Valve radio auxiliary input sockets. - UK Vintage Radio Repair and Restoration Discussion Forum

brett · 29th May 2005, 1:27 pm

HI guys,
I have recently purchased a Stromberg-Carlson model 355 valve radio from about 1932. I was wondering how I go about getting an AUX input for my Ipod? On the back it has 3 plug holes with the words Pick Up above them.

Any ideas?? I love the sound but where I live in Australia we only have 1 AM station which is mostly talk back.

Cheers
Brett

paulsherwin · 29th May 2005, 2:48 pm

I don't know this radio, but most pickup(US)/gram(UK) inputs are designed for a high impedence high output crystal cartridge producing about 1V. One of the sockets will be ground, and another will be signal. I don't know what the third is for in this case, you'll need to trace the wiring.

A headphone output will struggle to drive this input properly because it is intended to drive a low impedence load. You can improve things by using a stepup audio transformer, such as a transformer from a scrap transistor radio. Alternatively, you could build a simple preamp using an op-amp chip or even a single transistor.

An alternative approach is to build or buy an AM microtransmitter to 'broadcast' to the radio. You should find lots of info about this if you search this forum for 'transmitter' or 'modulator'.

You might like to try using the radio with a decent longwire aerial and earth connection. These radios were intended to be used with aerials more than 10 metres long, the longer the better. You'll be surprised what you can pick up even in rural Australia, especially after dark.

Good luck, Paul

Andrew_Keith · 29th May 2005, 2:56 pm

Paul, Just a question that has always eluded me, is it safe to use the pick-up input on a valve radio if the chassis is an ac/dc transformerless one?. Even if the mains is connected in the correct polarity. Is the earth to these inputs isolated or normally connected straight to the chassis.

paulsherwin · 29th May 2005, 3:04 pm

Quote:

Originally Posted by Andrew_Keith

Paul, Just a question that has always eluded me, is it safe to use the pick-up input on a valve radio if the chassis is an ac/dc transformerless one?. Even if the mains is connected in the correct polarity. Is the earth to these inputs isolated or normally connected straight to the chassis.

Andrew, most AC/DC radios don't possess gram sockets. Those that do have the earth connection isolated by a capacitor, though I'd still be wary of using it unless the capacitor was changed for a modern X2 rated component.

Best regards, Paul

29th May 2005, 1:27 pm	#1
brett Retired Dormant Member Join Date: May 2005 Posts: 1	Valve radio auxiliary input sockets. HI guys, I have recently purchased a Stromberg-Carlson model 355 valve radio from about 1932. I was wondering how I go about getting an AUX input for my Ipod? On the back it has 3 plug holes with the words Pick Up above them. Any ideas?? I love the sound but where I live in Australia we only have 1 AM station which is mostly talk back. Cheers Brett Last edited by Darren-UK; 30th May 2007 at 7:05 pm. Reason: Spelling errors corrected for the benefit of the search facility ( Namely, make of radio ).

29th May 2005, 2:48 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,931	Re: Aux input on Valve Radio???? I don't know this radio, but most pickup(US)/gram(UK) inputs are designed for a high impedence high output crystal cartridge producing about 1V. One of the sockets will be ground, and another will be signal. I don't know what the third is for in this case, you'll need to trace the wiring. A headphone output will struggle to drive this input properly because it is intended to drive a low impedence load. You can improve things by using a stepup audio transformer, such as a transformer from a scrap transistor radio. Alternatively, you could build a simple preamp using an op-amp chip or even a single transistor. An alternative approach is to build or buy an AM microtransmitter to 'broadcast' to the radio. You should find lots of info about this if you search this forum for 'transmitter' or 'modulator'. You might like to try using the radio with a decent longwire aerial and earth connection. These radios were intended to be used with aerials more than 10 metres long, the longer the better. You'll be surprised what you can pick up even in rural Australia, especially after dark. Good luck, Paul

29th May 2005, 2:56 pm	#3
Andrew_Keith Retired Dormant Member Join Date: Nov 2004 Location: Salford, Greater Manchester, UK. Posts: 150	Re: Aux input on Valve Radio???? Paul, Just a question that has always eluded me, is it safe to use the pick-up input on a valve radio if the chassis is an ac/dc transformerless one?. Even if the mains is connected in the correct polarity. Is the earth to these inputs isolated or normally connected straight to the chassis.