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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

DIY Raspberry Pi Receiver, DAC, R2R Preamp, Crossover
DIY Raspberry Pi Receiver, DAC, R2R Preamp, Crossover
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Old 27th March 2020, 09:56 PM   #1
benproiii is offline benproiii  United States
diyAudio Member
Join Date: Aug 2010
Default DIY Raspberry Pi Receiver, DAC, R2R Preamp, Crossover

I built this for a friend of mine awhile ago wanted to post this build to get some feedback. It's preamp is the LCDuino from AMBlabs it's a great sounding relay based 256-step volume control. It is volume controlled and also controllable over the custom web interface that run on the Pi. The USB port on the back is for a flash drive that when plugged in will load any music on it and will display on the web interface you can select the song over that site. It also has a TOSLINK optical input and 1 analog input. The other RCA jacks are for the crossover, he has a bi-amp system with a separate subwoofer it has all the active filtering built-in. The front large knob is a motorized volume control it connects to the main Arduino CPU and switches the relay volume controller. The two smaller motorized pots on the front are to control the volume of the sub out and the high pass out, all volume controls can be adjusted by the web interface or a normal remote. The DAC is the γ1 from AMBlabs. Everything was hand soldered and all the brownish colored boards are all my designs I used EAGLECAD to layout the boards and also wrote the program for the second Arduino on the power board it controls the power switching, motor control, and IR input selection, it was a really fun project. Here is a link to a YouTube video of it in operation YouTube
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Last edited by benproiii; 30th March 2020 at 03:46 AM.
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Old 30th March 2020, 04:25 PM   #2
Mark Tillotson is offline Mark Tillotson
diyAudio Member
Join Date: May 2018
Location: Cambridge UK
Looks very neat with the SpiraWrap cabling. Quote a labour of love I suspect!

There's an aweful lot of filter poles there, is it 12 opamp stages per channel in total? How many cross-over outputs?

What was the rationale for going analog for the crossover, rather than digital in the Pi?
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Old 3rd April 2020, 06:19 PM   #3
benproiii is offline benproiii  United States
diyAudio Member
Join Date: Aug 2010
Thank You! I went all analog with the crossover because he wanted an analog input for a turntable. We listened to both a DSP crossover on my system and my analog crossover I use its based on the ESP Linkwitz-Riley 12db 3-way crossover. We both preferred the sound of the analog crossover, the one I build for him sums the R+L channels together for the sub output, the crossover frequencies are 20-75Hz for the subs, 75-200Hz for the woofers, and 200-20K for the main 2-way speakers which has a passive crossover for the tweeters.
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