Mario TJ 2c51pp The Magnificient

For those of you unfamiliar with Mesh plates,please note that these beasts can handle a meager 28watts of anode dissipation compared to the standard 300B and therefore extra care should be taken when replacing normal 300B's with mesh plates. In normal single ended use max outputpower is limited to 7.98 watts and that doesnt include the losses of the circuit and output transformer.

What is so interesting about this tube is that its reputation precedes it, therefore i had to check it and i noted the µ is lower then standard 300b amps.

They also glow much nicer and have this blew glowing that i very much like and that scares many customers as they think the tube is defect but rest assured its not. The Mesh also makes you see the glowing of the filaments as well and that is rather romantic.

The Mario series is basically just a name that sums up the following criteria:

Stereo integrated in one chassis.

Moderate cost

Good engineering. ( slim chassis, meters,practical)

The Schematic :

As you can see this is a special driver for the 300B.

The idea was to mix a push pull stage with a single ended outputstage, since i didnt want to crowd the thing with tubes and the ideal fase splitter is a transformer ( or a very good designed long tail fase splitter ) I choose the transformer solution.

This complicated filament power supplies, had to add a second transformer as the upper tube is floating at approx 150 volts DC to gnd.

As a driver I choose the 2C51 as previous experience learned that this is a super tube especially the Western Electric version.

Gain was not a problem as i was not aiming to get max power, i measure 4.5 watts before clipping.

Filaments are DC regulated to avoid hum and negative bias is the preferred way to go as well.( except for the input stage ).

The use of Elna and copperfoil paper in oil capacitors from jensen on the strategic places pays off.

Dale resistors used everywhere and good chokes and good electrolytics but nothing fancy does the job.

The output tube is classicaly connected with a 3K load in order to have low distortion, the LL1623/80mA connected alt C can handle 13watts of output power which is ample and the Lundahls has excellent specs, the low frequencys are absolutely shattering, tight but tight basses are the trademark of most of my tube amps.

This one sounds georgiuos, silk but with the correct authority on all notes and a finesse that equals the 2A3 or surpasses it.

Sound is excellent and the spektrum analyser shows this to be true.

The powersupply

What you see is a dual mono construction after the tube rectification of the high voltage

Also all filaments have chokes to smooth the significant currents ripping through the diodes and very low ESR capacitors as storage and ripple smoothing caps. I also added a switch to invert polarity of the filament DC voltage across the output tubes to prolong filament life.

A few pictures of the beautifull inside of this amp

Please note the frequency response is limited due to the input transformer is load sensitive, meaning the pre amp has to have low impedance drive.

On the other hand i have never had an amp with such low noise on the output terminals, except for one that i had to modify as it had to much hum.

This is really one of my most impressive sounding amps, it sounds like a 100Watt amps, bass is tighter and deeper then my 100Watt home theater amp.

copyright webdesign 2004 Aquablue Benny Glass