Hi I was looking through RS components product line and found this cheap output transformer.
RS number 123-7237, OEP V78A01F
https://docs.rs-online.com/127f/0900766b8152890d.pdf
Has anyone tried one of these? RS offers free delivery in Australia making these a cheap transformer. The low frequency response graph looks like it was derived using a low Z source into the primary; it's primary inductance is only 19H, this may work OK with triode drive. I would like any reviews or comments.
Keep Covi-19 safe; my condolences to those that have lost loved ones.
from Ken Kranz in Adelaide Australia.
RS number 123-7237, OEP V78A01F
https://docs.rs-online.com/127f/0900766b8152890d.pdf
Has anyone tried one of these? RS offers free delivery in Australia making these a cheap transformer. The low frequency response graph looks like it was derived using a low Z source into the primary; it's primary inductance is only 19H, this may work OK with triode drive. I would like any reviews or comments.
Keep Covi-19 safe; my condolences to those that have lost loved ones.
from Ken Kranz in Adelaide Australia.
I posted, and then changed my mind, erased it and started over.
It is 5k push pull, 25 Watts.
But . . . only 19 Henry primary, way to low for push pull, the idea of using interleaved E's and I's should cause the inductance to be much higher.
Higher inductance is needed for low frequency bandwidth.
I do not see a spec for weight.
What is the price?
What tubes are you going to use?
What output stage mode, Pentode/Beam Power, Ultra Linear, Triode or Triode wired?
And it looks like it has a dip in the frequency response that starts before 10kHz.
In class A, each output tube will be driving 9.5 Henry, and when one tube cuts off (in class AB), the other tube will be driving 4.75 Henry.
I have been experimenting with a Hammond 5k 15 Watt Push Pull output transformer, and I would rather use it in most cases than
the one you spotted.
Just my opinion.
It is 5k push pull, 25 Watts.
But . . . only 19 Henry primary, way to low for push pull, the idea of using interleaved E's and I's should cause the inductance to be much higher.
Higher inductance is needed for low frequency bandwidth.
I do not see a spec for weight.
What is the price?
What tubes are you going to use?
What output stage mode, Pentode/Beam Power, Ultra Linear, Triode or Triode wired?
And it looks like it has a dip in the frequency response that starts before 10kHz.
In class A, each output tube will be driving 9.5 Henry, and when one tube cuts off (in class AB), the other tube will be driving 4.75 Henry.
I have been experimenting with a Hammond 5k 15 Watt Push Pull output transformer, and I would rather use it in most cases than
the one you spotted.
Just my opinion.
Last edited:
You could ask the manufacturer. They are in the UK.
http://www.oep.co.uk/contact
This approach has worked well for me in the past. Price is easy to look up at your local rs online shop. Where I live in Switzerland it is quoted at CHF 73.55 each (which is pretty good for free shipping).
V78A01F | Audio-Transformator 4 Ω, 8 Ω, 16 Ω, 25W Frontplattenmontage | RS Components
19H is quoted at 1kHz. Its listed on RS as weighing 2Kg.
I'm with 6A3sUMMER's assessment. For cheap stuff you often get what you pay for... But it might be OK enough if expectations are not overly high and you are driving it in UL. Forget driving it with triodes...
Ian
http://www.oep.co.uk/contact
This approach has worked well for me in the past. Price is easy to look up at your local rs online shop. Where I live in Switzerland it is quoted at CHF 73.55 each (which is pretty good for free shipping).
V78A01F | Audio-Transformator 4 Ω, 8 Ω, 16 Ω, 25W Frontplattenmontage | RS Components
19H is quoted at 1kHz. Its listed on RS as weighing 2Kg.
I'm with 6A3sUMMER's assessment. For cheap stuff you often get what you pay for... But it might be OK enough if expectations are not overly high and you are driving it in UL. Forget driving it with triodes...
Ian
Hi 6A3
Thank you for your reply, I agree with your statement that the primary inductance is very low hence my comment it may suit a triode output stage.
I wish the manufacturers would show how they make their measurements.
I agree the Hammond transformers do have a much better transformers available,you tend to get what you pay for.
Cost in Australian dollars is $137 each delivered, Hammond transformers are close to $200 each and the expensive freight is on top of that.
Everything has its place and they may well suit certain applications. I have wound output transformers in the past; with the cost of good laminations and wire this is not a cheaper option. My current thoughts are a semiconductor powered sub-woofer with a HPF on the main amplifier. I am currently designing and building a tube tester so any new amplifier is a long way off.
BTW I have just tested the relay board I designed for switching the tube socket pins, it has 15 relays on it, three boards will be used for a total of 45 relays. The linear high voltage supplies have been built and tested (3rd iteration) the entire device will be controlled from a dsPIC that I'm coding when time permits.
I have found pulse testing tubes is not the way to go for tubes that have been in storage for years, my thoughts are to let them run at power for a couple hours before testing. My tester will soak, test and then print out a report on a built in receipt printer.
ken k
Thank you for your reply, I agree with your statement that the primary inductance is very low hence my comment it may suit a triode output stage.
I wish the manufacturers would show how they make their measurements.
I agree the Hammond transformers do have a much better transformers available,you tend to get what you pay for.
Cost in Australian dollars is $137 each delivered, Hammond transformers are close to $200 each and the expensive freight is on top of that.
Everything has its place and they may well suit certain applications. I have wound output transformers in the past; with the cost of good laminations and wire this is not a cheaper option. My current thoughts are a semiconductor powered sub-woofer with a HPF on the main amplifier. I am currently designing and building a tube tester so any new amplifier is a long way off.
BTW I have just tested the relay board I designed for switching the tube socket pins, it has 15 relays on it, three boards will be used for a total of 45 relays. The linear high voltage supplies have been built and tested (3rd iteration) the entire device will be controlled from a dsPIC that I'm coding when time permits.
I have found pulse testing tubes is not the way to go for tubes that have been in storage for years, my thoughts are to let them run at power for a couple hours before testing. My tester will soak, test and then print out a report on a built in receipt printer.
ken k