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

[Teddy]

anyone? bumping...

=)

-Teddy

[kothoma]

It's distorting either because of the diode clamp across the feedback pot

But the diode clamp is after the pot and he said it distorts at any feedback level.
I understand that already the first (not feedbacked) repeat is distorted.
So I would exclude this.

or simply because PT2399s will distort with a signal larger than 2.5v.

Either this or one of the feedback loops around the internal op amps is wrong, causing too much gain.
So either the input level of the delay line is too large or the output level gets too large somehow.
That's my best guess.

[kothoma]

Ok... i tried the ZP SDX with a drum machine, output level @ max
i hear no distortion ! crazy...

Then with a guitar, distorts badly.

Are the two input levels comparable? Can you measure them?

I built myself a simple audio probe, to listen to the signal.

OK, what do you hear after the first PT2399?

[Teddy]

hey, did you check the .zip files containing mp3's?

they were posted an hour ago

please, comment on them
is there anything wrong, or am i just dreaming...

Thanks
-Teddy

[kothoma]

hey, did you check the .zip files containing mp3's?

they were posted an hour ago

please, comment on them
is there anything wrong, or am i just dreaming...

As I don't have one to compare (yet), I don't really qualify to comment on them.
Through notebook speakers it doesn't sound too bad to me
Need to listen again through my nearfield monitors.

What settings did you use?

[Teddy]

Hey, im not sure of the settings, as i haven't put knobs on it =) =) =)

I think there's too much noise when using the long delay time

Oh, and to your suggestion on debugging the circuit:



When you say, probe after the first PT2399:

do you mean to sound probe after R14?
Where it connects to R21,R15, and R16?

[kothoma]

Yes, or before R14 directly after C16.

[Teddy]

Okay, i probed after c16

probe result: i hear a delay, that has a slightly noisy artifact.

-Teddy

[kothoma]

Noisy or distorted?
Next queck at C31.

[Teddy]

noisy, not distorted...

ps. i did reflow some solder joints that seemed bad, and i think the distortion vanished.

but now i'm struggling with the noise/hiss issue

[kothoma]

ps. i did reflow some solder joints that seemed bad, and i think the distortion vanished.

Bingo! Congratulation!

[Teddy]

I presume this is the same point as point A on the rotary selector.

I hear a delay, its ok sounding. A bit of hiss.

But the problem with hiss is, that when i play while the delay is sounding,
the noise somehow amplifies. it's hard to say how it is, but that's
why i posted those sound files. =)

Thanks,
-Teddy

[kothoma]

but now i'm struggling with the noise/hiss issue

Perhaps you should try a few different PT2399 more?
They seem to vary much in quality.

[Teddy]

will do!

i'll report after changing PT2399's.

- Teddy

[Teddy]

Okay, i changed the PT2399. Last fresh pair i have.... =)

Tone changed a bit, but the hiss problem is still there.

I'll post a new sound sample soon.


Thanks,
- Teddy