[Phono-L] Scott AW23 volume expander
Douglas Houston
cdh041 at earthlink.net
Sun Jun 28 14:58:18 PDT 2009
Indeed. The EM fields on the tweets didn't surprise me, only because I
knew that permenent magentic dynamic speakers wereen't made until just
before WW II. But, here's one for ya. There WERE PM dynamic speakers around
1932. I have a Majestic set from about '32 with one. They simply used great
big globs of iron, hanging on the speaker fra,es, and went away contented.
Philco also had some on battery sets around that time. I sort of think that
they need a shot of magnetizmuss now.
> [Original Message]
> From: Greg Bogantz <gbogantz1 at charter.net>
> To: Antique Phonograph List <phono-l at oldcrank.org>
> Date: 6/28/2009 4:57:09 PM
> Subject: Re: [Phono-L] Scott AW23 volume expander
>
> Hi Doug,
>
> Yes, the volume expander for the AW-23 was an optional item,
contained
> on a separate chassis as Andrew says. The unit contained two 6A7 tubes
as
> variable-gain audio amps, one 6C6 control signal amplifier, and a 76
wired
> as a diode. The circuit is in the Riders PPT manual, volume 16, page
Scott
> 16-1. Scott was a strong and early proponent of hifi circuitry, and the
> AW-23 exemplifies this with the use of balanced, push-pull circuitry all
the
> way thru the audio section, including small signal amps, drivers, and
> outputs. That's why the volume expander uses two 6A7s - they are a
balanced
> pair inserted into the existing balanced audio circuit.
>
> E.H. Scott can be considered the "pioneer" of component hifi in the
> 1930s. His radios were sold with numerous options available, including
the
> addition of record players, record cutters, optional speaker systems, and
> the cabinets themselves which were separately ordered by the buyer. The
> tweeters available for the AW-23 were also sold as an optional addition.
> They were sold as a set of two cone tweeters with crossover network.
They
> are interesting because of their early date and the fact that they were
also
> electrodynamic (ED), with field coils. Philco also put ED tweeters in
their
> top end sets, particularly the 37-690 and 38-690 radios (from 1937, 38
> respectively) as standard equipment. As a kid, I never ran into tweeters
or
> "high fidelity" radios from this early period, so I was pretty astounded
> when I first discovered these early ED tweeters were available so many
years
> before I imagined. The concept of an electrodynamic tweeter still twists
my
> mind :o)
>
>
> Greg Bogantz
>
>
>
> ----- Original Message -----
> From: "Andrew Baron" <andy at popyrus.com>
> To: "Antique Phonograph List" <phono-l at oldcrank.org>
> Sent: Saturday, June 27, 2009 11:50 PM
> Subject: [Phono-L] Scott AW23 volume expander
>
>
> > Hi Doug ~
> >
> > The volume expander on the Scott AW-23 was an outboard unit, contained
in
> > a small, rectangular, chrome plated box that mounted outboard of the
main
> > chassis on rubber vibration absorbing pads. The box contained four
tubes
> > although I don't know off hand what the tube numbers are.
> >
> > It has three umbilical cords: One that went to the receiver chassis
and
> > brances off to interface with two of the tubes that are near one
another
> > (with substitute grid clips and caps for each of these two receiver
> > chassis tubes, so the components in the chrome box were put in series
> > with these tubes grid circuits). A second cord goes to the expander
> > control knob, which had its own appropriately stamped escutcheon to
match
> > the stock ones. The third cord goes to the dynamic speaker and
> > terminates in a female-male plug that sandwiches between the stock
> > speaker plug and the amplifier/PS chassis, if I recall correctly. I
> > assume this is for filament and plate supply voltages.
> >
> > On the Tasman cabinet, the metal box mounted directly behind the
chassis
> > on the left side of the same shelf, and the expander control knob was
> > mounted toward the back of the left side of the cabinet, not far from
the
> > top. I don't know if all the expander equipped AW-23s had the (also
> > optional) tweeters, but I should think that most of them would have
had
> > them.
> >
> > Thanks for your various accounts and reminiscences. I always read
them
> > when you post here and on Levnet as well.
