RME Radio Manufacturing Engineers Australia 45A1 Germanium Preamp

[NOON]

I recently picked up this interesting relic of the Australian electronics manufacturing industry. It was in the original box with the manual, but looks like it had been modified by someone to add XLR in and out. Put the scan of the manual here. https://groupdiy.com/threads/rme-radio-manufacturing-engineers-australia.80118/#post-1028691
A quick recap and tidy up later and it's up and running. Looks like all germanium transistors except for one BC107, specs in the manual are excellent and bench testing so far seems to match or exceed specs. There's some wobbles at the bottom end and the top end keeps rising from about 20kHz up past the limit of my test gear so I need to look at terminating the TXs properly. Lots of gain, very low noise and enough output grunt to drive a speaker, all the qualities you want in a utility preamp. Seems to ease into distortion nicely too.

Now I have to find a rack mount case to suit, some nice vintage knobs and a VU meter.

Anyone got any coments of the design? I can recommend it so far if anyone has some old germaniums they need to use up.

 

[NOON]

 

[NOON]

Here's an image of just the preamp board for faster viewing

 

[bowanderror]

I recently picked up this interesting relic of the Australian electronics manufacturing industry. It was in the original box with the manual, but looks like it had been modified by someone to add XLR in and out. Put the scan of the manual here. https://groupdiy.com/threads/rme-radio-manufacturing-engineers-australia.80118/#post-1028691
A quick recap and tidy up later and it's up and running. Looks like all germanium transistors except for one BC107, specs in the manual are excellent and bench testing so far seems to match or exceed specs. There's some wobbles at the bottom end and the top end keeps rising from about 20kHz up past the limit of my test gear so I need to look at terminating the TXs properly. Lots of gain, very low noise and enough output grunt to drive a speaker, all the qualities you want in a utility preamp. Seems to ease into distortion nicely too.

Now I have to find a rack mount case to suit, some nice vintage knobs and a VU meter.

Anyone got any coments of the design? I can recommend it so far if anyone has some old germaniums they need to use up.

How does it sound as a dirty preamp? Looks simple enough to rig up on a breadboard, so I might give it a shot.

 

[NOON]

Seems to ease into distortion gradually rather than hitting hard clipping nastiness, should make a nice dirty preamp if you run it in that zone.