🚀 go-pugleaf

In article <niall-0510941103460001@47.34.3.64>, niall@bnr.ca (Niall Gallagher) writes:
> In article <36ue41$880@bcarh8ab.bnr.ca>, stud7b11@bcars564.bnrottawa wrote:
> 
> 
> > In an amplifier circuit that I am currently fiddling
> > with, the spec. says to use a toroidal transformer in the
> > power supply.  Why is this important?  How would I be
> > degrading the performance of the amp with a plain-vanilla
> > transformer?
> 
> Less flux leakage, most likely. The leakage could cause 60Hz noise to be
> induced in the amplifier. Electronically, there is little difference.
> 
> Niall
> 
> -- 
> Niall Gallagher
> niall@bnr.ca

	Try this! Take same turn toroidal transformer and the plain-vanilla
one and measure the impediance.  If your multimeter doesn't have that function
then try getting a ruff estimate by setting the meter on the ohms measurement
and get the greatest peak.  Did that make any sense? 

	Tell us your results,
	Dave

In article <36ue41$880@bcarh8ab.bnr.ca>, stud7b11@bcars564.bnrottawa wrote:


> In an amplifier circuit that I am currently fiddling
> with, the spec. says to use a toroidal transformer in the
> power supply.  Why is this important?  How would I be
> degrading the performance of the amp with a plain-vanilla
> transformer?

Less flux leakage, most likely. The leakage could cause 60Hz noise to be
induced in the amplifier. Electronically, there is little difference.

Niall

-- 
Niall Gallagher
niall@bnr.ca

In article <36ue41$880@bcarh8ab.bnr.ca>, stud7b11@bcars564.bnrottawa wrote:

> Hi everyone.  Sorry about the crossposting, but I think
> this applies to all newgroups in question.
> 
> In an amplifier circuit that I am currently fiddling
> with, the spec. says to use a toroidal transformer in the
> power supply.  Why is this important?  How would I be
> degrading the performance of the amp with a plain-vanilla
> transformer?
> 
> Thanks in advance,
> 
> Tom Nagy
> 
> Please post responses, as I don't have email access.

There was a nice article about transformers in a German electronics
magazine (elrad) some years ago, I'll try to remember the basic points:

(all of the below concerns transformers with similar power ratings)

-toroidal transformers have less stray field than simple EI-core transformers
-toroidal transformers have a lower inner resistance (? I hope you know
what I mean) than simple EI transformers.

This leads to a faster charge-up of the capacitors, and to bigger problems
when turning them on (a 500 VA toroidal transformer will surely blow the
mains fuse, a similar EI-transformer probably won't)

- you can overcome these problems by using an EI transformer of a higher
power rating (more space, but probably still less money)
- or, for best performance, you can use other rectangular type
transformers (don't know the core types offhand), in conjunction with
oriented sheets (? you know, the flat metal parts that make up the core).
Price and weight, if produced in small series, is then roughly equivalent
to toroidal transformers, but performance is supposed to be better (and
they need more space).  

Sorry, can't find the exact refernce without the magazines - their
electronic database just isn't what it is supposed to be :-(

Bye
  Markus

Tom Nagy, stud7b11@bcars564.bnrottawa asks:
>
>In an amplifier circuit that I am currently fiddling
>with, the spec. says to use a toroidal transformer in the
>power supply.  Why is this important?  How would I be
>degrading the performance of the amp with a plain-vanilla
>transformer?

Tom,

Here's some wisdom guzzled from that Texas mickey of wisdom,
the net. (yes I'm being sarcastic!)

Dave Dal Farra (gpz750@bnr.ca)
'83 GPz750/no fairing/no ABS/damn near no damping

-----------------------------------------attached----------->
Subject: Toroids
From: stephen.soyka@canrem.com (Stephen Soyka)
Date: Thu,  4 Nov 93 02:24:00 -0400

As a general rule, toroids are never a no-no. The usual overiding factor
in transformer topology is cost. Cost of the core, cost of the windings,
set-up time etc. In general, toroids are very expensive due to the high
labour costs involved. Every winding must be set up by hand becuase
winding machines use a rotating shuttle which must be pre-loaded with
the required length of conductor. I have a winding machine and can
attest to the pain-in-the-ass nature of this process.

