Remix/ReMangle" Challenge is Closed. Now to work on the file management, uploading, playlist, voting thread, etc. Thanks to all that participated. Get ready to vote!

Prizes generously donated by:
ADDAC System (Eurorack 3U)
Endorphin.es (Eurorack 3U)
Fred's Lab (DIY Paraphonic Synth)
Northern Light Modular (Buchla-format h-series OR Eurorack3U)
Rattly and Raw (Wiggler Approved Kontakt Instrument)
Studio.h (Buchla-format 4U)

Challenge rules and format thread is here.

EFG build issues

Discussion and support for users and builders of Oakley Sound musical products.

Moderators: Kent, Synthbuilder

Post Reply
User avatar
Leverkusen
Super Deluxe Wiggler
Posts: 2454
Joined: Mon Jul 29, 2013 2:26 am
Location: Rungholt

EFG build issues

Post by Leverkusen » Mon Jul 13, 2020 6:04 am

Hi there,

I just completed an EFG (board 6, simple version) and it basically seems to work, just not quite right.

What does work is, that an audio signal gets boosted as I would expect and I can grab it from the PRE OUT.

Also a CV signal that is somehow related to the audio amplitude is emmited at CV OUT and the LED goes with the CV amount.

GATE LED ist lighting up as expected too and reacts to THRESHOLD and RESPONSE.



Now what does not to seem right is that on GATE OUT I get something like a very, very fast gate rolls when the LED is on, while I would expect a single gate. This does not react to RESPONSE in a noticable way.

Also the CV OUT is very heavily slewed. There is no way to get a fast response. SPEED control has the effect that at about 8:00 (not fully CCW) there is the shortest resonse, which is still quite slewed but one can recognize the original amplitude flow. Beneath and beyond the slew gets heavier from mid position on it just increases and does not go down anymore until it reaches maximum.


I deviated from the buidling guide at some points but cannot judge how or if this could be related to my issues:

Firstly I ha no 10k lin dual pot for the GAIN control and thought a 50k lin should also work. Then I accidentally got on the deluxe part of the BOM ant some point and populsted the two 2u2 film capacitors at C43, C45. I left them there as I expected them to be not connected to the rest of the ciruit.

Worst mistake was placing U6 in the wron orientation. The whole system did not power up then. I noticed the mistake, turned it around and it worked like described. My first atempt to fix it was replacing the IC with a new one, but with no effect.

Unfortunately the behaviour is too unspecific and my understanding of circuits too basic to find a strating point in the schematics and I would appreciate any ideas where to start. I can't even make out what the misplaced IC could have damaged...

User avatar
Synthbuilder
Super Deluxe Wiggler
Posts: 3214
Joined: Tue Mar 24, 2009 9:12 am
Location: Cumbria, UK

Re: EFG build issues

Post by Synthbuilder » Tue Jul 14, 2020 4:07 am

Leverkusen wrote:
Mon Jul 13, 2020 6:04 am
Firstly I had no 10k lin dual pot for the GAIN control and thought a 50k lin should also work.
It won't work as it should. You'll get a mismatch of gains between the two stages. You should replace that with a dual 10K linear as soon as possible.
I accidentally got on the deluxe part of the BOM ant some point and populated the two 2u2 film capacitors at C43, C45. I left them there as I expected them to be not connected to the rest of the circuit.
They won't do any harm if you have fitted them. Although you could take them out and use them in another project as they are quite expensive parts to leave doing nothing.
Worst mistake was placing U6 in the wrong orientation....
Since replacing U6 didn't change the fault the problem is likely to be elsewhere. However, U6 does control the V2164 (U5) directly, and maybe when U6 was put in backwards it may have damaged the V2164. The V2164 is configured as a low pass filter. The cut-off frequency of the low pass filter is what the 'speed' control affects. How fast the CV output is allowed to change is controlled by the speed control.

Check that the control voltage to the V2164 is responding correctly. Measure the voltage on pin 1 of U6 and rotate the Speed control. Check that the voltage goes from around +2.5V to 0V. If it does, it could be that the V2164 has been damaged. However, it would be wise to check all the components are correct around U5 just in case.
Now what does not to seem right is that on GATE OUT I get something like a very, very fast gate rolls when the LED is on, while I would expect a single gate.
Check that C17 is a 680nF capacitor and that R27 is 10K.

User avatar
Leverkusen
Super Deluxe Wiggler
Posts: 2454
Joined: Mon Jul 29, 2013 2:26 am
Location: Rungholt

Re: EFG build issues

Post by Leverkusen » Tue Jul 14, 2020 11:54 am

Thank you Tony, for the support!

What I already tried last night was (apart from desoldering those two caps) exchanging the V2164 (from Coolaudio) with a new one, checking every single part in the filter section and replacing D9. I also tried replacing U4. Voltage at U6 pin 1 goes from 2.2 to 0.0 when turning SPEED clockwise. C17 and R27 are right too.

