Antrim Transformers

[NickG]

I don't know if this will be of interest to anyone, but for some time, its annoyed me that its hard to find 230:230v isolation transformers. I knew of Antrim, but they had a minimum order of 10 transformers.

Well, it seems that they have removed that restriction and I have a nice 230:220 300va torroid on the desk next to me now :-)

http://www.antrimtransformers.com/

Now to find out if voltage doublers do have any sonic cost.

Oh dear, I just realised, it would make a ideal source of B+ for a 6c33c amp :-).

[Richard]

Hi Nick

I see they also do Mains toroidals

http://www.antrimtransformers.com/catalogue.php?sec=632

and Output p-p toroidals

http://www.antrimtransformers.com/catalogue.php?sec=634

with reassuring specs of "Full output rating at 20Hz"

all as single units. Not cheap but I'd like to hear some.

On the voltage doubler thing, the drawbacks would be needing to double up on current rating for the TX and smoothing for the dc I think?

[NickG]

On the voltage doubler thing, the drawbacks would be needing to double up on current rating for the TX and smoothing for the dc I think?

Yes, I agree all thats true, but what I want to know though, that if the extra switching noise produced by the bigger current through the diodes will be a disadvantage if (in this case) the supply is feeding two series regs before it hits the amp.

Of course the other disadvantage of the doubler is the lower regulation, but again, thats offset in this case by the use of the regulator in the supply.

[Richard]

Hi Nick,

Will there be "extra switching noise produced by the bigger current through the diodes"? I'm really not sure if this would be a "linear" problem - perhaps the diodes only hold just so much charge and hence will produce a fixed amount of noise, similar to the way they ramp up to a constant forward voltage drop after an initial draw. You could use schottkies... or bypass caps...

[A Stuart]

And they do the klpp1 mains transformer, in case anyone is interested. (although it is not advertised on their list)

[NickG]

Well, the plan seems to have worked, one 230:220 tx, into voltage doubler, one 10H choke two dual regulators (6080, ecl82, 0d3) and I have a dual variable voltage source, 350v - 550v 100ma a chan, could be more, but its only a 200ma choke. No sign of nasty switching artifects, hum and noise on the line at 420v is about 500uv P/P

[Hardy]

Doublers:
Interesting if you can find a sonic degradation....I went off the idea once I found such a circuit in Uncle Tims' 834P phono stage.... Usually done for cost only I think.

May measure ok under no load but when music pumping through could go haywire.......

Let us know what it sounds like....

Rich.

[NickG]

Sounds ok at the moment.

Remember I have two series regulators between the doubler and the amp, so I think a lot of the potential degredation has been prevented from getting past the shunt tube. Also I am using different TXs to provide the heater supply for the rest of the amp, so thats another path that switching noise could take blocked.

[Hardy]

Good, good....