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help needed need transformer prim 230/110 sec 300v appr. 20ma +6,3v or 12,6v

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Alettagla

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Joined 2008
#1
Dear tubelovers

I have been searching the internet for many hours to find a small (preferably toroidal) powertransformer that need to power three 12ax7 tubes.

Application is for a smal guitar effects pedal. Which means that a lot needs to sqeezed into a small box. Therefor size matters!

Something like 300v and 25ma would be fine.

Also it should be from a relaible source (preferably) in europe because in the future more of these will be needed.
(I do have a source for a 300v 56ma torroid at Euro 34,- but I need something cheaper and smaller)

Your help is most appreciated.
Cheers René
 
#2
Hello René,

I like to buy Power Trafos from industrial control-panel Trafo makers.

for example, JMS will supply any kind of small single-phase trafo. On the Web-shop, you decide what secondary voltage you need, up to 1000V, and order.

A 25VA trafo is only about Euro 14:

http://www.jmsonline.co.uk/product_info.php?products_id=30

JMS is in UK, but many countries have a maker like this. In Italia, please try Ideomat SpA, Modena. Maybe there is a maker like these near you.
 
#3
O, and BTW, the EI split-bobbin type like this are usually much superior to Toroidals trafo for valve B+ supplies. Toroidal has very high primary-secondary capacitance (often 1nF or more), which lets all the mains noise rush in! And since the core cannot usually be grounded, no screening is easily achieved. The EI may have only 50-90pF, and a grounded core. Much better!
 
#5
artosalo said:
I have used this supplier for a while. Good price and fast delivery.
Would these two types do ?

TSTL 15/001 INDEL - Transformer: toroidal | Transfer Multisort Elektronik

TSTL 40/001 INDEL - Transformer: toroidal | Transfer Multisort Elektronik
Click to expand...


No I do need a little sized 300v 25 ma (or 6VA...to..8VA) and 6,3 or12,6 filament voltage.

But like Rod Colemans reply it gives me confidence that somewhere a transformer with the right specs will available for a decent price. Thanks so far. I hope some more options will be suggested here
 
#6
Alettagla said:
No I do need a little sized 300v 25 ma (or 6VA...to..8VA) and 6,3 or12,6 filament voltage.

But like Rod Colemans reply it gives me confidence that somewhere a transformer with the right specs will available for a decent price. Thanks so far. I hope some more options will be suggested here
Click to expand...

Hi René,

there is a Manufacturer here in Germany who has a tranny which fits your requirement. Here:



Netz-Transformatoren

Look at N20/1.


73
Wolfgang
 
#8
Rod Coleman said:
O, and BTW, the EI split-bobbin type like this are usually much superior to Toroidals trafo for valve B+ supplies. Toroidal has very high primary-secondary capacitance (often 1nF or more), which lets all the mains noise rush in! And since the core cannot usually be grounded, no screening is easily achieved. The EI may have only 50-90pF, and a grounded core. Much better!
Click to expand...

I use toroids and have no problem with noise. Common mode chokes at power line and filters at B+(4 ... 6H) choke eliminates it.
No need to afraid toroids, just connect them properly.

PS. Ask for low-flux versions, about 1.4T - 1.5T, they run absolutely silent, radiate no heat, and induce no hum.
 
Last edited:
#9
LinuksGuru said:
I use toroids and have no problem with noise. Common mode chokes at power line and filters at B+(4 ... 6H) choke eliminates it.
No need to afraid toroids, just connect them properly.

PS. Ask for low-flux versions, about 1.4T - 1.5T, they run absolutely silent, radiate no heat, and induce no hum.
Click to expand...

You may not suffer for using Toroids - but whether your experience can be repeated by others will depends on the amount of broadband noise present on the mains at their location.

The noise problem on mains supplies seems only to get worse with time, with Solar Feed-In converters being a notable recent addition to the problem.

Filters may help somewhat, but it always seems best to me, if you stop the broadband noise getting in, to begin with.
 
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