Aquaboy Deluxe-15V-distorted repeats and runaway oscillation

[chromesphere]

Hey Maoriente,
i had distortion issues with the aquaboy for such a long time...i was using v3205's and there was NOTHING i could do to stop that distortion.  I frankensteined my build to the point of almost self-destruction...
The second i put mn3008's in, the distortion was gone.  Now i know you said you are using mn3008's, just wondering if they have been relabelled.  Where did you get them if you dont mind me asking?
The only noise you will get from mn3008's will be good noise, but i guess more like 'darkness' (no treble).
The whine sounds like the clock is still in the audio range, make sure you are biasing it properly.
This was the first video i made of the aquaboy (where it wasnt working properly), see if the sound samples sound the same as yours:

And here is where its working successful.  Again, point of reference for you and your build:

Hope that helps!
Paul

[MAO]

Thanks Paul, I watched your 1st Aquaboy vid yesterday, sounded like you were working with my PCB.

I bought the MN3008s from Sharpseller off EBay. They supposedly offer refunds, we'll see.

I also just purchased a set of MN3008s from you 2 days ago, hoping they will save the build.

Questions,

With legit MNs, when audio probing BBD 1 pin 3, is the signal completely clean or do you just bias for lowest distortion on pin 3? And then the circuit filters out the rest?

Also, the signal going in to the NE570 is completely clean, but comes out on pin 7 sounding a  bit overdriven. Is that normal? Same result with 2 different NE570s.

Thanks,
Mike

[teknoman2]

Questions,

With legit MNs, when audio probing BBD 1 pin 3, is the signal completely clean or do you just bias for lowest distortion on pin 3? And then the circuit filters out the rest?

Also, the signal going in to the NE570 is completely clean, but comes out on pin 7 sounding a  bit overdriven. Is that normal? Same result with 2 different NE570s.

Thanks,
Mike

When audioprobing on pin3 of BBD the signal is never completely clean, thats why you need to bias it to find the "sweet" spot with the lowest distortion.

Also are you using jumpers for R55 and R27?

When you have the delay pot on max and try to bias it you will always have a little bit of distortion when you hit hard your guitar.
Try to bias it with the delay pot halfway up and see how it goes.

Cheers,
Panos.

[march500]

Hey Maoriente,
i had distortion issues with the aquaboy for such a long time...i was using v3205's and there was NOTHING i could do to stop that distortion.  I frankensteined my build to the point of almost self-destruction...
The second i put mn3008's in, the distortion was gone.  Now i know you said you are using mn3008's, just wondering if they have been relabelled.

Interesting... If they were relabelled v3205s would they work at 15v? I just built an aqua puss on vero (similar to aquaboy right?) and had horrible distortion using 2x v3205's. Put in two working mn3205s from an old ad3208 build and it worked perfectly. The v3205s work fine in my ad3208 too! Funny how this circuit is sensitive to the v3205s. Hope you get this sorted Maoriente it's a good delay. Some legit mn3008's may do the trick.

[MAO]

When audioprobing on pin3 of BBD the signal is never completely clean, thats why you need to bias it to find the "sweet" spot with the lowest distortion.

Also are you using jumpers for R55 and R27?

[/quote]

Thanks, good to know there is going to be some distortion on pin 3. I was thinking there should be no distortion on pin 3. I did have the delay pot 1/2 up and had varying degrees of distortion when biasing with the trimmer, I would usually set the trimmer in the middle of both extremes.   

I originally had R55 and R27 jumpered, then tried 100k in R55 and 470k in R27. Didn't help, but left the sockets in place and currently have 1K in both R55 and R27.

At one point I did have the Aquaboy sounding fairly good with my humbuckers in split coil mode and when picking lightly in full humbucking mode. But if I hit an a chord, I still got ugly distortion on the 1st repeat. 

The strange thing is it seemed to sound better running at 9V rather than 15V. I've since re-biased the NE570 for the 9V supply.

Question; should the output of the NE570 sound a bit overdriven? It's not an ugly distortion but it sounds like an overdriven sound to me. The input to the NE570 is perfectly clean.

Now that I know there is going to be some distortion on pin 3, I'm going to try a reset things for 15V and give it a go again.
 

[Scruffie]

Half the 570 is working as a compressor, that means signal after it may be noisy and yes possibly overdriven sounding as it's bringing lower signal levels up.

There's no chance of a 3205 or 3208 being relabeled as a 3008, just wouldn't work.

An ESD damaged BBD could distort and be excessively noisy, that's quite possible and if you didn't properly handle the chips could be on the seller or buyers side.

The v3205 is not a drop in with a lot of stuff we build, it's an option and can work fine for some which is why it's nice to have the option on builds but firstly there have been a few batches of bad chips (high biasing point, hot outputs) and secondly a circuit specifically designed for them is going to sound better.

The issue of distortion could also be tracked down to an incorrect value, bad solder joint etc though, everyone is always quick to blame the BBD as it's the most expensive part and the heart of the circuit but there's a lot that goes in to a delay that can go wrong and the BBD is a small part. It can also just be down to expectations.

You're running at 9V sounding better suggests it may be your pickups, 15V does increase the headroom of the BBDs but 9V means there's less signal swing. But it could be that there's another issue that just means while that still holds true, it's less apparent.

The series resistance before the BBDs isn't really ideal for distortion reduction... it's not how i'd have done things but it is what it is.

[MAO]

Hello again, I received the MN3008s I ordered from Paul so it's time to give this a go again.

I've re-flowed the solder for the entire board and have double checked all part values.

Unfortunately, after replacing the MN3008s and re-biasing, the end result is the same.

At this point I have to assume the Dimarzio Tone Zone output may be causing the distortion, if I back off the volume knob and/or pick lightly the distortion isn't noticeable. But at the same time it's hard to believe this build can't handle a Tone Zone pickup...so I'm not convinced.

I'm going to get an Air Norton for the neck position, 270mv output as opposed to 375mv for the Tone Zone.

More later...

   

[chromesphere]

My Gibson SG is my go to, its got humbuckers, not sure how that compares to your guitar as far as output goes but it doesn't distort my aquaboy. 

The mn's should sound "dark" (lacking of treble) and maybe a little dirty, but not distorted (overloaded transistor or broken speaker cone distorted if you know what I mean), or "clipped", that's not working correctly. 

Have a listen to those videos of mine to work out if its the same sounding as the 'success'  video.  If its not, im not sure.  Assembly error (bridge, component value, etc), dead / fake compander, etc??