There won’t be much room in the mobile home to set up any “real” speakers so I‘m going to set up my first serious experiment with a “small” speaker system. I added a sub out to my 14 watt per channel 10EM7 amp. Another 12SL7 with degeneration to get the effective mu down to about 20, passive mix and 200 Hz low pass (to get rid of unneeded HF voltage swing). Speakers are the little brother to my 3 way 10” shop background system - 2” mid/tweet and 7” midbass. Powered sub is a sealed 10” GRS and 150W class H home brew. Linkwitz- transformed to be anechoic to 22.5 (In theory). Crossover is at 60, right where the mains cut off naturally (Dip switch adjustable). I don’t mind the sound of a little room gain - been living with and enjoying my 2x10 flat to 23 monkey coffins for almost 2 decades now.
Oh yeah, and “BOX 2” is coming with me out to the site tomorrow, while I work on decking in above the back room and getting the rest of the 2X10’s up. 60 watts per channel feeding a pair of BOFUs. The car stereo head is only the media player - I don’t believe any 50 watt x 4 power rating, since I only measured 6 volts peak to ground on each side of the BTL, as one would expect. I needed to use speaker out instead of line out because thats what comes up in factory default. No backup battery (yet). Forcing it into limited-output class A with resistor to ground, of course. I hate the high crossover distortion inherent to 12V chip amps.
Oh yeah, and “BOX 2” is coming with me out to the site tomorrow, while I work on decking in above the back room and getting the rest of the 2X10’s up. 60 watts per channel feeding a pair of BOFUs. The car stereo head is only the media player - I don’t believe any 50 watt x 4 power rating, since I only measured 6 volts peak to ground on each side of the BTL, as one would expect. I needed to use speaker out instead of line out because thats what comes up in factory default. No backup battery (yet). Forcing it into limited-output class A with resistor to ground, of course. I hate the high crossover distortion inherent to 12V chip amps.
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Very cool. A little more power than my office set up built around Mission 760 bookshelf speakers and a 6.5" Parts Express sub kit, driven by one of their little class D subwoofer amps. Mains are driven by a 5W per channel pure pentode high feedback design with 6V6 and 6J7 - somehow manages to sound good. Source is an RPI4 based Roon endpoint into a Topping DX-3 PRO dac driving my hybrid 6N6P hybrid parafeed pre. Sounds surprisingly good for a desk top system.
This little thing was originally designed to be 10 watts in class A push pull. Very high perveance triodes - it would be as efficient as pentodes if it weren’t for the 37 volts of cathode bias. High enough damping factor with zero global feedback thanks to the 900 ohm Ra. But there is enough gm compression near cutoff that it pushes a bit into class B and gives me 14W at clip. I’ll take the extra 4 watts. All cheap Antek iron. I’ve always wanted a little tube amp on my desk - and not just a 12AX7 driving a Tripath chip. The sub amp is an adaptation of a tiny class H (100W 8 ohm, 150W 4 ohm) “tweeter“ amp for my small format PA. Tailored for LF and adding the crossover, of course. I had the design, I had extra transformers so that determined what was built.
The source will end up being Virtual DJ and my little Hercules console. Same one I use in headphones late at night.
The source will end up being Virtual DJ and my little Hercules console. Same one I use in headphones late at night.
The 6J7 is very linear and the amplifier which was inspired by a nearly 80 year old design has survived the churn here for over a decade has multiple feedback loops and 12V (A123) batteries for grid bias in the output stage. I built it about 14 years ago IIRC.
Details here: https://www.diyaudio.com/community/...-fixed-bias-se-amp.173454/page-4#post-3707157
It's a long thread I started when I observed some odd behaviors in this design,
Details here: https://www.diyaudio.com/community/...-fixed-bias-se-amp.173454/page-4#post-3707157
It's a long thread I started when I observed some odd behaviors in this design,
