Presenting: Crowminius

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oldcrow
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Post by oldcrow » Wed Aug 05, 2015 3:02 am

Working on a front panel while waiting for the SMT parts to arrive. This is the v1.2 (SMT) panel which is slightly different. I will make a v1.1 panel once I verify this one fits. It is contoured to fit around the 1/4" jacks and in order to save on panel price, it does not cover the entire board. :sb: :goo: :party:

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wahee
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Post by wahee » Wed Aug 05, 2015 6:01 am

hi Crow that panel looks great, love the logo, I think I will order another board once I finish this one completely.

Have you any advice to get the range tuned better. I have the oscillators all in tune as per the Minimoog service manual using the 2' range. But when I drop to 4' or 8' the scale does not drop a full octave down. I have to readjust OSC2&3. Adjusting the RANGE pot throws the entire oscillator tuning off.

It's not a huge deal as I an just adjust OSC2&3 frequency controls a bit to compensate, but would be nice to fix if at all possible.

s it also possible to increase the noise gain as on my build it's quite low compared to the oscillators. I have not tried to tweak the VCA balance as I got a bit confused with the Minimoog manual - connect point A to point A malarkey
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Post by sk23 » Wed Aug 05, 2015 6:34 am

I have the same issue.. honestly I can't either get the scale A to A to the upper octave.
A guide would be really useful.

I use midi din input, and I have 121k 1% for R4 and R6.

wahee wrote:hi Crow that panel looks great, love the logo, I think I will order another board once I finish this one completely.

Have you any advice to get the range tuned better. I have the oscillators all in tune as per the Minimoog service manual using the 2' range. But when I drop to 4' or 8' the scale does not drop a full octave down. I have to readjust OSC2&3. Adjusting the RANGE pot throws the entire oscillator tuning off.

It's not a huge deal as I an just adjust OSC2&3 frequency controls a bit to compensate, but would be nice to fix if at all possible.

s it also possible to increase the noise gain as on my build it's quite low compared to the oscillators. I have not tried to tweak the VCA balance as I got a bit confused with the Minimoog manual - connect point A to point A malarkey

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Post by sk23 » Wed Aug 05, 2015 11:53 am

Guys I discovered that if I tune the synth to the high A and I switch down the octave using the octave switch the tune keep perfectly, but if I play on the midi keyboards the A at a lower octave the tune is loosed (it play a C note).

So I suppose that is something wrong with the cv \ midi section.

Assuming that I want to use the synth only via midi din, maybe I should use 100k for for R6 and 102k for R4?

Thank you

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Post by medbot » Wed Aug 05, 2015 1:18 pm

Have you guys done the octave calibration? That's a separate thing from the initial note-to-note calibration. You need to do both. I used a combination of the service manual and this text file I copied from somewhere to calibrate mine. It's been a while since I did it so I don't remember all the specifics, so you're on your own there, but these documents and a few comments from Crow in this thread will be everything you need to get it calibrated. I think you use the calibration notes for the third VCO type. You might also want to grab a free software frequency counter if you don't have a good tuner. Good luck!
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Post by sk23 » Wed Aug 05, 2015 1:41 pm

Thank you Medbot for the manuals.

I did both indeed the tune is kept if I scroll between octaves with the octave selector.

The problem appear when I use the midi input (no CV).
I suppose that the problem is the value of R4 and R6 resistors, at the moment they are both 121k.

If I want to use Crowminius via midi which between 1v/oct and 0.815v/oct is the correct configuration?

Thank you

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Post by medbot » Wed Aug 05, 2015 2:06 pm

The MIDI input does not bypass the CV, it gets mixed in with the external CVs before going into the exponential converter, which is what you're calibrating. You would most likely have the same tuning issues using a CV controlled keyboard with no MIDI, unless there is something wrong with the chip or your controller somehow. I wouldn't go changing resistor values arbitrarily unless I knew what I was doing (which I don't, in this instance). Do you have any experience calibrating VCOs before? It took me a while the first time I did it, and it sounds like you just haven't quite gotten yours zeroed in yet.

