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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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22nd Feb 2021, 7:43 pm | #1 |
Diode
Join Date: Jan 2021
Location: Ottawa, Ontario, Canada.
Posts: 8
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Adding external speaker to Wireless set 19
Working on a Wireless Set 19 Mark II (Canadian). Anyone had experience(s) adding an external speaker (e.g., connections to output, impedance transformer, etc)? Thanks.
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23rd Feb 2021, 1:48 pm | #2 |
Pentode
Join Date: Nov 2015
Location: Maidstone, Kent, UK.
Posts: 131
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Re: Adding external speaker to Wireless set 19
Hi
Assuming you want only the A set output from PL2- a Pin 4, drive it into a computer sound system with stereo inputs in parallel - no problem. You will even have an amplifier as well. This assumes the B set & intercom are not required. PL2-a Pin 4 comes from a tap on the secondary of output transformer T2A which is a low impedance source. Orakle42 |
23rd Feb 2021, 3:35 pm | #3 |
Diode
Join Date: Jan 2021
Location: Ottawa, Ontario, Canada.
Posts: 8
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Re: Adding external speaker to Wireless set 19
Thanks, that's an option I had not thought of. Yes, only using A set as a receiver.
Thanks again. |
23rd Feb 2021, 7:58 pm | #4 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
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Re: Adding external speaker to Wireless set 19
In times-past it was Not Unusual [sorry, Tom Jones] for the 6V6 in the WS19's intercom-amplifier to be reworked to serve as an amplifier able to deliver 4 or 5 Watts of audio power: great for listening-on-the-speaker to shortwave broadcast stations on the 41- and 49-Metre bands.
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24th Feb 2021, 7:24 am | #5 |
Pentode
Join Date: May 2013
Location: Deal, Kent, UK.
Posts: 139
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Re: Adding external speaker to Wireless set 19
The output impedance at pin 4 is 100R. It was designed that way to drive multiple headsets. Most speakers are 3-8R so the impedance mismatch will result in lower audio out. By using a matching transformer you'll get best signal. Hammond type 144B is 200R CT to 3.2R so by using 1/2 of primary you'll have a perfect match.
Is the set stand alone or part of a system, ie control box or display? |
24th Feb 2021, 9:05 am | #6 |
Hexode
Join Date: Oct 2007
Location: Bristol, UK.
Posts: 440
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Re: Adding external speaker to Wireless set 19
On my mk3 ws19 I use an LS3 which is a military loudspeaker with a matching transformer which I believe gives 600 Ohms. This works well.
As I don't have the B set the unused aerial plug has been replaced with a 1/4" jack socket. I haven't changed the main wiring so I can still use the original headset if I need to. I have also successfully used a 3 Ohm speaker with a 100V line transformer as used in public address systems, I think these are available. Don m5aky |
24th Feb 2021, 11:42 am | #7 |
Heptode
Join Date: Jan 2003
Location: Tewkesbury, Gloucestershire, UK.
Posts: 690
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Re: Adding external speaker to Wireless set 19
I drive the headphones output through a transformer from a defunct Philips domestic valve radio. This had a third winding that was originally used for the negative feedback arrangement. This gives approximately the right impedance match and provides ample volume in a small room from an 8 ohm speaker. I have also used a small mains transformer successfully - we're not looking for hi-fi, after all.
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Keith Yates - G3XGW VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm |
24th Feb 2021, 12:54 pm | #8 |
Diode
Join Date: Jan 2021
Location: Ottawa, Ontario, Canada.
Posts: 8
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Re: Adding external speaker to Wireless set 19
thanks for the response, I use the set as a receiver only for SW listening, with a mains PS and not a complete set up.
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