• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

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Pete Millet Mighty Midget

Hi, I thought to share with you my lastest project: Mighty Midget from Pete Millett. As I wanted to make a white Amp I called it the mighty white midget.

Best regards
Christoph
 

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I just finished a complete rebuild on these Dynaco Mark VI monoblocks. Nearly every resistor was out of tolerence and I replaced all the film and electrolytic caps. All new tubes as well.
These are my first tube amps and first project.
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Also acquired these Tube Technology Genesis monoblocks. Don't know much about them and I am in need of a manual.
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Sure. Here is the GM-70 SE amp that I've just (almost) finished.

My own schematic, but it's nothing really special.

It outputs a measured 29W RMS before distortion shows. The first stage is a CCS loaded, LED biased D3a (the photos were taken with an E186F in that position). The D3a has enough swing to drive the GM70 into clipping.

The GM-70 are fixed bias. They are constantly monitored by an Arduino microcontroller that I've programmed, which switches off the amp in case of problems. It also does soft start and temporisation, plus LED control to indicate status, problems or overload/clipping.

OPTs are custom gapped (90mA) Lundahl LL1688.

The supplies are in a separated chassis. There are no filtering chokes in my supplies - it's done with Mosfets and SiC Schottky rectifiers, including the 1050v GM70 supply. The kilovolt supply is not stabilized, only filtered;
the 350v supply is stabilized, not regulated (I do not like the sound of regulated supplies).

Together with Rod Coleman's filament supplies, this makes the amplifier absolutely silent, ear to the (95dB) speaker.

It sounds great.


Awesome ! I hope you have a lot of spare GM70 tubes. They are not much sold on ebay anymore except the copperplate version.