Hmm that diagram is confusing to me, but i am by no means an electronics wizz like others here. If you need 2x+ve and one negative how about one dual secondary 27V transformer for the + rails and a separate transformer for the RIAA section?
Well, we're back to a space problem, and it's probably not the most cost effective, but it will work. Also 27v dual secondary isn't really standard is it ?
The design needs a minimum of 2v dropout so I calculated my components for about 2.5v.
The design needs a minimum of 2v dropout so I calculated my components for about 2.5v.
Still, after rectification you get 38V from a dual 27V secondary, so you could probably go further down (it may even be better since you'd be dropping a lot of heat through the reg). 2x27V is available from Toroidy (takes around 14 days for them) in pretty much any VA rating you like and with different amounts of shielding, but toroidal. I dont have much experience with different transformers, but i've used theirs for both an F6 and am using one in a current BA-3 preamp build and they are good quality as far as i can judge. I am not sure what would be a better way to get three separate rails for your PSU requirements.
From the research I have done (and this is my first real build, I have only been repairing and restoring so far) toroids are really good for power transformers but not so much for preamps (I don't doubt the quality of the transformers you suggest). 38v would be without a load and not counting the 1.4v drop from the rectifier. almost every clone for the naim preamps you see out there use only 24v. that would be 24*1.41 - 1.4 = 32.44v after the rectifiers. So this would be perfect (except for the fact that I won't get my negative rail from this) : Transformateur R-CORE 30VA 24-0-24V - Audiophonics
or even this if I connected the 2 12v windings in series to get another 24v 220V 100W R-Core Transformer for Audio AMP Amplifier Preamps DAC 24V+24V 12V+12V | eBay
Well, i am no expert either but i must say from reading that site that i detect a fair amount of hyperbole woven in with the factual bits here and there. I am sure people more knowledgeable can comment on this more specifically, but if you browse the forum for preamp builds you will come across tons of very high end examples using toroids. I cannot help but notice that the picture examples he puts up also are using toroids, which kind of runs counter to his arguments...
As to the negative rail, if you need just something like 20-30VA, you're probably still saving space with 2 transformers over a single 500VA 🙂
As to the negative rail, if you need just something like 20-30VA, you're probably still saving space with 2 transformers over a single 500VA 🙂
I think you're probably right, I might have been blinded by the obvious clues something was wrong by the fact I loved the rega planet mods they suggested (which I did on mine) and didn't go looking elsewhere. I think the last link I posted, to the one on ebay might be perfect.
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