Re: [LAU] Clipping as a 64-bit issue?

Am Samstag, 26. Mai 2007 schrieb Ken Restivo:
> I've noticed the same strange behaviour in two completely different peices
> of software/hardware, and have to wonder if it's a integer-size issue.

> Integer overflow? Byte order? In other words, are lower-order bytes getting
> swapped around with higher-order bytes, and thus sending the signal level
> through the roof?

Lets look at it...

> First of all, the AZR3 LV2 softsynth clips on my 64-bit machine. Really
> bad. Lars looked at it, and gave me the action item to go digging through
> the source and test the sound at various points in the processing chain, to
> try to isolate it further. Which I am still going to do.

I can't comment on the insides but any plugin should use floats/doubles. But
swapping bytes of a double results in _very_ funny numbers and therefor very
_strange_ noise...

> Then, I noticed the exact same problem with the *inputs* on my M-Audio
> Audiophile USB interface (it is big-endian). This is a new problem too, and
> I don't know what could have changed to cause it. The noise floor on the
> line inputs went way up into the -30db range, and even the lowest, faintest
> mic-level input will cause it to clip! There is no ALSA mixer interface on
> this unit so I don't know of any way to lower the levels. But seems very
> similar to the problem with AZR3 on the same 64-bit machine.

If this was a byte-swapping-issue you would hear real ugly sounds at this
problem too.

I would suspect a hardware-problem: Probably the input has a preamp to raise
the volume (that works well) and a preamp to pad the volume down again and
that second stage failed. (Maybe only the feedback of last stages OV failed
rendering the pad-unit useless.)

> Anyone else had these kinds of problems?

I do have some similar problems with my tascam: every year the input preamps
fail. But in my case its the feedback of the preamping OV which causes the
preamp to have an ultra fast rise in the amplification curve. It was in
repair several times and needless to say that this happened again (at least
on one channel) after the warranty expired. :-( Have to talk to my electronic
expert at university...

Arnold

-- 
visit http://www.arnoldarts.de/
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