POOR MAN'S HIGH-END SYSTEM
Above is an approximate drawing of my current high-end system with the exception of
tube amplifier versions (KEW/P-92A and KEW807-91B).
The audio I/O quality has (obviously) been a priority. Right now I don't even have
the decoded video scart-returned to my VCR. While I then is recording thru several
meters of cheap, low quality RF-cables the video quality is of quite bad shape.
The main reasons is that I've been lazy as well as the RF-outlet being placed behind
my rack, which is approximately 10 meters away from my TV. This is actually "bad luck"
cause I then need 3X10 meters (outlet-decoder@TV-VCR@outlet-TV) of RF-cable before
a decoded (amplitude modulated...) broadcast picture is being recorded.
The recorded (low sensitivity) FM audio is however only RF-attenuated from outlet-decoder-VCR
and then routed via VCR Scart2 output to my Yamaha Cassette Deck. The reason for audio
routing thru a Cassette Deck is actually several but most importantly that the power amplifier
needs approximately 1.5V for full output power (this is at least true as long as my recommended
standard feedback of 17dB is used) whereas a standard scart-output level is lower than 0.5V
(150mV at f.i Tuner output).
Using my later pre-amp versions (i.e KEW/P-92B+) will however eliminate this additional voltage
step-up need. The reason for this is that the pre-amplifier itself has a (inverted) 1.5V pre-out output.
This pre-out output is however (due to lack of tubes as well as space...) of a quite high output
impedance (8k appr) which makes it hard to both drive long cables (20kHz@10m*100pF/m) as
well as loading it with both the input of the PA (47kB at separate vol/bal/sens pot. 1M without)
AND the TV-Scart audio input as shown in my drawing. The low Scart input impedance (10k) will
alone make the PA-drive audio level drop almost 6dB.
There's no real simple way to drive BOTH the TV and the PA DIRECTLY from current pre-amp's pre-out
(i.e source-direct) other than accepting this modest loss of "pure-tube-sound" driving level and
consecvently a 6dB output power loss (still some 4 to 5 TUBE Watts, though...). A "brute-force"
way to "eliminate" this problem is to connect to RIAA-out directly (330Ohm). The output power
will then however drop some 20dB...unless PA feedback is removed...
With my later pre-amp versions (i.e KEW/P-92B+) it's however also possible to route tape output
to pre-amp source-in yielding a constant (still high impedance) PA driving level at pre-out. The
Cassette Deck will then work as an all-source's volume as well as (except itself...) balance controller.
Because of the high pre-out impedance being a quite small but unwishful problem,
I'm thinking of adding a J-FET (BF245A) as an (optional and additional) 0dB low impedance
output in my next pre-amp version. Using my dedicated 0dB controller (KEW/CA-00A+) will on the
other hand COMPLETELY take care of this problem regardless of pre-amp version.
In short this "poor man's high-end system" works very well all drawbacks considered and I'm
actually in full control of 5 sources WITHOUT any dedicated controller pre-amp what so ever!
This is specially true when all source's IR protocols (except TT and current shitty Tuner & CD)
has been programmed in a single "One for all" programmable remote control!
I thereby have all the remote source control functions as well as standard (TV) audio features
(like volume, balance, tone and even DSP!) built in!
The "mysterious" Scart 1 and 2 TV connections will, by the way, make it possible for me to
listen to an optional audio source while watching a TV program (usually controlled by the decoder).
While watching a video tape, the only other audio source is however the cassette deck.
But on the other hand, how often do you wish to watch a video-tape with irrelevant audio?
Hmm, there is perhaps one special occasion...
It should finally be noted that tube power amp's seldom has really low output impedances
(i.e high damping factors). This is specially true if no feedback is used
(approx 1Ohm for open looped KEW88-91D). Due to this fact it is strongly recommended
to place the power-amp(s) as close to the speakers as possible. It is also and therefore
NOT recommended to use high capacitance speaker cables like some Supra models. Use for
instance an ordinary AC-mains cable (like I do) instead. For output power below some
20W's and speaker loads greater than 4 Ohm, a few meters of this cheap(!) speaker cable
is actually perfect!