Installation manual

RA the Egyptian sun God was the inspiration behind this new product. He is considered
the father of Gods, and was the most important and worshipped king of Gods in ancient
Egypt..
We are sure that our humble version of RA will also be “worshipped”. It is truly a unique
pre amplifier.
The purpose behind RA was to enable the user to have substantially more control over
the sub woofer’s sound than just a simple remote volume control which is supplied with
every mono block. These remote volume controls work in one of two ways, either a simple
shunt potentiometer with the attendant problems of running low level audio up and down
unshielded telephone cable. The second and more elegant way is to use a VCA (Voltage
Controlled Amplifier) whose gain is varied by the application of a varying DC voltage.
Thus only raw DC is run on the telephone cable. Unfortunately the VCAs used are noisy
and have high distortion and the more exotic VCAs which perform well are never used
owing to their high cost.
Another issue with these tethered remote volume controls is exactly that, they are
tethered to their “mother” amplifier and cannot be used with a different manufacturer’s
product.
Zed made a decision to design a stand alone remote which has no allegiance to any
amplifier, it is universal. On board is a small switching supply which of course requires
three wires (+12v, ground and remote) to power it. Our opinion is that the small
inconvenience of having to run these three low current wires (#18 is quite sufficient) is
well worth the results which RA will produce.
RA is a mono pre amplifier which receives a stereo signal and mixes it to mono. If desired
a mono input may be applied to either the left or right inputs and the 6dB loss in gain due
to the missing input may easily be made up by RA having extra built in gain. Alternatively
a simple y-adaptor may be used to feed the signal to both inputs.
The first order of business once the signal is converted to mono is a 24dB/octave
Linkwitz-Riley Low Pass crossover variable from 45Hz to 230Hz. We have included this
crossover for one reason and that is if RA is used with an amplifier whose low pass
crossover is not “up to snuff”......well then RA will take over.
If the user decides to use the crossover in either the associated amplifier, signal
processor or head unit all that is done is to set the low pass on RA to 230Hz which
effectively removes it from the pass band.
Conversely if the user wants to use the crossover on RA, then the crossover on the
amplifier, signal processor or head unit is turned up to its highest frequency or if a bypass
switch is available to set it to the bypass position.
Page 62