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

[Teddy]

Here i go again =)

attachment long_delay_2.zip
contains long_delay_2.mp3

Is it just me, but do i hear a lot of sizzling noise on the repeats?

Thanks,
-Teddy

[kothoma]

OK, I can hear the hiss. Don't know how much is normal.

Is it the same in every filtering mode?
It shouldn't. Depending on the selected filter more or less hiss should go away.

[Teddy]

Yes, the hiss is the same on every filtering mode.

Hiss goes away a little, when delay is shorter.

I'll try probing to find out when the hiss starts.

- Teddy

[Teddy]

Well, the odd thing is, that the hiss is louder when guitar signal is present while the delay sounds.
Like, playing a chord and holding it, instead of quickly strumming and muting strings.

Any ideas?

Also, when delay is turned down, the hiss is less audible.

Thanks,
-Teddy

[kothoma]

There's no hiss on the dry signal with mix all the way down?

The hiss is on the wet signal (the delays) only?
It is stronger while there's also a dry signal?

[Teddy]

Dry signal is good, with mix down. No hiss, when mix is all the way down.

The hiss is on the wet signal only (delays).

The hiss is stronger when there's also a dry signal.

Thanks,
-Teddy

[kothoma]

The hiss is stronger when there's also a dry signal.

But the hiss is already in the dry signal (after the mode switch or at the mix pot)?

[Teddy]

No hiss in the dry signal.

-Teddy

[kothoma]

Oops, sorry, wanted to ask:

But the hiss is already in the wet signal (before or after the mode switch or at the mix pot)?
So we can rule out the dry path and the mix stage.
The hiss comes from somewhere in the wet path.

Does this his go away with lower guitar levels?
The dry signal always also goes into the first delay line.
So the hiss could come directy from within the first PT.

[Teddy]

I'm not sure, if the hiss is present before or after the mode switch or mix pot.
(i will probe it today)

Hiss doesn't go away with lower levels.

Thanks,
-Teddy

[gtr2]

I don't see voltages anywhere in this thread.  Posting voltages of the IC's may possibly help.

Josh

[Teddy]

Hello!

What voltages do you need, specifically?

Thanks,
-Teddy

[Teddy]

Hello!

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.

Oh by the way, the distortion exists before the filtering section, probed it.

Thanks,
-Teddy

[Teddy]

Voltages of IC3 measured against GND

1 VCC = 5.02V
2 REF = 2.436V
3 AGND = 5.5mV
4 DGND = 5.5mV
5 CLK O = 2.997V
6 VCO = 2.436V
7 CC1 = 0.690V
8 CC0 =0.690V

9 OP1-OUT = 2.437
10 OP1-IN = 2.434
11 OP2-IN = 2.433
12 OP2-OUT = 2.433
13 LPF2-IN = 2.436
14 LPF2-OUT = 2.442
15 LPF1-OUT = 2.436
16 LPF1-IN = 2.436

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

1 VCC = 5.02V
2 REF = 2.439V
3 AGND = 5.7mV
4 DGND = 5.7mV
5 CLK O = 3.043V
6 VCO = 2.436V
7 CC1 = 0.685V
8 CC0 =0.690V

9 OP1-OUT = approximately 2.45volts, every pin from 9 - 16
10 OP1-IN =
11 OP2-IN =
12 OP2-OUT =
13 LPF2-IN =
14 LPF2-OUT =
15 LPF1-OUT =
16 LPF1-IN =

[Teddy]

Well, if there's anything more that comes to mind, that would help with my build of ZPSDX,
i'd really appreciate it.

Thanks,
-Teddy