RW-40-9.5
Single-Ended 5K / 9.5K ohms 40W type
Audio Output Transformer


The right on the photo is the R core output transformer in bare condition. The product is enclosed in the square case on the left.

RW-40-9.5 is R core audio output transformer for single ended type amplifier. Excellent magnetic properties of R core as well as precisely wound construction of the coil by the computerized manufacturing system achieve the wide bandwidth, low distortion, and low magnetic loss of the transformer.

Outline

Specifications



Type for Single-Ended
Output capacity 40W at 35Hz
Primary impedance 5,000 ohms, 9,500 ohms, with UL tap
Secondary impedance 4 and 8 ohms
3rd. cathode feedback winding
16 ohms X 2
Frequency bandwidth 25Hz to 35Khz (-2dB), input=4V, signal source impedance=5,000 ohms
25Hz to 35Khz (-2dB), input=4V, signal source impedance=9,500 ohms
Primary inductance (H)

17H(min.), 23H(max.) (5,000 ohms, DC current 80mA)
38H(min.), 42H(max.) (9,500 ohms, DC current 60mA)

Primary permissible DC current 110mA(5,000 ohms), 90mA(9,500 ohms)
Recommended primary DC current 90mA or less (5,000 ohms),
80mA or less (9,500 ohms)
Power loss 0.21dB 8ohms
DC resistance Primary B to 9.5K : 227ohms
Secondary 0 to 8 ohms : 0.18ohms
3rd. 0 to 16 ohms : 4.21 ohms
Dielectric withstanding voltage between primary, secondary and 3rd. . 2KV AC
Maximum permissible voltage of primary B to 9.5K 1KV AC
Core Type R160 160W core
Shape Enclosed in square case, the same mounting dimensions as those of Tango XE60,FC-30
Connections Lead wires
Overall dimensions and weight W: 110mm, D: 100mm, H: 150mm, Wt.: 3Kg
W: 4.33inch, D: 3.94inch, H: 5.91inch, Wt.: 6.6lbs.
Case color black, silver
Price US$220 (excluding tax and shipping)

Selection of load impedance and phase

The table below describes the selection of load impedance and the relation of the phase between the primary and secondary and 3rd. You can select non-inverted connection between the primary and secondary and 3rd for two-stage amplifier and inverted connection for three-stage amplifier. When the load is selected to 9,500 ohms, two taps for UL are available; its feedback factor is 50% or 25%. The higher factor makes the plate resistance and distortion lower, however, the sensibility and output power will be reduced.

Connected to

Non-inverted
9,500 ohms
Non-inverted
5,000 ohms
Inverted
9,500 ohms
Inverted
5,000 ohms

Plate

Yellow

Blue

Orange

Green

Screen grid
(UL tap factor)
Red(50%)
Green (25%)

Green (33%)

Red (50%)
Blue (25%)
Blue (33%)

Power source

Orange

Orange

Yellow

Yellow

Cathode feedback winding

When using the cathode feedback winding, the connection of primary winding and cathode feedback winding is as follows.
There are two cathode feedback windings in RW-40-9.5. The cathode feedback ratio can be selected by two windings being used in parallel or in series.
The cathode feedback ratio decreases if it uses in parallel. The cathode feedback ratio increases if it uses in series.
In addition, a different wire connection adjusts to RW-40-9.5 by the Non-inverted or the Inverted. The table below shows the connection of each situation.

Non-inverted Inverted

cathode feedback winding
parallel

Low
feedback


Non-inverted Inverted

cathode feedback winding
series

High
feedback

Calculating the closed-loop gain and feedback ratio
It explains here as 9.5K Primary and in parallel cathode feedback winding.
The gain and ratio for 5K Primary and in series cathode feedback winding is described in the last table.

The load of the output tube is both the primary winding and cathode feedback winding in the cathode feedback circuit.
The load impedance of the output tube is not 9.5K ohms.
The load impedance is as follows.

              Rl = ( SQRT(9500) + SQRT(16) ) **2 = 10296 ohms
丂丂丂丂                  SQRT    : Square route operation
丂丂丂丂                  **           : Factorial operation

The open-loop gain on the primary side before feedback
丂丂         Aopen = gm * ( 10296 // Rp )
丂丂丂丂                  gm         : Transconductance of the output tube
丂丂丂丂                  Rp         : Plate resistance of the output tube
丂丂丂丂                  //            : Parallel value operation

The feedback factor 兝 is a voltage ratio (a winding ratio) of load Rl and the cathode winding .
丂丂         兝 = SQRT ( 16 / 10296 ) = 0.039

The closed loop gain on the primary side after feedback
丂丂         Aclosed = Aopen / ( 1 + Aopen * 兝 )

丂丂         Feedback ratio = 20 * log( Aopen / Aclosed ) dB

Example
Value that uses 211 for output tube
              gm of 211 = 3150uS
              Rp of 211 = 3810 ohms

The open-loop gain on the primary side before feed back
丂丂         Aopen   = gm * ( 10296 // Rp )
丂丂丂丂丂丂            = 3150 * 10**-6 ( 10296 // 3810 )
丂丂丂丂丂丂            = 3150 * 10**-6 * 2781
丂丂丂丂丂丂            = 3.15 * 2.781 = 8.76

The closed loop gain on the primary side after feedback
丂丂         Aclosed = Aopen / ( 1 + Aopen * 兝 )
丂丂丂丂丂丂丂       = 8.76 / ( 1 + 8.76 * 0.039 )
丂丂丂丂丂丂丂       = 8.76 / 1.34 = 6.54
The feedback ratio
丂丂         Feedback ratio   = 20 * log( Aopen / Aclosed ) dB
丂丂丂丂丂丂丂 丂丂丂丂丂          = 20 * log( 8.76 / 6.54 ) = 2.54 dB



