[jh[_2_]]

Am 23.02.2014 03:18, schrieb Stephie Bench:
So, I thought as a curiosity, I'd spend a couple hours in Spice land and see if those interesting specs Patrick came up with could be achieved. Lets review them... bass, mid, treble controls. At midpoint on all controls, +6dB at 100Hz, 0 at 400Hz, and +6dB at 5kHz. Max bass, 10dB at 100Hz, min not too important. Mid, + and - 9dB at 400Hz, with little effect at 200Hz znd 3..2kHz. Max treble, +15dB at 5kHz, min not too important. I put a couple added constraints: power=250v, 12AX7s only, overall more or less unity gain, insensitive to input impedance or output loading, supports 1v input level, and no inductors.

What I achieved uses 2 12AX7s and has the following characteristics.
Input Z, 1meg, and insensitive to input Z.
Output: cathode follower and no effect on response by reasonable load.
Bass: mid, +6dB at 100Hz. Max, +10.5dB at 100Hz. Min, -1dB at 100Hz.
Mid: mid, 0dB at 400Hz, max, +10dB at 400Hz, min, -11dB at 400Hz. Effect of the mid pot is less than a dB at 200Hz and 3200Hz.
Treb: mid, +6dB at 5kHz. Max, +15dB at 5kHz. Min, +3dB at 5kHz.

The bass and mid are implemented as tuned circuits, using a section of a 12AX7 each as gyrators. I was actually intrrested in seeing whether that would work reasonably well; and it does.

Incidentally, setting things up for flat rather than boosted response provides symetrical boost/cut for all 3 controls.

The pots for control are all 50k pots, and I alloeed for 1k residual resistance at the pot extremes.

Anyone wanting the Spice file can email me.

-Stephie


Hi Stephie,

....as Patrick is searching for something "guitar related" - is there any
possiblitiy that a real guitar player can taste the reaction and the
sound of an amp incorporationg the gadget?

regards

Jochen