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Oakley ADSR/VCA V1 2001 Issue
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author Oakley ADSR/VCA V1 2001 Issue
abelovesfun
Hello,

I built a V1 Oakley ADSR/VCA but while setting it up I discovered an error. Instead of the approximate 5V I should be getting from the ADSR + output, I'm getting approximately 13V.

I pored over the schematic last night, and tested all components and connections - All is as it should be, including power and ground on chips, with one exception:
Even though the R79 is a 100k resistor, as it should be, I measure only 25k.

Any hints? I had some extra TL072s and swapped those, but don't have extra of the other chips to swap out at the moment. Has anyone else ran into this?

Thanks so much - very humbling.....

Abe
Synthbuilder
Are you getting an ADSR type signal on the NC lug of the CV input? That is the ADSR pad on the PCB. You should be getting an ADSR signal that goes from 0V to around 8V, when triggered by a gate, on that point.

What are you getting on the -OUT?

Tony
abelovesfun
Synthbuilder
My apologies for the late response, I only just received my oscilloscope. I am still learning to use it, but I think I'm doing it right. I can see the envelope out of my TTSH properly.

Here is what I see from the ADSR pad (linked to the CV pad):
https://www.youtube.com/watch?v=Hd2iCcULktE

I get nothing from the - out.
Synthbuilder
I'm not seeing anything on the video link as it requires me to sign in to a Youtube account.

However, I did notice on your photo of your module that pin 3 of the power header on the PCB doesn't appear to be connected to anything. Can you make sure that pins 2 and 3 are connected together. I would use a small piece of solid core wire, like a resistor lead clipping. It may not make any difference but without it the ground tags of your sockets will be floating.

Tony
abelovesfun
Synthbuilder
thank you for your reply and assistance! Pins 2 and 3 are connected on the other side of the board, here is a pic:

My apologies for the bad video link, here it is again:
https://www.youtube.com/watch?v=Hd2iCcULktE
Synthbuilder
OK, I can see the video now. I'm not sure what's happening there. My first thought is that the scope input is set to AC. You'll be wanting it on DC to measure the output of the ADSR. AC is useful for measuring small AC signals riding on top of a much larger steady DC voltage.

If it is on DC then I've no idea of what it wrong - possibly the 4052 or its control signals.

Tony
abelovesfun
Synthbuilder
Wow! You were totally correct, I had it on AC. Sorry, I'm still learning the scope. Here is a video of the output when in the DC mode.
https://youtu.be/pV7jy2gMfkg
The video starts with nothing probed to establish a base, then I probe the ADSR pad. I'm struck by how much voltage the envelope is putting out, that is probably a clue, yes? Thank you so so much for your help.
Synthbuilder
Alas, there's not much more that I can suggest without having it on the bench in front of me. It's clearly misbehaving.

All I can suggest is to run through each component in turn and make sure it is what it is supposed to be. For example, a 10K resistor is just that and not a 10R and so on.

One easy one to check is to make sure that U7 is definitely a 4066 and not a 74HC4066.

Also, check the voltage on pin 7 of U8. It should move up and down with the position of the sustain pot. That is, it should go from 0V to around 9V.

Tony
Ytoki
Question about modular levels into an audio interface and the ADSR/VCA module itself:

i) I have a Steinberg UR22 with specs as shown below. Is it ok to run an output from the Oakley modular directly into one of these inputs? (eg for calibrating VCOs when building etc) or do they need to go through a VCA to attenuate? I understand the modular levels are far hotter than line level but the dBU, dBV & p-p relationships are beyond me!

LINE INPUT 1/2 (Balanced)
Maximum Input Level +24 dBu
Input Impedance 20 kΩ
GAIN Range -14 dB to +30 dB

HI-Z INPUT 2 (Unbalanced)
Maximum Input Level +5.8 dBV
Input Impedance 1 MΩ
GAIN Range +0.8 dB to +44.8 dB

ii) With the ADSR/VCA module am I correct in thinking the peak output (after the attack stage) is always going to be the full level of the input into the module - the module itself won't attenuate the peak? Does this mean you need to go through another VCA to bring the peak output down before going into an audio interface or mixer?

All help greatly appreciated.
Synthbuilder
Ytoki wrote:
I have a Steinberg UR22 with specs as shown below. Is it ok to run an output from the Oakley modular directly into one of these inputs?

The line level is the one to use. +24dBu is very big - bigger than the Oakley modular can produce even with the outputs at clipping. So your interface will be handle anything the modular can throw at it.

Here's a nice page to convert dBu into volts:

http://www.sengpielaudio.com/calculator-db-volt.htm

The norminal signal level in a MOTM modular is expected to be 10V peak to peak (7.2dBu).

Quote:
With the ADSR/VCA module am I correct in thinking the peak output (after the attack stage) is always going to be the full level of the input into the module - the module itself won't attenuate the peak? Does this mean you need to go through another VCA to bring the peak output down before going into an audio interface or mixer?

The gain of the VCA within the ADSR module is unity (no gain, no attenuation) at the attack peak and sustain at 100%. There is no need to attenuate further when going into a decent audio interface or mixer.

However, I find that sometimes the modular does produce a very hot signal for other things like effects units and some less pro interfaces and mixers. I then use a 10dB pad (attenuator) which cuts the signal down by about a third.

Tony
Ytoki
Thanks for the advice Tony. It's good to hear the modular will play nicely with my other gear!

I'll be in touch to place an order for some PCBs.
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