Calibrating an Aqua Puss/DM-2

[BDuguay]

I've got a scope and a function generator and found some info online but my experience with a scope is very limited not to mention it was 31 years ago that I was first introduced to a scope.
I'm asking a lot I know but would someone be interested in guiding me through the procedure step by step so I have a better understanding please?
Thanks,
B.

[Govmnt_Lacky]

Not sure from thread title if you want the AquaPuss or the DM-2 but... this might help with the DM-2 side

http://www.hobby-hour.com/electronics/s/schematics/dm2-adjustment.gif

[BDuguay]

That's one of the pieces of info I have, yes. The Aqua Puss is practically identical to the DM-2. I'm just not sure how to use my scope to get those results.

[Govmnt_Lacky]

Calibrating any BBD based pedal is usually (not always) the same. You need to check for 2 basic things:

1) CLOCK - You need to make sure the clock circuit is feeding the BBD the proper clock signal. That means proper timing AND proper signal level.
2) BBD BIAS - This is to ensure that the BBD is getting a good biased signal at the input.

Sometimes, there is also BALANCE adjustment and that is just to make sure that the (2) BBD outputs are aligned properly for the best output.

Are we talking about the AquaPuss or the DM2? If it is the AquaPuss, is it the MN3005 or 3205 version?

[BDuguay]

I've built an Aqua Puss, which, apparently and according to the schematics, is identical to a Boss DM-2. Mine uses the MN3005. Thanks for replying G.L.
You've been very gracious in the past spending your time to help me and for that I'm very grateful.
B.

[armdnrdy]

Here is a link to Brian's version of the Aqua Puss.

http://www.madbeanpedals.com/projects/Aquaboy/docs/Aquaboy2012.pdf

Scroll to the end of the PDF for calibration.

[Govmnt_Lacky]

Larry beat me to it... 

Brian's method is almost identical to that of the Boss DM2 info I posted above. Now, you just need to hook it all up and follow where it leads you 

For the Clock, use your oscope to measure at Pins 2 & 6 (independently) of the BBD. You are looking for around 6.8KHz at each pin.

For the Distortion measurements, you will need to feed the circuit with a good clean signal. Do you have a signal generator? If not, you will have to do this by ear with guitar.

BTW... Brian does not state it but, when measuring clock, you will want the Feedback full CCW, Mix at full WET, and the Delay is either going to be full CW or CCW to get the 6.8KHz. You will know when you see it.

Good Luck.

[BDuguay]

Yup, I built a Function/Signal generator from a kit I bought at my local electronics supply store. As for the Clock measurements, could I not use my DMM set to frequency and use that? My scope is an older one that doesn't give a frequency read out and I'm entirely sure how to do the math and figure it out from the wave on the screen.
Thanks all!
B.

[armdnrdy]

could I not use my DMM set to frequency and use that?

Yes you can.

Some years back...I had a problem while calibrating an A/DA Flanger build.

It turned out that my Fluke 87 had an upper limit below the upper frequency range of the A/DA.

I built a frequency counter with a 1Hz - 10mHz range from schematics on the net...added a power supply, and was good to go.

[BDuguay]

I had that exact same problem same with an A/DA Flanger too. My meter's range wasn't bog enough so I tok it to work and had a more experience co-worker measure it on a one of them there 'high faluutin' digital scopes. That's cool to know there are potential diy solutions to that problem. I'll try and get this calibration sorted first and then look into building my own frequency counter!
B.

[BDuguay]

Okay, I got the clock all set. Now for the BBD bias. I feed the pedal input with my signal generator set for 200z and scope exactly which pin of the BBD?
B.

[armdnrdy]

The output pins.

Here is the build document I made for the Mutron Flanger project.

Scroll to bottom of page. (reply #19)

http://www.diystompboxes.com/smfforum/index.php?topic=104959.0

There are instructions and useful images for biasing BBD circuits.

[Govmnt_Lacky]

Here is the build document I made for the Mutron Flanger project.

I remember that! Wonder why there weren't more builds of that beautiful pedal?   

[armdnrdy]

Here is the build document I made for the Mutron Flanger project.

I remember that! Wonder why there weren't more builds of that beautiful pedal?   

Well Greg...

I'm no doctor but....I believe that the DIY community is afflicted with the dreaded...FOTNFBC!
And there ain't no cure! 

[BDuguay]

The output pins.

Here is the build document I made for the Mutron Flanger project.

Scroll to bottom of page. (reply #19)

http://www.diystompboxes.com/smfforum/index.php?topic=104959.0

There are instructions and useful images for biasing BBD circuits.

I figured it would be the output pins but considering the luck I've had lately, I leave nothing to chance. And what in Sam Hill is FOTNFBC stand for?
B.

[armdnrdy]

And what in Sam Hill is FOTNFBC stand for?
B.

Fear Of The Non Fuzz Box Circuit.
I believe that it's a virus! 

[Govmnt_Lacky]

Fear Of The Non Fuzz Box Circuit.
I believe that it's a virus! 

I have actually had very good luck with BBD based circuits. I don't use uber ESD handling procedures either. Never (to this day) had one go belly up from handling. As long as you take your time and be diligent during building... things will work out!

Back on topic...

Doesn't the AquaPuss/DM2 have trimmers for BBD Input AND Output?

[armdnrdy]

Doesn't the AquaPuss/DM2 have trimmers for BBD Input AND Output?

I took a look at the PDF that I posted above....

Typical bias trimmer at the input and clock cancel trimmer at the outputs.

[PRR]

Biasing a BBD mostly means:

Bias too low, bottom of wave is cut-off; bias too high, top of wave is cut-off.

Of course if input signal is too big, top AND bottom are clobbered.

It is mostly a matter of finding least-distortion.

We used to do it (when BBD were still experimental) by ear or 10 seconds on the 'scope. Do not be intimidated.

For Hi-Fi, the dead-lowest THD is not-quite the same as what passes the largest signal without much harm. For guitar, I think fretting 0.4% or 0.5% THD on super-small signals is pointless, you want large near-clean signal.

[BDuguay]

Biasing a BBD mostly means:

Bias too low, bottom of wave is cut-off; bias too high, top of wave is cut-off.

Of course if input signal is too big, top AND bottom are clobbered.

It is mostly a matter of finding least-distortion.

We used to do it (when BBD were still experimental) by ear or 10 seconds on the 'scope. Do not be intimidated.

For Hi-Fi, the dead-lowest THD is not-quite the same as what passes the largest signal without much harm. For guitar, I think fretting 0.4% or 0.5% THD on super-small signals is pointless, you want large near-clean signal.

This is good to know, thanks!
FY'sI, I was going to finish up calibrating this bad boy when I discovered my delay pot was actually Log and Linear. They were mis-labelled at my local store. Argh!
It has the proper pot now and I will get this thing done and report my results.
I can't thank you all enough!
B.