Why should a gainclone sound worse with seperate transformers? - diyAudio
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Old 18th August 2003, 05:55 PM   #1
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Default Why should a gainclone sound worse with seperate transformers?

I have read at least two reviews on the 47 gaincard where it was indicated that using two seperate Power Humpty's made the sound "flat, uninvolving" etc compared with just one Power Humpty.
Hence the question: why should the gainclone sound worse with seperate power supplies?


Has it been anyones experience that using two seperate transformers and diode bridges improves the sound quality of the gainclone or is it gainclone lore that one larger transformer sounds better than two seperate transformers? I also saw a post by analog_sa that using a single large (1000VA) tranformer made the sound worse....

I am in the process of building a gainclone and have two 300VA 22v (ac) transformers that I am going to use. So far, the one channel I have built using 1 transformer sounds exceptional.

Thanks for any ideas.
Ryan
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Old 18th August 2003, 06:27 PM   #2
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Quote:
saw a post by analog_sa that using a single large (1000VA) tranformer made the sound worse....
the 1000VA i tried with a discrete PP classAB amp... no idea how it would sound with the GC. I seem to think that every amp/speaker combination has an optimal transformer/cap. Very difficult to draw any meaningful conclusions unless you have transformers identical in every respect but VA. Of course such transformers do not exist - variations in VA will bring along variations in many other parameters. I resist the temptation to order a whole lot of different (core types and sizes and wound for different flux densities) transformers and pick up the best sounding but for a manufacturer like Peter Daniel this would be quite feasible.
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Old 18th August 2003, 06:33 PM   #3
cm961 is offline cm961  Canada
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I'm no expert, but perhaps a sound system sounds better with a little crosstalk. I might get hammered for saying that, but its just a thought. With two seperate transformers, the crosstalk has got to be very small compared to with one. I think since these chips have a very high PSRR anyway, so maybe the effects are basically nill.

Pete
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Old 18th August 2003, 07:19 PM   #4
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Hi
Ryan

My gainclones have evolved from a single Tx to this.

I would hardly say a single Tx was better,let alone without a buffer.

Peter

http://www.petemoore.pwp.blueyonder.co.uk/music/
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Old 18th August 2003, 07:27 PM   #5
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Default Re: Why should a gainclone sound worse with seperate transformers?

The only disadvantage of using two transformers are cost (if you pay for them) and size. Otherwise only advantages
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Old 18th August 2003, 07:32 PM   #6
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Hi
Very true the project didn't come cheap

BTW the GC's are powered using Thorsten's ultimate supply (2 Tx per channel)

Each Tx is 250 VA 40Volt secondries,primaries are series wired to give 20V on UK 240V mains..Other Tx are for buffer and GC timer delay to allow tube to pre-heat

Peter
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Old 18th August 2003, 07:43 PM   #7
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Thanks for the responses. Pete, what a whopper! Where can I get a schematic of the ultimate power supply?

Can you maybe provide a description of the benfits of going from single to dual to quad like you did?

Thanks again.
Ryan
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Old 18th August 2003, 07:54 PM   #8
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Hi
Ryan

Here is the schematic...


Thorsten stated thus..Who am I to argue :-)

Series connection halves the flux in the core. Less noise, better efficiency. The transformer manufatcurer could have used more turns.

The capacitors AC couple the transformer, so the few 100mV DC on the mains which are common cannot cause DC current to flow and hence the core is not already partially saturated with DC. The transformer manufacturer could have used an airgap. The Diodes BTW protect the Cap's from excessive voltages.

The opposite winding start orientation effectively cancels any leakage between primaries and secondaries, this is known as larger common mode rejection, the transformer manufatcurer could have used shields and wound the transformer symmetrically.

So, in effect we are fixing cost accountant designed mains transformers so we can get away using off the shelf parts. It's nearly as good as a seriously custom wound C or R core transformer....


Peter
btw. I used single Mur860 Diodes not the dual as shown.
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Old 19th August 2003, 03:09 AM   #9
ashwin is offline ashwin  India
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Well, one advantage I found when I used two transformers is that if I wired their primaries correctly, the hum picked up by the source cables reduced drastically. Both primaries were in parallel, but swapping the leads of one primary reduced the hum. I guess this is leakage flux cancellation, as peteM mentioned. (BTW, this was for EI transformers, I don't know if two torroidals placed close by would cancel their leakage flux)

- Ashwin
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Old 19th August 2003, 01:30 PM   #10
ronc is offline ronc  United States
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Default roncla

The only way i see 2 adjacent trans. cancelling out their feild flux is for them to be 180 deg. out of phase?
ron
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