Hi all,
Help will be much appreciated to determine what I should ask to the transformer builder for an OPT to a hi-fi Single Ended Triode tube amp and a power transformer.
Such as electric insulation, lamination thickness, core type and shape, electrostatic shield, wire thickness etc
Core shape desired is C core for OPT, output expected are 4Ω and 8Ω 30W RMS.
For Power Transformer EI are better than C core?
For best cooling I will ask open air transformer, no encapsulation or poted.
Gracias
Help will be much appreciated to determine what I should ask to the transformer builder for an OPT to a hi-fi Single Ended Triode tube amp and a power transformer.
Such as electric insulation, lamination thickness, core type and shape, electrostatic shield, wire thickness etc
Core shape desired is C core for OPT, output expected are 4Ω and 8Ω 30W RMS.
For Power Transformer EI are better than C core?
For best cooling I will ask open air transformer, no encapsulation or poted.
Gracias
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A competent builder will only need to know the desired primary and secondary Z, and the power required. Plenty of off the shelf transformers that fit your description, why not use one?
I think I would ask how many high quality OPTs has he wound? Which interleave scheme does he intend to use? etc.
If you do not know what to ask for, and he has little or no experience of OPTs (except possibly rewinding broken guitar amps), then the chance of a good outcome is quite small.
If you do not know what to ask for, and he has little or no experience of OPTs (except possibly rewinding broken guitar amps), then the chance of a good outcome is quite small.
Agree and add: being a single ended amplifier, he must also include a substantial gap in the calculations.
And doubly agree that unless *you* can supply him with a full detailed blueprint, Hi Fi SE transformers are completely away from scope and experience of 99% of modern winders.
I very much you can trust him to design it from scratch.
And doubly agree that unless *you* can supply him with a full detailed blueprint, Hi Fi SE transformers are completely away from scope and experience of 99% of modern winders.
I very much you can trust him to design it from scratch.
Also you need to specify MINIMUM frequency of operation as it defines Bmax in the core and core area (Section).
to summarize the situation, I think it would be better to get closer to a known schema with opt known as giving good results
But as it is said below, newbie transformer manufacturers ignore almost all of the art of audio transformers. It is better to indicate exactly what he expects from the trafo.
For SE OPT, you would need to check the following:-
1. Primary impedance and inductance.
2. Output impedance and tapping available for matching the impedance of the speaker say 4, 8, or 16 ohm.
3. The idle current rating, say 120mA idle current. However, Lundahl offers various idle current ratings that you may choose for optimize the inductance when running lower idle current.
4. frequency response e.g. -3dB at 20Hz and 40KHz. It will be nice if there is a graph available.
my 2 cents.
Johnny
1. Primary impedance and inductance.
2. Output impedance and tapping available for matching the impedance of the speaker say 4, 8, or 16 ohm.
3. The idle current rating, say 120mA idle current. However, Lundahl offers various idle current ratings that you may choose for optimize the inductance when running lower idle current.
4. frequency response e.g. -3dB at 20Hz and 40KHz. It will be nice if there is a graph available.
my 2 cents.
Johnny
I'm building a headphone amp. Using 45's in a Tubelab SE board.
I ordered some iron from Electraprint and ordered
5K@50 ma with 46 and 300 ohm secondaries, approximately 2-3 watts. Jack did the rest.
I would not order iron from a winder if I thought I knew better how to design the tx than the winder. Find a good winder, give them your parameters, and let them figure out how to do it.
Randy
I ordered some iron from Electraprint and ordered
5K@50 ma with 46 and 300 ohm secondaries, approximately 2-3 watts. Jack did the rest.
I would not order iron from a winder if I thought I knew better how to design the tx than the winder. Find a good winder, give them your parameters, and let them figure out how to do it.
Randy
I could like to know what electric insulation, electrostatic shield and wire thickness I should ask?
The tube is 6C33 around 12W SE class A1 conservative.
The tube is 6C33 around 12W SE class A1 conservative.
Electric insulation is enamel for a transformer. AFAIK, they always use enameled wire.
Wire thickness would be based on the current and power, 50ma and 2-3 watts in my case. The tx maker will choose the correct wire to supply the power you are looking for.
I don't know about electrostatic shield.
My transformers has multiple taps on the secondaries, that provide 56 and 300 ohm outputs. These values look strange because they are for headphones.
But same idea as getting a transformer with taps for 4 and 8 ohms, or 8 and 16.
But you missed my point. I only specified a few things, as mentioned before. The transformer maker decided what wire he needed. I went with Electraprint based on their reputation, and because Jack (the head guy there) has many years of experience winding transformers.
Pick a good company, send them an email, tell them what you want to do, and let them help you out. That's what I did with electraprint. I gave him the background on what I was trying to do, we traded emails for a couple days, then I ordered a transformer that I am very happy with.
I expect you will need the primary impedance, I don't know what a 6C33 likes for impedance, and the bias current.
BTW, my 2-3 W transformers are pretty big, so an eletraprint 12W tx would be huge. I expect other companies are not as conservative, and would call a smaller transformer good for 3 watts.
Randy
To be able to spec that, you need the full design "recipe", either designed by yourself or pulled from a respectable book.
A couple oldtimer amp books included detailed transformer designs besides raw schematics.
A couple oldtimer amp books included detailed transformer designs besides raw schematics.
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Thanks for your input.
Usually 6C33 builders use primary 600Ω, but 500 and 1000Ω also was used some years ago.
I have see on web a brown paper used as insulation, but tape or some kind of cloth also could be used.
Operation point could be:
B+ 198V, Plate idle current 190V, Fixed Bias
The Valve Amplifiers/Morgan Jones have only 10 pages on OPTs.
This book have the full recipe?
Not a critical question, just out of interest, What made you decide on C-core?
Thanks