Playtime new idea on severe amp control


Junior Member

Some new toys I am playing with, with A - A/B select and remote cable sense and Balance and Un-balance input Mono amps about 70W max 8Ohm. 1 channel shown here.

Each channel (1 shown) 4 off 47,000uF 2 off 300VA at 15V transformer. 12 output devices, 4 temperature sensors.Ag wire in PTFE for input and output wires. Poly Carbonate input caps. BW 1Hz - 400KHz flat 70W/8R 140W/4R bias from 30W Class A to 5W Class A in A/B mode. SECA driver stage max 140MHz BW to control with ease silly loads. Very expensive to make lots of time and very costly bits.

Not switched it on yet it has taken two weeks to make it so far and 4 lovely days with maths and a drill. Board 2 to complete and mount then Alan will blow his neighbours away with it.
I am hoping to get the DC offset to 10uV and drift of 5uV in 100Hrs max, Max Temp A/B Amb + 22C in AA/B Amb +40C
Max cable sense depending on driver wire about 50M.
Max sense current full power.

Picture of front panel, showing on/off L&R, and bias switches above (class A/AB), and a single switch for balanced/single ended input.

The other pic shows both circuits and the four transformers placed in situ.

All working.
75W/8R 140W/4R as it is a pair of Mono Amps
Low A Class setting 5W 8R
High A Class setting 30W/8R
BW 1Hz - 326KHz flat
Balance or Non Balance input 1V full power.
Input RCA 22KR
Input Balance XLR 600R nom (1KR)
Max short term current peak 62 Amps
Damping Factor (silly)

To select amp function there are switches to select Balance and High/Low A Class
THD Low A Class 0.001% into 8R at 20Hz - 50KHz
THD High A Class ( silly) 0.00001% 8R at 10Hz - 100KHz

More tests to be done on sense load input.


Senior Member
Damn. Is that fully balanced signal path all the way through? Yeeps. I feel like Donny in the Big Lebowski- I’m out of my depth.