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Post by sk23 » Wed Aug 05, 2015 2:52 pm

thank you for the reply.

This is my first time in calibration, but on monday I went to a technician that projects and builds euro modules, he is 50 years old and has a lot of experience in tuning new and vintage synths.
He didn't menage to tune the crowminius across the midi keyboard.
In my opinion the fact that the synth keep the tuning when the octave is changed by the octave switch selector is an important indicator, you agree?

Today I read this note for R4 on the BoM

For 1V/Oct operation from external CV, change to 121K. 102K is for 0.815V/Oct using onboard DAC

I though if this 0.185v difference could be the reason for the variation of few semitones between A and A at the upper o lower octave when played with the midi keyboard.

This is possible?

Thank you

PS: My build has the pre programmed MCU offered by Crow.
medbot wrote:The MIDI input does not bypass the CV, it gets mixed in with the external CVs before going into the exponential converter, which is what you're calibrating. You would most likely have the same tuning issues using a CV controlled keyboard with no MIDI, unless there is something wrong with the chip or your controller somehow. I wouldn't go changing resistor values arbitrarily unless I knew what I was doing (which I don't, in this instance). Do you have any experience calibrating VCOs before? It took me a while the first time I did it, and it sounds like you just haven't quite gotten yours zeroed in yet.
Last edited by sk23 on Wed Aug 05, 2015 3:00 pm, edited 3 times in total.

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Post by Altitude909 » Wed Aug 05, 2015 2:55 pm

So is the panel designed to fit the PCB with all controls PCB mounted?

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Post by oldcrow » Thu Aug 06, 2015 12:54 am

This particular panel is. I can make a rectangular version that can be used off-board, however. I mainly wanted a panel for the briefcase for now. :sb:
Altitude909 wrote:So is the panel designed to fit the PCB with all controls PCB mounted?

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Post by oldcrow » Thu Aug 06, 2015 1:01 am

To use the MIDI MCU make sure R4 is 102K. If you are going to use the external CV/gate for 1V/oct keying make sure R4 is 121K. The onboard DAC uses an internal 4.096V reference, so in order to get 5 octaves of range I scaled the key CV response to 0.815v/oct. External CVs are not constrained to this 4.096V reference and so the more common 1V/oct. can be applied.

Crow
/**/
sk23 wrote:thank you for the reply.

This is my first time in calibration, but on monday I went to a technician that projects and builds euro modules, he is 50 years old and has a lot of experience in tuning new and vintage synths.
He didn't menage to tune the crowminius across the midi keyboard.
In my opinion the fact that the synth keep the tuning when the octave is changed by the octave switch selector is an important indicator, you agree?

Today I read this note for R4 on the BoM

For 1V/Oct operation from external CV, change to 121K. 102K is for 0.815V/Oct using onboard DAC

I though if this 0.185v difference could be the reason for the variation of few semitones between A and A at the upper o lower octave when played with the midi keyboard.

This is possible?

Thank you

PS: My build has the pre programmed MCU offered by Crow.
medbot wrote:The MIDI input does not bypass the CV, it gets mixed in with the external CVs before going into the exponential converter, which is what you're calibrating. You would most likely have the same tuning issues using a CV controlled keyboard with no MIDI, unless there is something wrong with the chip or your controller somehow. I wouldn't go changing resistor values arbitrarily unless I knew what I was doing (which I don't, in this instance). Do you have any experience calibrating VCOs before? It took me a while the first time I did it, and it sounds like you just haven't quite gotten yours zeroed in yet.

