto [21030572]

another pro-thumper

Even though my thumper used to drive certain roomates crazy, I found it to be invaluable in a live band situation. I could hit a number, and a good thump would save me having to double check visually. Those few split seconds of extra time gave me the courage to branch out from my usual settings momentarily for a certain licks, by hitting the button a second time, I could get back to where I was supposed to be. The thumper gave me confidence to try tricky stuff constantly. I got pretty good at it after several hundred gigs. It was like a quick change palette. Very spontaneous, and lots of fun in the live creativity department.

Kurt Otto - San Antonio, Texas
Chromaniac with Claude Morgan And The Blast, 83-88

Chris Smalt [21010280+]

the essential thumper

My thoughts exactly. I'd like to add that under a lot of stage lighting conditions, I couldn't read the program number display, so I was really "flying on" the thumper.


RE: Chroma: Rev. 14/14a differences

Go to first message in thread (April 2000)

Dave Bradley [16330135]

FWIW, I get this lockup also. Although it's not as annoying as the lockup I get every time I boot up! I guess I need to look at my power reset line. Switching back off, waiting 1 second, and powering up a second time always works.

Dave Bradley
Principal Software Engineer
Engineering Animation, Inc.

Dave, Chroma reset

Russ Lyons [21030574]


Just a little warning. If you keep cycling the Chroma power, either the power supply will eventually fail or worse it will take some of the Chroma circuitry with it. I was lucky. I replaced the stock supply pretty much the way Don Tillman described. I also replaced two caps on someones Chroma with the same problem you're having and it fixed that problem. Maybe you know a hardware guy that can help.

Good Luck,

Dave Bradley [16330135]

Oh sure, make me paranoid <g>! Just what I need, another electronics project...

Sigh, I suppose you are right, it's time to do the Tillman transplant.

Poly Aftertouch

Bill Lacey

BTW, someone on the net is selling a Chroma with the Polyphonic Aftertouch. I'm trying to get some more info from the seller. I thought they were never shipped. It will be nice to get clarification from Phil.

Here is the response I got from the seller:

The particular keyboard was one of ARP/Rhodes test bed units that they installed pre-production options on and beta tested them until they got them right. The keyboard has poly aftertouch, an extra bank of 50 programs, and improved power supply, and a fan installed. The aftertouch unit is a huge system running the entire length of the inside of the keyboard. It works well and is surprisingly enough polyphonic. As far as the lacquer/foam interaction from the case there is none. The keyboard wood does have nicks on it, but no foam residues.

This is really tempting to buy, but I don't know the guy and have no idea if any of this is verifiable. Hey Chris, can you forward this description to Phil for comment?

Dave Bradley [16330135]

Hmmm. I thought the entire reason you don't see aftertouch on Chromas today was that they DIDN'T get it right...

What's he asking for it?

Bill Lacey

$1100 w/anvil

Chris Ryan [21030691]

This is really tempting to buy, but I don't know the guy and have no idea if any of this is verifiable. Hey Chris, can you forward this description to Phil for comment?

One of the questions concerns the pressure sensor option (see my previous e-mail). I don't want to bother him too much; he's busy and it's a lot of questions.


Bill Lacey

More feedback about the Chroma with Poly Aftertouch from the seller:

I have not MIDIed the expander in a long time - I only ever had a JL cooper interface that was jive - I use a Chroma Polaris to control it (thru the proprietary 25 pin interface) The extra 50 sounds are accessed by a switch on the right side of the keybed. You flip the switch and it changes to the second bank (kind of like an A and B bank on a current keyboard) The voices never fail when booting up. I was blessed with a pile of new old stock chroma voice boards a few years back. One voice failed in this chroma a year or so ago and the card was swapped out for a new one. The chroma had a notoriously bad power supply in its original version causing all kinds of difficulties. The new power supply runs hotter - or so I'm told, - and the fan help keep things under control. It is a rhodes logo - as well as all internal parts (the poly aftertouch, voice boards, etc.) are Rhodes logos as well. I believe they were developing these addtional after ARP transferred the basic design schematics to Rhodes.

I've sent an email to seller to inquire about what Rev of the Eproms he has in that machine. My ChromaCult manual suggests the Rev 14 Eproms as being the preferred (and specifically doesn't like the Rev 12). It does support the Poly Aftertouch, though. But being that this is a "beta" model, I'm not sure if this would work.

I'm on the fence about buying this. Anyone have any advice?

David Clarke [21030085++]

Development Chroma

... just curious, did anyone on the list actually buy the Chroma w/pressure interface (and dual memory banks) mentioned on the list a while ago?


Russ Lyons [21030574]

I almost thought about it. The guy lives pretty close to me.

Price was a little high, and I already have a regular Chroma.

I am thinking about adding mono pressure to the Chroma, since it would be fairly easy.

Bill Lacey

I passed on it. I didn't get enough feedback from the group to give me confidence to go forward. I don't have as much technical ability that some here have, so if things go awry it's going to be a hassle to fix. Of course, when Phil Dodds gets back to us and says Chromas with Poly Aftertouch are the only ones worth owning, I'll be kicking myself. In the end, if I get another Chroma, it will be an Expander (if I can ever find one).

The price has come down. Here is the info (don't know if still available):

Rhodes Chroma - Recently serviced and 100%. No Midi w/ poly aftertouch, anvil case, etc. $1050.00 shipped in US. Seller: J. Douglas Tyler. [Contact information removed]

For detailed information on the pressure sensor, see David Clarke's subsquent article, The Chroma Pressure Sensor & Interface, based on an examination of a rare Chroma with the sensor installed.

Coal-fired Chroma

Eirikur Hallgrimsson [21030467+]

Ick. Just as I get started on trying to use the beast again, I'm having the crash-on-boot problem get worse on me.

This Chroma, and actually, the other one I had a few years ago, does not power-up correctly after it's cooled-down.

Symptom: Switch it on, and some unique random combination of LEDs light, or no LEDs even, sometimes. Sometimes the the tapper taps once. Powering the beast on and off does no good at this point. What works is to wait for the power supply (or???) to warm up, then power off/on and I get a good boot.

Does this mean anything to anyone? I'd sure like to fix it.


Don Tillman

Crazy behavior? Check out the power supply voltages. If the +5.0 V digital supply isn't within 5% things will generally go haywire.

-- Don

David Clarke [21030085++]

... and if isn't a voltage level issue, I would next guess a weak/sick component in the RESET circuitry of the PSU. If you have a 'scope or a voltmeter, you can check to see if this is the problem by looking at the blue wire leaving the power supply (the blue wire on the PSU connector closest to the front of the machine). If you have a good 5v rail, yet the voltage on the blue wire stays at or near 0 volts, then the reset circuit is not performing properly.