BL3208 reverse voltage

[Dimitree]

Hello
I have done a PCB design of the EH Deluxe Memory Man, using 4x MN3008 (based on the reissue original schematic). The power is -15V.
Now since I'd like to build another one or two copies, I'd like to use the much cheaper BL3208B.
The pinout is the same but the voltage required for this chip is 10V max.
I was wondering, since I've seen DMM clones with MN3005 that was powered reversed using +15V instead of -15V, could I do the same and power BL3208 using -9V (-9V on -V pin and Ground on +V pin)? If yes, I would only need to supply -9V to BBDs pins and the rest of the circuit with -15V, with minor modifications to my PCB and partlist.

[armdnrdy]

I've never seen a positive voltage BBD IC powered with negative voltage but......in theory....it should work.

The ground pin (- 9 volts) would be more negative than the VDD pin (0 volts)

You would also have to change the VGG resistors to compensate for the difference from -15 to -9 volts.

Edit:
That's odd...I just looked at the -15 volt DMM....the VGG pin is connected directly to -15 volts.

[Fender3D]

...
The pinout is the same but the voltage required for this chip is 10V max.
...

Just to be....

the pinout is the same BUT 32xx needs Vdd positive respect GND.
It will need output pulldown resistor(s) too...

BTW
If you copycat DMM schematic, remember that you must reverse supply and GND refs for 3208 only

[Dimitree]

but what happens if I power the whole circuit with -15V as intended, and then I supply +9V only to BL3208?

[armdnrdy]

Since you have a working -15 volt DMM, check the clock output voltage (pins 10 & 11) of the 4047.

Check the MN3208 data sheet to see if the clock inputs can accept the stock DMM clock voltage.

[Dimitree]

Yes they should be compatible since people over madbeanpedals forum clone the DMM using the CD4047 and on the same PCB they can put MN3005 or MN3205.. They use positive voltage for the BBD.
I need to do exactly the opposite..so the question is: can I supply MN3208 with +9V and at the same time the rest of the circuit with -15V?

[armdnrdy]

Since you are starting out with -15V....why not feed the BBD -9V through a negative regulator?

[Dimitree]

yes, but I guess to do that I need to order some BL3208 and try

[bean]

Cross posting from the MBP forum in case it is helpful here:

You can use BL3208 in place of MN3005 (if you use 2x for every one MN3005). You do not need to use reverse polarity to power it, but you need to set the BBD jumpers on the board to match the v3205 instead of the MN3005. This flips the power and ground between pins 1 and 5. The Dirtbag runs on negative ground no matter what BBD you are using...the needed change is in the jumpers.

Sonically, I much prefer the BL3208 to the v3205 and you will get closer to an MN3005 with them IMO. They do have better headroom and also the decay sounds better to me. However, the max voltage you can use is 10v on the BL3208. So, you might consider using a charge pump on a 9v supply then regulating it down with a 10v regulator (yes they do exist). Also, you will need to adjust the two resistor values on the compander so that the output voltage on pin 7 of your NE571 is about 5v.

A side note: you know that hugely expensive Toneczar delay? It's 8xBL3208 running on 10v (the rest of the audio path is 15v). FYI.