Measurements of the Revox B-215S

[A.N.T.]

I've bought this unit for a friend (as I already have another B-215S). This deck happens to be in a good condition, the mechanics is OK (<0.06% DIN wtd W&F), the head is not worn. The frequency response is from less than 10 Hz to about 30 kHz on all tape types.

Alex

[tapetech]

These curves might subjectively sound a bit dull (we can hear 8K a lot better than 20K). If noise-reduction is used, the 8K dip would be amplified futher. I'd reduce the record bias so that the dip observed at 7-8k is flat with respect to 1k (as long as this keeps you within the acceptable bias range: under 3%THD at peak level). This will cause 20k to be boosted quite a bit relative to 1K, but could be brought back down to flat by adjusting or modifing the record EQ circuit. This is assuming the 20K play response is flat (if not, it may be contributing to some of the 20k boost).

[perry]

What exactly is that last plot showing us, Alex? Are those all no NR curves?

[A.N.T.]

These curves might subjectively sound a bit dull (we can hear 8K a lot better than 20K). If noise-reduction is used, the 8K dip would be amplified futher. I'd reduce the record bias so that the dip observed at 7-8k is flat with respect to 1k (as long as this keeps you within the acceptable bias range: under 3%THD at peak level). This will cause 20k to be boosted quite a bit relative to 1K, but could be brought back down to flat by adjusting or modifing the record EQ circuit. This is assuming the 20K play response is flat (if not, it may be contributing to some of the 20k boost).

I'll leave it to my friend to deal with these irregularities. He is an experienced cassette deck collector and restorer.

What exactly is that last plot showing us, Alex? Are those all no NR curves?

All plots are without NR. The last curve shows the modulation noise at 10 kHz, which is pretty good for a cassette deck, and also shows that there no significant AM in the signal.

Cheers

Alex