Adding a line input socket to a spectrum 128+2b

[CHRIS-F]

Hi Guys,

I'm not sure if this is the right section for this Question but I know some engineers have helped me out in here previously :-)

I have a retro spectrum +2b the model with the built in tape deck, on previous models and the +3 disc version the ear socket can be used to load games via an external source usually a stand alone cassette tape recorder, but the problem is on the +2 the ear socket is only an output, I recently found a program called O.T.L.A. that takes emulator compatible files such as tzx and creates custom loaders which you can output as wav or mp3 and the spectrum can handle up to 12000bps so you can load games in around 30 seconds, I could buy a load of tapes and transfer the wav files to tape, but I would much prefer to add a 3.5mm jack to the back of the computer to load from my phone/mp3/laptop/pc etc.

Now according to the schematics the tape head output is sent through a little amplifier and then sent to pin 34 of the ULA, as a novice in electronics I thought why not just attach a 3.5mm mono socket on the back and connect it to pin 34 of the ULA as the tape player does, so I had a look on Google and Youtube and found the following video. https://www.youtube.com/watch?feature=player_detailpage&v=qUIv-A_DOc0#t=978

I am just wondering what is wrong with my Idea of connecting straight to pin 34 of the ULA and why this guy says it wouldn't be a good Idea, I don't doubt his excellent knowledge, but it seems like using a wheelbarrow to carry your watering can to me not really necessary, especially if I add a switch so the tape and external input would never be active at the same time.

Thanks in advance for any help,
Chris.