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ChromaTalk Archives: January 2020

As I have to catch up on the list archives for the last few years, and I'm starting with 2020, I will link back to previous threads when I get to 2019 (and other years).

AS3350 Filter

Werner Schöenenberger [21010114]

Am 31.12.2019 um 18:40 schrieb David Clarke:

… I've just tried the AS3350 on a voice card for the Chroma. While it nominally seems to 'work' as a filter (if you override the auto-tune), swapping it in for a CEM will have the CEM3350 pass auto-tune while the AS3350 will fail.

Thanks for the update, David.

Maybe finally a piggyboard might be the solution. It is really a pity that it does not seem to be simply exchangeable. Did you already discuss your findings with Alfa?



David Clarke [21030085++]

Maybe finally a piggyboard might be the solution. It is really a pity that it does not seem to be simply exchangeable.

Based on what I saw I suspect that the part could be successfully used if some of the values of the discrete components on the voice-board were changed.

That being the case, I suspect it would work fine for 'new' designs - but it may just not be something that can be assumed to function as a 100% drop-in replacement for existing designs.

Did you already discuss your findings with Alfa?

No. I had picked up the parts just to evaluate their potential use in the Chroma. I didn't specifically 'need' them, and so knowing that the part many not be an exact replacement is all I needed to know for now.

Chroma Dual footpedals

John Simmons [21030454]


Happy New Year!

I’m looking to purchase a Chroma Dual Foot-pedal unit if anyone can help?

Best regards


Re: EPROMs for the USA and Abroad

Brian McCully [21030361]

Hello David - I would greatly appreciate receiving some updated EPROM's.

thanks, -Brian

On Monday, September 30, 2019, 7:33:37 PM PDT, David Hobson [21030506] wrote:

An update, and information about the 220 EPROM burn from David Hobson:

I have enough interested Chroma users to start burning the 220 firmware within a week to a week and a half. It would be best if everyone who is interested in the 220 firmware to email me off-list with their requests.

The EPROMS are $20.00 USD a piece, and shipping will be $3.50 inside the United States and $7.50 outside the States.

Please send me an email off-list with the following information: The number of EPROMS you will be needing, your name and address, and your preferred Paypal email so I can send you a request for the funds.

Make sure you have read up on the newest firmware to see if you actually want it of course, and in the meantime I will also be waiting for any Chroma users who do not check their email often.

Best Regards,
David Hobson.

Ron Joseph [21030042+]

I’m considering the eprom as well. I went to look up what the changes were in this batch but the Chroma site hasn’t been updated with the information. I recall Chris looking for someone to take it over).

Does anyone have a listing of the changes ? Thanks ,Ron

See The Chroma CPU Plus (CC+): Firmware - 220 (September 2018).

David Clarke [21030085++]

Changes up to and including the 219 version of firmware are discussed on the Chroma Site (see The Chroma CPU Plus (CC+): Firmware)

The changes for the 220 release were outlined in an earlier discussions on the mailing list and are reproduced below:

A new version of firmware for the Rhodes Chroma CC+ had been created in September.

Firmware Release 220 adds:

  • The ability for the user to defeat an initial pressure response based on velocity

The release also has the following specific changes:

  • Correction of MIDI base channel handling for controllers when running in 'Play' mode.
  • [Set Split 36][P25] now returns 220

Ability to defeat initial pressure response based on velocity

There is a provision in the original Chroma firmware code (carried over to the CC+) which assigns an initial pressure value for high velocity key strikes.

Paul DeRocco [21030230] had advised on the ChromaTalk mailing list that this feature was intended to account for a lag in pressure data by assigning an 'initial' pressure value.

In practical terms though, what that means is - if you're hitting the Chroma's keys hard enough to get very fast velocity (e.g., one of the top 7 of the 32-possible Chroma velocity levels) then inside the Chroma there is an initial pressure value assigned to this keystrike.

A few users have stated that they don't like this behaviour and would like a way to defeat it.

A new CC+ configuration parameter called "Initial Pressure from Velocity" has been added [Set Split 36][P32].

When this parameter is set to "On", the CC+ behaves as it has in the past (which is also how the original Chroma CPU behaved) - namely an initial pressure value is assigned based on key velocity.

When this parameter is set to "Off", the CC+ will _not_ assign an initial pressure value based on velocity - and will instead always assume an initial key-strike pressure of '0'.


  • This parameter only affects the 'initial' pressure value. It does not change how pressure is otherwise detected from the pressure sensor (if installed).
  • An interesting quirk of the original feature was that even if you did not have a pressure sensor installed, it would be possible to have a patch response to this 'initial pressure'. When this parameter is set to Off, it defeats the initial pressure (regardless of whether a pressure sensor is installed or not).

