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Old 22nd January 2003, 04:28 PM   #1
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Default Dual Power Transformers

I've noticed that some High-End Amplifiers use 2 Power Transformers for the Power Supply; a separate Transformer for each channel.

Is this something quite new? I've always only seen 1 Power Transformer used in most Amplifier Power Supplies.

Are 2 Transformers used only on Higher-Power Amps? Or is it a matter of better separation between the 2 channels to acheive a higher-level of Sound Quality?

I'm referring to Solid-State Amplifiers only.
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Old 22nd January 2003, 04:39 PM   #2
tiroth is offline tiroth  United States
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Nothing new. Generally two would be used in a higher-quality amp, to achieve two monoblock type designs in a single chassis. You are correct that this leads to better separation and sound quality (in theory).
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Old 22nd January 2003, 07:32 PM   #3
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Quote:
Originally posted by tiroth
Nothing new. Generally two would be used in a higher-quality amp, to achieve two monoblock type designs in a single chassis. You are correct that this leads to better separation and sound quality (in theory).
Thanks. So, are you saying that it's the "Separation" of both channels and an independent Power Supply for both the left & right channels that really makes the difference?

It's not an issue of Power (Watts) that this kind of design is necessary? Another words: Is it a better design regardless of whether the Amp is designed to put out only 1 Watt or 500 Watts?
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Old 22nd January 2003, 08:15 PM   #4
paulb is offline paulb  Canada
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Quote:
Originally posted by Tom D

Is it a better design regardless of whether the Amp is designed to put out only 1 Watt or 500 Watts?
Yes.
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Old 22nd January 2003, 08:36 PM   #5
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Quote:
Originally posted by Tom D
It's not an issue of Power (Watts) that this kind of design is necessary? Another words: Is it a better design regardless of whether the Amp is designed to put out only 1 Watt or 500 Watts?
You can buy VERY large transformers. If you were building a VERY powerful amp, then you could need to use 2 tranformers. Only in very extreme cases would two tranformers be a "necessity".

Using two smaller transformers will almost always be more expensive.

If the amps have a high enough PSRR, then the benefits of two separate supplies will be minimal.

All told, two separate supplies are theoretically better than one, but in most cases, I don't see the benefit.(considering the cost)
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Old 22nd January 2003, 08:38 PM   #6
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Tom

It's basically about reducing intermodulation distortion to a minimum. If one channel is sucking a lot of power from the supply, and if your supply is a little weedy, your rails will then sag, and the other channel has a lower voltage to work with.

It's quite common to have two sets of smoothing caps and bridge rectifiers as once your caps are charged, you should be okay. Doubling transformers provides less benefit. Some people even have two power cords! You could take independent cables back to your fuseboard. The channels have to meet somewhere. As with all audio, how far do you want to go?

Separation is a bit misleading: intermodulation can affect one channel on its own. The interesting thing to compare is two separate supplies versus one twice the size. I would be surprised if you could hear a difference, as long as the supply is big enough.

Two transformers look impressive and it's a good sell.
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Old 22nd January 2003, 10:19 PM   #7
JoeBob is offline JoeBob  Canada
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You could always use a transformer for each rail (if using both positive and negative rails) then you'd look even better to those you're trying to sell to ...

If you won't want to buy two transformers (expensive) you could always get a transformer with dual secondaries.
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Old 23rd January 2003, 07:02 AM   #8
gpapag is offline gpapag  Greece
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Default 2 xformers

What the two last corresponders wrote, coundn't be more true!
Yes, somewhere there has to be fixed a limit. The quest for absolute channel separation is wrong. Now that CD provides more than 60 dB separation, people have started to realise that music is better heard if the two channels are deliberately mixed (there are "black boxes"sold which do this thing)! Cartridges were providing 30-40 dB separation. Then, we were satisfied! I wonder, how much live music do we hear, in order to understand that more than 20-30dB channel separation is never heard, even if are sitting on the first row.
In the past, i was was trying to separate everything. By the time, i realised that i was doing more harm than good. 2 xformers=2 sources of 50Hz electromagnetic radiation.Also more space. Also, they had to be positioned 90 degrees to each other. Also double mains wiring. So, what's the use? The most you have to do, is to use two separate bridges and caps. Simple is correct.
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Old 23rd January 2003, 09:28 AM   #9
miguel2 is offline miguel2  Portugal
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When using 2 xformers (or dual secondaries/single xformer) there is always the earth connection that is common. The channels can be wired directly or through a few ohms and I believe this causes interference as well. One only have to hear a bad earthed amp to feel this!
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Old 23rd January 2003, 11:09 AM   #10
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One possible advantage of using two transformers is when you can't use toroidal core transformers (for whatever reason, such as cost or availability), putting two smaller E-I transformers in place of one can reduce the minimum height requirement of the amplifier's case. Of course, smaller transformers will sag more, and are also less efficient. They put less of a strain on the filter caps, with respect to their ripple current ratings.
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