Tape Machine Input Levels

Bob Katz

Hi Bob!

I hope you and Mary are doing well!

I have a question for you…It’s been such a long time i recorded on a 16 tracks tape machine…

Maybe you can help me.

Do you remember what were the true max input line levels we could achieve in a tape machine?

Was it +24 dBu for true peaks, or was it more around +16 dBu for true peaks ?

The VU meters were not anywhere as fast as my Dorrough meters (rms and peaks), so all i remember is that i had an “idea” of what were the levels.

Thanks a lot!



Antoine Fabi

Hi, Antoine. We’re doing well.

I prefer to define the peak level as X number of dB above the 0 VU calibration…. but if. your VU is calibrated for +4 dBu at 0 VU, then dBu is the language we’ll use

Yes, a VU meter is not fast… but it does eventually react to peaks and will warn you, depending on how high the peaks are above 0 VU and of course their duration, so it’s not a science. But for sure a VU meter calibrated to +4 dBu receiving short term peaks at +24 dBu will read WAY over 0 VU, warning you that the signal is too hot to begin with. So if you were feeding a VU metered tape machine it would warn you to begin with, on the VU meter.

Peaks closer to +16 dBu (about 12 dB over 0 VU) will be tolerable by any modern tape stock so it would work. This is why we tend to calibrate our digital systems — which are also feeding analog tape machines —- to 0 VU = -14 dBFS or even -12 dBFS, and then watch the peak levels and we’ll be fine.

So you’re better off, if you start with a digital system, and the digital signal is approaching 0 dBFS, to calibrate the analog tape machine to 0 VU = -14 dBFS or even -12 dBFS at 1 kHz with a sine wave. 

Hope this helps,