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-   -   Adding external speaker to Wireless set 19 (https://www.vintage-radio.net/forum/showthread.php?t=176941)

Ottawaboy 22nd Feb 2021 6:43 pm

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.

Orakle42 23rd Feb 2021 12:48 pm

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

Ottawaboy 23rd Feb 2021 2:35 pm

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.

G6Tanuki 23rd Feb 2021 6:58 pm

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.

M0SOE_Bruce 24th Feb 2021 6:24 am

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?

vosperd 24th Feb 2021 8:05 am

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

Keith 24th Feb 2021 10:42 am

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.

Ottawaboy 24th Feb 2021 11:54 am

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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