While I'm fiddling with the Morris ...
I have a spare radio, fairly modern, complete with USB socket, but stereo, of course. The Morris has one speaker, in a pod. Were I to wire both stereo outputs to that one speaker, in parallel, would I risk damaging the radio?
Interesting question. Would that result in the speaker output being the difference between the sounds on each channel? Does the radio have the ability to output mono sound?
Almost certainly. Could be in a bridge output format and this will not work. What about putting two speakers in the pod? If you are modifying the interior with a new radio, why not add two decent speakers in any case? What was the earth line in a Morris, plus or-? Brian
It would only be the difference if wired out of phase, but so many output stages use a bridge config, that i'd not want to chance either way. Brian
The OP would be connecting the two live outputs together. That could result in very large currents unless the two channels were broadcasting the same signal exactly in phase. There might be overload protection on the radio. Unless there's a mono setting on the radio, I wouldn't chance it.
In message , snipped-for-privacy@yahoo.co.uk writes
I need to rewind here. Just looked at the radio more closely, and it has outputs for four speakers (two each, front and rear) so I may have to buy a pair of pods.
Rewritten question - assuming I have a pair of speakers, can I connect front and rear left to one speaker, and front and rear right to the other? Or better to connect front only and ignore rear?
In message , Brian Gaff writes
The Morris was positive earth, but was converted to negative a few years ago.
For speakers, I am looking at something like eBay item 263453272331
Yes, better to connect front only and ignore rear. Just double check the manual that it's okay not to connect to the rear speakers.
Yes. It will do no harm to just have one speaker connected, though. But you'll only get the left or right signal.
It would not be difficult to modify the radio to give a mono output from both channels, though.
Amplifiers should have a lower output impedance than the speaker they're driving. Paralleling outputs presents this as a load to the other amp. Way lower than the designed load.
Yes Given just use one channel and put the thing into mono mode.
If you cant do that then wire a couple of 2.2 ohm 5W resistors together in series across the outputs and feed the speaker from the function
The quality will suck a bit, but not as amuch as a 70s single car radio speaker.
There has not been an amplifier since early valve sets that was not safe to NOT connect a loudspeaker
Definitely. Just connect one feed per speaker & all's well. Maybe you can find somewhere to hide a decent speaker, like under the seat.
NT
Yes, but the issue is often not this. the issue is that they do not have either side of the speaker as earth, and hence the effect is almost to short out the supply via the output device. Most are protected so the net result would probably be click, then nothing. Also of course, the old speaker in a Morris will be a sensitive cheap oval one meant for old fashioned low output radios, usually class A stages with a transformer employing one big power transistor, not a sophisticated, often surround sound gadget with two or more amps running in class a/b bridge configuration to get the extra output needed for the inefficient speakers one finds nowadays. Brian
Reminds me, parents used to have a valve car radio. It started in an Armstrong Siddeley car (don't know if it was original fit, or if my dad fitted it). Dad transferred it to a
1965 Vauxhaul Victor. The dashboard part had the tuner and preamp valve stages, which was connected with a thick umbillical cable to a box in the passenger footwell which had the power output stage and transformer, and the HT generation and rectifier valve. The HT generation was driven by a plug-in vibrator which was basically a changeover relay operating as a buzzer in a metal can with sound and vibration absorbing material around it, driving a centre-tapped primary of a step-up transformer. The vibrator was worn out and the box usually needed a kick to get it started. It was supposed to be regularly replaced, but they were no longer available, so I would keep opening it up and repairing it as the contacts wore out. Eventually, I replaced it with a transistor multivibrator circuit, and the HT rectifier valve with semi- conductor diodes.
Remember my father getting a car radio fitted. Mid '50s and totally valve. But IIRC the first of such which was all the one unit. RadioMobile. Quite an exercise in packaging.
My first FM car radio - found on a scrap LHD Opel in a yard - was also valve, with two units. And 6 volts. We converted it to 12v. No UK FM car radios at that time.
When I worked at Technical Trading (q.v.) the shop manager (Chris, I think) had an Armstrong Siddeley.
That is just how I remember Chris's radio, so perhaps it was standard fit. (I also remember the strange hinge arrangement on the doors, and the preselect gearbox)
I remember those things. Also used in various military sets. I had a box of them, 'won' from the Royal Marines in Portsmouth.
Somewhere I still have a car radio that proudly says 'Transistor' on the front panel. It is of course a valve radio except for one output transistor, which oddly runs cold.
NT
Yes. Possible to make low HT valves for RF etc. But not for the power output. Some time before they got rid of an output and driver transformer, though.
I just did some googling, and this is the floor unit:
It looks like it has some type of standard interface which can be used with many tuners. I searched but although there are pictures of hundreds of 1950's radio tuners, I can't find the one we had, which I remember very well.
So did dad's. This might have been standard on Armstrong Siddeley. Wikipedia says they used Wilson pre-select gearboxes. Apparently, Wilson started off designing tank gearboxes in WWI, and developed the first gearbox allowing tanks to be driven by one driver, instead of needing two drivers shouting instructions between them.
The top picture is similar, but the vibrator had no mechanical connection to the case, and pushed into some foam or felt (I forget) which insulated the vibration from the can. Also, it was 12V.
The circuit diagram is what I remember too, except it had a valve diode and not a voltage doubler rectifier as shown in the picture.
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