Anti-NAB network for 1.875, 3180us/70us simulations

[dreamth]

Did anybody see anything about simulating an anti-NAB characteristic for simulating tape head amplifiers in cassette recorders? Is there a subject like this already? I'm particularly interested in chrome oxide 1.875 inch/second 3180/ 70us characteristic.

 

[PRR]

Every good (hi-gain opamp) head preamp has an inverse tape-EQ network: the NFB network.

Steal a good plan. This appears to be a car-audio, maybe not the finest, and not CrO2, but we'll fix that.

Re-draw as reverse-EQ connection.

There is a fat cap on the bottom for amplifier DC stability, short it out. Here they aimed it at 34Hz, which seems high compared to 3180uS/50Hz, but it IS a car deck. Don't want/need it for passive EQ.

Check the math. This plan rounded 0.0318uFd to the common 0.033uFd value, un-round. The top corner is approximately 150uS and CrO2 wants 70uS? Fix that.

We now have the middle plan.

If you are really going to *build* and *test*, your choice of precision caps is limited, while any resistor is possible with combinations of cheap parts. Scale everything the same ratio (cap up, resistors down) so the C comes out something you can buy. Last plan.

"96.38k" is 100K 1% shunted by 2.7Meg 10%. "2,120r" is 2.21k 1% shunted by 58k 10%.

 

[jazbo8]

It's much simpler to use a VCVS with a Laplace transfer function, search for RIAA playback for some examples, just change the RIAA time constants to NAB.

 

[dreamth]

Thank you for your effort!

 

[dreamth]

http://www.onsemi.com/pub/Collateral/LA3161-D.PDF I found your source in my Yamaha kx-400 which was a surprise to me.The sound is not really good as my other decks(pioneer ct-777 ...)but there are many other components that do not fit the bill for a good sound.I didn't realized that i asked you the time constants for the 9.5 cm/s speed though...i'm learning the abc of tape reproduction now, in my 40's...