Hi, colleagues. I'm new to this list although I've known ARSC since 1997.
I'm a member of 78-L since then, too.
Just a question, related to tailored EQ curves, etc.
Years ago I bought an Esoteric Sounds Re-Equalizer, a device that added
within the chain, eliminates the RIAA from the phono stage, and adds
whatever curve you want, among 6 turnover and 6 rolloff settings
(independently). It worked fairly well. But one sad day the transformer
burnt out, when connected at 220 volts with the selector accidentally set
at 125 volts. Bye-bye to the Re-Equalizer. I cannot find replacement for
that transformer. It is 220 volts (125 too) to twin opposite 12 v AC
signals to feed the Equalizer cockroaches.
So I then had to return to the old system I used when I did not have any
Eq, which is to use the tone controls to lower the bass response and raise
the treble. My question is: How do the tone controls work? Do they shuffle
up and down the 6dB/octave ramps? Do they raise the overall level
horizontally? Do they increase the ramp slopes? Mine is a common home use
Pioneer A209-R (MOSFET). Not Hi-End...
I worked out a tricky scale supposing the tone controls simply shuffle the
6dB/octave ramps up and down the freq scale, starting from the RIAA points,
and moving to the left or right,
I recalculated the turnover and rolloff points resulting from this
hypothesis, for several positions of the controls, assuming also a
logarithmic linear response. Based on the information from the manual
specifications, which says that the tone controls increase the response +/-
8 dB at 100 Hz (bass) and at 10 kHz (treble). So I worked out a new scale
for the control knobs.
The bass control lowers the zero point from 500 Hz (RIAA, central position)
down to 198 Hz when twisted down completely to the left, or up to 1260 Hz
when twsted to the right. I worked out intermediate positions (supposed
linear variations of freq with knob angle) and drawn a scale with four
intermediate points at left and four points at right, being 198 - 250 - 315
- 397 - 500 - 630 - 794 - 1000 - 1260 Hz. For the treble it is more simple,
as the dB added or removed are the usual familiar numbers, so from left to
rigth, adding the RIAA -13.7 dB we have eigth positions which are -22, -20,
-18, -16, -14, -12, -10, -8, -6 [log in to unmask] So I made a paper scale which I
slide over the control knobs and I use these for approximate re-equalizaton
of 78s using only the control knobs. I have to say that it more or less
works. The only thing is that I cannot get rid of the -6 dB@10kHz, as the
treble cannot be raised further... Am I right or wrong?