CUSTOM DESIGNED OUTPUT TRANSFORMERS
This is a custom service for replacement or upgrade of output transformers in existing equipment and for new builds. We are not able to do rewinds.
The price depends on the size which is governed by the power rating and the lowest frequency for full power. It is possible to increase the size of the transformer to reduce losses and/or increase the bandwidth.
All output transformers are built to order in about 5 weeks and we do not make any charge for design.
We need a precise specification to work from and we guarantee to performance to this specification. Below is a form which you can submit to us with your requirement. Once we have accepted the specification we will email you a Design Reference which you can use to order on this site or by telephone to Sales.
| SIZE OPTIONS |
SIZE
Click for DIMENSIONS and STYLES
|
PRICE
(UK Pounds) |
WEIGHT
(kg) |
Approximate
Power rating PP
(Watts at 20 Hz) |
Approximate
Power rating SE
(Watts at 30 Hz) |
| D |
£117.43 |
1.0 |
5 |
5 |
| F |
£135.77 |
1.5 |
10 |
5 |
| I |
£159.53 |
1.8 |
15 |
10 |
| J |
£174.72 |
2.1 |
20 |
10 |
| H |
£166.82 |
1.9 |
20 |
10 |
| K |
£182.39 |
3.1 |
25 |
15 |
| L |
£180.20 |
3.1 |
25 |
15 |
| M |
£185.44 |
3.6 |
50 |
20 |
| N |
£190.98 |
4.9 |
75 |
15 |
| P |
£235.68 |
7.0 |
100 |
30 |
| P(Encapsulated) |
£339.36 |
8.5 |
100 |
30 |
| Q |
£300.06 |
8.8 |
175 |
50 |
| T |
£379.82 |
10 |
200 |
55 |
| R |
£486.65 |
11 |
225 |
60 |
PUSH-PULL TRANSFORMERS We normally design for full power at 20Hz . Other ratings are available for example, for guitar amplifiers our customers often request full power at 50Hz which greatly reduces the size of the transformer. As a guide, a transformer rated for 20 Hz would be about the same size as a transformer rated for approximately double the power at 50 Hz. The bandwidth will be from the specified full power frequency (e.g.20 Hz) to at least 25 kHz. bandwidth up to 80 kHz can sometimes be obtained for low impedance transformers of generous size. We will always optimize the design for bandwidth within the design constraints.
SINGLE-ENDED TRANSFORMERS The key design parameters are the reflected load impedance (Rl), DC standing current, the power rating and the lowest frequency at which the rated power is specified. The transformer will be very large if you specify the full power frequency too low. The bandwidth depends strongly on the driving source impedance (rp). Triodes generally have a much lower rp than pentodes. If we know the driving source resistance we can optimize the primary inductance and the coupling factor which determine the low and high frequency cut off frequencies. It is possible to have a transformer with full rated power at say 40 Hz but a frequency response extending down to say 10 Hz.
REPLACEMENTS AND UPGRADES
Size If you would like us to quote for a new transformer for a specific piece of equipment we first need to make sure it will fit into the space available. It is usually best to use a larger transformer to improve the performance and ensure it is properly rated for the job. Please choose the size and package style you need form our "Dimensions and Styles" page. You may find that your original transformer uses Metric dimensions in which case choose a size which is about the same volume or weight and then go to at least the next size up.
Primary load impedance Rla-a Next we need to know the reflected load impedance of the primary winding. Usually is is possible to get a schematic from the internet though often this is not specified. It is possible to determine the anode load for the output valves from the valve specification which can be found using Franks Electron Tube Pages. If you forward the schematic to us at support@sowter.co.uk we will be pleased to help with this and any other points. If you have a working transformer you can measure the Rla-a quite easily with a low voltage ac supply and a voltmeter. See our FAQ.
Secondary impedance options You can specify various configurations.
Once you have determined size, package style and the specification please complete and submit the form below. We will analyses the specification and if we can make it we will send you a formal quotation. There is no obligation to order. Feel free to specify an alternative design point for us to quote if this helps you get the product you want.
