AMB α24 fully-differential pre-amplifier

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Thermionic Idler
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#1 AMB α24 fully-differential pre-amplifier

Post by Thermionic Idler »

Not sure how long it's going to take me to make this a reality but here goes… I will say this is likely to be rather a slow build log.

If I'm going to build power amps with balanced inputs, first I need a pre-amp that has fully differential balanced outputs and my plan is to get there by means of modules available from Ti Kan a.k.a. AMB audio. Specifically the Alpha 24 differential line amplifier http://www.amb.org/audio/alpha24/ together with the LCDuino control system http://www.amb.org/audio/lcduino1/ linked to the delta1 and delta2 relay based volume control and source select systems. Yes the Alpha 24 is op-amp based… but, I researched it and found that it passes a 100kHz square wave perfectly, has output impedance in the 10's of ohms and ridiculously low distortion figures which are all documented on the AMB web site. Gotta be worth a try, right?

Anyway I've initially sent off for a lot of the hardware, including a couple of these beauties to decorate the front panel with (which will be driven by their own buffer circuitry): https://www.youtube.com/watch?v=K0NM2YxhWtI a proper old RCA style bakelite knob for level control/data entry https://www.don-audio.com/Bakelite-Knob ... -RCA-black and a chromed spring-return toggle switch to act as the power/config "button" for the control system. Here's a rough mock-up of how the front panel will look (thanks to my wife for a bit of photoshop on the bits):

Image

I wanted to make something that would match the style of my Garrard 301, and I was inspired by this beasty http://www.retroinstruments.com/product ... uct_id=op6 as well as the professional sound gear made by Shadow Hills Industries, here's a demo of their mastering compressor: https://www.youtube.com/watch?v=7OJyYafBLPM
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
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