Tascam 388 Calibration and Bias

No worries Dave! As usual... some good suggestions.

My buddy and I stayed up 'til 3am the other night struggling with this.

He came over earlier this evening and through brute force (and... as you say, some logic) I think we've happened upon the theoretical parabolic curve shape we were looking for, but it's near the very beginning of the pot's range (seemingly impractically low).

However, our thinking is that maybe that is to facilitate as much space as possible for the overbias?? :rolleyes: Yeah... who knows.

Finally my formal science education is coming in handy though... All those long hours spent in biology lab, etc.

We're gonna get back into it tonight.

We've been successively plotting (using an MS Excel X-Y scatter plot) the mV value measured at the bias pot during record mode vs. the playback signal from tape measured with a DMM (not true RMS, but with a high enough sample rate to get us an accurate AV mV reading out to 3 decimal places).

I'll post back here with our initial pot values for one of the machines and some of the plots (assuming more data points reveal them to truly be good representations of the slope up to MOL and into overbias territory.

(Thanks again for all the info you've provided over the years... I'm psyched o be getting back into this stuff and corresponding again!) Rock and Roll! :guitar:

Stand by for more.

Hi migrant worker. I am using 21T204 as well for calibration. Did you use the reference fluxivity or the frequency response section. Seems the frequency response is at -10 db and reference fluxivity at 0 db. I used reference fluxivity, but I’m needing to turn my preamps up louder than I have before, so I was wondering if I should calibrate to the -10 signal