That being said, a totoid is nothing more than a standard E-core wherein
the magnetic path is a perfect circle. This drastically reduces the
effects of eddy current losses and losses due to mutual inductance.

I'm not sure what you are getting at in the area of frequency response
and linearity. Aproperly designed XFMR is a properly designed XFMR.
Although it is somewhat difficult to control the physical linearity of
the actual winding, this is less of a problem with a toroid than with a
standard E-core.

-----------------------------------------------------------------------
---
From: dstock@hpqmoca.sqf.hp.com (David Stockton)
Subject: Re: Torroids for tube amp supply?
Date: Mon, 29 Nov 1993 16:37:44 GMT

 Toroidal transformers use tape-wound cores, explioting GOSS
(grain-oriented silicon steel) which has better mag properties in one
direstion than the other, The tape wound toroid ensures the mag field
always is optimally oriented. 

  Nearly all manufacturers have exploited this to the limit to run very
high flux levels, allowing them to reduce the number of turns per volt.
This can lead to a transformer that buzzes loudly, and also leads to
turn-on surges. Overrunning the voltage soon leads to saturation and
blown fuses (if you're lucky..)   44v windings may not have adequate or
legal insulation at line voltage.

  European transformer shops sell 240 to 110v isolating transformers for
operating power tools etc, running 110 into the 110 winding of one of
these, and bridge-rectifying the 240v winding to get over 300v DC may be
better  1) all windings running ar rated voltage, 2) isolting
transformers have special "safety class' insulation.

  For a good amplifier, I personally would have a custom transformer
done, with reduced flux level for acoustic noise reduction, and an
inter-winding electrostatic shield to prevent interference from line
transients.

-----------------end attachement---------------------------------

----------------
In article <36ue41$880@bcarh8ab.bnr.ca>, stud7b11@bcars564.bnrottawa (Tom Nagy) writes:
|> 
|> Hi everyone.  Sorry about the crossposting, but I think
|> this applies to all newgroups in question.
|> 
|> In an amplifier circuit that I am currently fiddling
|> with, the spec. says to use a toroidal transformer in the
|> power supply.  Why is this important?

Because audio electronics is a field more rife with superstition
than any twelve "dial-a-Psychic" chat lines you could name. 

|>  How would I be
|> degrading the performance of the amp with a plain-vanilla
|> transformer?

You'd be making it cost less and have less snob value.

In article <36ue41$880@bcarh8ab.bnr.ca>, stud7b11@bcars564.bnrottawa (Tom Nagy) writes:
|> 
|> Hi everyone.  Sorry about the crossposting, but I think
|> this applies to all newgroups in question.
|> 
|> In an amplifier circuit that I am currently fiddling
|> with, the spec. says to use a toroidal transformer in the
|> power supply.  Why is this important?  How would I be
|> degrading the performance of the amp with a plain-vanilla
|> transformer?
|> 
|> Thanks in advance,
|> 
|> Tom Nagy
|> 
|> Please post responses, as I don't have email access.
Yes, as another poster mentioned, there is a difference.
Pound for pond, and cubic inch for cubic inch, the toroid
is alot more transformer. Yes, there is a problem with 
inrush current, but just build a delay circuit that first
connects the primary with a 50 ohm to 100ohm series resistor. 
Then shunt this resistor with a power relay when the cap 
voltage  reaches 80 to 90 % of final value. This is easily done
with a zener and series resitor giving base drive to a common
emitter NPN, using the collector to pull the negative
coil pin to a VCEsat above ground. While you are doing a 
circuit such as this, also add a delayed switching of the
output relays. This avoids pops caused by transients in
the amplifier supply line.