Description

Guarantee program for first owner.

At EML we have the normal guarantee. In addition to that, the first owner can register the tube within 4 weeks after receival, at the Emission Labs ® web site, to participate in the 5 years guarantee program.

Our Guarantee conditions

Register here for the 5years guarantee

Features

• Gold Plated Grid. (See Notes)
• Soft rubber suspended tube base
• Hard metal Construction (See Notes)
• Extra large getters
• Hand blown Glass bulb
• Anti-microphonic Anode- and grid suspension
• These tubes are shipped in a high quality dual box
• Tube printing with 24k gold, and red color burned into the glass
• YAMAMOTO tube sockets highly recommended.
• Gold Plated, black ceramic socket

Sound Character of the EML 12B, 20A, 20B, 30A Series

• Used as OTA (One Tube Amplifier).
• Used as a driver tube

20A/20B vs 30A

The 30A tube is just made for higher gain, and less gain of it's driver stage is needed. However output impedance of 30A is accordingly higher, and the design must be made with more care. Whereas the lower output impedance of the 20A /20B Series is generally easier to work with. (Here is a measurement, showing 60dB distance from 2nd to 3rd harmonics, using the 30A tube. This graph is for the tube + transformer together).

The new 20B-V4 tube

We recommend this tube for new designs, because it is upwards compatible to the classical 20B, but offers the advantage of the Cathode Tapped heater. By adding a Cathode Tap connection to the filament, we get a real cathode connection, for a simpler circuit, yet with better performance. This requires an socket with more than 5 electrical connections pins, so we choose for the Octal socket.

With the Balanced Heater, we enter a new field of applications. When biasing a DHT tube, there is no cathode to connect something to. The cathode connection must be artificially constructed, either by two resistors, or by a Cathode Tap on the heater transformer. Both these methods are a compromise to the signal path, and this compromise is now eliminated by the V4 version.

It must be said, the V4 is a beautiful tube, which fulfills the needs of designers, the best possible way. Link to Application Note AN-6 about balanced (Cathode Tapped) heater.

Recommended LUNDAHL SE Output transformers

SPEAKER OUTPUT APPLICATION LL2735B. Specially designed by Per Lundahl, for the EML20B. The specialty: When using an 1:4 input transformer, it is possible to build a complete SE amplifier with just one tube. Such concept is called One-Tube-Amplifier (OTA). We have a programmable (1...4x) gain PCB for this purpose, using LL1544A. . Some Examples of OTA amplifiers Pic1 - Pic2 Designed for 20B, this transformer works also on 12B. When using 12B, you need a driver tube in addition, but not the step up input transformer any more.

INTERSTAGE APPLICATION For 12B, 20A-Mesh or 20B, we recommend Lundahl inter stage LL2756. 20A or 20B can be used 1:1. 12B can be used 1:1 or 1:2 step up With this 1:2 inter stage, and an additional 1:2 INPUT transformer this will be a one-tube driver system, for tubes like 300B, 45 or 2A3. Thus bringing down noise, hum, and distortion to an incredible low level as not possible otherwise. This is because the first tube (as in a 3-tube triode amplifier) is not used. The first tube however is the main source of hum and noise. We recommend the programmable (1...4x) gain PCB for this purpose, using LL1544A

Filament Ratings
	Standard tube 12B, 20A, 20B, 30A 4Pin Socket (UX4)	Cathode Tapped 20B-V4 8Pin Socket (Octal)
DC voltage recommended	= 5Volt	= 2.5 - 0 - 2.5Volt
Tolerance on filament voltage	5%	5%
Filament Current	~ 1,4Amp	~ 1,4Amp
Filament Current	~ 1,4Amp	~ 1,4Amp
Maximum Time on Stand By (Heater voltage only)	2hours	2hours
Filament Current	~ 1,4Amp	~ 1,4Amp

