Stereo to mono converter - UK Vintage Radio Repair and Restoration Discussion Forum

johnny english · 2nd Oct 2014, 10:02 pm

Today I purchased 4 phono sockets and a miniature DPDT 6 terminal slide switch to make a stereo to mono converter with the provision to switch between mono and stereo as neither my phono amp or intergrated amp has a mono switch. I have never tackled making anything like this before but I am sure I could make it. The problem I have is with the circuit and the switch not knowing how to wire everything up safely. I have looked on the web and seen a simple circuit showing L+ switched to R+ and L- switched to R- and another using resistors in a similar configuration.

Thanks Ed.

Radio Wrangler · 3rd Oct 2014, 12:16 am

Pick one circuit or the other. Both should work. The resistors one will be a bit quieter, but might be a bit more accurate in applying the correct loading to the cartridge.

Use metal film resistors because they are less noisy than thick film or carbon types. They're cheap so you can try both circuits and take your pick.

David

peter_sol · 3rd Oct 2014, 2:30 pm

There is no need to use resistors.
The cartridge manufacturers usually state in their literature simply to parallel plus to plus and minus to minus with no change in performance.
You may connect all the earths together and just join both plusses up with your switchbox.

3rd Oct 2014, 3:03 pm

peter_sol is right, the paralleled cartridge would want half the load, the paralleled inputs would give half the load, perfect and simple (you could read it as twice the load, the effect is the same). I wouldn't bother paralleling the grounds, that's done at the amplifier anyway, a simple on/off switch twixt the signal leads will do (and it saves making any earth loops).

johnny english · 3rd Oct 2014, 8:53 pm

Thanks for your advice everyone much appreciated.

Stevie342000 · 30th Oct 2014, 7:40 pm

You may find this of more use try this link http://www.americanradiohistory.com/Audio-Magazine.htm you are looking for August 1958 copy page 24.

I saw you post and then found this some days or weeks later, meant to have posted it earlier.

It is a schematic for a stereo compatibility translator, which should serve your purpose.

There are lots and lots of other magazines both British or American for anyone to peruse for free.

2nd Oct 2014, 10:02 pm	#1
johnny english Retired Dormant Member Join Date: Nov 2013 Location: Liverpool, Merseyside, UK. Posts: 160	Stereo to mono converter Today I purchased 4 phono sockets and a miniature DPDT 6 terminal slide switch to make a stereo to mono converter with the provision to switch between mono and stereo as neither my phono amp or intergrated amp has a mono switch. I have never tackled making anything like this before but I am sure I could make it. The problem I have is with the circuit and the switch not knowing how to wire everything up safely. I have looked on the web and seen a simple circuit showing L+ switched to R+ and L- switched to R- and another using resistors in a similar configuration. Thanks Ed.

3rd Oct 2014, 12:16 am	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,866	Re: Stereo to mono converter Pick one circuit or the other. Both should work. The resistors one will be a bit quieter, but might be a bit more accurate in applying the correct loading to the cartridge. Use metal film resistors because they are less noisy than thick film or carbon types. They're cheap so you can try both circuits and take your pick. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

3rd Oct 2014, 2:30 pm	#3
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,906	Re: Stereo to mono converter There is no need to use resistors. The cartridge manufacturers usually state in their literature simply to parallel plus to plus and minus to minus with no change in performance. You may connect all the earths together and just join both plusses up with your switchbox.

3rd Oct 2014, 3:03 pm	#4
Guest Guest Posts: n/a	Re: Stereo to mono converter peter_sol is right, the paralleled cartridge would want half the load, the paralleled inputs would give half the load, perfect and simple (you could read it as twice the load, the effect is the same). I wouldn't bother paralleling the grounds, that's done at the amplifier anyway, a simple on/off switch twixt the signal leads will do (and it saves making any earth loops).

3rd Oct 2014, 8:53 pm	#5
johnny english Retired Dormant Member Join Date: Nov 2013 Location: Liverpool, Merseyside, UK. Posts: 160	Re: Stereo to mono converter Thanks for your advice everyone much appreciated.

30th Oct 2014, 7:40 pm	#6
Stevie342000 Hexode Join Date: Jan 2006 Location: Greater Manchester, UK. Posts: 373	Re: Stereo to mono converter You may find this of more use try this link http://www.americanradiohistory.com/Audio-Magazine.htm you are looking for August 1958 copy page 24. I saw you post and then found this some days or weeks later, meant to have posted it earlier. It is a schematic for a stereo compatibility translator, which should serve your purpose. There are lots and lots of other magazines both British or American for anyone to peruse for free.