This sounds really interesting and I'm tempted... but...
I assume there's no chance of hearing a good quality before/after recording with identical patches played identically? :P
I want to judge the noise level myself before tearing things apart :)
BR,
Peter
----- Original Message -----
From: Oakley Sound
To: PolySix@yahoogroups.com
Sent: Friday, July 12, 2013 6:37 PM
Subject: [PolySix] Making the P6 brighter
I've been following Chip's progress with interest. And his recent post
on the dynamic noise reduction filter on the effects board spurred me
onto to investigate further. I too have noticed that the P6 is somewhat
duller than other synths and I had always assumed that with the ensemble
mode off the output was as bright as it could be.
Chip's findings that all four ensemble modes pass through the DNR filter
was something I hadn't really thought about before.
http://synthhacker.blogspot.co.uk/2013/02/mystery-circuit-polysix-post-effects.html
In summary: the P6 has a 12dB/octave low pass filter that is set to
around 600Hz (the actual value depends on whether the BBDs are engaged)
when no notes are playing. This filter opens up when it detects audio
from the voice card. As Chip noticed it takes a finite time for the
filter to open and the filter doesn't always open fully in all cases. I
measured the filter took up to 100mS to open fully. That's a significant
loss of high frequency sound at the start of each note.
Yesterday I went a stage further than Chip. Chip's mod basically forces
the filter open. I decided to remove the filter from the circuit
altogether. This has the advantage of no dynamic filtering (which is of
dubious amenity) and reduces the circuit pathway that the audio has to
go through. The LM13600 isn't a hi-fi part and removing it improves the
signal quality.
The mod:
Remove links J28 and J29. Remove R115 and R109 (which disables the
envelope follower). Remove C73 and C61.
Link out, with a piece of solid core wire, the two left hand holes of
J28 and J29. Now connect with a piece of insulated wire the lower of
these now filled solder pads to the lower pad of C73. The filter is now
bypassed.
Link out, with a piece of solid core wire, the two holes of C61. This
capacitor serves no useful job that I can see.
Result: the P6 can be as bright as any synth. Percussive sounds ring out
where they didn't before. String sounds are really very majestic - you
can really pull off sounding like a string machine now. The slight
increase in background hiss is not a problem for me.
Tony
http://takla-makan.bandcamp.com/
http://www.oakleysound.com
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