Not just an replacement, but an improvement! 

Mesh Version


Did you know? Emission Labs ®was the first company to re-introduce the AZ4 in the year 2005.


The first owner can register the tube at the Emission Labs ®website, to participate in the 5 years guarantee program.


The AZ4 was in the next generation rectifier tubes, which followed up the famous RGN Series of Telefunken. Whereas the AZ1 was mostly used rectifier for small radios, the stronger AZ4 can do higher current. This makes it an ideal candidate for HiFi applications. It can easily supply a stereo amplifier using a pair of AD1 or 2A3, as done for instance in the Yamamoto A06-03 amplifier. The base of this tube is an original old bakelite base, that we remove from NOS tubes.

For ultra low ripple,  it is recommended to use the Lundahl LL1673 dual coil choke in low CMR configuration. In this configuration, there is virtually no field radiation from the choke. (See  link to circuit diagram, at the bottom of this page). 

  • Hard metal filaments (Note1), series connected.
  • Each tube  is numbered, inside the bulb  with a metal Tag
  • Hand Blown glass, and two extra large getters.
  • These tubes are shipped in a high quality box.
  • Tube printing with real gold (metal),  red color is burned into the glass. 
  • NOS bakelite socket.


Previous Type
Later Type
Max Transformer AC
Max Capacitor
Heater Current
Max DC output
2x 300V
2x 350V
2x 300V
2x 500V

Some rectifiers as made around 1930..1950


Typical application notes below here, applies for AZ4 as well

Large Image
Anode Detail

Ceramic Socket


Filament Ratings
Filament Voltage
= 4 Volt 
Filament Current 
~ 2.3 Ampere 

Maximum ratings

IMPORTANT: Please read the notes at the bottom of this data sheet

AC input voltage
DC output current
200 mA
Minimum Copper Resistance of transformer minimum value. Add normal resistor if copper resistance is too low. (so if you have 120 Ohms, you need to add 80 ohms or more)
2x 60 Ohms
First capacitor,  connected to Anodes
60uF  max
AZ4 Mechanical Data

Size of Glass Bulb
125 x 58 mm

Tube weight:
130 Gramm
Shipped weight for a single boxed tube:
400 Gramm


Note 1) Good care should be taken when making the design of any DHT rectifier. It must be prevented to have strong current peaks, through the first capacitor, because consequently this flows through the tube anode, and transformer windings as well. The transformer will produce mechanical hum by this, most specially if windings symmetry fails. Also the tube will suffer. For this reason, the first capacitor (C1) should never be larger than stated in this data sheet.   The mechanical transformer hum, and also tube current peaks are greatly reduced by smaller capacitor values, and use higher choke values instead. Although higher capacitor values are at lower cost, using lower capacitors and higher chokes values instead, is always more satisfactory in the end. The result will be: Lower transformer hum, less electrical field radiation into the pre-amp, and more lifetime from the rectifier tube. This is why we recommend using largest chokes. From Lundahl, high value chokes are achievable at the same price as HiFi capacitors, like from a Mundorf or Black gate. So we have to go back to the roots, and use high quality, large value chokes, like in the old days of radio design. For best ripple suppression, increase the choke to any value you need, or even use a C-L-C-L-C circuit, as also advised in the historical RCA data sheet.
Note 2) As a rule of thumb, high voltage power supplies are best build with large size chokes, specially at high output current, whereas low voltage power supplies can be build more easily with large capacitors.
Note 3) Windings symmetry is needed with HV transformers to prevent hum. A HV winding with center tap, requires FOUR separated HV windings inside the transformer, which are arranged for the end user as TWO windings which are in series. It is remarkable to see, this is widely unknown today by many transformer manufacturers. Also this is more expensive. So often, they build tube rectifier windings only from two internal windings, and not FOUR windings as needed for tube rectifiers. However we have a tube data sheet here, no transformer construction manual, so we can not explain this in more detail.


Design note-1

Design note-2

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