Primary 9.5K
parallel cathode feedback winding

Primary 9.5K
series
cathode feedback winding

Primary 5K
parallel cathode feedback winding

Primary 5K
series
cathode feedback winding

Impedance of cathode feedback winding

16

64

16

64

load ImpedanceRl

10296

11123

5581

6195

Feedback factor 兝

0.039

0.076

0.054

0.102

Open-loop gain by 211

8.76

8.94

7.12

7.43

Closed loop gain by 211

6.54

5.32

5.16

4.22

Feedback ratioBy 211

1.34
2.54dB

1.68
4.5dB

1.38
2.8dB

1.76
4.91dB

Shape and Dimensions

Characteristics

1. Frequency Characteristics

2. Frequency Characteristic: with different signal source impedances

The frequency characteristic of the audio output transformer varies with the signal source impedance that drives the transformer.

Frequency bandwidth by signal source impedance

Signal source impedance Bandwidth
9.5K ohms (Standard) 25Hz to 35KHz -2dB
2.5K ohms (Triode tubes) 12Hz to 55KHz -2dB
20K ohms (beam tubes) 35Hz to 27KHz -2dB

3. Phase Characteristic

4. Primary impedance Characteristic

5. Cathode feedback winding Frequency Characteristics

6. Cathode feedback winding Phase Characteristic

7. Primary Inductance Characteristic

The primary inductance of the single-ended output transformer has a characteristic of constant inductance. With this, the output transformer can drive steadily the loudspeaker without being influenced by the level difference of the superimposed DC current or AC input signal. The less the inductance fluctuates under various conditions, the more solid and stable sound quality can be obtained.

Primary inductance

Primary

Minimuminductance

Maximuminductance

DC current

9.5K ohms

38H

42H

60mA

5K ohms

17H

23H

80mA



Use of RW-40-9.5 as push-pull output transformer

The primary coil of RW-40-9.5 is perfectly symmetrical the center of which is set at red lead wire. This construction enables RW-40-9.5 to be used as constant inductance type push-pull output transformer, fairly suitable to build a DC unbalance current proof, maintenance-free type push-pull amplifier. The table below describes the connections and specifications as constant inductance type push-pull output transformer.



Type Constant inductance type Push-Pull
Output capacity 80W at 45Hz
Primary impedance 9,500 ohms, with UL (50%) taps
Secondary impedance 4 and 8 ohms
3rd. cathode feedback winding
16 ohms X 2
Frequency bandwidth 40Hz to 25KHz (-1dB), input=4V, signal source impedance=9,500 ohms
Primary inductance (H) 38H(min.), 42H(max.)
Primary permissible DC current 220mA (for 2 tubes)
Primary permissible unbalance DC current 90mA (recommended within 80mA )
Power loss 0.21dB 8ohms
Dielectric withstanding voltage between primary and secondary 2KV AC
Maximum permissible voltage of primary P-P 1KV AC
Core Type R160 160W core
Shape Enclosed in square case, the same mounting dimensions as those of Tango XE60,FC-30
Connections Lead wires

1.Cathode feedback winding of push-pull use
When using the cathode feedback winding, the connection of primary winding and cathode feedback winding is as follows. In the case of self-bias, a self-bias resistance and a bypass capacitor are connected between K1-Brown and a ground and between K2+ white and a ground.

Calculating the closed-loop gain and feedback ratio
The load of the output tube is both the primary winding and cathode feedback winding in the cathode feedback circuit.
The load impedance of the output tube is not 2.38K ohms of a usual pp circuit (1/4 of 9.5K ohms).
The load impedance is as follows.
丂丂Rl = ( SQRT(2380) + SQRT(16) ) **2 = 2786 ohms
丂丂丂丂SQRT : Square route operation
丂丂丂丂** : Factorial operation

The open-loop gain on the primary side before feedback
丂丂Aopen = gm * ( 2786 // Rp )
丂丂丂丂gm : Transconductance of the output tube
丂丂丂丂Rp : Plate resistance of the output tube
丂丂丂丂// : Parallel value operation

The feedback factor 兝 is a voltage ratio (a winding ratio) of load Rl and the cathode winding .
丂丂兝 = SQRT ( 16 / 2786 ) = 0.075

The closed loop gain on the primary side after feedback
丂丂Aclosed = Aopen / ( 1 + Aopen * 兝 )

丂丂Feedback ratio = 20 * log( Aopen / Aclosed ) dB

Example
Value that uses 211 for output tube
丂丂丂丂gm of 211 = 3150uS
丂丂丂丂Rp of 211 = 3810 ohms

The open-loop gain on the primary side before feedback
丂丂Aopen = gm * ( 2786 // Rp )
丂丂丂丂丂丂 = 3150 * 10**-6 ( 2786 // 3810 )
丂丂丂丂丂丂 = 3150 * 10**-6 * 1609
丂丂丂丂丂丂 = 3.15 * 1.609 = 5.068

The closed loop gain on the primary side after feedback
丂丂Aclosed = Aopen / ( 1 + Aopen * 兝 )
丂丂丂丂丂丂丂 丂= 5.068 / ( 1 + 5.068 * 0.075 )
丂丂丂丂丂丂丂 丂= 5.068 / 1.38 = 3.67
The feedback ratio
丂丂Feedback ratio = 20 * log( Aopen / Aclosed ) dB
丂丂丂丂丂丂丂 丂丂丂丂丂= 20 * log( 5.068 / 3.67 ) = 2.8 dB

2. Frequency Characteristic of push-pull use

3. Phase Characteristic of push-pull use

4. Other Characteristics
The impedance and inductance characteristics are the same as those of the single-ended connections. Please refer to those characteristics.

Ordering

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