RE: Amplifying rear speakers separatly

["Mark Harrison" <Mark.Harrison@xxxxxxx>]

Nikola,

If you have a volume control, you have variable gain.

If you don't have a volume control, you have fixed gain.


Mark Harrison
Head of Systems, eKingfisher

-----Original Message-----
From: Nikola Kasic [mailto:nikola@xxxxxxx]
Sent: 26 March 2002 17:04
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Amplifying rear speakers separatly


I think that trick is then in amplifiers:
You have 3 amplifiers: 2 for front and 1 for rear speakers.
Integrated amp on front drives treble speakers
Power amp drives basses on front
Pioneer drives rear speakers

I asume that we can simplify this to having two amps, one for front, one
for rear speakers. But it seems that the trick is in amplifiers:

A power amp has FIXED GAIN, rather than a variable gain, so you need
something else to control the volume, otherwise it would always be at
max.

What does this mean? How can I know if amplifier has fixed or variable
gain?
E.g. I have Sony STR DB 1070 amp, which has 5.1 channel outs and 5.1
pre-amp outs. I asume that pre-amp ones are interesting ones. Then I
should connect pre-amp outs for rear speakers into line in of some small
stereo amplifier.
I plan to find some small, compact, stereo amplifier with volume control
only, which can be easily hidden, and connect Sony pre-amp out
->KAT5->
small amp Line in.
Is that O.K.
Then, I plan to adjust the level of rear amp with sound level meter at
some reference level and from then on, not to touch it anymore.
When I raise or lower the volume on the main amp (Sony), the volume
should change on all speakers.
Is my theory O.K.?
Nik

-----Original Message-----
From: Mark Harrison [mailto:Mark.Harrison@xxxxxxx]
Sent: 26 March 2002 15:51
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Amplifying rear speakers separatly



Git!

OK, here goes, how I do DVD playback:

ALL SIGNALS FROM HERE GO AS DIGITAL STREAMS, EITHER PCM OR DOLBY DIGITAL
DEPENDING ON THE SOURCE MATERIAL

- The source is a Pioneer DVD player (second black box from the bottom
on the right-hand stack)

The audio goes, via SP/DIF (the single reddy-pink cable), down onto the
floor, then into the source switch

- The source switch is a Meridian 562V, (middle black box, narrower
width, on the left-hand stack)
--- It's worth noting that the other sources, such as the DDAR (top
black box, narrowest width, on the left-hand stack) that go into the
562V as analogue get CONVERTED into DIGITAL at this point... All the DSP
stuff happens entirely in the digital domain.

Assuming that the selected source is "DVD", this goes, via (a
virtually
impossible to see) SP/DIF cable into the processor

- The processor is a Meridian 561 (lower black box, narrower width, on
the left-hand stack)

WHILE THE PROCESSOR IS CAPABLE OF OUTPUTTING UP TO 8 CHANNELS OF AUDIO,
IN EITHER ANALOGUE OR DIGITAL FORMAT, AT PRESENT I ONLY USE 4 CHANNELS,
AND OUTPUT THEM ALL AS ANALOGUE AT LINE LEVEL

Front pair

The main stereo pair come out on a (virtually impossible to see) pair of
phono connectors into the integrated amp

- The integrated amp is a John Shearne Phase 2 (wider width, but thinner
depth top black box on the right-hand stack.)
--- the black speaker cables go out of this and drive the treble drivers
on the front speaker pair

The integrated amp also has a line-level passthrough on the
(purpley-pink) analogue pair to the power amp

- The power amp is a John Shearne Phase 2 (wider width, but thinner
depth second-to-top black box on the right-hand stack.)
--- The pinky speaker cables go out of this and drive the bass drivers
on the front speaker pair

Rear pair

The rear stereo pair come out on a (virtually impossible to see, but you
can see the red and white boots on the processor) anlogue pair, into a
KAT5 TX

- The KAT5 TX is almost out of shot, on the floor, but you can just see
a corner of it at the far right on the bottom edge of the picture, to
the right of the mains block

.... this goes into a CAT5 socket in the wall, back to the patch panel,
where it's patched to a CAT5 socket at the other end of the room. This
goes into a KAT5 RX, which drives an old Integrated amplifier (Pioneer
A-400), which drives a the rear pair of speakers.

Volume controls

The logic in this is that the "changing the volume" circuitry
(pre-amp)
is kept separate from the "amplifying lots" circuitry (power amp)
to
avoid interference.

A power amp has FIXED GAIN, rather than a variable gain, so you need
something else to control the volume, otherwise it would always be at
max.

The pre-amp, which is the only volume control that ever gets touched, is
on the processor. The processor, as we've seen purely operates on a
DIGITAL input, and turns it into line-level, ANALOGUE outputs.

In practice, both the front and rear amplifiers actually have volume
controls, but these are just left "whacked up to about 75%", and
the
volume adjustment is done on the processor.

Mark Harrison
Head of Systems, eKingfisher

-----Original Message-----
From: James Hoye [mailto:james.hoye@xxxxxxx]
Sent: 26 March 2002 15:07
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Amplifying rear speakers separatly



Ahh I see a man about to be initiated into the "real" audio club
:-)

Go mark go mark go mark :-)

And feel free to refer to
http://groups.yahoo.com/group/ukha_d/files/mharrison_avkit.jpg
<http://groups.yahoo.com/group/ukha_d/files/mharrison_avkit.jpg>
< http://groups.yahoo.com/group/ukha_d/files/mharrison_avkit.jpg
<http://groups.yahoo.com/group/ukha_d/files/mharrison_avkit.jpg>
>  as
you
explain!!!

James H