> >
> > Best,
> > Andy Baron
> > Santa Fe
> >
> >
> > On Jun 27, 2009, at 9:15 PM, Douglas Houston wrote:
> >
> >> As usual, greg, nice take. I wasn't aware that Scott had an expander
on
> >> his
> >> AW23. I have one, and never knew it! The expander control tube would
> >> have
> >> had to be a 6A7 in that set. He certainly did have it on the
> >> Philharmonic!
> >>
> >> By the way, the 6A7, while a pentagrid tube, doesn't actually have
five
> >> grids! The second "grid" is two rods, serving as an anode for the
> >> oscillator. Withe the intro of metal tubes, the 6A7 became the 6A8.
> >>
> >> The tube that really opened up as the ideal control tube for
expanders
> >> was
> >> the 6L7, introduced in 1935, as one of the original 9 metal tubes.
It,
> >> and
> >> the 6H6, dual diode, were the duet that made expanders easy to
happen.
> >> I
> >> have both the D22 and the R99, as well as the U 109: the 1938 version
of
> >> the D22. On those big RCA combos, the expander operated only on the
> >> phonograph, and not on radio reception. The D22 has a little "dynamic
> >> amplifier", with three tubes ( I believe), and they feed the amplifier
> >> directly. :Likewise, it's similarly done on the U-109. Those big RCA
> >> hunkers really roar!
> >>
> >> It sounds amusing, I suppose, but Midwest incorporated a volume
expander
> >> on
> >> its model 20-38, which was their masterpiece for 1938. I once had
one,
> >> but
> >> didn't yet understand the expander, so I swapped off the set to a
> >> friend.
> >> I'd like to have that monster now!
> >>
> >> In the fifties, when microgroove recording was becoming more
> >> sophisticated
> >> as time passed, Mercury, for one, used what was called: Reeves-
Fairchild
> >> Margin Control. High level passages automatically widened the groove
> >> pitch,
> >> so that dynamic range could be preserved, without using compression. A
> >> microscope shows it easily.
> >>
> >>
> >>> [Original Message]
> >>> From: Greg Bogantz <gbogantz1 at charter.net>
> >>> To: Antique Phonograph List <phono-l at oldcrank.org>
> >>> Date: 6/27/2009 3:51:11 PM
> >>> Subject: Re: [SPAM] Re: [Phono-L] Young collectors
> >>>
> >>> An interesting thing about dynamic volume expanders/compressors for
> >> readers
> >>> of this antique phonograph forum is that they date back to the early
> >> 1930s.
> >>> dbx didn't invent them by any means. The earliest appearance of this
> >>> circuit in consumer products was in models by E.H. Scott in the
Allwave
> >> 23
> >>> (a massive 23-tube radio divided into two or more chrome-plated
> >>> chassis -
> >>> the volume expander was yet a separate chassis sold as an option),
and
> >> the
> >>> RCA R-99 record player and D-22 radio/phonograph, both of which
> >>> included
> >> the
> >>> volume expander as standard equipment. These models appeared about
> >>> 1935.
> >>> Professional compressor circuits were being used a little earlier,
> >>> mostly
> >> to
> >>> compress the signals for AM radio broadcasting (FM wasn't available
> >>> yet).
> >>> These circuits really weren't technologically feasable until the
> >> invention
> >>> of the pentagrid tube (it had FIVE grids!) which was originally
> >>> designed
> >> for
> >>> the purpose of providing the oscillator and mixer functions in a
single
> >> tube
> >>> in superheterodyne radio circuits. But the extra grids allowed this
> >>> tube
> >> to
> >>> be used as a DC-controlled transconductance amplifier - the variable
> >>> gain
> >>> element necessary to accomplish dynamic volume control. Pentagrid
> >>> tubes
> >>> were used for this purpose for many years until the development of
> >>> solid
> >>> state technologies that could do the same thing. Curiously, though,
> >>> the
> >>> most popular DC-controlled amplifiers used in recording studios then
> >>> and
> >>> even NOW are a simpler technology employing light-dependent resistor
> >> (LDR)
> >>> elements. Even though this technology is 50 years old, modern
> >>> recording
> >>> engineers still prefer the sound of LDR compressors over the more
> >>> modern
> >>> circuits.
