Monday, February 24, 2014

Tube Review: The Mullard XF2 EL34 pentode

The Mullard EL34 - though perhaps not the best sounding of this family of tubes - is famous for a big and rich sound favored by guitarists and hi-fi nuts.  The XF2 version, like many early tubes, has welded plates, along with that thick, dark getter that is a trademark of the valves that rolled out from the Blackburn factory.  Later ones have similar construction but used crimped plates - I've never sat down and compared the different XF models, but needless to say they're all pretty good.

 The Mullard "sound", for whatever reason, has always been on the darker scale than neutrality.  Perhaps there is some secret mojo in the cathode chemistry or the metal quality, but this sound difference is easily noticeable in comparison to an original Philips EL34 or even any modern EL34.  This romantic sound, in the wrong amplifier, can lead to a syrupy sound - I'm thinking of something like a stock Dynaco 70 or any vintage amplifier with weak power supply capacitors and/or oil coupling capacitors.  So, like anything else, system balance is important.

The pair of Mullard XF2 EL34s I'm reviewing here are high mileage units pulled from my Eico HF-60 monoblocks.  Though they have plenty of hours on them, they still test almost as new - longevity is something that vintage tubes seem to do well and is needed, especially when running in something as abusive as the HF-60.  For this amplifier with a plate voltage of 400VDC and a screen of 250VDC, 60mA was chosen as a nice cruising speed.

Listening Tests:
The Immortal Otis Redding has a nice and punchy sound, albeit a tad stripped down.  The Mullards conveyed this simple recording with excellent clarity, depth, and dynamics.  Otis's voice sounded very natural as did the instrumentation.  The sound never became harsh or strident with this output tube.  There was also a nice projection to the vocals, pushing the sound beyond the speakers.  This seems to be a trait of vintage tubes - an enveloping sound with a 3-D effect: layered depth, wide and stable imaging, and a sense of being tangibly involved in the music.

Frank Sinatra - Sinatra at the Sands appears to be a three channel recording with instrumentation on the left and right with Frank right in the middle of the action.  The dynamics - on the right system - are truly breathtaking.  The Mullard EL34 excelled here, sounding almost as big as the Tung Sol 6550.  On the quieter songs like Don't Worry 'bout Me, all the emotion came through with the sensitivity that only Sinatra could surprisingly pull from that playboy act.

The last record in this listening test was Steely Dan - Aja which is a modern recording with deep bass, shifting dynamics, and crafty compositions.  The Mullard EL34 wonderfully captured the trailing edges of the reverberation and gave a soundstage that was big and organic.  The instruments floated nicely in space too.  There was a touch of darkness to the music, giving a not quite neutral sound compared to a Tung Sol 6550 or the ultra-vividness of the Philips metal base.

The Mullard EL34, compared to the new production tubes I've heard, has a real magic.  The music flows with more ease - a naturalness that is hard to describe, but the sound that is reproduced is cut from the same cloth in a grain-free way that makes me forget that I'm listening to a stereo.  Even the Shuguang GEKT88 - which is very good - doesn't capture this ability of convey the real soul of the recording.

However, the Mullard is not the most hyper-detailed and bends the signal to a darker, more romantic spectrum.  But this is a nice place to be - especially in the world of hot digital recordings and aggressive moving-coils.  If you're searching for the most transparent or an abundance of detail, then this may not be the tube for you.  But - and this varies from listener to listener - any sins are easy to forgive.  This is a tube for the music lover, not the nitpicker.