[Boatanchors] Audio matching xformer

Bob Peters rwpeters at SWBELL.NET
Sun Oct 14 20:48:23 EDT 2007

What you are saying is partially true...In a true 70V Sound System there
is a transformer on each speaker and depending on what kind of speaker
the secondary is mostly 8 ohms. The Primary is normally 25V or 70V with
taps from about 1/4 watt to 15 watts... Better quality transformers are
from 5 to 30 watts...These are all Hi Impedance taps but normally a 600
ohm input will give you a 8 ohm output... If I were you Barry I would
use common and the 10 watt tap...My company manufactures these
transformers...If you need a higher wattage yell at me and I will send
you one...I actually have a couple of 100 Watt transformers...They are
heavy  HI... There is a lot of info on 70V stuff at my company web
site... www.penton-audio.com
For educational purpose only  HI...These are not amateur products...

Bob W1PE

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of WA5CAB at cs.com
Sent: Sunday, October 14, 2007 7:15 PM
To: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] Audio matching xformer


The concept is that if you have (in this case) a 10 watt audio
amplifier with 500/600 ohm output and from one to 16 remote
loudspeakers, you 
run parallel pairs of wires from the amp to each of the speakers (or you
run a loop or buss - it doesn't matter).  In the speakers (which is
where the 
transformers are located) you connect the wires to common and to the tap

correlating to the total number of speakers in the system.  For one, use
the 10 watt 
tap, for two, use the 5 watt tap.  Etc.  Local volume controls (if
will be on the secondary side between the transformer and the speaker.

To get back to real boatanchors, this is why loudspeakers like the LS-3
LS-7 have matching transformer primarys rated at 7000 or 8000 ohms and
like the HS-23 are 8000 ohm while the receiver audio output transformer 
secondary is rated 4000 ohms.  You can jack one to three of them into
the receiver 
without much effect on the ones already connected.  Likewise the later
war 600 
ohm components work with receivers with 250 ohm output impedance.  

In a message dated 10/14/2007 6:42:08 PM Central Daylight Time, 
robert at isquare.com writes: 
> At 07:11 PM 10/14/2007, Barrie Smith wrote:
> >Hello, All:
> >
> >I usually listen to my SX-73 using an old and tired Hallicrafters 600

> >ohm
> >speaker, because 600 ohms is the audio output on that receiver.
> >
> >I'd like to try a better quality speaker, but the speakers I have are

> >all
> >8 ohm.
> >
> >I have a 70 volt, 10 watt line-transformer, but I can't make sense of

> >the
> >schematic.
> >
> >The secondary is marked 4, 8 and 16 ohms, so that's FB.
> >
> >The primary is marked in watts: Common, 10, 5, 2.5, 1.25 and .62 
> >watts.
> >
> >I would think that if this transformer could match 600 ohms to 8 ohms

> >the
> >primary would be marked in ohms.
> >
> >I do not want to damage the receiver, so does anyone have an idea 
> >what's
> >going on?
> >
> >73,
> >Barrie, W7ALW, DN36au,
> >QRV 6M, 432 &1296 EME

Robert & Susan Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
<wa5cab at cs.com> (Primary email)
<wa5cab at comcast.net> (Backup email)
Boatanchors mailing list
Boatanchors at mailman.qth.net
** List Administrator - Duane Fischer, W8DBF/W9WZE **   
** For Assistance: dfischer at usol.com **         
$ For vintage radio info, see the HCI web site $      

This list is a public service of the City of Tempe, Arizona

Subscription control - http://www.tempe.gov/lists/control.aspx?list=BOATANCHORS
Archives - http://listserv.tempe.gov/archives/BOATANCHORS.html

More information about the Boatanchors mailing list