I-Pod to Gram input of vintage radio options

[Yorkie]

Sensible suggestion Alan!

I used my homebrew audio sine wave generator to poke a signal into the gram socket, and found that to attain the same volume on the radio in the gram position as when tuned into a station on MW/LW, required a p-p voltage of 1.5V. That suggested to me that the output from the I-pod - ordinarily intended for use with headphones (on which it gives ear splitting volume if turned up to max) is  of an insufficient level for the gram input. (No different with an I-pad or I-phone BTW).

Some time ago, on impulse, I bought a couple of dinky little 386 mono amp modules, which at the time were only about £2.00 each post free. (They have an on-board volume control/switch which would surely cost that much). Nothing ventured, nothing gained, so I hooked one up between the I-pod and the gram socket. Result? Bags of volume. I did wonder if it would make any difference to include an LT700 transformer back to front on the output from the amp, with the 4 Ohm side connected to the amp output and the high impedance side into the gram socket, to maybe be a better impedance match. Didn't make a scrap of difference.

I've attached a pic of the lash-up, which I'll house in a little project box. As can be seen, the module is only about the size of a PP3 battery.

The little amp module that I used now costs £6.90 post free:

http://www.ebay.co.uk/itm/Battery-Supply...1445845861

There are cheaper smaller ones - the PCB on these is 41mm x 13mm! 99p each, buy 3 and get 5% off, so I've ordered three for the ludicrous price of £2.82 post free, 94p each!

The world's gone mad:

http://www.ebay.co.uk/itm/LM386-Audio-Am...0792769118

The same thing can be had from a UK supplier  so no waiting, at £2.79 each post free:

http://www.ebay.co.uk/itm/LM386-Audio-Am...1507760671

They have an on-board pre-set volume control and no on/off switch as compared to the one that I used, but in my application and external volume control confers no benefit.

So that's that - all sorted now.

A lot of the cheap mini-amp modules on ebay are stereo in/out, and I'd wondered about connecting the outputs in parallel to feed into the mono gram socket, but no - can't do that - the technical info makes it clear that stereo outputs must not share a common ground, and if there's any connection between the two channels, all of the smoke in the module will leak out in a big puff, so all of £2.09 would go down the gurgler:

http://www.ebay.co.uk/itm/PAM8403-5V-Ste...1379192476

Thanks everyone for your input on this topic.