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Siemens CCa (Enhanced E88CC) Gray Shield Matched Pair - Munich A0 1‡ 4E/5I - NOS

Siemens CCa (Enhanced E88CC) Gray Shield Matched Pair - Munich A0 1‡ 4E/5I - NOS

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Siemens CCa (Enhanced E88CC) Gray Shield Matched Pair - Munich A0 1‡ 4E/5I - NOS

Product Summary

Made for BP (Bundespost - German Federal Post of Berlin) by Siemens, later also approved for military use and various broadcast applications, these tubes carry a long and mysterious history, which might take months time to recount. Yet we picky audiophiles approve of their superior qualities on all accounts: matched triode, low noise screening, minimum 10,000-hour heater life expectancy, carefully controlled frame grid winding and anti-vibration build - this is about as good as it can ever get in the entire vintage tube world! And we look for "A0 1‡" date code, the unmistakable Munich code combination seen on all the gray shield CCa/E88CC tubes, whether it is acid etched in the glass or printed on the getter support metal tag inside the glass (even rarer!) 

Sound Qualities

As a major step-up of Siemens E88CC, the CCa tube naturally posses all the greatest traits of the family: the airy and transparent natural tone unrivaled even to this day, the extended yet never tizzy top end, the incisive, neutral and balanced midrange presentation, the clearly defined and deeply controlled bass that's always there with the perfect amount of weight. All these fantastic sound characteristics multiplied by three and that's what you should expect from the Siemens CCa.  And the most defining sound characteristic of Siemens tubes is their ability to retrieve the deepest levels of detail in sound, and these hidden sonic layers can go a long way to reveal the subtle ambient clues that help complete building a truly 3D holographic sound reproduction. The sound stage of Siemens CCa is amazingly wide and feels like the holographic field gets "flattened" into a panoramic view of your music, still curvy and enveloping, and with added head room - nothing in the sound can escapes your ears (or eyes.) While as quiet and analytical as the Telefunken CCa/E188CC tubes, Siemens CCa's also create a warmer, smoother and sweeter German tone (and VERY German) that's rarely heard elsewhere. 

Professional Sound Evaluation

The pair worked wonderfully and sounded terrific in our professional studio setup for monitoring. 

 - Input: Cambridge Audio CXC V2 dedicated CD transport + Schiit Audio Bifrost 2 Multibit DAC
 - Amplification: Liquid Platinum Tube Amplifier by Alex Cavalli 
 - Output: Focal Clear MG Pro open-back headphones

Our full tube sound review was written 100% based on the actual listening experience while this pair of tubes were running in the system described above.

Professional testing & sound evaluation

Both tubes tested Super Strong NOS (120%+ mutual conductance) on a Mercury 2000 tube tester with the following result (mutual conductance both in uMhos and in percentage of nominal):

Tube 1: 15,800/15,900 (126%/127%) 
Tube 2: 16,100/16,000 (129%/128%)

Good tubes start at 7000 and new tubes (incl. NOS/NIB) 12,500 - 13,000, and the Mercury 2000's rated mutual conductance (nominal) for new tubes is 12,500. Test result can also be seen in the pictures. In case you wonder what all these numbers mean to your sound experience, it's actually quite straightforward: mutual conductance directly translates to a tube's ability to amplify sound so the higher the numbers the stronger. 

Appearance & Cosmetic condition

Although little silkscreen is left on the tubes, the Siemens logos are still recognizable and traces of "CCa" can be seen on both tubes. 3-line Munich date codes are perfectly visible on both tubes:

Tube 1 (acid-etched code): A0 1‡ 4E (A0 1‡ = Munich CCa/E88CC Gray Shield, 4 = 1964 or Rev. 4, E = May)
Tube 2 (printed on metal tag): A0 1‡ 5I (A0 1‡ = Munich CCa/E88CC Gray Shield, 5 = 1965 or Rev. 5, I = September)

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