Clementine CV345 12E1 fixed bias

sweet & juicy SE amp for 1626 Darlings and the 6L6 family

Clementine CV345 12E1 fixed bias

Postby Jeffytube » Thu Dec 04, 2014 2:20 pm

Here is my latest build. Has anyone tried the CV345? Tube lineup is 5U4, 6SL7 (green LED bias at 1.8v) and CV345. I tried cathode bias the CV345 but the cathode resistors were dissipating too much heat so I modified the circuit to fixed bias. The anode voltage is at 350vdc, bias voltage is 90v, 0.76v at pin 8. I don't know if this setup is optimal but the sound is awesome, similar to single ended 300B. While it is not as velvety as the high frequencies of the 1626 but the low frequencies are definitely more substantial than the 1626 Clementine. To my ears, the sound of the CV345's have less distortion than the 6L6, 5881.

The power supply is a NOS Merrit 350-0-350V @235mA, 6.3v @9A, 6.3v @3A, and 5v @2A for the 5U4 filament. The choke is a Hammond 2.3 H @ 38 Ohms A0-25319-0 made by Midwest. OPTs are Edcors GXSE10-8-5K, 5K primary and 8ohm secondary. Hammond case 12x8x3. I chose gray paint to match my vintage Ampex preamps.
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Re: Clementine CV345 12E1 fixed bias

Postby Shannon Parks » Thu Dec 04, 2014 4:54 pm

Looks great! Awesome use of the NOS Merrit power transformer for dramatic effect.

So are these a standard pinout? I've used 6BG6s, but they required some cuts-n-jumpers.

Shannon
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Re: Clementine CV345 12E1 fixed bias

Postby Jeffytube » Fri Dec 05, 2014 11:00 am

Shannon,

The CV345 tubes have the same pinout configuration as 6L6 or el34 tubes, therefore no cuts or jumpers required for the Clementine board. The anode plate top hats can be unplugged so I roll with any 6l6 type tubes. I have used 6l6, 5881, El34 tubes with this amp at different grid bias levels.

Jeff
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Re: Clementine CV345 12E1 fixed bias

Postby Shannon Parks » Sun Dec 14, 2014 7:00 am

Jeffytube wrote:Shannon,

The CV345 tubes have the same pinout configuration as 6L6 or el34 tubes, therefore no cuts or jumpers required for the Clementine board. The anode plate top hats can be unplugged so I roll with any 6l6 type tubes. I have used 6l6, 5881, El34 tubes with this amp at different grid bias levels.

Jeff


Fantastic! One last (silly) question: are those Bakelite or Micanol bases?

Shannon
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Re: Clementine CV345 12E1 fixed bias

Postby Jeffytube » Tue Dec 30, 2014 2:53 pm

Shannon,

The bases are brown and appear to be Bakelite to my eyes. I believe these were made by Mazda in England with the slotted getter.

Jeff
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Re: Clementine CV345 12E1 fixed bias

Postby SteveH » Wed Dec 31, 2014 7:59 am

I wish companies would make PT's like those again...great looking build !
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