28-05-2015, 10:43 AM
That was an earlier thread - the more recent one, which I started in March is here, in the correct section:
http://golbornevintageradio.co.uk/forum/...p?tid=4657&page=2
Despite all my best endeavours trying various methods seen on internet - LT700 transformers etc, I discovered that an I-pod (I-phone, whatever), does not have sufficient output to simply plug into the gram socket without a small preamp. I settled on the little Velleman pre-amp kit suggested by Dr Mark. I boxed it up, it works very well and my (adult) son is very chuffed with it, and has it running for hours on end. Didn't take a pic of the finished unit. I combined the stereo input via a couple of resistors into the input of the pre-amp, then used a couple of 'wander plugs' for the output to go into the gram socket of the radio.
Later I tried one of these ludicrously cheap and tiny LM386 audio amp modules, which also worked fine:
http://www.ebay.co.uk/itm/LM386-Audio-Am...1507760671
I poked a sine wave into it and adjusted the on-board pre-set volume control while observing the output on a scope till the gain was as high as it could be without going into distortion. The higher the input level from the amp, the lower can be the volume control on the receiver can be set to give a good output. (Better to thrash the pre-amp than the receiver!).
Hope that helps.
http://golbornevintageradio.co.uk/forum/...p?tid=4657&page=2
Despite all my best endeavours trying various methods seen on internet - LT700 transformers etc, I discovered that an I-pod (I-phone, whatever), does not have sufficient output to simply plug into the gram socket without a small preamp. I settled on the little Velleman pre-amp kit suggested by Dr Mark. I boxed it up, it works very well and my (adult) son is very chuffed with it, and has it running for hours on end. Didn't take a pic of the finished unit. I combined the stereo input via a couple of resistors into the input of the pre-amp, then used a couple of 'wander plugs' for the output to go into the gram socket of the radio.
Later I tried one of these ludicrously cheap and tiny LM386 audio amp modules, which also worked fine:
http://www.ebay.co.uk/itm/LM386-Audio-Am...1507760671
I poked a sine wave into it and adjusted the on-board pre-set volume control while observing the output on a scope till the gain was as high as it could be without going into distortion. The higher the input level from the amp, the lower can be the volume control on the receiver can be set to give a good output. (Better to thrash the pre-amp than the receiver!).
Hope that helps.
Regards, David.
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'







