Aquaboy DLX - compander voltages all over the place...

[Cortexturizer]

The MN3008s that I got from our dear Paul have arrived so I thought I should assemble the Aquaboy DX board.

IC1, IC5, IC6 voltages are spot-on on my build. The transistor voltages look fine as well.

The compander is all over the place. I used NE571N. I am powering the build with 14.9V provided via voltage doubling circuit using ICL7660SCPA and then stabilized down to 15V via a 7815. The compander voltages are as follows:

1. starts at 6 or so volts and then gradually falls down to 0.03 (?!)
2. 11.82
3. 11.82
4. 0.00
5. starts at 10.72 then slowly falls down
6. starts at 2V then slowly falls
7. same as pin 5
8. starts at 0.7 then falls

9. 12v stays like that
10. 9.32
11. flashes 11v then falls down (similar behavior like pins 5 and 7)
12. 0.00
13. 14.9
14. , 15., 16. - free fall, which results in almost zero volts

W the actual F?

Any ideas?

[Cortexturizer]

Guys, anybody?

What should I check first? As I said, my IC1, IC5 and IC6 voltages are spot on. Transistor voltages are as follows:

Q1: 6.60/6.89/14.9
Q2: 6.56/7.17/14.9
Q3: 5.07/5.65/14.9
Q4: 4.47/5.06/14.9

BBDs are getting voltage like they should, I think. Modulation works fine.

My compander behaves like I described in the first post. No idea what to look for. I've triple checked resistor values and caps, all fine. I have attached a picture of my particular compander.

[chromesphere]

Hey man,

Not sure about the compander voltages, I never got into it with my particular build (my problem was v3205's distorting).  Falling voltages sounds like you've definitely got a problem, obviously...I wont bomb you with the usual check points as your experienced im sure you have checked those (values,solder bridges, blah blah).

The mn3008's are verified so probably not the problem UNLESS you fried them somehow.  They are sensitive devices.  I would look at that compander first though.  Where did you get it?  I have heard there are knock offs going around.  Don't tell me that's ANOTHER component I have to start testing
Paul

[Cortexturizer]

Hey Paul, I got it from Musikding here in Europe. Thank you for your response. Dunno where to start looking for a possible error. I know that the BBDs are okay, I am getting ok voltages on them, and they came from you so I'm golden.

My voltages on the IC2 socket WITHOUT the compander in the socket are also weird. For example, on pin 6, which I would expect to see 7.4V after the 1uF capacitor, I get some dropping oscillation even without the compander in there. Majority of the troubling pins from my first post here are exhibiting a similar behavior. I have checked all resistors and they are good. My capacitors are good as well, they all have values written on them so it's easy to check.

In comparison with these voltages by Marioente (hold on in there dude!):



I even get the correct voltage on pin 1 on IC1, and all of my other voltages are similar to his if not downright exactly alike.
But when it comes to the compander, for example py pin 2 on the compander is 11.8 volts...

Complete madness.

[gitaar0]

A voltage doubler with a ICL7660SCPA is not going to provide enough miliamps to work well with an ABDX. It might be the source of your problems.
Maybe swap that ICL7660SCPA for a LT1054. Watch out as they need a little different set-up.

[Cortexturizer]

Hm, what is the current draw of the ABDX?
Luckily I have one 1054 at home.
Will report after trying. Thanks for the response

[teknoman2]

You don't need to swap the ic doubler, tc1044scpa and ic7660 gonna work very well.
Try to swap your compander with another one. Those are very sensitive.
A while ago when I was building a similar BBD analog delay I had some similar issues,
pin4 and pin12 where grounded. For pin4 is normal but not for pin12.
Get your multimeter on diode mod and check pin4 with pin12 if its beeping your compander is off.

Cheers,
Panos.

[Cortexturizer]

thank you teknoman2! you are very kind to response

I will report as soon as I've tried it at home. thanks again, I really appreciate it

[teknoman2]

No prob mate,
I am pretty sure your compander is off.
You shouldn't have ground on pin 12.
That's the most odd value of voltage on your compander.

Cheers.

[Cortexturizer]

Alright! This has been resolved, funny as it was, I actually did receive a damaged compander, as soon as I've put a new one in there I got textbook voltages. Did some more troubleshooting on a couple of places, gave a couple of resistors a good waggle and proceeded with the biasing by ear. I am very very happy with the sound!

But, now I have a problem with the output - it's way below unity. I can get the repeats to be above unity but the dry signal is ugly sounding and it's below unity gain. It also sounds kinda like...out of phase. But this may be me just trippin'.

Here's a sound sample of what it sounds like, starting with Mix on zero, then gradually increasing to full.

https://drive.google.com/file/d/0B--6F_4JB7SYMW9uam5tZG9jRU0/view

Panos, my dear analog delay mentor (teknoman2), proposed increasing R10, but I've done that all the way to 680K with gradual increments and it doesn't help. I am impatient to get this resolved so I wanted to hear your opinion guys. What do you think I should do judging from the clip? How do you like the sound overall?

Cheers

[Scruffie]

Your mentor i'm afraid has it wrong, what you've done there is adjusted the pole of the de-emphasis network, if you want to increase the delay level you should reduce R38s value and reduce R8 to increase the dry level.

The output should be non-inverted so perhaps you have an issue with Q1 or IC1A, it should be unity with some bass reduction. Quite possible you have a wrong value in the Pre-emphasis/De-emphasis network from the sound R5,6,7,9 & 10 and C3 & 6 in particular.

Also, I see early in the thread some questions about the charge pump chip, are you using the vactrol for the modulation? That adds some heavy mA draw, an 1044 or 7660 probably doesn't put out enough for the circuit to work properly.

[teknoman2]

I am afraid Scruffie got it right again.....
Try what Scruffie suggests and probably you will solve your issues.
Also when I built my aquaboy I used a tc1044  and a vactrol for the modulation and didn't have any issues.

Cheers,
Panos.

[Cortexturizer]

Scruffie the man! Thank you so much. Just tryng out the changes, will report shortly.
And no, I use a roll your own led/ldr combo and it works great on the modulation side of things.

[Cortexturizer]

alright!!
I had to decrease the R8 resistor all the way to 18K to get unity gain.
Here's what it sounds like with some fuzz - https://drive.google.com/file/d/0B--6F_4JB7SYcnRoUlAxak4xb1E/view

there is a lot of bass loss but I guess that's inherent to the design, right?

now I have to tickle with T1 to remove the oscillations happening early and it will be done I guess. thank you scruffie!

and to my mentor, the Greek powerhouse, mr Panos!

[Scruffie]

alright!!
I had to decrease the R8 resistor all the way to 18K to get unity gain.
Here's what it sounds like with some fuzz - https://drive.google.com/file/d/0B--6F_4JB7SYcnRoUlAxak4xb1E/view

there is a lot of bass loss but I guess that's inherent to the design, right?

now I have to tickle with T1 to remove the oscillations happening early and it will be done I guess. thank you scruffie!

and to my mentor, the Greek powerhouse, mr Panos!

18k is a big reduction to something that should be unity gain... I would look for a build issue.

Bass loss is inherent to a point...

I guess I was wrong on the modulation front, the delay portion isn't exactly current hungry but I assumed that'd push it over the edge with a (I think?) 20mA max draw.