UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Adding external speaker to Wireless set 19

M0SOE_Bruce · 24th Feb 2021, 7:24 am

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, 7:24 am	#5
M0SOE_Bruce Pentode Join Date: May 2013 Location: Deal, Kent, UK. Posts: 139	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?