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Old 17th August 2016, 06:04 PM   #1
PauloPT is offline PauloPT  Portugal
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Default Two transformers Vs one with 4 secondaries

Hi,

All other things being equal, is there a perceived audible difference between using a true dual mono setup with two transformers and a single transformer with 4 secondaries?

Thanks
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Old 17th August 2016, 06:59 PM   #2
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If the transformer is designed and built correctly, there will be no difference.
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Old 17th August 2016, 07:13 PM   #3
PauloPT is offline PauloPT  Portugal
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And about rating, are two 300VA transformers 2 sec. equivalent to a single 600VA with 4 secundaries?
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Old 18th August 2016, 10:43 AM   #4
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2 smaller transformers will normally have more parasitic capacitance, so more line-noise will enter the Amp. Better line filters are needed. They will be bigger, than one 4-sec. transformer with same VA ratings. -> space issues
P.S. For audio - the VA ratings are not the only thing to look at.
The equivalent windings series resistance is very important.
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Old 18th August 2016, 11:07 AM   #5
PauloPT is offline PauloPT  Portugal
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I plan to use audio grade transformers (Canterbury or Toroidy) with an electrostatic shield, so I'm hoping EMI will not be an issue.

If I go with the 4 sec. model I can only afford 600VA. If I go with two transformers I can afford 400VA each. The problem is that with the two transformers option chassis space is a problem. Audio ground wire to chassis will be very close to an auxiliary EI transformer (for the speaker protection circuit) and I don't know if I'll have noise into ground.
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Old 18th August 2016, 11:27 AM   #6
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Audio grade transformers? You must get out more. There is no such thing!
All reasonable quality mains transformers have an electro static screen and are as good as the rating. Being 'audio grade' means nothing in the real world except they will charge much more for them than standard same spec transformers and may be in a decorative box.
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Old 18th August 2016, 11:32 AM   #7
PauloPT is offline PauloPT  Portugal
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What about the GOSS band, normal transformers don't have that. Before I start thinking in audio grade I was thinking to buy some Talema. These Talema don't have a ground wire so I guess no electrostatic shield. Audio grade for sure have this shield and a Goss band. Canterbury Windings and Toroidy aren't good?

My options:

http://www.tme.eu/en/details/55174-p...ormers/talema/ - I guess no electrostatic screen (can't see a ground wire) and no GOSS band, 300VA ( 2 of them)

http://sklep.toroidy.pl/en_US/p/TTS0...ge-to-50-V/173 - I guess no electrostatic screen (can't see a ground wire) and no GOSS band, 400VA ( 2 of them)

http://sklep.toroidy.pl/en_US/p/TTSA...ge-to-50V-/318 - Audio grade with electrostatic screen and GOSS band, 400VA (2 of them)

http://www.canterburywindings.co.uk/ordering.html - Audio grade with electrostatic screen and GOSS band, 600VA (one with 4 secondaries)

What's the best choice? I'm confused!
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Last edited by PauloPT; 18th August 2016 at 11:50 AM.
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Old 18th August 2016, 12:14 PM   #8
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RS keep a few toroids 0500P1-2-030 | 2 Output Toroidal Transformer, 500VA, 2 x 30V ac | Nuvotem Talema
Because of the way most toroids are wound, it is not practical to add an interleaved screen between input and output windings. Chassis mounted transformers if wound with the primary under the secondaries, a copper/brass band is used as an electrostatic screen to stop any flashover. If the correct type and value of mains filtering is employed, there will be no mains borne interference as your filters will remove any.
Good luck with your search.
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Old 18th August 2016, 12:26 PM   #9
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If I understood correctly, the Talema have this copper/brass band acting like a shield and have the primary under the secondary, correct? Are they a good choice then?

Edit: the RS 500VA Talemas are a bit pricey for my pocket, what about these Toroidy Standard grade? - http://sklep.toroidy.pl/en_US/p/TTS0...ge-to-50-V/174

About mains filtering - I have some filtered IECs but they aren't medical grade (they have those capacitors between line and ground), can I use them?
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Last edited by PauloPT; 18th August 2016 at 12:49 PM.
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Old 18th August 2016, 02:42 PM   #10
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I don't know as my anti malware/virus programme won't let me view the site as it is unsafe.
I wouldn't worry about removing mains borne noise until you have built it as you probably won't get any.
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