Correction of MIDI base channel handling for controllers when running in 'Play' mode

An issue was detected when wanting to use an external MIDI CC source (e.g., BCR2000, etc.) to make permanent program changes ( [Set Split 36][P24]. = Prog ) while the Chroma is configured in 'Play mode' ( [Set Split 36][P2] = Play ) AND then the MIDI base channel ( [Set Split 36][P1] ) is modified.

When determining whether a controller should impact just the 'instrument' or the 'program', two checks are made.

First - we look at the user's setting for Prog/Inst [Set Split 36][P24].

Second - assuming the setting is configured for 'Prog', we look to determine whether the incoming message is on the 'base channel' or not.

The CC+ implements MIDI running status - meaning that it will take a snapshot of the last full message, and remember both the message type and the last received channel.

When we do the check for whether the incoming message is the one on the 'base channel', we use the channel value which was determined from the running status calculation. (e.g., we are using a stored 'last channel' value).

It was found that the MIDI 'last channel' value used in the Prog/Instrument CC mode determination was only being updated only when running in the 'normal' mode (and not in the 'play' mode.)

That meant that when play mode was being used, the 'last channel received' wasn't being dynamically updated - and so it will remember whatever the last received channel was for a message when configured in 'normal' mode.

So - a problem in properly updating the local program data via MIDI CC's would occur if:

  • we had the Chroma in 'normal' mode and allowed it to successfully receive a message on MIDI Channel X.
  • we change the mode to 'Play' Mode
  • we are set for CC 'Prog' Mode
  • we have changed the MIDI base address set to a channel other than Channel X.

The current firmware has been updated so that the 'last channel' value is properly updated in either Play or Normal mode of operation.

  • If you are already using Play mode - and MIDI CC's are being received/controlled as expected - then this issue isn't impacting you and no update is needed.
  • If you don't use "prog" mode for the MIDI CC's, then this issue doesn't have an impact for you (whether you're using Normal or Play mode)
  • If you are impacted by this issue, but don't wish to update firmware, then the issue can be worked around as follows:
    • Go into Normal Mode
    • Change your MIDI base channel to whatever you'd like
    • send a message in on Channel X (the desired base channel)
    • Go back into Play Mode

No further changes are needed unless/until you decide you wish to use a different MIDI base channel in Play Mode.


Special thanks to Werner Schöenenberger [21010114] for raising the MIDI Channel/MIDI Controller handling in Play Mode issue.

Re: Looking for Chroma IO board

Votek Mendo

Hi im still looking for an i/o board for a chroma and would really like if you could help me source one. Maybe you have seen one for sale somewhere or have one for sale. The I/O board has receive battery damage.

Do you know if its possible to build this board from scratch? Cloning it kind of.

Thanks for helping me

Paul Hackett-Evans [21010094]

Hi Votek,

My friend Peter Riani is also looking for an I/O board and has exhausted most avenues of enquiry. He believes that cloning I/O boards will be necessary.

I know of two non-working boards that were recently sent to a tech for appraisal on Peter's behalf, they were both in need of considerable work with no guarantee they would come good at the end of it all. Perhaps you and Peter could liaise about the possibility of cloning a couple of I/O boards?? I'll send him a copy of this, although I believe he's on the Chroma list, too Best regards Paul

ulfur hansson

you could try converting the pcb design scans found on the chroma website to gerber and send it off to a fabrication service like or iteed, and take it from there!

Daniel Rickenbach [21010172]

I have done this a few years ago, still have the gerber data, also files for designspark, will have a look for and can send then

There were two boards made from the data, both are working fine

Paul Hackett-Evans [21010094]

Daniel,Please see my reply to Votek. My friend Peter wants also to find or make an I/O board. Please can you send the data to us, too?

Can you tell us more about getting them made, who did them for you, and the component sources you used, too, please?

Votek, perhaps you and Peter can collaborate on having boards made??

ulfur hansson

if someone is actually planning to clone a few I/O boards, count me in as well!! i’d like a healthy board replacement for my chroma...

Paul Hackett-Evans [21010094]

Ulfur, I'll speak to Peter in the next day or two. It seems there's a need for this.

ulfur hansson

amazing, thank you!


Votek Mendo

Thx a Lot Daniel That is a very good news. If you can tell us more about the project, that would be really appreciated. I will try to get the same thing done if not too complicated. I have a good tech for my synths so is help will be very helpful too.

You estimate the price for a build like that to how much in parts? Any parts really hard to find? If everything rolls out nicely i could try to get a few of these built if there is a demand for it, will see. Don't want to get into a too ambitions project on my own.

Maybe i can reach you on the phone so we can talk about it?

Thanks to everyone helping so far, i really appreciate. If this work, it means i will have a very nice chroma for sale eventually.