53KU CV378 CV5745 U54 GZ33 GZ37 VALVE RECTIFIER VARIOUS MANUFACTURERS

octal based biphasic HT rectifier valve
Manufacturers: Brimar , Cossor , GEC Valves , Mullard , Osram
Wowee, where to start with this bad boy. Well, let’s take the baddest of the lot, the Cossor 53KU often labeled CV378. Introduced in 1948, this octal based indirectly heated full wave rectifier in which the reservoir capacitor should never exceed 16μF and to avoid peak current spikes and minimum load series resistance of at least 75 Ohms is recommended.

Let's start with the exquisite electrode structure which has a beautiful staggered parallelogram twin anode cage. Each anode within the cage is pressed to shape and stitched together enclosing the anode support rod. The top mica shows the oval cathodes and a sequence of insulated heater wires that pass the length of the cathode four times. To the rear of the staggered cages we have the elegant swan neck getter plate all contained within a gorgeous full baluster envelope – it looks like no other rectifier and so my ears sounds like no other too. The envelope rides on a beautiful curved micanol base ala KT66. The classic envelope is 56 mm in diameter, and excluding the IO base pins is 122 mm tall.

Cossor went on in 1958 – along with Mullard to manufacture the no less impressive performing but nowhere near as visually stunning tall form GZ37 also labeled CV378. In this format, each section posesses a tubular cathode which is strapped to one side of the heater to avoid the need for the additional heater power and consequent increased heat output which could be detrimental with such a narrow envelope. The tall form envelope is 42 mm in diameter, and excluding the IO base pins is 130 mm tall.

The GZ33 shares the same tall form envelope with the GZ37 (Mullard)/U54 (GEC) which in turn shares a family base connection sequence with the GZ32 and the GZ34. All of these devices are full wave rectifiers having a 500 Volt anode rating. As the numerical progression might suggest, the GZ32 is a 120mA rated device, the GZ34, a 160mA rated device and the GZ37 is a 250mA rated device. The GZ33, like it’s identical twin GZ37 is a 250mA rated device however, has a maximum reservoir capacitance of 120uF as compared to the GZ37’s maximum reservoir capacitance of 16uF.

Whichever brand or numbering is your preference, be assured that these are the daddies when it comes to octal rectifiers – simply the best - as you might expect as these are used in current high end amplifiers such as: -

Art Audio PX25

Diavolo.

Jota

 

 

 

 

 

Picture of MULLARD OLD SHIELD TALL FORM CV378 MILITARY GZ37 FROM 1963
MULLARD OLD SHIELD TALL FORM CV378 MILITARY GZ37 FROM 1963
A very nice EX EQUIPMENT device this, carrying the full Mullard Old shield markings in white ink on the front surface and on the obverse in white ink a CV378 military date code for MARCH 1963 and the Mullard Blackburn factory code. Device tests as full emission for eachsection within the envelope.
Stock Code: y98
Availability: 1 in stock
Delivery date: 1 week
£45.00
MULLARD OLD SHIELD TALL FORM CV378 MIL SPEC GZ37 FROM 1955
A very nice EX EQUIPMENT device this, carrying a military cartouche with the date code for June 1955 and the Mullard Blackburn factory code. Device tests as full emission for each section within the envelope.
Stock Code: g7
Availability: 1 in stock
Delivery date: 1 week
£45.00
Picture of MULLARD TALL FORM BROWN BASE GZ33
MULLARD TALL FORM BROWN BASE GZ33
A simply super example of one of these fine devices. This one has slightly smudged Old Shield white print, and envelope tight to the brown low loss micanol base with each section showing full emission and superb matching.
Stock Code: g12
Availability: 1 in stock
Delivery date: 1 week
£85.00
Picture of MULLARD TALL FORM BROWN BASE GZ33
MULLARD TALL FORM BROWN BASE GZ33
A simply super example of one of these fine devices. This one has slightly smudged Old Shield white print, and envelope tight to the brown low loss micanol base with each section showing full emission and superb matching.
Stock Code: 8.5.3
Availability: 1 in stock
Delivery date: 1 week
£95.00
Picture of MULLARD TALL FORM BROWN BASE GZ33
MULLARD TALL FORM BROWN BASE GZ33
A simply super example of one of these fine devices. This one has slightly smudged Old Shield white print, and envelope tight to the brown low loss micanol base with each section showing full emission and superb matching.
Stock Code: b9
Availability: 1 in stock
Delivery date: 1 week
£85.00
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