[sdiy] Odyssey square wave not square?

[Chris Kay]

Hi Grant,

I removed the HPF slider pot and it tested OK - around 1Meg at its maximum
extension, which is the position it needs to be in for the HPF lowest
setting. Sweeping the HPF does exentuate the tilt, so I had come to the
conclusion that it was HPF related. Somebody also suggested that there may
be a problem with a DC blocking cap, so I'm going to replace all of the
tantalum caps when I can summon enough enthusiasm to pull the whole thing
apart again.

I've  managed to do all the board A and B calibrations and it's sounding a
lot better than when I got it, so for now, I think I can probably live with
this square wave problem.

Cheers,
Chris

On 11/29/05, Grant Richter <grichter at asapnet.net> wrote:
>
> You don't mention what frequency you are talking about.
> The amount of tilt should vary with frequency.
> My guess:
> The high pass filter section is not going to it's lowest setting.
> What you are describing is simply the effects of high pass filtering
> (the one after the low pass before the VCA).
> The cap or slide pot may be bad.
>
> On Nov 26, 2005, at 8:56 AM, Chris Kay wrote:
>
> > Hi,  I have an Ody MKII (2813) which I 've been trying to
> > calibrate. If I set it up as follows:
> >
> > osc. 1 keyboard tracking on
> > osc. 2 sync off
> > PW slider fully down
> > filter freq. slider fully up
> > VCA gain slider fully up
> > osc. 1 (or 2) to audio fully up
> > all other sliders down
> >
> > I've noticed that when I monitor the high gain output with a scope
> > and send a square wave from one of the osc's, I don't get a square
> > wave out. I get something that resembles a shark's tooth pattern
> > and doesn't sound square, it's sort of buzzy, not hollow. I've
> > calibrated both square wave ouputs from board B(II) using the osc.
> > PW trimmers to get nice looking 50% pulse waves.
> >
> > Further more, when I select the sawtooth on either osc. and monitor
> > the high gain, I don't really get the classic ramp, rather an
> > initial spike followed by an exponential downward curve with some
> > small 'wobbles' on the tail. Again the sawtooth output from board B
> > looks like a nice classic sawtooth.
> >
> > Clearly something's happening to the signal in board C(II). Does
> > anybody have any ideas? All suggestions gratefully accepted.
> >
> > Cheers
> > Chris
>
>
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