EML1605, EML1605-V4 Data Sheet

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Description

EML 1605 tube

This powerful triode is designed for amplifiers without compromise. This tube is not directly in the family of 300B tubes, but rather related to the famous PX25.

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Description

This tube is not directly in the family of 300B tubes, but more related to the famous Marconi PX25. The Marconi company had two tubes in thier program, , the PX25A which was the low gain tube, similar to 300B , and the PX25 which was the high gain tubem which is now similat to the 1605. This tube is s characterized by a silker sound, if compared to the low gain tubes.

In few words, it is made for somewhat higher voltage, and it has almost twice the gain of a 300B tube. The PX25 is characterized by a silker sound, if compared to 520B. The Marconi company had two tube for this, the PX25A which is the low gain tube, almost a 300B, and the PX25 which was the high gain tube.

The higher gain has a practical reason. The amplifier designer (or the ready amplifier) may already have a good working 300B drive circuit. Due to it's higher gain, the 1605 will produce the higher output signal, at the same input signal as a normal 300B driver stage will deliver. (This is maximum 60 Volt AC)

The higher output power is achieved by the higher Anode voltage, keeping the Anode current at the same level of tubes like 300B-XLS or 520B. The transformer manufacturer can easily make a good SE transformer for higher voltage, but has problems with much higher DC current. For this reason we have chosen the 1605 to be a somewhat higher voltage tube. Like this, it can be used with normally available SE transformers. All in all, this will make it convenient to make a new design with the 1605, which is inspired by existing 300B amplifiers. Finally, the lower bias voltage of the 1605 will help to make the power supply more efficient in case of auto bias amplifiers.

Even amplifiers that are designed for the 520B-V3 can be adapted for the 1605 in many cases with only minor changes. Provided the amplifier has enough Anode voltage of appr 580V, all you need is adapt the tube bias, and check if the heater current can be supplied.

The high filament current, stands for excellent emission, which on a glance can be recognized by the good linearity of the tube curves, and on the long term, high filament current is the source for higher tube life as well. Basiclly everythig what makes a tube, improves at higher filament power.

We have two versions for the heater.

Normal heater, or Center Tapped heater.

With the center tapped tubes, we enter a new field of applications. This has not been done before with Audio tubes. When biasing a DHT tube there is no cathode to connect something to. The cathode must be artificially constructed, by a resistor network. Since many years, all EML tubes already feature a center tapped heater, which is a way to enforce better electrical field geometry. Only, to this center tap there was never an electrical connection. So to the tube itself we had to make no changes. To the center tap of the heater, is now connected a wire, which becomes the third connection to the heater. Now the tube has five wire connections, and for this reason we can not use the 4 Pin UX4 base any more. We have chosen for the Octal base. It must be said, the V4 is a very special tube, which fulfills the needs of Circuit Design purists the best possible way. Depending on how you do it, you can enter new design fields, or you may choose to connect the center tapped tubes just the classical way. Even so, for tube testing you can ignore the center tap, and just connect the tube the regular (four pole) way. In that case, the EML1605-V4 will behave like a standard four pin tube. In the case you own center tapped tubes, but you whish to connect them like a non-center tapped tube, this is possible too. In that case just do not connect the center tap.

Here is an application note, for how to use the 1605-V4 (center tapped heater) Version.

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 triode sound character gets lost. The 1605 is constructed to avoid this problem. It has wide, box-shaped Anodes, same as Marconi PX25, which tube is legendary for it's sweet, silky sound also at low power. 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.

