[Vintage-Audio] H. Scott Center Channel

Mon Feb 10 23:24:01 2003

Chuck, 	

Thank you for some excellent information. 	

I do have a mono tube amp on the top shelf. I have not used it in two years. I
think it is a home brew cross between a mono sound system and a PA system
design. It has a pair of 6V6 in push/pull, line inputs and mike inputs. I do not
recall if only the mike inputs have level controls or not. Gong to have to lift
it down and check her out tomorrow. 	

Seems like the output should be adequate to drive an 8 ohm two-way cabinet with
eight inch and Aluminum dome tweeter. Any thoughts?	

More after I climb up. lift it down and check it out.   	

Duane W8DBF	

----------
From: JM/CO <[email protected]>
To: [email protected]
Subject: Re: [Vintage-Audio] H. Scott Center Channel
Date: Monday, February 10, 2003 5:03 PM

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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