RE: MKS-80 VCO Tracking - Update

From mikekent
Sent Tue, Sep 10th 1996, 00:35

>From: Larry Andersen <larry@merge.com>
>Date: Mon, 9 Sep 1996 10:13:41 -0500
>Subject: MKS-80 VCO Tracking - Update
>
>I just spoke to a tech  at a Roland service center.  He says that this is a
>minor adjustment in tracking.  I'd love to buy that except the fault doesn't
>seem linear across the keyboard.  One octave high, the next one low, etc.
>Wouldn't a tracking problem be linear causing the drift to be larger as you
>move down the keyboard?

Not necessarily. Some synthesizers do have a linearity adjustment which can
cause this type of problem.

Does the tuning problem exist immediately after you press the tuning
button? If I remember correctly, the initial tuning on power up and when
you press the tuning button on the CEM VCOs in the MKS-80 is digitally
controlled. There may be a fault in this part of the synth.

Some CEM3340 as used in the MKS-80 were prone to these problems even when
new from the factory. The digital tuning overcomes this. If the digital
tuning procedure is not working correcly then this problem might be
explained. Roland used to test each CEM for tuning problems. The best CEMs
were used in SH-101 where no digital tuning procedure existed. Other CEMs
were used in MKS-80 and Jupiter-6 where the digital tuning could easily
adjust for tuning problems in each VCO.

Actually, your problem may be related to tuning between voices, not between
various notes on the keyboard. Does a note play the same pitch every time
it is played? To find out you should rotate through voices:
  1. Set Poly 1 Mode.
  2. Set the VCOs to Sync or turn balance to hear only one VCO.
  3. Press the tuning button.
  4. Play C4 and note the tuning
  5. Play a cluster of more than 8 notes in a different range of the keyboard.
  6. Play C4 and note the tuning
  7. Repeat steps 4 and 5 several times.
Is the tuning in steps 4 and 6 consistent? If not, the tuning is different
between voices. If so, then I think the tuning is related to overall scale
linearity of all voices. To test only voice 1 for scale and linearity:
  1. Set Poly 2 Mode
  2. Set the VCOs to Sync or turn balance to hear only one VCO.
  3. Press the tuning button.
  4. Play Each C across the keyboard and note the tuning
Is the tuning correct between octaves?

Regards,
Mike.

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