Zero Point SDX, help needed: Why the delay distorts when strumming loud?

[kothoma]

Voltages of IC3 measured against GND

3 AGND = 5.5mV
4 DGND = 5.5mV

Voltages of IC 2 measured against GND (they are essentially the same as IC3...)

3 AGND = 5.7mV
4 DGND = 5.7mV

Shouldn't those be at 0.0V?

[Teddy]

I put the GND of multimeter to 9V wall wart power supply -

when checking with continuity meter, i get 0.6ohms resistance, measured
from AGND/DGND to GND.

I quess, that explains why i see 5.7mV.

[kothoma]

What do you get if you check against the G pad on the board?

[Teddy]

When measuring against board GND, i get 0.00V

[kothoma]

So that's fine.

The other voltages look reasonable to me.
Perhaps someone can compare them to an actual build.

[Teddy]

Ok, what's next?

[kothoma]

One more audio clip.
long_delay_noise_3.zip

Delay = MAX
MIX = MAX

This clearly shows the issue.

When delay is backed down, to almost minimum, then there is almost no noise.

So the dry signal is clean as long as there are no delays mixed in.
The delays are OK as long as there is no dry signal.
While the dry signal sustains and delays are mixed in there is hiss.

As this also happens at lower levels I don't suspect the mix stage (IC1B).
So the hiss probably is generated within IC2/IC3 or around them.
The ghost switch is off? (Have you checked R21/R22? They are on a path where dry signal could bleed into the delays if they are too low.)

[Teddy]

R21 checked = 220k
R22 checked = 150k

[kothoma]

This hiss. You not only hear it at the output but also in the wet path after the first delay line?

[Teddy]

yes, it's in the wet path as well.

but i have to sound probe again, to be sure about first delay line.

But when probed from after C31, i'ts hissy and dirty. (selector point A)

And, when i turn delay time to shorter, the dirtiness vanishes.
When delay time is minimum, sound is ok.

[kothoma]

when i turn delay time to shorter, the dirtiness vanishes.
When delay time is minimum, sound is ok.

As already mentioned this is to be expected, to a certain degree.
PT2399s are far from being HiFi.
But these are really hissy. And I suspect it's them.
All from the same batch?

[Teddy]

yes, all are from the same batch
from the same vendor

[Teddy]

I will go tomorrow to shop more PT2399
From a different vendor.

But hell, i went through 6!! of the PT2399, and none work.

damn... if it's the PT2399's.

=)

-Teddy

[kothoma]

If you're positive that the component values and the soldering are right then perhaps you should try to get different PTs.

You don't happen to have a Rebote Delay or Cave Dweller nearby to test them?

Sorry, I have no more ideas, at least for today.

[Teddy]

No, i don't have other delay pedals to try PT2399 with.