Pro Audio Design Forum

Thanks Holger and Paul. We will be operating the forum for support for an indefinite time and I, and hopefully others, will continue to post new ideas here as well as documents for older semiconductors and pro-audio equipment. The MS matrix and bruno2000's upcoming mic preamp serve as an example of ...

Thanks John! Was that a Popular Electronics or TAA schematic?

I could scratch something up this weekend if there is interest, but probably not worth it for a one off.

Particularly since we all have extra power amps laying around. I think the ratio of amp channels to speakers here is at least 5 to 1.

Just had an idea. Take this current booster circuit with a 1646 (shown below) and make it a swinging op amp by voltage bootstrapping the rails as in the MCI drawing: https://www.ka-electronics.com/images/jpg/THAT1646_Current_Boost.JPG This gives you lots of output current, the bootstrap transistors ...

I used to write a column in RE/P so have some old issues laying around. John - Thanks for posting here in this neck of the woods. I think that ad ran in '77 or '78. MCI treated it like a major breakthrough. I think it was a cartoon but everytime I saw it I thought of Little Feat's "Dancing Sho...

Note: the "swinging opamp" if it's what I think it is (common emitter transistors driven by opamp power leads) is a relatively simple way to get there. Yep - that's what it is. Pretty simple circuit with widely available parts. Wished I had an old RE/P or dB magazine with the original MCI...

I'd go with the "MCI Swinging Op Amp" using a solo 5534. You might also try an NJM2114 there. They've got almost twice the output current of a 5532. Parallel the inputs of both sections and ballast the outputs through maybe 10-47R and you should be able to get 100-120 mA. Have the summed o...

Oh, so you want 100V? I did that when I was 17:

https://www.ka-electronics.com/DC_Pream ... 261974.jpg

This one is 70 V p-p. I made it ~100 Vp-p but it was a follower since more than about 70V exceeds the range of the op amp.

Do this with a pair of 5534s for balanced output. Note that Q1 is drawn with incorrect polarity. It should be an NPN. The base-collector capacitors, C114 and C115, are also incorrect and are 680 pF in the MCI. https://www.ka-electronics.com/images/jpg/MCI_Swinging_Op_Amp.jpg Image courtesy of MCI an...

I would go the power amplifier route. I think I have an HP200 with a high level option that might do it. Do you need +30 dBu or +30 dBm? You can get +27 dBu with a 1646. You might be able to squeeze +30 out of a good one using supply voltages above the absolute max and a heatsink. :geek: I actually ...