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Post by wahee » Thu Aug 06, 2015 3:36 pm

thanks medbot. I'm using 102K resistors and midi.

on the txt file there's

SHIFT
SCALE
HI-END
RANGE

on the Crowminius;

ZERO
SCALE
OCT
COMP

apart from scale, can you recall which matches with which

thanks
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Post by oldcrow » Thu Aug 06, 2015 4:20 pm

SHIFT = ZERO
HI-END = COMP
RANGE = OCT
wahee wrote:thanks medbot. I'm using 102K resistors and midi.

on the txt file there's

SHIFT
SCALE
HI-END
RANGE

on the Crowminius;

ZERO
SCALE
OCT
COMP

apart from scale, can you recall which matches with which

thanks

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Post by wahee » Fri Aug 07, 2015 5:50 am

oldcrow wrote:SHIFT = ZERO
HI-END = COMP
RANGE = OCT
wahee wrote:thanks medbot. I'm using 102K resistors and midi.

on the txt file there's

SHIFT
SCALE
HI-END
RANGE

on the Crowminius;

ZERO
SCALE
OCT
COMP

apart from scale, can you recall which matches with which

thanks

That's great Crow. Helped a lot

Osc1 & 2 calibrated good

Cant get Osc 3 to calibrate. It's fine at both ends of the range but a single octave can vary by as much as 40%. It's especially bad at range 8'

I'm using 102k for direct midi operation and all components are at least visually correct. C1 is 18pf as per BOM revision (although just a brown disk version I had in spares)

Any ideas where I could check

thanks
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Post by sk23 » Fri Aug 07, 2015 2:28 pm

Hi,
did you check if the OSC 3 control is on? I read on the calibration manual that should be on during the calibration.

Hope this help

That's great Crow. Helped a lot

Osc1 & 2 calibrated good

Cant get Osc 3 to calibrate. It's fine at both ends of the range but a single octave can vary by as much as 40%. It's especially bad at range 8'

I'm using 102k for direct midi operation and all components are at least visually correct. C1 is 18pf as per BOM revision (although just a brown disk version I had in spares)

Any ideas where I could check
thanks[/quote]

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Post by tuttlerecall » Wed Aug 12, 2015 7:45 pm

I am working on a rev 1.1 first round board. Is there a socket I can use on the board for the ATMEGA chip in case I want to try to update the firmware on it in the future without having to de-solder it?

Should all of the ICs except the LM3046 (with smt underneath) be socketed? Will the rest of the ICs make it without sockets?

Crow- You referenced earlier being at a point on a 1.1 board that you were done with all the components that use flux core solder. What do you use for the rest of the components?

Also it looks like currently there is no way to do both 1v/oct external CV and 0.815V/Oct using onboard DAC without re-soldering R4 and R6?

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Post by oldcrow » Wed Aug 12, 2015 10:56 pm

You can use any 300mil 28pin IC socket ("skinny DIP") such as
http://www.digikey.com/product-detail/e ... ND/4147600

You can socket all of the chips if you want. The VCO 3046s gain a small advantage in not being socketed but most of the temperature equalization between the 3046 and the tempco is made through the circuit trace, given the tiny thermal mass of the tempco.

I use water-washable solder aka Kester "331" (Kester part no. 24-6337-6401) for all hermetically-sealed parts. This means resistors, transistors, ICs and some capacitors.

I use a low-residue flux solder such as Kester no. 24-6337-8800 for things like pots, switches, aluminum caps, headers and jacks.

For external CV control you only need to worry about R4. In a future rev. I might add a jumper option for this.

--Crow
/**/

tuttlerecall wrote:I am working on a rev 1.1 first round board. Is there a socket I can use on the board for the ATMEGA chip in case I want to try to update the firmware on it in the future without having to de-solder it?

Should all of the ICs except the LM3046 (with smt underneath) be socketed? Will the rest of the ICs make it without sockets?

Crow- You referenced earlier being at a point on a 1.1 board that you were done with all the components that use flux core solder. What do you use for the rest of the components?

Also it looks like currently there is no way to do both 1v/oct external CV and 0.815V/Oct using onboard DAC without re-soldering R4 and R6?