> >>>
> >>> Greg Bogantz
> >>>
> >>>
> >>>
> >>> ----- Original Message -----
> >>> From: <Zonophone2006 at aol.com>
> >>> To: <phono-l at oldcrank.org>
> >>> Sent: Saturday, June 27, 2009 5:46 AM
> >>> Subject: Re: [SPAM] Re: [Phono-L] Young collectors
> >>>
> >>>
> >>>> does anyone remember the expanders of dbx fame
> >>>> i have and had used a lot of them back in the 70's for expanding and
> >>>> constricting the music
> >>>>
> >>>>
> >>>>
> >>>> In a message dated 6/26/2009 11:47:39 P.M. Eastern Daylight Time,
> >>>> phonographs at charter.net writes:
> >>>>
> >>>> I used to work at a hi-fi stereo shop in Madison, WI about 2 years
> >>>> ago
> >>>> and
> >>>> found that many young people were into turntables and vinyl. They
> >> tended
> >>>> to
> >>>> be high school and college age students. The biggest reason why
they
> >>>> liked
> >>>> vinyl was because it was cheap. They could buy used records at
used
> >>>> record/CD stores and at garage sales for 99 cents or less, while
the
> >>>> average
> >>>> used priced CD for popular music was $8.99.
> >>>>
> >>>> Even though these vinyl enthusiasts understood records and were
> >> familiar
> >>>> with them, they had little to no knowledge of 78s or cylinder
> >>>> records.
> >>>> When
> >>>> I would share this technology with them, they thought it was the
> >> coolest
> >>>> thing.
> >>>>
> >>>> Records have been making a comeback now for several years and new
> >> vinyl
> >>>> is
> >>>> being produced, although expensive at nearly $30 or more for an
> >>>> album.
> >>>> Just
> >>>> a few years ago there were high-resolution formats of digital music
> >>>> called
> >>>> SACD and DVD Audio. These formats were near record quality, but
> >>>> never
> >>>> really caught on as they needed special players to play these
discs.
> >>>> Records actually began to overtake these formats and within a few
> >>>> years
> >>>> SACD
> >>>> and DVD-Audio was dead.
> >>>>
> >>>> When CDs came out around 1983-84, it was thought they would be
record
> >>>> killers and records would go the way of the cassette tape. While
> >> there
> >>>> was
> >>>> a huge decline in record and turntable sales, the market never
died.
> >> It
> >>>> faded away for a few years, but is coming back. There are many
young
> >>>> people
> >>>> who appreciate the quality of high-end turntables and stereo
systems
> >>>> to
> >>>> give
> >>>> these records the respect they deserve. A good stereo system will
> >>>> make
> >>>> records sound better than a CD. Records have an ambiance that CDs
> >> lack
> >>>> and
> >>>> can produce a 3D audio effect, while CDs have a monodimensional
> >>>> sound.
> >>>>
> >>>> Online music, including MP3, MP4, WMAs, etc have become very
popular
> >>>> in
> >>>> recent years by people of all ages. It is a matter of convenience.
> >>>> Convenience always wins over quality. Take disc records to
cylinders
> >> for
> >>>> example. Discs were more compact and soon provided two songs on
one
> >>>> disc,
> >>>> even though they didn't sound quite as good as cylinders at the
turn
> >> of
> >>>> the
> >>>> century. Online music also allows you to buy only the songs you
> >>>> want,
> >>>> eliminating the waste of a full album and is more cost effective.
> >> This
> >>>> is
> >>>> proving to be the demise of the CD. Many stores have reduced the
> >>>> space
> >>>> used
> >>>> to carry the once mighty CD. Perhaps the CD will one day go away
as
> >>>> well.
> >>>> This awaits to be seen.
> >>>>
> >>>> Many of the younger people who are a product of the iPOD generation
> >> may
> >>>> not
> >>>> have heard records and probably have never heard a good sounding
> >>>> stereo
> >>>> system. That is a shame because it is an experience to behold.
