How to calibrate AOUT_NG

[julienvoirin]

I'd like to know how i can calibrate the aout_ng without the MB6582 using a seq V4?

(clock is ok, start/stop is ok, gates are ok, IIC are OK, I got voltages on the AOUT_NG but i do not understand how to setup)

I do not understand the "bipolar " stuff : is it done for the Moog synth (-5V to +5V) ?

The only Cv/Gate stuff i know is the one of the x0xb0x : CV from 0 to 4V (1V/oct) and a gate at +12V (very fast)

thanks in advance

[seppoman]

I'm not familiar with SEQ V4, but I guess there's some menu page where you can set values for each CV channel. If that's not the case and you got some PIC core you can connect the NG to it and use the MBCV application for calibration.

The basic principle to calibrate it for 1 V/Octave mode is to first set the output value to maximum and adjust the trimpots so that the output is at 10.67V. As most synths only make use of a few octaves, you can then determine a few other measurement points and try to get as close as possible to e.g. 1V, 2V, 4V, 8V. All DACs have some nonlinearity so maybe there's a setting of the trimpot where e.g. the range of 0..4V is matched better although e.g. the error at 8V is larger than with another setting. To get it really as good as it can get, you can easily spend one evening with a multimeter and a screwdriver ;)

Calibration using the MBCV app is described on the MBCV manual page.

And the bipolar mode - there's some synths that require bipolar CVs, e.g. if you use it as one of several CV sources for a VCA in a modular synth, you might have one envelope and one LFO that is mixed on the VCA input, so a bipolar CV will enable you to have the LFO not only add but also subtract a value from the EG. - If you don't know what to use it for at the moment, I suppose you don't really need that function right now :)

S

[julienvoirin]

to calibrate it for 1 V/Octave mode is to first set the output value to maximum and adjust the trimpots so that the output is at 10.67V

let's focus on channel one. the seq send G8 as note, the highest one

1 - without jumper i got -10.62V

2 - with jumper in unipolar, i've got 0V. Whatever i turn P1 it doesn't do anything, it stays at 0V. Changing Note doesn't affect the value.

3 - when jumper are in bipolar, i have -2.6V or -1.4V depending if I put only one or both jumpers.

I badly cabled the AOUT_NG at the beginning and let it during 1 min like this. The DAC was very hot. Is it possible it burned ?

[seppoman]

1 - without jumper i got -10.62V

without any jumper, the output OpAmp has an open input so the output will show a more or less random value.

2 - with jumper in unipolar, i've got 0V. Whatever i turn P1 it doesn't do anything, it stays at 0V. Changing Note doesn't affect the value.

not good :/

3 - when jumper are in bipolar, i have -2.6V or -1.4V depending if I put only one or both jumpers.

only one jumper isn't a valid setting, the output won't be connected to the DAC either. It doesn't make sense to use the bipolar setting at all as long as there's no output in unipolar mode. As you've got 0V in unipolar, you can only add a negative offset to your 0V.

I badly cabled the AOUT_NG at the beginning and let it during 1 min like this. The DAC was very hot. Is it possible it burned ?

Hot ICs are always bad, that should never happen. I once fried a DAC during testing, so it is possible to destroy them. What did you do when it got hot? As long as you don't apply any voltages or ground to the jumper pins (especially to the one pin coming from the DAC output) you shouldn't be able to do anything with the jumpers that kills the DAC.

When I fried my DAC, it was only one channel that was damaged. So maybe first try calibrating another channel to find out if the DAC is still partly alive and if the connection to the core etc. is alright.

Special offer - if the DAC is really broken and you don't know how to replace it, you can send the module to me together with a new DAC and I will swap it for you :)

S

[julienvoirin]

Special offer - if the DAC is really broken and you don't know how to replace it, you can send the module to me together with a new DAC and I will swap it for you :)

S

thank you

i will check this afternoon now that i burned the bootloader into PIC at work using the midibox_cv

thanks for your offer but i got 4 spares in advance and i know how to desolder this s**t ! :ninja:

moreover i did not test with the aout_ng #2

can i update the wiki thereafter if it works ?