Optimum voltage of pin 8 of MN3101 and MN3005

[chordball]

I'm currently working on converting a BYOC delay to accept MN3005's. Yes, 4 of them.

In doing so, I have only tested on the "short" function (the BYOC has a switch to bypass the last 3 chips using only 1 for shorter delays). I have made a perf daughter board to swap power and ground between pins 1 and 5, and have also removed from the board the 100K resistors to ground off pins 3 and 4 and placed these on the daughter board to power as needed for the MN3005.

It does work, but only one repeat. I suspect this is another problem altogether.

My main questions are as these: What is the optimum voltage of pin 8 on both the MN3101 and MN3005? (they are tied together) And what is the purpose of the 1n4148 diode (or similar) on pin 1 of the MN3101?

On the aquaboy and my Ibanez AD202, the voltage is around 0.95-0.97 VDC. On the BYOC, it is 1.60 VDC. Now, whereas the aquaboy and AD202 have a diode between the power and pin 1 of the MN3101, the BYOC has the diode between pin 3 and ground. I have experimented with the BYOC here and with no diode anywhere I get 0.99 VDC on pin 8. With a diode on pin 1 I get 0.94 VDC.

I do get delay with the 1.60 VDC, so is it worth modifying to have the diode on pin 1 and lowering the voltage, or should I leave it as is?

If you have any guidance here, please share! Thanks for reading

I've attached the BYOC delay schematic.

[madbean]

What is the optimum voltage of pin 8 on both the MN3101 and MN3005? (they are tied together) And what is the purpose of the 1n4148 diode (or similar) on pin 1 of the MN3101?

With the MN3101/MN3005 pin8 can either go to ground or left filtered by electrolytic cap. I've seen it both ways, so either is fine AFAIK. If you are reading a high voltage there, I suspect some kind of mistake somewhere...it should be close to 0v. However, on a 3205 type build, pin8 should be 14/15 of the Vdd voltage.

If you see a diode on pin1 of the MN3101, it's likely to drop the supply voltage a bit so it is slightly different than the audio supply voltage. There are different ways to handle it. The ABDX does it with a small resistor. In the same way, the ABDX uses a diode to drop pin8 down to the approximate Vgg voltage when doing a MN3101 and MN3205 combo.

[chordball]

Hey, thanks for the reply Brian!

I'm not seeing a high voltage there on the BYOC, just 1.60 V. But having experience only with the aquaboy and this AD202, should I be shooting for something lower (0.95ish V or maybe closer to 0.00 V)?

Do you have a quick explanation for why the clock supply voltage should be less than the audio supply, or perhaps have a reference I could read up on?

Thanks again!