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In Reply to: Re: power transformer advice needed posted by drlowmu on March 6, 2007 at 11:44:18:
As Jeff says, toroids have a very wide bandwidth, which is exactly what you don't want in a power tranny, because HF noise from the mains can be an unwanted 'feature'! You can get them with an electrostatic shield between the windings but I don't know how effective that would be. The advantages of toroid trannies are compact size, high efficiency and relatively little hum irradiated to the rest of the circuit.
Follow Ups:
Thanks for jogging my memory. I recall reading an article about this particular disadvantage of toroids.I wonder, though, if the PS filtering won't eliminate HF noise.
To quote from a site I read up on sometime ago (http://members.tripod.com/~gabevee/mypwrsup.htm ) where the author was talking about SS diode induced hash in a power supply...
"
A 3 henry choke at 120 hertz has a reactance of about 2300 ohms. The same choke at 10 to 20 kilohertz, the region where hash likely is, will have a reactance of:Xc=2PiFL=6.28x10 000x3=188400
A whopping 188 Kilohms!, How the heck can hash get past that
"
A 3 henry choke at 120 hertz has a reactance of about 2300 ohms. The same choke at 10 to 20 kilohertz, the region where hash likely is, will have a reactance of:Xc=2PiFL=6.28x10 000x3=188400
A whopping 188 Kilohms!, How the heck can hash get past that
By capacitive coupling.
But I agree, with proper layout and perhaps throw in an extra small choke for filtering it should be possible to get rid of the noise. If it's possible with a transformer (as claimed) than it should be possible with a filter as well.
Hi Zobsky,Why have to correct a problem - when one can easily AVOID it all together?
Besides, who wants a 3HY choke anymore?? Certainly not I !!
exactly.I'm not convinced the toroidal transformer or the rectifier hash issues are anything other than theory. I have amps utilizing both, and there is no audible effect. I would not hesitate to use toroids or SS diodes again. "dr"lowmu, above, may also tell you to use transformers with no more than 2ohms DC resistance or your amp will suck... so theres that.
Ask Gary Gallo, Walt Jung and his crew all about standard versus toroid PTs. They even had graphs of HF response, vs a standard one, published in a Dell magazine ten years ago.Pooh pooh on toroids they all said .... and showed the data.
You, Jeff, are the one who proposes, listen and you will belive.
Untill you have heard a torid powered amp how can you put them
down?
No TextJeff Medwin
I promised myself that I would not respond to your follow-up post.
Why? Because I do not come here to argue, I am here to discuss
diy tube audio.However, since you don't seem content with that here we go.
First of all, I did not say that torids are the best solution to
amplifier design. In fact, I don't belive that they are at all
the best solution. I simply said that they can and do sound very
good.Unlike you, I have an open mind when it comes to designing and
building amps. I build it, I listen to it, then I decide if I
like it or not. And I do not limit my possibilities to what I
have read or heard.If I (we) had listened to the so called experts about how tubes
vs transistors measure, I (we) would be still listening to SS amps.Think about it Jeff, just because you don't agree with something
doesn't mean that it is wrong.But then, maybe in your world it does.
Cal
But not on Power Transformers, but Greg's 245 amp uses Plitron SE toroidal output trannies and they are really realy nice sounding and wideband.
What makes them good as outputs makes them bad as power transformers.Why would I want to listen to them on the other end of the amp, where I know from articles I've read and graphs I've seen that toroids allow high frequency line hash to pass into the B+ filters. ... I don't see any logic at all. So your amp has em, BFD. That doesn't mean its the best solution to the amplifier design problem. Sorry.
Jeff. Could I not use the same arguments with regard to your power supply theories?
Touche'. You are right, you could. Nice point !!But you will be missing out one heck of a good power supply implementation that simply sounds way superior. The difference in sound between a toroid PT and a regular PT will not be anywheres NEAR the magnitude of importance.
Why argue over anything??
Just spend under fifty dollars and get the L1/C1/L2/C2 power supply parts I outlined and hear and enjoy it for yourself. It is REALLY good !! All who have implemented it as suggested - just LOVE it !!
I also have built several amps useing toroidal transformers. They all sound very good. World class sound? Mabye, maybe not, and certainly not Dr lowmu approved, but they can and do work well.Also the seller you mentioned provides an excellent transformer (standard disclaimer here) I have bought many from him and am
very satisified.
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