Hum through PA

[abraun]

I play a passive Fender Jazz bass for my church. Usually I connect my bass to an active di to the PA system. An electric guitarist will be joining us and will also need an active di-problem is we only have one in the church. The other night I tried to use the line out on my Markbass combo to connect to the PA but there was a lot of hum in the PA system even when I changed the ground switch. The church has a new sound system and my Markbass combo line out worked fine on the old PA system. Any way to get rid of the hum? Thanks.

 

[BR Audio]

You can try a transformer isolating block. You can usually find them around some music stores. You put it between our line out and PA. Are you sure the hum is coming from your rig? not the guitar rig?
Make sure you have the ground lift on the guitar DI on as well, specially if the guitar is also plugged in to an amp.

Good luck.

 

[TimmyP]

A good isolation transformer won't be any cheaper than a good DI. The least expensive DI's I'd recommend are the ones from Audiopile.net

 

[tobie]

The other night I tried to use the line out on my Markbass combo to connect to the PA but there was a lot of hum in the PA system even when I changed the ground switch.

Your Markbass' line out is probably sending out a high impedance unbalanced signal and the PA is expecting a low impedance balanced signal? A DI between your line out & the PA is a solution - but then you're back to square 1: buy a DI for the guitar player and let him go straight to the PA.

 

[T-Bird]

Hi.

Another vote for a DI.

Regards
Sam

 

[tobie]

I'm not familiar with your Markbass amp, but it might have a low/high impedance switch (usually marked 'DI/PA') which might solve your problem.

 

[abraun]

Thanks for the input. I don't believe the amp has a low/high input switch on it-just a ground switch. I am sure the hum is from my amp, not from another source because I noticed it with nothing else plugged into the PA except my amp. I am thinking I just have to buy another di. I am considering of a Radial J48 or a Countryman though they are fairly expensive. The current di we use is a BBE DI 100x.

 

[Eublet]

Thanks for the input. I don't believe the amp has a low/high input switch on it-just a ground switch. I am sure the hum is from my amp, not from another source because I noticed it with nothing else plugged into the PA except my amp. I am thinking I just have to buy another di. I am considering of a Radial J48 or a Countryman though they are fairly expensive. The current di we use is a BBE DI 100x.

Both excellent choices. The J48 is my personal favorite over the Countryman, but if you want to save a bit of money and be able to run without Phantom power, the Countrman is excellent.

 

[SteveC]

Get a Radial J48.

 

[tobie]

I am considering of a Radial J48 or a Countryman though they are fairly expensive.

Yep - $200 is quite a bit for a DI box. How about rather going with a preamp with DI functionality (e.g. Behringer High-End Vacuum Tube Preamplifier MIC200 - http://www.amazon.com/Behringer-Hig...8&s=musical-instruments&qid=1268900299&sr=1-1). It has an XLR out (for the PA) as well as line out (for your amp) and lots of other features you can use for a magnitude of other applications - for $40!