I ordered a single 10k pot (ouch!) from Banzai and will try again when it is replaced.

User avatar
Leverkusen
Super Deluxe Wiggler
Posts: 2454
Joined: Mon Jul 29, 2013 2:26 am
Location: Rungholt

Re: EFG build issues

Post by Leverkusen » Sun May 16, 2021 12:09 pm

I had put this on the shelf for some time but now finally got back to it and got it to work. It seemed that some of the 100nF caps actually weren't 100 nF, which I cannot understand how this could have happened. I might have sorted them in the worng box when I got them. Stupid. Also the soldering on one pin of one IC looked suspicuos.

Anyway, now I get CV and gates following the input and all knobs do what they are supposed to do which is great. Though the Pre-Output signal is quite distorted as soon as I crank the input gain up to near clipping level. On the other hand when I dial it back to clean the CV output won't be hot enough to open a VCA or a filter to a reasonable amount - is this to expect? I have the switch set to 1x and feed an external piano module into it at the the usual 'line level' output vollume.

The distortion sounds nice but I would rather like to have it as an option. And yes, I did change the gain pot to 10k.

Or is it just like that?

User avatar
Synthbuilder
Super Deluxe Wiggler
Posts: 3214
Joined: Tue Mar 24, 2009 9:12 am
Location: Cumbria, UK

Re: EFG build issues

Post by Synthbuilder » Mon May 17, 2021 2:02 am

Leverkusen wrote:
Sun May 16, 2021 12:09 pm
Or is it just like that?
No, that doesn't sound right.

There are several possible reasons for this but I'd be tempted to look at the full wave rectifier circuit first. That's the bit at the top of page 1 on the schematic. Check that D12 and D13 are the right way, and that R2 is 2K and R24 is 470K.

If you have a scope then put a triangle wave signal from a VCO at around 220Hz and look at the signal at pin 7 U2 (it should be a triangle wave from -5V to +5V), and then at pin 8 U6 (this should also be a triangle wave but at twice the frequency and from 0V to 5V). That same signal should be seen at pin 14 U6.

User avatar
Leverkusen
Super Deluxe Wiggler
Posts: 2454
Joined: Mon Jul 29, 2013 2:26 am
Location: Rungholt

Re: EFG build issues

Post by Leverkusen » Mon May 17, 2021 7:55 am

Thanks Tony! Though I am confused now - the building guide says R2 should be 100K but R23 and R5 should be 2K. That's a typo in your post above, right? The values on teh board are as listed in the guide. The Diodes are alright.

When I feed in a triangle wave and set the input gain so that the output goes from -5V to +5V than pin 7 U2 mirrors the same wave. At pin 8 U6 I get a clean triangle at double the frequency, though from 0 to -5V and on pin 14 U6 the same wave but from 0 to +5V and with a small distortion at the upper peak of the wave. All signal amplitudes are reacting to the input gain pot in the same way.

EDIT: Also from looking at the scope, my impression is indeed that the preamp is fine and the signal distorts later in my mixer because I have to crank the amp up to get a usable CV signal out of it. That's why the distortion does sound so good... ;-)
Last edited by Leverkusen on Mon May 17, 2021 9:15 am, edited 1 time in total.

User avatar
Synthbuilder
Super Deluxe Wiggler
Posts: 3214
Joined: Tue Mar 24, 2009 9:12 am
Location: Cumbria, UK

Re: EFG build issues

Post by Synthbuilder » Mon May 17, 2021 8:49 am

Leverkusen wrote:
Mon May 17, 2021 7:55 am
Though I am confused now - the building guide says R2 should be 100K but R23 and R5 should be 2K. That's a typo in your post above, right?
Sorry, my mistake. Yes, that should be R23 is 2K. I missed off the 3.
When I feed in a triangle wave and set the input gain so that the output goes from -5V to +5V than pin 7 U2 mirrors the same wave. At pin 8 U6 I get a clean triangle at double the frequency, though from 0 to -5V and on pin 14 U6 the same wave but from 0 to +5V and with a small distortion at the upper peak of the wave. All signal amplitudes are reacting to the input gain pot in the same way.
OK, that looks good. And yes, my original reply had the wrong polarity for the voltage on pin 8. That'll teach me for posting in a hurry.

Presumably the audio output at 'pre out' sounds undistorted with that level of signal?

With the same +/-5V triangle wave input and with the gain control set to get a 0 to +5V peak signal at pin 14 of U6, the peak LED should not be lit. Now turn up the gain control to get the peak LED to just light up. What's the signal voltage at pin 14 of U6? It should be still a triangle wave at 440Hz but now going between around +10V and 0V.

What's the voltage at the slew output socket look like with the speed turned up full? And what does it look like when the speed control is turned to its minimum setting?

Post Reply

Return to “Oakley Sound Systems”