What’s the minimum power transformer required to build a gainclone amplifier? - diyAudio
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Old 27th November 2005, 01:51 PM   #1
Katapum is offline Katapum  Europe
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Default What’s the minimum power transformer required to build a gainclone amplifier?

Hi all,

I have two power transformers with 2 separated winding each (2x12V/3.33A +2x12V/3.33A). Is it enough to build an inverted gainclone (Thorsten style)?

Any comments or suggestions are very welcome.

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Old 27th November 2005, 07:17 PM   #2
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if you can get 2x24v 3.3a each thats about 160 VA which should be enough for stereo pair. or use one each side if you prefer . then you will have power to spare.
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Old 27th November 2005, 09:18 PM   #3
Katapum is offline Katapum  Europe
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Hi,

Just to clarify I have two power transformers:

One (two separated windings and no centred tap):
12Vac/3.3A
12Vac/3.3A

Another (two separated windings and no centred tap):
12Vac/3.3A
12Vac/3.3A

I don´t have any 24Vac transformer.

(att. IGC schematic)

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Old 27th November 2005, 10:05 PM   #4
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They might do if your average output power is far from 100%. If the transformers are getting real hot they are probably too small for your needs.

If I understand you right you have two transformers of 80 VA each. This will do. I'm quite convinced of it.
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Old 27th November 2005, 10:28 PM   #5
tja is offline tja  Netherlands
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Quote:
Originally posted by Katapum
Hi,

Just to clarify I have two power transformers:

One (two separated windings and no centred tap):
12Vac/3.3A
12Vac/3.3A

Another (two separated windings and no centred tap):
12Vac/3.3A
12Vac/3.3A

I don´t have any 24Vac transformer.


Put the secondaries of each transformer in series, that will give you two transformers with 24V. One for + and one for -.

Take
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Old 28th November 2005, 01:43 AM   #6
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AC12V from a transfomer still sufficient to power a gainclone,only the output power get reduced.
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Old 28th November 2005, 05:37 AM   #7
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if you do as Tja said

you can use the transformers together to be equivelant to a 160 VA 24 + 24 which will work very well.

you have to connect the 2 winding of each transformer in series, so you will need to make sure you know the phase.
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Old 28th November 2005, 09:49 AM   #8
Katapum is offline Katapum  Europe
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Hi all,

I built the amplifier. It’s incredible bad. I need to turn the pot at 3 o’clock to get some power (but not too much). Maybe I have done something wrong. The amplifier worked with 95dB diy open baffle speakers.

I have also a 300B tube amplifier (9W) and it has much more power.

What do you think?


Amplifier also has a little hum problem but I think it’s because the power input is too near input line and output speakers. Am I right?


Quote:
so you will need to make sure you know the phase.

How can find winding transformer phase (I have only a DMM)?


Katapum
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Old 28th November 2005, 09:54 AM   #9
tja is offline tja  Netherlands
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How did you wire the transformers?

Take
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Old 28th November 2005, 10:00 AM   #10
Katapum is offline Katapum  Europe
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Hi,




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