AD3208 & the pinout problem

[rufustf]

Had a post up about my building woes and as it turns out one of my music students solved it! Others may benefit from this info so here it is.
The pinout of the 3208A available from small bear elec. is NOT THE SAME as the older ones the GGG board is designed for, aside from the fach that the board is sized to fit the "14 pin sized" 8 pin chip, and the available ones are the standard 8 pin size.
Here is the pinout for the small bear chip:
gnd=1
cp1=2
in=3
vgg=4
vdd=5
cp2=6
out1=7
out2=8

Here is the pinout that the board is designed for:
gnd=1
cp2=2
out1=3
out2=4
vdd=5
cp1=6
in=7
vgg=8

If anyone else has been pulling out their remaining hair trying to get the chips to work I hope that this will help. Now, I still only get one repeat out of the thing and the amt. of repeats pot doesn't do much, though I hope it's just a matter of dialing in the trimmers on a scope. I remember reading a post of some mods done to this circuit for more repeats/delay time. Anyone care to hip me to that? Or should the unit be kicking out more than one repeat as is? (How 'bout that, I get it working but still need help with it.)
Thanks-
Jason

[george]

The build notes on ggg have mods for increasing the delay level and no. of repeats - I've done them and they work well.

To increase the delay time adjust the 1M trimmer near the clock chip (MN310something) - I cranked mine all the way and still don't get any clock noise coming through with the delay control at max.

It's a great design - I bought a DM-2 on eBay just to compare and ended up selling it again, because the AD-3208 sounds exactly the same.

I'm surprised at the 3208 pinout issue, I used a BL3208 from smallbear and it works fine? (I've got an MN3205 in the other socket)

hth ...

[rufustf]

Yeah, I tried the mods and I socketed the resistors in question but still get only one repeat, only the whole thing is a lot louder with the 10K R for the unity gain. Think I'll put the 22K back. Only the delay time control seems to work so I've still got some work to do on it. It's good to hear a nice review of the unit, makes all the troubleshooting worthwhile.
I think the pinout issue is because I used the 3208A purchaced recently, when did you build yours? Could be different stock, or the BL3208 is different than the 3208A.
BTW, is the difference with the 3205 in one socket a great one or a small one?

[george]

I built mine about a year ago, so something may have changed ... probably best if you contact Steve Daniels, because his website says BL3208As are pin-for-pin compatible with MN3208.

The MN3205 just gives more delay - I was too stingy to get 2 MN3205s so I compromised and got 1 MN3205 and 1 BL3208A

My suggestion would be to re-check every component and go over the PCB in minute detail to check for cold solder joints and solder splashes that might be bridging PCB traces (easy to do with IC pins).  Maybe also check the value of the pots too.

I recall when I first tested mine, the effected level was a bit loud and distorted.  Doing the above check, I found that I had used a 1K resistor in the feedback loop of the 2nd op-amp stage instead of 10K - it's easy to mix up resistor values even if you are familiar with the colour coding.

Good luck - as you say it's well worth the trouble!