[Vintage-Audio] H. Scott Center Channel

Mon Feb 10 17:04:01 2003

OK- Memory fails again.
I just took a look at some schematics for H. H. Scott amps of this vintage.
I don't have one for the LK-72-B, so I cannot give an exact reply here. I
have, however enough other schematics of similar vintage Scott units to
postulate a reasonable explanation.
Your set is the kit version of the 299-D, which uses 7591 finals. The 299-D
schematic clearly shows two screw terminals which are intended for direct
connection to a speaker. But---
You have stated that your rig has only an RCA jack. Obviously further
research required here.
The schematic for the LK-48 ( a kit version of the 222-B/C ) has no center
channel provision. Nothing to be learned here.
The schematic for the LK-48 / 200-B does have a center channel output, and
( guess what ? ) It's an RCA jack !!
A brief study of the schematic clearly shows that the signal available at
this jack is sampled from the secondary of the output transformers, but is
run through an attenuater / summing circuit which converts it to high
impedance / line level. It obvious that this is intended to be run through a
separate power amplifier.
One could run this through ANY power amp, but as the output present at this
jack is from the final end of the LK-72-B, it is subject to all actions of
all controls. I would think that the best solution here would be to run this
into a single channel power amp with ONLY an input level control.
An H.H. Scott 208 mono power amp would be a perfect match, as it uses
basically the same circuit as the 299-D / LK-72 . A 240 would be fine too,
but a bit of overkill with it's EL-34 finals. Even a smaller ( than 7591 )
amp would be fine, as the ctr. channel speaker is generally run at a lower
SPL than the main speakers.
Chuck N1LNH
----- Original Message -----
From: "JM/CO" <[email protected]>
To: <[email protected]>
Sent: Saturday, February 08, 2003 7:37 PM
Subject: Re: [Vintage-Audio] H. Scott Center Channel


> This was not an un-common feature on amps of this vintage. The output is
> summed from both channels, and is at "speaker level". It is not generally
> possible to do this trick with solid state, hence the disappearance of
this
> feature from the industry.
> Just connect a suitable speaker, and enjoy. Three channel systems are
great,
> especially when using rather small speakers in a large room where they are
> spread apart. The third speaker eliminates the "hole in the middle" effect
> of such a rig. You may want to place an attenuater in line, in order to
> compensate for the relative efficiency differences of the speakers. The
best
> set-up of this type was used by McIntosh and others who made separate pre
> and power amps. The three channels came out of the preamp at line level,
and
> each could be run through an appropriate power amp to it's respective
> speaker. This system enabled the independent setting of main and center
> channel levels.
> Chuck N1LNH
> ----- Original Message -----
> From: "Duane Fischer, W8DBF" <[email protected]>
> To: <[email protected]>
> Sent: Saturday, February 08, 2003 6:18 PM
> Subject: [Vintage-Audio] H. Scott Center Channel
>
>
> >
> >
> > The H. Scott LK-72b integrated stereo amplifier has provisions for a
> center
> > channel output. Can someone please tell me about it?
> >
> > I am presuming it is a mix of the left and right channels?
> >
> > I am also presuming that to utilize this center channel requires a power
> amp?
> >
> > What controls the center channel: the primary amplifier or the power
> amplifier?
> >
> >
> > A rather innovative concept for 1963.
> >
> > Thanks.
> >
> > Duane Fischer, W8DBF
> > [email protected]
> >
> > _______________________________________________
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> > List Administrator: Duane Fischer, W8DBF
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>
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