lscangus, welcome to the club!
For the DC Voltage Rails, do you mean a +20V positive rail and a -20V negative rail, or do you mean 26V from positive to negative (i.e. +10V and -10V). That will help us to give you proper advise.
In the meantime, for the settings you are quoting, a 225VA transformer will definitely be too small, and 8 output Fets per channel will also be too few.
In my Aleph-X I run the Fet's harder than most people are comfortable, and I also made the mistake of undersing my transformer. The settings for my Aleph-X are:
Transformer Rating: 225VA (one per channel)
Transformer Secondaries: 2 x 12V
Supply Rails: +15V / -15V (after CLC filter)
Bias Current: 5A
Number of Fets / channel: 4
My transformer produces a mechanical hum that is audible if there is no music playing. I have been considering relpacing the trafo's with a 300VA to eliminate this.
For your settings, I'd suggest a 600VA transformer as a minimum (assuming that you mean +20 and -20V rails), and I'd also recommend increasing the number of Fets to 12 unless you are planning on using forced air cooling (i.e. a fan).
Hope this helps give you some perspective.
Cheer, Terry
For the DC Voltage Rails, do you mean a +20V positive rail and a -20V negative rail, or do you mean 26V from positive to negative (i.e. +10V and -10V). That will help us to give you proper advise.
In the meantime, for the settings you are quoting, a 225VA transformer will definitely be too small, and 8 output Fets per channel will also be too few.
In my Aleph-X I run the Fet's harder than most people are comfortable, and I also made the mistake of undersing my transformer. The settings for my Aleph-X are:
Transformer Rating: 225VA (one per channel)
Transformer Secondaries: 2 x 12V
Supply Rails: +15V / -15V (after CLC filter)
Bias Current: 5A
Number of Fets / channel: 4
My transformer produces a mechanical hum that is audible if there is no music playing. I have been considering relpacing the trafo's with a 300VA to eliminate this.
For your settings, I'd suggest a 600VA transformer as a minimum (assuming that you mean +20 and -20V rails), and I'd also recommend increasing the number of Fets to 12 unless you are planning on using forced air cooling (i.e. a fan).
Hope this helps give you some perspective.
Cheer, Terry
Thanks for all you advice
You know there is a voltage suppliy to the main board. If i use a 500va, the minium output voltage of the transformer is 25 volt, which mean after the AC-DC and the capacitor, the votage will be about 36V. +36-0- -36.
I wonder if this voltage will be too high? and also, does the rail need +20-0- -20, becasue i think the rial is the output fets voltage.
Sorry for so many question...
And last, can i parallel tow tranformer to increase the overall output?
Angus
You know there is a voltage suppliy to the main board. If i use a 500va, the minium output voltage of the transformer is 25 volt, which mean after the AC-DC and the capacitor, the votage will be about 36V. +36-0- -36.
I wonder if this voltage will be too high? and also, does the rail need +20-0- -20, becasue i think the rial is the output fets voltage.
Sorry for so many question...
And last, can i parallel tow tranformer to increase the overall output?
Angus
You can pretty much calculate the A-X needs in this nice spreadsheet made by wuffwaff
Steen
http://www.diyaudio.com/forums/showthread.php?s=&threadid=49640&highlight=
Steen
http://www.diyaudio.com/forums/showthread.php?s=&threadid=49640&highlight=
steenoe said:You can pretty much calculate the A-X needs in this nice spreadsheet made by wuffwaff
Steen
http://www.diyaudio.com/forums/showthread.php?s=&threadid=49640&highlight=
because there are two voltage. one is the supplied voltage to the board, one is supplyied voltage to the fets. What value would you recommand?
and can i parallel tranformer?
but 15V / 0.69 is 21V, will 21V be alright?
Here's an example of how i did it. There is only one voltage for the AlephX as Steen explained.
I think you are confused by cell B11 and B12 in the spreadsheet.
B11 is equal to B12 if you don't use CRC or CLC. (Capacitor - resistor - capacitor or capacitor - coil - capacitor).
The final voltage at the fets is important and every R or L in the supply line will lower that voltage. Plan accordingly.
/Hugo
I think you are confused by cell B11 and B12 in the spreadsheet.
B11 is equal to B12 if you don't use CRC or CLC. (Capacitor - resistor - capacitor or capacitor - coil - capacitor).
The final voltage at the fets is important and every R or L in the supply line will lower that voltage. Plan accordingly.
/Hugo
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