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Re: Vortex live (long)

Julia & Dave wrote:

> Incidentally, I had a JamMan and a Reflex, and both seemed to
> be humming a little.  I thought this had to do with the adapters,
> but now that I have the Vortex which is the quietest device I
> have ever heard in the lower price range, I am beginning to
> suspect the hum was being carried thru the MIDI input.  Is this
> possible at all?

David,

it is possible. The MIDI connector uses pins two and four (directly to
left & right from the centre pin) for the MIDI signal, using a
opto-coupler (and thus theoretically hum-free) current loop, BUT the
connector shell is used as a shield, connecting the ground levels of the
two connected devices via the cable shield (MIDI specs require a twisted
pair for the signal, shielded together, although youĞre not very likely
to find any of these cables). This connection can create a ground loop
and this way hum.

Remedies:
1. Cut through shield connection in the MIDI cable. This is not possible
with some devices, especially with things like Anateck Pocket products,
which get their power supply via the MIDI cabling. Also you might pick
up interference with long MIDI lines.

2. Disconnect the unfused earth connector of one of the devices. This is
only possible if the device has this connector, and should be used with
caution - I would only recommend it with devices with no touchable metal
parts.

3. Experiment with the ground connections in the devices, where possible
(like in the EMU Proteus).


        Rainer

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