Not just an replacement, but an improvement!

EML 45
EML 45-V4
uploaded: 24-Mar-2016


45 years after the last American tubes of "Type 45" were made, EML was the first company taking this tube back in production again in the year 2001.  At that time we used the larger glass bulbs of the 300B. Later, several of the general improvements we made to all of our tubes, were implemented. The main change, optically was the smaller glass size, and changes to the filament making this tube a "slow starter" and also reduce harmonic distortion. All critical parts are made of hard metal for higher reliability and reproducible quality.  They have 4  four original V-shaped filaments like found in vintage 45 tubes. (See note4) This tube has fully original specifications of the American RCA Type. 

Sound character of the 45 tube

We are often asked to describe the sound of our 45 tubes. If you are looking for real triode sound, the 45 tube is very interesting. It is important that tubes and speakers fit together well. So low power tubes sound best at high efficiency speakers, and vice versa. Best sound of the 45 is developed at the very sweet first Watt. The 45 will reward you with best sound when you are using high efficiency speaker systems, starting at 96..99dB. At the same time, here comes a drawback for the amplifier and the tubes as well. Such speaker systems of 100dB and above will make smallest imperfections audible, and the amplifier must produce as little hum and noise as can be. This is difficult. When you are thinking of 108db horn systems this stresses the design limits of tubes and amplifiers a lot. A quick way to test the noise level of your amplifier-tube combination is, to measure the AC signal out of the amplifier with the inputs muted, but the speaker connected. Anything below 3 millivolt at 8 Ohms is a good achievement, and such an amplifier below 1 millivolt can be called a fine piece of work. If an amplifier will produce low hum with many different tubes, this is definitely a better design, than such an amplifier that is critical on the tubes. Of course, here the tubes play a major role too. At EML we have greatly reduced hum and distortion of all tubes, by a new filament construction. This was done by a real, physical filament center tap, that is positioned outside of the plates, but inside the glass bulb. The result was, we reduced the hum level of the EML45 even below that of many good NOS tubes.

We have two versions for the heater: Normal heater with UX4 Base, or Center Tapped heater with Octal base .

With the center tap connected 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 pole 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 a link to Application Note 06, describing the center tapped tubes in general. Link here.

Distortion of the EML tubes is probably the lowest you can have. Here is a link to detailed test results, made for us by Roger Modeski from RAM LABs. From this you can see, the EML 45 is having the best results, most specially at higher signal level. For equal loudness, the human ear needs higher power at lower frequencies, and this is present in all music in a natural way. The result is though, bass tones of amplifiers have the highest electrical signal level, so bass distortion appears always first. This will change the sound character, making the bass less "dry". At medium volume you don't hear this as distortion. What you do hear is, the overall sound picture gets less precise, less natural, and it makes your ears tired from listening sooner. This is a very important mechanism to understand. The EML45 tubes give a strong contribution here, by reproducing the bass sound with smallest distortion a 45 tube can do.

We have added a gold grid to all EML tubes, some time ago, also to the 45. Very few NOS tubes have this. You can see the gold color of the grid wire when you look into the tube in the sunlight. The gold grid will give better bias stability, and you will may see the EML tubes bias perfectly right out of the box, and no bias change during burn in. Also read the next table "features". As an overall total result, the standard 45 is a no compromise replacement for the original RCA 45. Check also the 45-mesh data sheet.


  • Gold plated Grid
  • Center tapped filament
  • 30% lower distortion compared to any other 45. Read here.
  • Hard metal Construction (Note1)
  • Two extra large 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.  (White bottom.)

EML 45

Side - Top - Bottom

EML 45
Standard UX4 Base

EML 45-V4
Special Octal Base.
(see the main text)

Plate curves


Nice 1929 Article


EML 45  Filament Ratings 
Filament Voltage 
= 2.5Volt (AC or DC) 
Tolerance on filament voltage
Filament Current 
~ 1.5Ampere 
EML 45 Maximum Conditions 
Plate Voltage 
Plate Current 
Continuous Plate Dissipation
Power Output in Class A 
2.5 Watt 
Grid resistor (Read note5)

500k Ohm

EML 45 Factory Test conditions 
Plate Voltage 
Plate Current
EML 45 Typical Data 
Plate Voltage 
Plate Current 
Plate Dissipation 
9.9 Watt
Grid Voltage 
Plate Impedance (Rp)
1750 Ohm
1670 Ohm
Amplification Factor 
Transconductance (Gm)
Power Output in Class A 
1.6 Watt 
2 Watt 
Load Impedance (Ra)
3900 Ohm
4600 Ohm
EML 45 Mechanical Data

Size including Socket
(but excluding pins)

145 x 58 mm 

Weight of one tube:
140 Gram

Pin 1: Heater1
Pin 4: Heater2
Pin3: Anode (Plate)
Pin2: Grid

Standard UX4 Base

Size including Socket
(but excluding pins)
147 x 60 mm

Weight per tube: 140 Gram

Pin 1+2: Heater1
Pin 6+7: Heater2
Pin 8: Center Tap (Cathode)
Pin3: Anode (Plate)
Pin5: Grid
Pin4: Not on tube base

Special Octal Base, V4 Version
Shipment weight for 
pair in gift box: 700 Gram
  • Note 1)  Hard-metal filaments prevent filament breakage with DHT Tubes.  This material has a higher melting point than the classical nickel wires. Wolfram grids  allow the most precise grid wire distance, because wolfram is an extreme hard metal.   This ensures better grid  precision, which gives uniformity and better linearity at the low end of the tube curves
  • Note 2)  Individual Test data:  Grid voltage, Plate current, Transconductance and Filament Current is the test certificate that is on the outside of the box. Each tube is numbered, inside the bulb  with a metal Tag
  • Note 3)  Tube Curves:  Made on the The Sofia Curve tracer, with courtesy of AMR, Wisconsin, USA.
  • Note 4)  The V shaped filaments will give different electrical fields inside the tube, as compared to parallel filaments. For keeping the original character of this tube, we choose for V-shaped filaments.
  • Note 5) EML45 first generation (from before 2004) and all VV45 have a maximum grid resistor value of 100k. In most cases it will be possible to exceed this 100k, though we do not guarantee this. If you do, check if the bias current stays as stabile as before, but you need to check this at maximum signal level.

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