"Miniblok" 13EM7/15EA7 (6EM7) Single Ended Triode
1 watt per block
15EA7 - Dual Triode (Driver/Amp) Silicon Rectifiers
Sold on eBay
Inspired by late Fred Nachbaur
Built on metal-on-wood chassis.
Finished product! 13EM7s are dual triodes that have one section capable of high gain but low power, thus ideal for a preamp stage, and the other capable of low voltage gain and high current, thus ideal for a power stage.
Under the hood. Again, like the 6080 SET, it's a bit crammed, but the layout is well thought of before hand and minimal wiring is employed. The power trannies are two 12.6 VAC filament transformers in parallel, powering the two 12.5 V 450 mA filaments and a reverse connected 12.6 VAC > 240 VAC transformer for the plate voltage. There is a bit of hum (hardly audible), which could be due to AC filament supply. Fred used -3o VDC for fixed grid bias. The man was genius. He knew how to use cheap (including tubes) parts to make amazing sound tube gears. The schematic for "Miniblok" is available here.
These amps sound real nice. Don't let 1 wps fool anyone - these probably are one of loudest amps I have heard save the ST-70. The sound is open and spacious with strong mids and a plenty of tight bass. I have a tube audio buddy who built one of these in stereo and think that it sounds better than his 300B that cost him a fortune to build! 13EM7s do make some nice SETs. It would be interesting to hear a Push Pull version.
1 comment:
I really love the look of your amp. I´m building the same circuit and your presentation was an inspiration
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