Aquaboy weird distortion

[Adam_DIY]

Have had a bit of a nightmare with this pedal it's been one of those builds where you think you have eveything then realise you're missing 1 part order it then when it arrives realise you're missing something else.  This happened 3 or 4 times. 

When I first tested it I wasn't getting any repeats then when checking voltages realised the ne570 was insanely hot.  I checked all my parts, reflowed a lot of solder joints then swooped the ne570 for another one ordered for my total recall.  W00t I now had repeats and the second ne570 wasn't getting hot like the other one.

I went on with trying to set the pedal up but no natter where I turn the bias trimpot I get a really nasty distorted farty noise if I hit the strings hard.  I swopped out the xvive mn3005 for another one and am getting the same problem.

I used the values for the aquapuss from the build doc.  My voltages are all very close to the ones in the build doc except for 3 pins on the ne570

Build doc.   My build
10 3.1          1.7
11 3.1          1.7
12 1.84        1.24

Anyone have any idea what could be wrong?  I'll upload some pics of the board if that might help

[madbean]

I would audio probe the circuit to see where the distortion is being introduced. You should check pins 6, 7, 14 or 15, and 10 or 11 of the NE570 as well as pins 7 and 3 or 4 of the MN3005.

Not sure about your voltage differences...where did you get your NE570 from?

[Adam_DIY]

I bought two of them from retroamplis.  The first one got really hot and was swopped for the one which is in it now which I thought was fine as i started getting repeats but am not so sure now I've checked the voltages. 

Are there other suitable substitutes I could use instead?  ne570 was pretty difficult to find from the uk.  I'll also probe the circuit tomorrow and see what I can find.

[teknoman2]

Probably your compander isn't legit and that's why you ve got stragne voltages or heat.
Try swap it with a coolaudio v571 and measure again your compander voltages.

[Scruffie]

The compander is just mis-biased on the expander outputs and so hitting the rails.

I can't remember the calculation off the top of my head but you should be able to stick a resistor from pin 12 to ground of the NE570 and that'll shift the bias, aim for 4.5V on pins 10 & 11 (or 3V if you prefer to keep it like the build doc, it shouldn't really matter).

Start with 10k.

Edit: If you get really stuck i'm in the UK too and probably have a spare compander.

[Adam_DIY]

Well I've ordered another two ne570s from Banzai which will probably take about a week or so to get here and I'll see how I get on with those. 

I'll report back when they're arrived and let you all know how I get on.

[madbean]

The compander is just mis-biased on the expander outputs and so hitting the rails.

I can't remember the calculation off the top of my head but you should be able to stick a resistor from pin 12 to ground of the NE570 and that'll shift the bias, aim for 4.5V on pins 10 & 11 (or 3V if you prefer to keep it like the build doc, it shouldn't really matter).

Start with 10k.

IIRC I think around 20k-24k from the old Aquapuss version...or maybe that was Bajaman's addition to his layout from around 2009.

Adam - I'd still suggest audio probing the pins I suggested. Esp. the inputs and outputs of IC2B (14/12 and 10/11) to make sure that's the only source of distortion.

[Adam_DIY]

Adam - I'd still suggest audio probing the pins I suggested. Esp. the inputs and outputs of IC2B (14/12 and 10/11) to make sure that's the only source of distortion.

Thanks Brian I'm going to do that when I get a chance but was ordering enclosures anyway and as they take about a week to get to me from Germany thought I'd grab some more ne570 from a different source just incase.

[Boba7]

Try different values for R13 and R14. In mine (running on 15v), I ended up with 56k for both to get 7.5v (half the power supply) on pin7 of the compander.
You could also try changing C30 : http://www.madbeanpedals.com/forum/index.php?topic=24783.msg241525;boardseen#new

[Scruffie]

Try different values for R13 and R14. In mine (running on 15v), I ended up with 56k for both to get 7.5v (half the power supply) on pin7 of the compander.

That biases the input compressor section which supposedly matches the build doc voltages so should be fine as is.

Although Bean's suggestion of audio probing would be wise to be sure it's not just the output bias affecting things.

[Boba7]

Try different values for R13 and R14. In mine (running on 15v), I ended up with 56k for both to get 7.5v (half the power supply) on pin7 of the compander.

That biases the input compressor section which supposedly matches the build doc voltages so should be fine as is.

Of course you're right, I just remembered it made quite a difference in my build and I ended up with values different from the build doc.

[Adam_DIY]

Well I've not had time to work on any pedals since I put this to one side a few weeks ago so hadn't probed it yet.  I came home from work today and an order from banzai had finally turned up with some enclosures and another two NE570. 

These are branded Philips and so far so good these work just fine the aquaboy sounds awesome I can't wait to box this up.  I'll check the voltages at the weekend and finetune the bias but there's no distortion and i'm pretty happy with the delay time.