Not just an replacement, but an improvement!

EML 1605
Description

This powerful triode is desigened for amplifiers without compromise. This tube is not directly in the family of 300B tubes, because the 1605 is made for higher voltage than the 300B, and it has somewhat higher gain. The transformer manufacturer can not make SE transformers for very high DC current, very high output power, and wide frequency range at the same time. For this reason we have chosen the 1605 to be a somewhat higher voltage tube. Like this, it can work at normal DC current level, as we are used from 300B. This will make it possible to choose transformers of not excessive dimensions, and good frequency range. To make circuit design easier, we have given the tube somewhat higher gain than 300B. This allows the user to drive this tube with any normal circuit, same as needed to drive a 300B tube. This will make it convenient to inspire a new design with 1605 on existing 300B amplifiers.

The high filament current, stands for excellent emission, which on a glance can be recognized by the beautiful linearity of the tube curves. On the long term, high filament current is the source for higher tube life as well.

Sound Character of the 1605 tube

When tubes are made larger and larger, such tubes often sound only good at high power. At low power, the sound becomes sterile, and the tube character gets lost. The 1605 is constructed to avoid this problem. It has wide, box-shaped plates, same as Marconi PX25, which tube is legendary for it's sweet, silky sound. This similarity gets also reflected by the tube curves of 1605, showing resemblance to PX25.

All together it can be said the sound of 1605 is in between 300B and PX25, though much higher power levels are possible.

Example of good transformer:

LL1623-120mA (Wire secondary for ALT B, C, D for : 4, 8, 16 Ohms in this order)

Features

  • Double Mica tube top
  • Gold plated, Wolfram Grid (Note6)
  • Soft rubber suspended tube base
  • Center tapped filament
  • Slow Start filaments, for best lifetime
  • 0.5 mm thick plates
  • 12 circular coolers (6 double plates)
  • Hard metal Construction (Note1)
  • Two side getters, one top getters
  • Hand blown Glass bulb
  • Anti-microphonic plate- and grid suspension
  • These tubes are shipped in a high quality dual box
  • Tube printing with real gold (metal), red color is glass burned into the glass
  • Machined, solid tube base pins for highest contact precision. YAMAMOTO tube sockets highly recommended.
  • Gold plated pins, black ceramic socket, with white bottom.)


1605
Detailed image
Side / Socket
Plate detail


Plate Curves
 Note3

 
Important !
Read all notes at the bottom of this data sheet before installing this tube.
.
Filament Ratings (See note 5) 
Filament Voltage (AC or DC)
5V
Tolerance on filament voltage
2 %
Filament Current
2,1Amp
.
 

Maximum Conditions
See also Note4.
(Not possible simultaneously) 
Plate Voltage 
650Volt 
Plate Current 
160mA 
Power Output in Class A 
30Watt 
Grid resistor
max. 50kOhm 
. 
 

Typical application
Recommended operating point
See also Note4.  

With auto bias or fixed bias

Plate Voltage 
580V 
Plate Dissipation 
64Watt 
Plate Current 
110mA 
Grid Voltage 
-88,7V
Plate Impedance (Rp)

861Ohms 
Amplification Factor 

5,8
Transconductance (Gm)

6,7mA/V 

Power Output in Class A
22Watt 
Load Impedance (Ra)
 2700-3600 Ohm
Grid resistor
100kOhm 
.
 
Mechanical Data 
 Size including Socket
(but excluding pins)  

200 x 68 mm
7.5 x 2.7 Inch 

Single Tube weight 
190 Grams 
Shipment weight for 
pair in gift box 
800 Grams

.


.

    Note 1)  Hard metal has a higher melting point than classical nickel. Hard metal gives a more precise material shape, and does not change the shape when heated.  This ensures  reproducible tube parameters, and long term stability. Hard metals allow the most precise grid wire distance, and ensures better uniformity and linearity of the tube.

    Note 2)  Individual Test data, such as:  Matching Data, Grid Current, Vacuum, Filament Current, etc.,  are on the certificate that comes with each individual Tube.  Each tube  is numbered, inside the bulb  with a metal Tag

    Note 3) This is a heavy power tube, and using it safely means avoid risks. The maximum conditions are destructive limits, which should not be reached even for a short moment. A "maximum possible" working point exists, but we do not specify it, because it is generally not a good idea to try this with any power device,both vacuum state or solid state. We found if we specify a "maximum" operating point, some users will try this out. What we publish here, is the recommended working point, which gives best reliability, optimized sound and safe use at the same time.

    Note 4) We specify 2% tolerance of the filament voltage, to indicate here that you should take great care in achieving exactly 5Volts. With DHT vintage tubes, you will often see only the filament tolerance unspecified. However this leads to a classical misunderstanding that in such a case one can choose 10% tolerance, which is not so for any DHT. NOS or new production.

    Note5) When using a slow-start circuit for the filament, you may not apply plate voltage during the slow start phase. Besides this tube has a slow-heat filament by itself, so a slow start electronic circuit has no advantage to use. This is so for all EML tubes. Also please read the guarantee conditions, about the use of electronic filament heater circuits.

    Note6) Gold Grids is a word generally used for gold plated grids, so not solid gold wire grids. The grids we use are made of specially purified hard metal, which is then thermally gold plated. The advantage of gold plated grids is better temperature stability, and lower grid current if the tube gets very hot, and (within limits) it protects the tube from overheating damage and gives some self repairing effect after accidental overheating.

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