Buchla with TSNM plus Analog Shift Register

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reverberation
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Buchla with TSNM plus Analog Shift Register

Post by reverberation » Wed Feb 19, 2020 6:15 am



Here's something I recorded last night.
A simple eight step sequence from the TSNM which goes to the Northern Light Modular 2OC (the old version) in Analog Shift Register mode which sends the sequence to three oscillator. A forth oscillator is playing the pulse drone.

I'm adding some fx off screen while recording.


Anyone else having trouble with their TSNM? It's always been acting weird. When I purchased it (built by the previous owner) I could sometimes clock it from an external source. That doesn't work anymore and hasn't worked at all for almost two years. Anyone else know this issue and how to fix it? The tempo knob is supposed to be fully counter clockwise in order for it to receive a clock signal. When I turn the knob to that position, all that happens is that the sequencer is being played super slow.

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batchas
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Re: Buchla with TSNM plus Analog Shift Register

Post by batchas » Wed Feb 19, 2020 7:37 am

Nice :tu:

Quite a serious system you have here :sb:
reverberation wrote:
Wed Feb 19, 2020 6:15 am
Anyone else having trouble with their TSNM? It's always been acting weird.
Yes. Not always doing the same. Something works and then does not anymore. Kind of weird.
I'm not refering to clock, but in general.
Pers. I'd need more time to spend on it, cause I stopped after trying it and being a bit annoyed (impossible to save a preset, touch pad reacting, then not reacting anymore, but it's not a soldering issue, etc).
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Re: Buchla with TSNM plus Analog Shift Register

Post by jimfowler » Wed Feb 19, 2020 7:39 am

First of all: cool tune.

I’d pull the tsnm and start by checking that the clock input (banana) signal is actually getting to its destination. A quick continuity test will confirm this.

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Re: Buchla with TSNM plus Analog Shift Register

Post by reverberation » Wed Feb 19, 2020 8:51 am

Thank you, good people!

I'm going to remove it and check now. It's sometimes stops triggering for a step or two as well. And the clock pulse from the internal clock isn't too stable. Fluctuates a bit from time to time.

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Re: Buchla with TSNM plus Analog Shift Register

Post by tarandfeathers » Wed Feb 19, 2020 9:03 am

jimfowler wrote:
Wed Feb 19, 2020 7:39 am
First of all: cool tune.

I’d pull the tsnm and start by checking that the clock input (banana) signal is actually getting to its destination. A quick continuity test will confirm this.
I don't think this is the issue. When the clock pot is fully CCW the Teensy should register that that pin 22 (analogue input 8) is at 0V and stop using the internal clock so if there were no external clock input it should just stop dead, not advance slowly. It sounds to me very much like the output of the pot is not sufficiently close to 0V.

I would unmount the TSNM from the case and measure the voltage on the wiper of the pot when set fully CCW, between the AGND pin and pin 22/A8 (see here for pinout: https://cdn.sparkfun.com/datasheets/Dev ... a_rev1.pdf), again with the pot set fully CCW, and between the AGND and GND pins on the Teensy.
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Re: Buchla with TSNM plus Analog Shift Register

Post by tarandfeathers » Wed Feb 19, 2020 9:16 am

reverberation wrote:
Wed Feb 19, 2020 8:51 am
Thank you, good people!

I'm going to remove it and check now. It's sometimes stops triggering for a step or two as well. And the clock pulse from the internal clock isn't too stable. Fluctuates a bit from time to time.
I think the missed triggers is kind of a known issue (I believe when this happens the step still advances but no trigger is generated at the pulse out jack, correct?). I don't think I have had any issues with clock rate varying or saving/recalling presets though.

It'd be nice if it was updated someday to at least address those but it doesn't seem like any development is happening anymore, I guess there was a plan at one point to make an expander panel with extra touchplates but that doesn't seem to have happened. I'd really love to be able to set note priority and allow holding one note down whilst changing notes over the top then returning to the held note (the MPR121 supports this as it outputs the status of all pads, not just the most recent one)
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reverberation
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Re: Buchla with TSNM plus Analog Shift Register

Post by reverberation » Wed Feb 19, 2020 10:31 am

I tried moving it to another case just in...well...case. Same issues. Both cases are original Buchla.

Tarandfeathers - Thank you for you input! When I have the time (hopefully tomorrow) I will measure the voltages. Note to self - bring the multimeter to the studio tomorrow!

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Re: Buchla with TSNM plus Analog Shift Register

Post by batchas » Wed Feb 19, 2020 11:51 am

tarandfeathers wrote:
Wed Feb 19, 2020 9:16 am
I don't think I have had any issues with clock rate varying or saving/recalling presets though.
If you know a link to a video showing saving/recalling presets working, I'd be very thankful. Or any well documented "how to do" actually, so I could exactly reproduce and compare, it would be great.
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Re: Buchla with TSNM plus Analog Shift Register

Post by jimfowler » Thu Feb 20, 2020 7:44 am

"It sounds to me very much like the output of the pot is not sufficiently close to 0V."

This was going to be my next suggestion (really and truly but was headed out the door for work) but it was going to be way less articulate because unlike tarandfeathers I don't know what the hell I'm talking about.

Since I'd like to learn, how exactly does this aspect of the module work? I see that the clock pot is attenuating the 3.3V input to analog input 8 (A8) on the Teensy. Is it in the code/firmware that if A8 input is 0V then watch for/activate pulse (pin 3)?

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Re: Buchla with TSNM plus Analog Shift Register

Post by tarandfeathers » Fri Feb 21, 2020 6:07 am

jimfowler wrote:
Thu Feb 20, 2020 7:44 am
Since I'd like to learn, how exactly does this aspect of the module work? I see that the clock pot is attenuating the 3.3V input to analog input 8 (A8) on the Teensy. Is it in the code/firmware that if A8 input is 0V then watch for/activate pulse (pin 3)?
That's pretty much it in a nutshell. That pin is configured as an ADC and when the value read by the ADC is in a particular range the external clock will be used in place of the internal clock to advance stages/trigger the arp/etc.

As an example, lets say the teensy has 12 bit ADCs (I'm not sure the actual spec without looking it up). That would give 4096 values across the range from 0V to 3.3V, just over 0.8mV per step. Lets also say we want the external clock to be used whenever the pot is less than 5% through it's travel - we know that 0% is 0V and 100% is 3.3V, so we want anywhere up to 3.3V*0.05 or 165mV, that would mean that any reading from the DAC between 0 and 205 results in the external clock being used. A reading of between 206 and 4095 will result in the internal clock being used, with the speed relative to the actual value read, so 206 might be 40bpm and 4095 would be 250bpm. If the scale is linear and goes in 1bpm steps thats 3890 ADC steps to represent 210 possible values, or about 18 steps per 1bpm change, and 18 steps equates to about 14.5mV change on the wiper of the pot.

In reality it's probably not that simple, because you'll never get a perfect 0V or 3.3V on the pot, there's noise on the signals (hence the 100nF cap on the pin in question to LPF the voltage from the pot), the ADC won't be perfectly linear in response, and you might want the behaviour of the pot to be something other than linear so that you have finer control in the most useful range of speeds so you might sacrifice resolution at the lower and/or higher end to make the control feel more usable/intuitive, but these are firmware/software issues, and I have no insight into how the firmware for the TSNM is implemented. If there's no intention to develop it further it'd be nice to have the source made available but I don't know how likely that is to happen....
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