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Maximum Conditions (See Notes)	EML 12B	EML 20AM	EML 20B	EML 30A
Anode Voltage	500V	450V	550V	500V
Anode Current	60mA	40mA	60mA	40mA
Continuous Anode Dissipation	25Watt	11Watt	25Watt	11Watt
Power Output in Class A	6Watt	3,6Watt	5Watt	3Watt
Grid resistor	below 470k	below 470k	below 470k	below 470k

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Typical Data	EML 12B	EML 20AM	EML 20B	EML 30A
Anode Voltage	390V	400V	420V	400V
Anode Current	40mA	25mA	42mA	25mA
Anode Impedance (Rp)	2k9	4k5	3k3	6k2
Amplification Factor	13.5	22,5	20	32
Transconductance	5.6 mA/V	5mA/V	5,9mA/V	5,2mA/V
Load Impedance (Ra)	8..16k	12..20k	11...19k	19k
Control Grid Voltage (actual voltage may differ, depending on test data)	-16V

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Recommended use	EML-12B	EML 20AM	EML-20B Low bias	EML-20B Med Bias	EML-20B Max Bias	EML-30A
Anode Voltage	390V	380V	380V	420V	500V	400V
Anode Dissipation	16Watt	9 Watt	12Watt	18Watt	25Watt	9Watt
Anode Current	40mA	24mA	32mA	43mA	50mA	22mA
Control Grid Voltage. See Notes	-16V	-10	-9V	-7,5V	-10V	-3V

	Curves 12B Curves 20A 20B Curves 30A
pdf Print Version	Print 12B Print 20A/B Print 30A
DOS Program, using curves as PTE Files 12B-PTE, 20B-PTE, 30A-PTE
SPICE Parameters

30A Some operating points
Anode Voltage	Control Grid Voltage See Notes	Anode Current (mA)	Trans- Conduc- tance (mA)	Anode Rp (Ohm)	Gain (mu)
300	-3	10	4.6	8k	36
300	-2	15	5.3	6k6	35
300	-1	20	5.5	5k9	33
.
360	-5	10	4.4	8k	36
360	-3.8	15	5.1	6k9	35
360	-2.8	20	5.7	6k	34
360	-2	25	6.2	5k6	34
360	-1.1	30	6.6	5k1	34
.
420	-6,7	10	4.3	8k5	36
420	-5.6	15	5.0	7k	35
420	-4.6	20	5.5	6k	33
.
480	-8.6	10	4.1	9k3	38
480	-7.5	15	4.9	7k2	35
480	-6.5	20	5.5	6k3	35
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Mechanical Data
UX4 BASE CONNECTIONS (UX4)	Size including Socket (but excluding pins) 155 x 58 mm 6.1 x 2.3 Inch Single Tube weight: 145 Gram Shipment weight for pair in gift box: 700 Gram
V4-VERSION OCTAL BASE CONNECIONS Pin 1+2: Heater1 Pin 6+7: Heater2 Pin 8: Cathode Tap (Cathode) Pin3: Anode Pin5: Grid

Notes.

• Hard-metals can be used in electron tubes, though these are more difficult to use, and more costly than the classical nickel. This ensures reproducible tube parameters, and long term stability.
• 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
• Plate Characteristics are made with the Sofia Digital Curve tracer.
• We are recommending the same values as Western Electric in their 1950 Data sheet.
• Some of our competitors claims to be the only one with a Center Tapped filament, but at EML we build since many years all tubes Cathode Tapped, not just this tube.
• Do not experiment with lower filament voltage, to expect better lifetime. If it was that easy, we would make the tubes like this ourselves. The specified filament voltage is the one for best lifetime.
• Gold Plated grids have a few advantages, such as increased bias stability, some protection against accidental overload, and better linearity of tube curves.
• With all DHT tubes, AC or DC heated operation makes the grid bias voltage shift with 1/2 the heater voltage. (With DC heating, the tube draws less current at the same grid voltage). With DHT tubes, AC heated curves can always be recognized, by the zero grid voltage line, going exactly through the crossing of the axis system (so at the zero Current point). From the same tube, DC or AC heated curves can always be made.