Art MPA II hiss problem

Hi,

I recently bought an Art Digital MPA II mic preamp. It seemed fine the first week (2 weeks ago) I had it but now there is so much hiss it's become unusable.

I'm using the S/PDIF output from the preamp into an inexpensive but reliable Tapco firewire interface.

I can unplug the mics and turn all the levels to zero and the hiss is still there so it's not my mics or settings ( I don't think ).

Most reviews of this unit that I've read give it fairly high marks but state that the tubes that come with it should be replaced...I haven't changed the tubes...yet.

So, before I replace the tubes or send it back, here are my questions:

1. Is it possible that the hiss is caused by bad tubes?
2. Would the tubes it came with, even if they're cheap, really wear out in 2 weeks?

Thanks for your help.

That is normal for an ART pre amp.

Sometimes I wonder if that is what people like about them and why they recommend them to others.

:-(

I used to try to advise people to avoid buying that stuff but was reprimanded here for my bad attitude.

I really think the ART gear is lower end than it's deep discount price reflects. The stuff isn't, in my personal opinion, worth the money.

Try to reseat the tube. Try a fresh tube. Nothing's really going on in the tube... IIRC, The tube stage in that circuit is a plate starved cathode follower current driving circuit with a voltage gain of "zero".

The tube sound most people are looking for is from a Class A voltage hi-gain circuit.

Can you return it an move on?

best regards,
mike