OUTPUT TRANSFORMERS >>

The designs are specified according to their reflected primary impedance, maximum recommended dc standing current and maximum power. Frequency response is typically within 1dB from 20Hz to 40KHz and 4 and 8 ohm secondary taps are provided. The power rating of the OPT should be twice the maximum power output of the stage. Open frame, fully shrouded or drop through can be supplied as required.

Standard Range
single ended output transformers

Part No.
Lam Size
Stack (mm)
Impedance (ohms)
Primary I (mA)
Power (W)
Valves
Bandwidth
SPE101
120
45
2K5:0-4-8
80
25
300B,2A3
15Hz-45KHz
SPE102
120
45
3K0:0-4-8
80
25
300B,2A3
15Hz-45KHz
SPE103
120
45
3K5:0-4-8
80
25
300B,2A3
15Hz-45KHz
SPE107
29
38
2K5:0-4-8
75
15
6080/6AS7
20Hz-40KHz
SPE201
120
51
1K25:0-4-8
150
30
P300B, P2A3
15Hz-45KHz
SPE202
120
51
1K5:0-4-8
170
30
P300B, P2A3
15Hz-45KHz
SPE203
120
51
1K75:0-4-8
170
30
P300B, P2A3
15Hz-45KHz
SPE206
78
45
:0-4-8
120
25
P5881

These transformers all have multi wound primary sections for enhanced performance and bandwidth
Single ended output transformers

Part No.
Lam Size
Stack (mm)
Impedance (ohms)
Primary I (mA)
Power (W)
Valves
Bandwidth
SPE108
120
64
2K75:0-4-8
120
30
300B,2A3,VV30B
10Hz-75KHz
SPE109
120
76
15K0:0-4-8
75
40
211
15Hz-25KHz
SPE110
120
76
6K8:0-4-8
75
40
845, SV811, SV572
15Hz-50KHz
SPE111
29
38
15K:0-4-8
30
5
71A, 10Y
15Hz-50KHz
SPE204
120
76
1K8:0-4-8
150
40
P 300B, P 2A3
15Hz-60KHz
SPE205
248
76
6K8:0-4-8
150
50
P 211, 845
15Hz-40KHz

All can have ultra linear taps at no extra cost, all can be supplied fully shrouded, open frame or drop through as required. Please enquire about any requirements not listed here.

Transformer Size Chart

Transformer Designs
Lam Size
A
B
C=(2H+G)
D
E=(2F+G)
F
G=Stack Size
H
29
78
64
N/A
48
N/A
9.5
N/A
23
78
97
80
N/A
64
N/A
11.5
N/A
29
120
116
95
N/A
80
N/A
13
N/A
30
196
86
72
N/A
N/A
N/A
N/A
N/A
N/A
248
135
111
N/A
92
N/A
13
N/A
38

All dimensions are in mm

MAINS TRANSFORMERS >>

Our mains transformers are all designed using the latest CAD technology to provide good regulation (usually <5%) and optimum performance together with cool running for increased service life. All transformers are varnish impregnated using a UL approved clear Solventless varnish which not only seals the windings against moisture ingress but also gives extremely low audible noise. Open frame, fully shrouded or drop through types are available as requested. Pricing for mains transformers is based upon having 3 secondary windings and the VA rating of all the secondaries added together.
VA Rating
Lam size
Stack Size
Price on application
75VA or below
29 or 78
as required
100VA
120
38
150VA
120
45
200VA
120
51
240VA
120
64
300VA up to 3 windings
120
76
300VA
248
51
350VA
248
64
400VA
248
70
450VA
248
76

INTERSTAGE COUPLING TRANSFORMERS >>

The 1:1 ratio transformers have a very wide, flat, frequency response and excellent sonic characteristics. The 1:1.5 designs are more compromised, but still extend beyond 40KHz. The initial designs have been based around using the following valve types for drivers: 5687, E182CC, 417A, parallel 6SN7, parallel ECC82. Designed around a 15mA-20mA primary current, approx. 3K5 anode impedance, or below. Other drivers such as 3A/167M and ML4 have been used successfully. They can be used with a large range of output valves, including 211, 845, 300B, 6080, 2A3 etc.

Part No.
Lam size
Stack Size
Description
Bandwidth (-3dB)
Price on application
SPIS101
29
38
1:1.5 ratio for SE driver to SE output valve
10Hz-40KHz
SPIS102
29
38
1:1 ratio for SE driver to SE output valve
10Hz-120KHz
SPIS103
78
38
1:1 ratio for SE driver to SE output valve
10Hz-120KHz
SPIS202
29
38
1:1+1 ratio for SE driver to PP output valves
10Hz-120KHz
SPIS203
78
38
1+1:1+1 ratio for PP driver to PP output valves
10Hz-80KHz

POWER SUPPLY INDUCTORS >>

Inductor smoothing is becoming popular factors, and better voltaagain as more people realise it was abandoned for reasons of cost, not quality. Inductors afford higher smoothing ge regulation, giving quieter operation and better dynamics. Using chokes enables lower values of smoothing capacitance to be used, allowing higher quality types to be specified. The ch109 has been specially developed for use in high current, high voltage, choke input filter power supplies. Its primary use is for choke input supplies for stereo 300B amps where you may be looking at 450Vdc rails at up to 200mA. It is available only as an open frame construction, but has been built to be quieter than normal chokes in a similar supply.

Part No.
Lam size
Stack Size
Inductance (Henries)
Typical dcr (ohms)
Max DC Current (mA)
Price on application
SPCH104
29
51
20
360
100
SPCH105
u clamp
N/A
30
1K8
15
SPCH106
120
76
3
15
200
SPCH107
u clamp
N/A
10
140
60
SPCH108
29
64
10
100
130
SPCH109
78
64
10
56
220
SPCH110
u clamp
N/A
12
180
40
SPCH111
120
76
50
110
120

300B CIRCUIT INFO & DIAGRAMS>>

Click on the links below to see the recommended circuit diagrams and descriptions that are specifically designed to give optimum performance using the 300B triode valve in Class A in single ended and push pull configurations.

INDIVIDUAL TRANSFORMER OUTLINE SPECIFICATIONS>>
MONOBLOCK PARALLEL SINGLE ENDED AMPLIFIER TRANSFORMER COUPLED>>
MONOBLOCK PARALLEL SINGLE ENDED AMPLIFIER R/C COUPLED>>
PUSH-PULL MONOBLOCK AMPLIFIER R/C COUPLED>>
PUSH-PULL MONOBLOCK AMPLIFIER TRANSFORMER COUPLED>>
SINGLE ENDED STEREO AMPLIFIER TRANSFORMER COUPLED>>
SINGLE ENDED STEREO AMPLIFIER R/C COUPLED Channel A>>
SINGLE ENDED STEREO AMPLIFIER R/C COUPLED Channel B>>