All
> >> we
> >>>> can
> >>>> do is educate and share this information with these younger
> >> generations
> >>>> in
> >>>> order to keep the analog recording alive and well.
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> -----Original Message-----
> >>>> From: phono-l-bounces at oldcrank.org
> >>>> [mailto:phono-l-bounces at oldcrank.org]On Behalf Of Robert Wright
> >>>> Sent: Friday, June 26, 2009 4:31 PM
> >>>> To: Antique Phonograph List
> >>>> Subject: [SPAM] Re: [Phono-L] Young collectors
> >>>>
> >>>>
> >>>> But because DJ'ing is 'cool', some of that mentality rubs off on
> >> (young)
> >>>> consumers. We have a more phono-conscious youth culture now than
in
> >> the
> >>>> last 20 years because of it. Meanwhile, analog (vinyl, strictly
> >>>> speaking)
> >>>> has been strengthening its foothold in the audiophile market (and
> >>>> publications) VERY solidly since '97 or so, and there are more
record
> >>>> labels
> >>>> (both large-scale that release on vinyl AND indie labels dedicated
> >>>> strictly
> >>>> to audiophile pressings) today than ever. Someone else on the list
> >> said
> >>>> it
> >>>> already -- it comes and goes in cycles, as it always has --
remember
> >> the
> >>>> pre-war blues 78 market back when Gayle Dean Wardlow risked his
life
> >>>> canvassing for them in the 60's?
> >>>>
> >>>> The truth is, we only know the state of things as we can see them,
> >>>> and
> >>>> none
> >>>> of us ever really has an accurate idea of the overall picture
> >>>> (thankfully).
> >>>>
> >>>> Best to all,
> >>>> Robert
> >>>>
> >>>>
> >>>>
> >>>> ----- Original Message -----
> >>>> From: "John Maeder" <appywander at hotmail.com>
> >>>> To: "Antique Phonograph List" <phono-l at oldcrank.org>
> >>>> Sent: Friday, June 26, 2009 3:30 PM
> >>>> Subject: RE: [Phono-L] Young collectors
> >>>>
> >>>>
> >>>>
> >>>> Yes, that was my line of thinking exactly what with club DJs
> >> scratching,
> >>>> etc., when I planned my talk. I think, perhaps, that club DJ's
are
> >>>> the
> >>>> primary consumer of vinyl and 'civilians' simply aren't exposed to
it
> >> in
> >>>> a
> >>>> hands-on home environment anymore. Having said that, I recently
read
> >>>> that
> >>>> vinyl record production is at its highest level in a couple of
decades
> >>>> right
> >>>> now, although still just a very small fraction of unit sales. I
> >>>> guess
> >>>> just
> >>>> music 'geeks' buy vinyl nowadays? Even CDs and DVDs are in sales
> >> decline
> >>>> now because of MP3 and MP4.
> >>>>
> >>>> John M
> >>>>
> >>>>> From: jay.horenstein at gmail.com
> >>>>> To: phono-l at oldcrank.org
> >>>>> Subject: RE: [Phono-L] Young collectors
> >>>>> Date: Fri, 26 Jun 2009 13:18:34 -0700
> >>>>>
> >>>>> Vinyl isn't a thing of the past. It's still used in clubs.
> >>>>> Turntables
> >>>> are
> >>>>> used as instruments in Rap, Hip Hop, R&B. Classes on how to use
them
> >>>>> as instruments are given to aspiring DJ's. Stereos are still
sold
> >>>>> in
> >>>>> almost
> >>>>> every large store, and new artists are still recording on vinyl.
> >> It's
> >>>>> my
> >>>>> guess that the young people ignorant of the record player, download
> >> all
> >>>>> their music from the internet, and are probably just as clueless
to
> >> the
> >>>>> CD.
> >>>>
> >>>> _______________________________________________
> >>>> Phono-L mailing list
> >>>> http://phono-l.oldcrank.org
> >>>>
> >>>> _______________________________________________
> >>>> Phono-L mailing list
> >>>> http://phono-l.oldcrank.org
> >>>>
> >>>>
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> >>
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> >>
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