Aquaboy - ridiculously noisy

[the3secondrule]

<edit> don't use 2n3904's in place of mpsa18's - 2n5088/9's work much better ....

i've bullt maybe 3 or so aquaboys, and this is the first one to give me grief
i'm using v3205, v3102, v571 and LF353
the only mods I have made are increasing r31 to 47k, to reduce feedback, and reducing r15 to 39k

I am getting extremely dirty delays, but the main problem is when the mix is turning anywhere past 0, i get a high pitched whine, that gets hugely loud, extremely fast

I need to go back over the board and check values are correct (for about the 10th time)
but I thought I'd post some voltages and see if anyone else can spot anything:

v3205
0
3.3
3.6
3.6
7.4
3.3
3.7
6.3

v3102
6.8
3.3
0
3.3
3.4
3.3
3.3
6.3

v571
1.1
1.8
1.8
0
1.8
1.8
2.9
1.8
1.8
3
3
1.8
9.16
1.8
1.8
1.3

lf353
4.5
4.5
4.5
0
4.5
4.5
4.5
9.1

[the3secondrule]

Also - didn't have mpsa18's so I subbed 2n3904's - would that cause a problem?

would 2n5088's be a better sub?

[gtr2]

The only other transistor I'd use besides the mpsa18 would be a mps6521.

Josh

[jimmybjj]

I use 2n5089's that sound good. My build was with mn3005

[the3secondrule]

I use 2n5089's that sound good. My build was with mn3005

cool -  have heaps of 2n5088/9's - i'll give them a try

anyone wanna chime in on my voltages though?

[gtr2]

On first glance they look ok.  If I get a chance I'll take a look at my v3205 build to compare.  It seems as though your clock noise isn't being filtered through the compander.  You may have to audio probe around and see if you can find the culprit.

Josh

[the3secondrule]

yeah, I ended up replacing the 3904's with 2n5089's -

Problem solved :-)

[Haberdasher]

Good to know.  I bet BC549c or BC550b would work as well- just be aware the pins are reversed.

[bigmufffuzzwizz]

Good to know.  I bet BC549c or BC550b would work as well- just be aware the pins are reversed.

That's good to know. I'll have to make note of it cause i just grabbed a bunch for some muff goodness...
I have 2 aquaboys to build so I'll make sure no 3904's! 
Do any of you know if there is anything sonically different between the two different aquaboy build options (IC's)?

[hoyager]

Apparently, and from personal experience, the v3205 chips work best at 7v and get more distorted above 7.3, and I guess the same when 'undervolting'.

Check this build report and thread

http://www.madbeanpedals.com/forum/index.php?topic=1553.0

It describes adding a resistor in series from the + leg of c15 (33k, 39k) which lowers the signal  going into the chips, clearing up the delay sound. This is when using 2 chips though, not sure if its necessary or whether it works with just 1 chip.

Andy