Volume pedal to use with Mainstage and keyboard. Also Macbook PSU earth issue.

[Owen]

I am souping up the church keyboard system. I am using an Ernie Ball volume pedal between the macbook and the stage box. It works on the last 10% of travel. Clearly not the ideal taper! What do I use?

While I have your attention, the PSU for the mac is not earth friendly. I can run it on the battery but inveriably when I am not there we get user error and I would like to make it as difficult as possible for them to get it wrong. New PSU o'clock?

[floFC]

Regarding the Mac, the issue is not the PSU as such but the detachable plug bit The short one is not earthed, but the long one (I.e a cable extension) is earthed.

[BigRedX]

Problem #1 the volume control.

Using a volume pedal most likely designed for instrument level signals on a line-level output is probably never going to be great. What you should be using is a pedal that sends MIDI messages directly to MainStage. CC#07 is the controller number for MIDI volume.

 

Problem #2 Earthing.

Are you actually getting earth hum? It should be the same with either plug/cable as with the cable version while the lead itself has an earth connection the PSU that it plugs in to only has live and neutral contacts. How are you connecting the Mac to the stage box? I use an ART DTI box between the audio interface and the PA which completely isolates it and kills any earth hum.

[floFC]

The PSU has an Earth contact, it is the round metal bit the adapter slides on. If you check carefully, the cable extension has some metal connectors in there, whereas the short adapter is all plastic (no earth).

[BigRedX]

3 minutes ago, floFC said:

The PSU has an Earth contact, it is the round metal bit the adapter slides on. If you check carefully, the cable extension has some metal connectors in there, whereas the short adapter is all plastic (no earth).

So it does. I'd never noticed that.

Weird I can't see any reason for the plug only not to include an earth contact unless the two versions are deliberately engineered that way so you have an easy way of choosing whether or not to have an earth connection to the PSU. In which case I would have thought it would be mentioned somewhere in the literature that accompanies the macBooks.

[floFC]

21 minutes ago, BigRedX said:

So it does. I'd never noticed that.

Weird I can't see any reason for the plug only not to include an earth contact unless the two versions are deliberately engineered that way so you have an easy way of choosing whether or not to have an earth connection to the PSU. In which case I would have thought it would be mentioned somewhere in the literature that accompanies the macBooks.

You’re quite right, it makes no sense at all. I imagine there is a small cost saving. I only know this because when I got my new laptop I was getting small electric shocks from the casing - the only difference with the old one was that I was using the short connector that came in the box.

Edited July 13, 2018 by floFC
Small typo due to electric shocks

[Owen]

I guess I could change the actual potentiometer in the volume pedal.  But which potentiometer?