• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tube power transformers

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#3
"Local" sources usually work out well. Still, if Triad Magnetics products are imported into "Oz", you might want to look into a Triad N-68X feeding a "full wave" voltage doubler for B+. A tad more than 100 mA. of DC at a bit more than 300 V. will be available.
 

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#4
If you have even numbers of the same types of tubes you might be able to wire the filaments in series for a higher voltage, lower current filament supply.

E.g. A design with 4x EL84 and 2x ECC83S can be wired to two series strings of filaments running off 25V instead of 6.3V. A 2x25V toroidal is very common.


Additionally, below is an idea I had to use 2x55V and 2x25V toroidals to make a 220-250Vdc B+ and 35Vdc filament supply. The motivation for doing this was that I effectively get 160Vac to rectify into a B+ voltage, and can tap off a low-ish voltage which can drive the filaments - the 35Vdc would be regulated using a buck converter to 25V @ 1A to run strings of four filaments.
The use of the full wave rectifier and centre-tapped connection shares the load of the B+ and filaments across both secondary windings.
Otherwise you would need to use a higher VA transformer as one secondary winding would be heavily loaded from the filaments while the other is only lightly loaded from the B+.
OjXGOfQ.png
 
#5
Thank you folks, much appreciated.........
Eli, Triad is not imported to Oz unfortunately.
HK, I have been using Voller transformers for twenty years but these days the labor in Oz is the highest in the world, so all his transformers start at about $200 and go up! He did a couple of very nice inductors a couple of years, they cost $300 then I had to spend a couple of hundreds more to set up the gaps. He left the gapping to me, I didn't have the expertise or equipment, so I asked Lucas to do it and he did a great job. But it's a fiddly job too and took him about five hours.

TMM, thanks for you great ideas.

Hugh
 
#6
Hi I live in Australia and face the same problems.

RS has free delivery so I often use two transformers back to back so you have an isolated 6V and 240V supply.

2 Output Toroidal Transformer, 50VA, 2 x 6V ac | RS Components
https://docs.rs-online.com/52f1/0900766b8157a9b3.pdf

As transformer normally are rated at the secondary under full load a 6V winding will produce the 6.3 required in most cases, often a small series R is required to drop the voltage. A 9V winding and series R can also be used.

Ken K
 
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#10
AKSA said:
I have been using Voller transformers for twenty years but these days the labor in Oz is the highest in the world, so all his transformers start at about $200 and go up! He did a couple of very nice inductors a couple of years, they cost $300 then I had to spend a couple of hundreds more to set up the gaps.
Click to expand...
Ok, looks like Mr Voller works very well and has built a reputation.
Excellent, but that sometimes leads to hogh price which in the case of something quite simple, such as your PT, may not be justified.

But I guess in Australia , a Country with MANY surprising similarities to my own Argentina (hey, we both kept making Ford Falcons forever) there MUST be one (or many) "guy with winding machine which can make transformers" and who would gladly wind "just one" for you.

Not sure if old Roly´s Ozvalveamps kept going on after his sad demise but certainly there must be other local Forums or resources where to ask.
Maybe some FB group?

Wonderful as it is, DIY Audio is "international" but heavily based around USA/Canada and a little UK/Europe,we faraway members are plagued by inconvenient and expensive freight and Customs barriers. 🙁
 
#12
AKSA said:
.. so I asked Lucas to do it and he did a great job. But it's a fiddly job too and took him about five hours.
Hugh
Click to expand...

Come to thinking, it was probably you who put me on to PV 20 years ago. Have used him probably 15 times and always excellent, thoroughly helpful. Always super nice product.

Is Lucas still winding?.. Since Bob S*gden retired, I've been buying signal transformers from overseas (Japan, Belgium, USSA). Be good if you had an inside contact on that. I was listening to a nice 300B amplifier with his Black A*t 2k7 OPT recently.

Sometimes you just gotta pay.. I don't see too many with ES and flux bands with custom service like PV offers. Couple hundred bucks, sure, so write it off through the business and use it for 100 years.

Regarding previous experience with chokes through PV, sounds like it could have been better organised. I digress back to topic.

HK
 
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