Just recently got an ISA428 unit, and I'm having a small problem interfacing it with my RME interface. It seems that when the RME is reading 0 (clipping) the focusrite is reading at what looks like -10db on it's peak meter. I'm still getting a fairly quiet signal, but I suppose that I should be able to turn the preamp up another 10db?

On my A-Designs MP1, the meters seem to match better, but the Mp1 has a VU meter, not a peak meter.

I'm not sure if this is something that I should be concerned about or not but I'm wondering if I could be getting an ever better signal. Anyone have any suggestions?

BTW, none of the mentioned units have a -10/+4 switch.

quote:

BTW, none of the mentioned units have a -10/+4 switch.

Your RME should.

In either case I don't see this as a problem. If it sounds good, then it's good.

This sounds like a typical misunderstanding:

The ISA meters are reading dBFS. -18dBFS = 0dBVU in most cases. When your ISA meter reads 0dBFS it is outputting +22dBVU!!! So at -10dBFS it's outputting +12dBVU. That's very hot! I'm just guessing that the RME is reading dBVU, or is calibrated differently.

Remember analog gear is meant to run at 0dBVU and has headroom above that point up to +XdBVU.

Digital meters use dBFS (the meters on the ISA are dBFS meters) and therefore 0dBFS is IT. NO MORE ROOM. The 'headroom' is BELOW 0dBFS.

I'll have to take a look into the RME manual and see what it is reading. I guess I had assumed that it was also measuring dBFS.

Also, I am not using the A/D option on the ISA428, so it is operating in the analog realm. The analog meters ARE labelled as peak meters though, not VU meters.

I'm going to take a closer look into each manual and see what the meters are referencing specifically. Thanks for you help!

The meters are FS meters, according to the manual. The manual says that when the meter reads "0" it is outputting +22dBVU at the analog out.

I know that when I was using the ISA analog output into my digi002, the digi could take up to +18dBVU, so it was maxed out at -4dB on the peak meters of the ISA 428.

In practice, running close to 0 is overdriving the analog circuitry, so by staying at -20dBFS AVERAGE, I was fine.

Remember, RMS is different from peak, of course.