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α24 based preamp - input is welcome

alpha24 (preamp/buffer, voltage DAC analog output stage, balanced ↔ unbalanced converter)

α24 based preamp - input is welcome

Postby mpa2 » December 2nd, 2019, 11:57 am

Hi everybody!

After building Beta24, I'm also looking for a suitable preamp. Here is the current status of the project:

IMG_20191202_195846-01_resize_76.jpg


The functionality I'd like to have:
-two balanced inputs
-three unbalanced inputs
-one (unbalanced) input with fixed gain (about -6dB) aka HT bypass
-balanced and unbalanced outputs
-remote controlled (on/off, volume, mute, input selector)
-12V trigger output

The HT bypass function and the 12V trigger are comparatively easy to implement, but the right control system is yet to be found.

The lcduino control could be a way to go, but I don't like the LCD :) These fancy OLED displays look very good :)

I'm experimenting with a MUSES-based volume control now, which sounds perfect, but these 7 segment displays...

Anyway, any thoughts about a suitable input selector and volume control are welcome :)

Michael
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Re: α24 based preamp - input is welcome

Postby amb » December 2nd, 2019, 12:16 pm

There is an OLED-based version of the 2x16 display that LCDuino-1 uses (made by Newhaven). I have tried it but it doesn't work reliably, often powering up with garbage characters. I suspect the initializing sequence that the Volu-Master firmware sends to the display is where the problem is, but so far neither I nor Linux-works have been able to crack this one (not that we tried very hard). If you could get this working then I'll be happy to incorporate any fixes into the released code.

Note that the OLED display doesn't have smooth partial-dimming capability. It's either full brightness or off. You'll need a color filter in front to dim the display some, or it will be quite bright. and annoying.
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