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Is 225h CV more accurate than 225e?
MUFF WIGGLER Forum Index -> Buchla, EMS & Serge  
Author Is 225h CV more accurate than 225e?
maxl0rd
Hi gang

The pitch outs (E-H) on my OG 225e are not quite accurate enough to drive my pair of 25S oscillators. They are OK for percussive stuff that just needs to be in the ballpark, but more tuning sensitive stuff sounds pretty off.

BTW the issue with the 225e seems to be quantization, not scaling, so it can't really be improved with further signal conditioning, attenuators, etc.

I'm curious if the 1.2V CV out in the 225h module is better calibrated or higher resolution, and a better choice for stuff with analog CV inputs.
tIB
Are you sure the 25s isn't the problem?
maxl0rd
Good question. Yea.

I checked the voltage out of the 225e on a meter and it’s kind of all over the place.
Drillionaire
The 225h uses the same DAC as the 225e, but the 225h has a precision voltage reference for its DAC, whereas the 225e uses the 5v rail of the system as its reference, which is far from precise.

I also seem to recall that there is a custom lookup table for the pitch voltage out on the 225h to compensate for the non-linearity of the particular DAC used. I don't know for certain though if that's the case.
tIB
maxl0rd wrote:
Good question. Yea.

I checked the voltage out of the 225e on a meter and it’s kind of all over the place.


I ask because I've never noticed an issue with my 225e driving a pair of 258. How all over the place is it- maybe reflashing the firmware on the 225 might be worth a shot? Drillionaire is probably the best person to have the ear of on this though so take my advice with a pinch!
ArguZ
If you want a proper front side Midi to CV, get a MUC-810 from Anthony.
That one runs circles around the 225e.
https://www.youtube.com/watch?v=v8KqcJvCJvo

Then again, i like my 225e just fine using the internal midi bus for the DPO and the 261e.
Synesthesia
yeah, i have a MUC-810 - brilliant module .

would only go for a 225e for the program manager smile
Nejrup
It's been up before, but my 225e puts out around 1.13v per octave. However you can just calibrate you 25S to compensate. Calibrated mine 25S and it tracks perfectly with the 225e

(I don't think you gain anything from reflashing the firmware..)
mutierend
I am in the process of selling/trading my 225e. I have the 282e on the way for preset management and I'm using a CV.OCD for MIDI.
maxl0rd
I got the meter out again, and my memory was wrong. The 225e really is just scaled down to 1.14 / octave as Nejrup notes. I also checked the 5V rail, since Drills says that's the reference and found it's 4.96V. So the 5V rail is within 1% tolerance, but the CV out is off by more like 5%.

But the scale is very regular, a steady .095/note. So it's def possible to get decent tracking by scaling the outputs.

Calibrating the analog vcos to match isn't an enticing option, since I also have a marf and a 251e which put out a reliable 1.2V.
JamieDrouin
Checking to see if anyone else has experience with the 225h driving a 25S and whether this combination provides accurate tracking results? I would like to add MIDI (front wired CV, not bus MIDI) to my small system if this combo will be a good match.
ArguZ
Actually, same as papz noticed the 218e is not output buffered, that might be the case for the 225e too.
So, if you use an original Buchla oscillator which inputs are high impedance it might work.
I am not sure if the 25S is the same.
Can you try to measure the outgoing CV at the 225e without a cable connected and then one time with it ?
If it drops 0.8V we found the problem.
The only thing i can think of that will fix for more than just one specific oscillator this is a buffered quantizer.
jimfowler
No dog in this hunt but there's just no acceptable excuse for such inaccurate output...and the notion that one should have to calibrate their oscillators to make up for this inaccuracy is just plain dumb. I've built a midi-to-cv converter for this format for substantially less that tracks flawlessly for as many octaves as you want. It's a combination of midisizer midi-to-cv and a quartet of synovatron's cv and gate-to-pulse converters.
blw
ArguZ wrote:
If you want a proper front side Midi to CV, get a MUC-810 from Anthony.
That one runs circles around the 225e.
https://www.youtube.com/watch?v=v8KqcJvCJvo

Then again, i like my 225e just fine using the internal midi bus for the DPO and the 261e.


Thanks for raising the issue. Timely for me . . . I've never used midi with my 200e and was just looking at a used 225e.

Am I reading above that the internal bus's outputs are quantized correctly but the external channels are not.
ArguZ
No, you are reading that the 225e has a certain output impedance that matches an original Buchla 200 e system input impedance and none of those are either input or output buffered as it seems.
So lets say you connect something with a low input impedance to a voltage divider on the input side, for example a trimmer that acts as CV scaler, you will see a substantial voltage drop that is the result of the two low impedances.
One of them needs to be buffered or the input needs to be lets say 100 times higher.
A good solution is to have lets say 500 ohm on the output and 100k on the input.
If you mix that with a pot it only drops 0.05V circa.

I need to recable my midi but i will make some test on sunday and see what my 225e produces..
I have seen the exact problem you describe, but not with system 200 e stuff but with third party things.
Especially with DIY things where the wrong pot has been used.
dougcl
blw wrote:

Am I reading above that the internal bus's outputs are quantized correctly but the external channels are not.


Yes in the case that the 225e delivers MIDI note information to the e-oscillators, the oscillators seem to do very well playing the correct pitch.

Meanwhile, the 225e CV outs are not 1.2V per octave. I got everything to track using a Studio H CSR. Unfortunately I did not note whether boost or attenuation was required, and I can't remember. Reports above that the output is 1.14V/oct suggest I was using the CSR to boost the signal to 1.2V/oct.

Doug
ArguZ
I just made some tests, using Doug's DPO and a 261e and i can absolutely confirm that.
I sent a 8 octave sequence or C notes to it and they come trough like this

0 - 1,19 - 2,37 - 3,55 - 4,73 - 5,90 - 7,07 - 8,26 - 9,44

So, that is not all bad and can be compensated for.
A quantizer with attenuated inputs could rectify that but then found out that the note output the 225e generates comes AFTER the pitch value...so the quantizer is alway one note behind :-D

The internal Bus A-D on the other hand fire the 281e, the 292e and track over the full range.

Conclusion, if you wanna drive anything pitch correct using patch cables, get a MUC-810
JamieDrouin
Feel like I might require a flame suit for asking this one: Has anyone (successfully) tried the Microfreak as a MIDI to CV controller of 200e modules? Arturia support claims that the optional 1.2v/oct and 10v gates are Buchla-friendly, and with no negative voltages. Has anyone put this to the test?
ArguZ
Technically i would support that idea.
Ethically, not so much lately.
JamieDrouin
Oh, I hear ya...just looking at my options as my faith in the 225h has been shaken after this discussion.
ArguZ
Well, i totally love it for what it does.
I essentially saves me around 16 cables, takes care of accurate pitch , clocks my 250 and 252 and also offers some modulation taken from the midi keyboard...stuff like a mod wheel, pitch bend or an XY pad.
WHat it is not for is to drive clones and third party oscis .
Both the impedance as the inability to outputs a proper 1,2V on the front makes that hard without extra quantizers or specially tuned sound sources.

But for that reason Anto32 built that amazing MUC-810
https://www.modulargrid.net/u/other-unknown-muc-810-

I had that one when i still had clones and it works perfectly fine.
The 225e really makes more sense with a lot of e only
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