Question about SCSI and audio hum...

1st of all, Hello to all. I am new to the forum, had my MPC about a month now, finally getting my head around it.

Wanted to say hello to everyone and to express my appreciation for this forum. It has been a source of infinite assistance while I have taken the plunge into the MPC learning curve. And just like everyone has always told me...soon as you start figuring out how to use it, it becomes attached to you. I only wish my 2000XL had an input that I could put my peepee in, cuz I'd like to hump it.

That being said, I took some advice and contacted Jim at scsiforsamplers.com and bought a 4.3 GB HD. I cant say enough about this guy...he is phenomenal, goes out of his way to help, and really knows his stuff. The HD even came with about a GB of sounds already on it, including the MPC60 and MPC3000 standard kits (wack though they may be, it was a nice touch).

Here is my question/issue.....When I hook up the external drive through the SCSI cable, my studio setup produces the dreaded 60 Hz hum, and it had never had that before. I have done some trouble shooting and narrowed it down to the SCSI cable because:

1) When the MPC is on, there is no hum.

2) When the MPC is on, but plugged by SCSI to the HD, there is a hum.

3) When I power off the MPC...and the HD...and remove both of their power cords from the wall....there is still a hum.

4) When I unplug the SCSI cord...hum is gone. The moment I plug the SCSI cord back in, whether the MPC or the HD is on or off, plugged or unplugged...the hum returns.

Before you flame, I already went the RTFM route, and it says nothing about grounding issues or hum. I did lots of web research regarding audio hum, and it mentioned not having AC cables and signal cables too close together, and keeping my components away from electromagentic fields (speakers, etc.) I have done everything from re-routing wires, to moving them, to putting rubber stoppers between cables to reduce interference, to getting a new SCSI cable. Nothing works.

Both the MPC and the HD work fine, and so does the SCSI cable, but the hum is a pain in the butt.

If any of you have some light to shed on the situation, and why a SCSI cable would cause a hum, please let me know.

I have a MPC2000XL, 32 MB upgrade, internal floppy, external HD (mentioned above).


Ideas, other than buying one of thoise noise cancelling devices? Why would a SCSI cable cause a hum when 5 turntables, an MPC, 2 keyboards, 3 computers, a ReelToReel, a mixing board and an amp dont cause any hum?

-TicToc

would it be possible to connect the HD to a separate outlet on a power strip or surge suppressor, and when not saving or loading you can have it turned off? I never had a problem with hum and I have a SCSI Zip, but I always keep it turned off when not saving or loading because I am cautious about it and don't want to lose my data...

4) When I unplug the SCSI cord...hum is gone. The moment I plug the SCSI cord back in, whether the MPC or the HD is on or off, plugged or unplugged...the hum returns.

As I said, it happens whether the drive is on or off, plugged or unplugged, surge strip or in a wall. I put it in several different surge strips, directly into the wall...etc. Still wont go away.

Anyone have ideas?

-TicToc

Have you used other scsi drives before with your mpc? That'd be the next logical step: if you can use a scsi zip with no hum, then its the drive. If you use a scsi zip and you get the hum, then the the problem is with your mpc.

also, try doing a search at the sound on sound website (www.soundonsound.com).

same problem with my SCSI CD drive.

I thought it might be that, already tried it. Hum is still there. At first I thought it was an MPC SCSI port issue, but both drives transfer data just fine through the SCSI port.

It's probably something stupid like a screw on the bottom panel of the MPC touching something metal inside the MPC. Or dirt in the mixing board.

Just called Jim from scsiforsamplers.com, and he told me to get a "ground lift", which is one of those adapters that adapts a 3 pronged (grounded) plug, like the ones on the MPC and the drives, to a 2 pronged (ungrounded). This would effectively unground the connection---wouldnt that make the hum problem worse instead of better?

-TicToc

Do that only on the HD, DO NOT GROUND LIFT THE MPC!!

Also, it is good to keep all your gear that is in any way connected to your MPC on the same outlet through a power strip. if you have an audio cable from the MPC to your mixer and they are on different outlets, you can get a ground loop.

Yo, is it possible fo you to copy them 60 & 3000 kits to your computer and sending them thangs my way? I have a fascination with factory kits.

Lemme know!

if you have an audio cable from the MPC to your mixer and they are on different outlets, you can get a ground loop.


This is interesting. But, when I had the audio cable coming out of the MPC into my mixer WITHOUT THE HD connected by SCSI, there was no hum. The calbe has always come out of the MPC into the mixer, even before SCSI became involved. The problem is centered 100% around the SCSI cable.

So why would the "ground loop" you suggest only happen AFTER I hook up the SCSI cable on the HD?

Regardless, I'll try your suggestions, see if it works.

-TicToc[/b]

'sup with the factory sounds bro?!!!

My guess would be that the scsi connector grounds to the chassis of the MPC and the scsi cable, and the differential is put over the top then and then the mixer's other outlet plays into the picture.

Do you have all your gear on one outlet?

Make sure that none of the power cords are running over or by the audio lines. Keep them seperate.