[sdiy] Graphic EQs? (was Output circuit)

[James Husted]

on 3/30/02 7:40 PM, Byron G. Jacquot at thescum at surfree.com wrote:

>> Almost always*... the highest and lowest bands are shelving EQ... the
>> lowest
>> band is a HPF and the highest is a LPF so... yes they attenuate all
>> frequencies
>> beyond the bands.
>> 
>> *meaning: I have never seen one that was NOT like this...
> 
> I've seen a bunch where they offer highpass and lowpass filters on knobs off
> to one side, and all of the sliders are narrow passbands.  Symetrix did it
> like that, at least, and I think Klark Technik did too.
> 
> Byron Jacquot
> 
> 
I am familiar with the Symetrix Graphic EQ's mentioned in this thread (I
designed the metalwork and graphics for them). They have fixed Q band pass
filters (31 of them) and also a Low pass and High pass filters (labeled low
cut and High cut). The range of these cut filters is well above and below
the audio range. Many EQ's are designed with band pass and shelving filters
as the end bands. Most are designed with the audio spectrum in mind and just
use enough band pass filters to cover that range. For cost sake the other
shelving and HP/LP filters are not seen on these cheaper units. We always
toyed with the idea of making a "paragraphic equalizer" which was to be a
graphic EQ combined with a couple of parametric EQ bands. You could use the
graphic section for room EQ (the main use of a Graphic EQ) and the
Parametric for problem fixing (feedback, hum, the main uses for a parametric
EQ). The in-shop name was "The Equalmetric Paralyzer".
-James
--
"Welcome to the first day of the rest of your money."

James Husted                        The ErsatZ Planet
james at ersatzplanet.com           www.ersatzplanet.com