[RonR]

Hi,

I've been thinking lately about making my Lifeforce 55s truly Monoblock, instead of having 2 separate amps in one case, which led me on to thinking about transformers.....

There's a French company offering R-core transformers, which are said by many to be the best for audio, at 120VA or 300VA.

I understand that these have advantages in Regulation (4%) and stray EMF, But...

1. Do the R-core trannies substantially cure the switch-on inrush current problem of the present Torroidals?

2. My PSUs are built to the latest AKSA design (i.e. Electro Caps, Resistors, Electro Caps, Film Caps). I would think that this arrangement would isolate the Amp modules from the Transformers much more effectively than the original PSU, so will the R-cores gain me anything?

3. Is 120VA in an R-core enough to run a 55W Amp or do I have to go for the 300VA?

Cheers,

Ron.

[AKSA]

Hi Ron,

Damn good question, thank you!

The smaller the trafo, the worse its regulation.  A 120VA R core might be 5% on a good day, a 160VA toroid would be closer to 8%.

Inrush current for a toroid is around 10 times max rated current, which would be around 7A for a 160VA.  For an R core I understand, though am not sure, that it's much lower, similar to an EI, around 5 times, say 2.5A for a 120VA.

Yes, your power supply does a sterling job of isolating the DC from the trafo, no question, so one of these R cores would not, in my opinion, deliver audible improvements.  The new LF/Soraya power supply modules are so good in fact that even a full on Felix power conditioner on NYC mains has little audible improvement on the sound.  I know because I did this precise experiment with Paul (aka Occam) in October.  There is an improvement, but it's very subtle, and the new ps topology is extremely cost effective.

Hope this helps,

Cheers,

Hugh

[RonR]

Thanks Hugh,

You've just saved me the cost of 2 transformers!

I'm already using something very similar to the Felix using 10A common mode chokes: http://www.triode-systems.com/?q=node/14. They've been in use since I had my first AKSA 55 and original Power supply, and TBH I never thought to try the Lifeforce without them. That'll give me something to do this weekend!

Cheers,

Ron.

[AKSA]

Ron,

I took a peek at your conditioner.  It's very good, though I felt a little light on for capacitance.  You really want it to chime in around 400Hz for 120Hz ripple;  this is almost an octave up from middle C.  At 400Hz, XL is around 1.5R, and Xc for 0.057uF is 7K, so the attentuation in each leg is not very great at all, even though it's a common mode CLCLC.  I'd be increasing the capacitance to around 1uF for better than twenty times performance from each leg, square it, that's 400 times.  It's common mode, so only differential currents are attentuated, not those where active and neutral currents are balanced.  At 60Hz, balanced AC currents flow like the breeze, but unbalanced currents are savagely attenuated.  For a trafo, this is precisely what is needed.

Your VSonics go out in an hour!!

Cheers,

Hugh

[RonR]

Hi Hugh,

Re: increasing the capacitance up to around 1uF (as used in the Felix BTW), I'll give it a try and let you know how it goes.

I'm looking forward immensely to building those VSonics! 

Cheers,

Ron.

[AKSA]

Ron,

VSonics despatched yesterday....  Express Courier Intl, we shall see how long it takes, they say 3-5 days.

I've just had a missive from Paul aka Occam in NYC, and he informs me my calcs are wrong.  This doesn't surprise me, magnetics have always been something of a closed book to me, so watch this space until I've talked to him more to find where my explanation is off the mark.

Cheers,

Hugh

[bluesky]

I just thought I'd mention VT4C as a possible source for R core transformers, and, relatively cheap.

My electronics mentor, a retired electrican and tube nut, told me they were better than toroids.  However Hugh has far better insight into such issues and how they pertain to his designs and I'd always stick with his advice.

And, hey.........it's raining here in Brisbane, we get excited about this these days.

Cheers

Bluesky
 

[RonR]

Hi Bluesky,

It rained a bit less in London today than it has for the past week or so!
The Forecast for the weekend is........

More Rain.

This doesn't get us excited at all!

Cheers,

Ron

[bluesky]

Hi Ron

Yes, I know rain is about off topic as you can get, but......

In some parts of Australia it is still drought and yet in other parts you need a boat to go to the supermarket!

In my area, Brisbane, we were recently allowed a "wet day".  The first time in several years when people are allowed to wash their cars, pity I was too lazy on the day to get up off my listening chair to do it, maybe next year! 

Bluesky