Toroidal Vs usuall power transformers....?

Are Toroidal power transfomers better for audio ? say for pre amps or limters is there much differece... do they hum less ?

thanks

yes toroidals are beter becose they have less electromagnetic radiation
puc

generally speaking, yes. But take a look at the last few pages of the china-made neve clones if you want to see a case where they may not be.  On the other hand, I took a look inside a UA LA-610 and it has a regular power trafo instead of a toroid. No noise, no problems, nothing. So it may depend more on the quality of either one.

Cool....so would it be fare to say that old type power trans are just as good as long as place correctly and or maybe further away

Yeah, I think you'd have to try it and see.

I have no toro trans to try n dont wanna spend cash to find it sounds no better... so I thought id ask if anyone can confirm either way ....I dont think it will make any difference in my case as I can get my PSU far enough away from my pre/limiters

Cheers

Both toroid and regular power trafo have EMI. 

But toroids have less EMI compared to the regular power trafo.

Also, the nice thing about toroids is you can loosen the bolt and rotate them around to find the "sweet spot" where almost all noise/hum disappears.

With a regular trafo, you can't do that. Well, yes you can but you'd have to make new holes in your case when you rotate your trafo and there may not be enough room also.

owel said:

Both toroid and regular power trafo have EMI. 

But toroids have less EMI compared to the regular power trafo.

Also, the nice thing about toroids is you can loosen the bolt and rotate them around to find the "sweet spot" where almost all noise/hum disappears.

With a regular trafo, you can't do that. Well, yes you can but you'd have to make new holes in your case when you rotate your trafo and there may not be enough room also.

Click to expand...

Toroidal Power transformers are typically more efficient than a conventional laminated core transformer, so given a certain VA Rating, they can be smaller than a similarly rated conventional EI laminated transformer.  Due to their typically low profile, they can be made to fit in a 1RU case better than most conventional transformers.

The amount of stray flux produced by either transformer in the near field (close to the transformer) is pretty much determined by the actual design of the transformer rather than its type. To minimize stray field, the transformer designer uses lower flux density than in a regular off-the-shelf power transformer.  Lower flux density in the core results from either more primary turns or bigger core or both than what would be typical for a transformer of the same VA rating.  If the core isn't pushed very hard, then fewer magnetic lines of force escape the confines of the core to get into sensitive circuitry. I have seen cheap plastic encapsulated toroidal transformers from India which were completely unuseable.  I have seen off the shelf conventional EI tranformers that worked great.

Conventional transformers are much more forgiving of unbalanced currents in their core than toroids due to the toroidal core being gapless and the laminated transformer having gaps in the core.  Never use a half wave rectifier with a toroid, it doesn't like it at all.

A very important element in all this is the layout of your audio circuit, both PCB and wire dress.  If your PCB layout and/or wiring has large loop areas they will act like transformer secondaries in the presence of stray magnetic flux and generate hum currents.  By keeping your loop areas small, you can avoid that sensitivity.  If your circuit contains inductors that are sensitive to stray pickup, then you may have to employ shielding to eliminate induced hum, even with a low stray field transformer.

Low noise, low hum audio circuitry, can happen by accident, but good engineering is usually required to really get the noise floor down.  That's why high-performance audio equipment usually employs custom made power tranformers as part of a total design solution.