Astron +1.
love this made in Irvine, CA little tank!
I bought an Astron RS-7A used but like new and retrofitted to enhance power delivery:
1) upgraded all wires to mil-spec silver plated 18/22 awg ( input / output use 18awg, voltage reference for LM chipset can be 18)
2) removed original filter cap (Nichicon 12000uF/25V), and replaced with 4 Rubycon 6800uF/80V in parallel. I ordered some NOS RIFA PEH169 10000uF but unfortunately they were way too big for RA-7A.
3) ditched speaker post voltage output, changed to aviation connector GX16-2pin and make a DC12V cable with 5525 dc jack.
4) adjusted to Dc12.0V output.
all materials plus shipping is $60-ish.
And I can obviously tell the sound difference versus AC 120V input into build in switching power - ouch!!! Gross!