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Post by evengravy » Sat Aug 15, 2015 12:44 pm

Sorry to stray off topic but have you looked at the teensy for USB midi. I've just did a major project with it and it is the business. The boards are more expensive vs arduino but worth looking at. I've just ordered from the August buy so might even have a crack at it. Doing it with an arduino isn't that simple unless the ftdi chip is replaced, the Leonardo can do it but otherwise I'd look elsewhere.

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Post by TheInherentFloyd » Sun Aug 16, 2015 6:29 pm

Quick question, 'cause I'm a little confused. Should the 2.32K resistors on Rev 1.1.2 (R23, R63, R101A) be used the with the SMT 3300ppm resistors or the their through-hole alternatives? Sorry, the BOM is worded strangely to me.

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Post by oldcrow » Sun Aug 16, 2015 8:03 pm

There are two things to note here.

1) If you use 2.32K, the tempco should be 100 ohms. If you use 23.2K, the tempco should be 1K ohms.

2) the type of tempco resistor can be either SMT or through-hole in either case of the above.

I provide a choice for these values and packages because some parts are easier to obtain than others, and some parts people already have on hand from other projects/repairs.

--Crow
/**/
TheInherentFloyd wrote:Quick question, 'cause I'm a little confused. Should the 2.32K resistors on Rev 1.1.2 (R23, R63, R101A) be used the with the SMT 3300ppm resistors or the their through-hole alternatives? Sorry, the BOM is worded strangely to me.

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Post by TheInherentFloyd » Mon Aug 17, 2015 10:29 am

oldcrow wrote:There are two things to note here.

1) If you use 2.32K, the tempco should be 100 ohms. If you use 23.2K, the tempco should be 1K ohms.

2) the type of tempco resistor can be either SMT or through-hole in either case of the above.

I provide a choice for these values and packages because some parts are easier to obtain than others, and some parts people already have on hand from other projects/repairs.

--Crow
/**/
TheInherentFloyd wrote:Quick question, 'cause I'm a little confused. Should the 2.32K resistors on Rev 1.1.2 (R23, R63, R101A) be used the with the SMT 3300ppm resistors or the their through-hole alternatives? Sorry, the BOM is worded strangely to me.
Ah, just a simple work around. Thank you very much. :bananaguitar:

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Post by wahee » Thu Aug 20, 2015 5:02 pm

sk23 wrote:Hi,
did you check if the OSC 3 control is on? I read on the calibration manual that should be on during the calibration.

Hope this help

That's great Crow. Helped a lot

Osc1 & 2 calibrated good

Cant get Osc 3 to calibrate. It's fine at both ends of the range but a single octave can vary by as much as 40%. It's especially bad at range 8'

I'm using 102k for direct midi operation and all components are at least visually correct. C1 is 18pf as per BOM revision (although just a brown disk version I had in spares)

Any ideas where I could check
thanks
[/quote]

hi yes I have set it up as per the txt file. It just won't track like OSc1&2.
All components are correct so i'm a bit stumped
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Post by oldcrow » Thu Aug 20, 2015 10:15 pm

Got the panel today. Aside from having to correct one hole the wrong size it all lines up perfectly. I need a few more 12mm brass screws for the front edge, and the actual production Crowminius will use PKES60 1/4 knobs for octave and waveform selectors (not the PKES90s shown), but otherwise this is how I originally envisioned the project. :sb: :sb:

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Post by mOBiTh » Fri Aug 21, 2015 4:24 am

oldcrow wrote: the actual production Crowminius
Looking good crow!

Can you clarify what your next step is with the Crowminius?

A more compact SMT version?

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Post by mrcase » Fri Aug 21, 2015 4:19 pm

Hey crow!

Thanks for this amazing project. I´ve preordered a board last week and was wondering if I could buy a preprogrammed chip with it. Will you have them back in stock and is it possible to add one to my existing order? It will be shipped to europe.

thanks and cheers
Martin

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