Features

  • Double Mica tube top
  • Gold Grid (Note)
  • Soft rubber suspended tube base
  • Center tapped filament (WIth V4 also electrically connectec)
  • Slow Start filaments, for best lifetime
  • 0.5 mm thick Anodes
  • 12 coolers (6 on each side of the Anode)
  • Hard metal Construction (Note)
  • Two side getters, one top getter
  • Hand blown Glass bulb
  • Anti-microphonic Anode- 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
  • YAMAMOTO tube sockets highly recommended.
  • Gold Plated pins, black ceramic socket, with white bottom.
EML 1605 Filament Ratings (See note 5)
 
Standard tube
EML1605
Center Tapped
EML1605-V4
Filament Voltage(AC or DC)
5.0V
5.0V with Balanced Heater.
( 2x 2.5V )
Tolerance on filament voltage
4%
4%
Filament Current
2,1Amp
2,1Amp
.
EML 1605 Maximum Conditions
See also Note4.
(Not possible simultaneously)
Anode Voltage
650Volt
Anode Current
160mA
Power Output in Class A
30Watt
Grid resistor
max. 50kOhm
.
Typical application
Recommended operating point
See also the notes.

With auto bias or fixed bias

Anode Voltage
580V
Anode Dissipation
64Watt
Anode Current
110mA
Control Grid Voltage
-82V
Anode Impedance (Rp)

861Ohms

Amplification Factor

7,5

Transconductance (Gm)

8.8 mA/V

Power Output in Class A
22Watt
Input Signal needed for full output Power
57Volt AC (RMS)
Load Impedance (Ra)
2700-5600 Ohm
Recommended Transformer(s)
Lundahl LL1623-120mA
Grid resistor to ground
Max. 100kOhm

.

EML 1605 tube curves

EML 1605 tube curves

Download these curves as PTE file

What is are PTE files?

alternate text Print Version for drawings

Some recommended Lundahl transformers
 
Primary
Secondary
Auto Bias Cathode resistor
Anode Current
Anode Voltage to ground

LL1623-120mA
16Hz @1.5dB
Order nr:
218-111-49

3000Ω
Alt.B = 4Ω
Alt.C = 8Ω
Alt.D = 16
800 Ohms
110mA
668V

LL1623-220mA
16Hz @1.5dB
Order nr:
218-268-58

1600Ω
800 Ohms
(each tube)
110mA (each tube)
580V
.
EML1605 Mechanical Data

Size including Socket, but excluding pins: 145 x 58 mm
Weight of one tube: 140 Gram


Ceramic UX4 Base

Ceramic UX4 Base

Ceramic Octal Base

Ceramic Octal Base

Notes

  1. Hard-metals can be used in electron tubes, though these are more difficult to use, and more costly than the classical nickel. Hard metal Anodes have a more precise Anode distance, and do not change shape when heated, or at mechanical shock. This ensures reproducible tube parameters, and long term stability. Wolfram grids allow the most precise grid wire distance, because wolfram is an extreme hard metal. Best grid geometry ensures uniformity and linearity of the tube curves.
  2. Individual Test data, such as: Matching Data, Grid Current, Vacuum, Filament Current, etc., are on the Certificate that is on the outside of the tube box. Each tube is numbered from the inside, with a metal Tag
  3. Average Plate Characteristics: Made with the Sofia Digital Curve tracer. Anode curves with courtesy of AMR
  4. We are recommending the same values as Western Electric in their 1950 Data sheet.
  5. The Western Electric 1950 Data sheet. says 36 Watt maximum dissipation. Later data sheets say 40 Watt. Though 40 Watt is possible, this is a peak value only, and no normal working point. When you intent to get the 'maximum' out of a 300B, and operate this tube at the limits of safe operation, it is a better idea to use the 300B-XLS in such a case.
  6. Some of our competitors claims to be the only one with a center tapped filament, but this is not true. At EML we build since many years all tubes center tapped, not just the 300B.
  7. Don't experiment with lower filament voltage, to expect better lifetime. If it was that easy, we would make them like this ourselves. The specified filament voltage is the one for best lifetime.
  8. Gold Plated grids have a few advantages, such as increased bias stability, some protection against accidental overload, and better linearity of tube curves.
  9. The curves for the 300B are plotted, with AC heating. This is in accordance with the historical WE data sheet.