hi everyone
i start ti build the class A amplifier according to "diyaudio-f5-build-guide" pdf.
today its my lucky day:
some friend give me big DC power supply module that supply up to 36v-DC. (picture)
i disassemble it and take the toroidal. the toroeid as 2 group of wire, i sepuse because the module have 2 DC channels.
i measure the voltage and i found 16v ac for each group.
the problem:
1) the guide for the amplifier required 18v-ac
2) the power supply module (not the toroidal only) can rise to 36v-dc
can i get with this toroidal 18vac for the amplifier?
maybe i need to do some mix with the wire?
the ampere is ok for this class A amp?
i add some picture.
thanks
i start ti build the class A amplifier according to "diyaudio-f5-build-guide" pdf.
today its my lucky day:
some friend give me big DC power supply module that supply up to 36v-DC. (picture)
i disassemble it and take the toroidal. the toroeid as 2 group of wire, i sepuse because the module have 2 DC channels.
i measure the voltage and i found 16v ac for each group.
the problem:
1) the guide for the amplifier required 18v-ac
2) the power supply module (not the toroidal only) can rise to 36v-dc
can i get with this toroidal 18vac for the amplifier?
maybe i need to do some mix with the wire?
the ampere is ok for this class A amp?
i add some picture.
thanks
Attachments
ok quick search in Google i understand:
1) for +16 and -16 DC i need 2 group of wire from the toroid, thats why AndrewT say its not work, because he see only one channel from the toroeid.
2)the too groups of wire are not internally connected, so now i can get +-18vDC
is 3A Enough for the class A amp? in the tutoriel the recomand one is:
Antek AS-4218, 0-18V x2 @400VA
thanks
1) for +16 and -16 DC i need 2 group of wire from the toroid, thats why AndrewT say its not work, because he see only one channel from the toroeid.
2)the too groups of wire are not internally connected, so now i can get +-18vDC
is 3A Enough for the class A amp? in the tutoriel the recomand one is:
Antek AS-4218, 0-18V x2 @400VA
thanks
The ClassA amplifier normally uses a transformer rated at 6times to 10times the maximum ClassA output power.
A ClassAB amplifier normally uses a transformer rated at 1times to 12times the maximum ClassAB output power.
A 149VA transformer could power a two channel ClassAB amplifier that is from 37W+37W to 74W+74W
For a two channel ClassA amplifier, this becomes 7.4W+7.4W to 12.4W+12.4W
Buy the correct transformer for your ClassA project.
A ClassAB amplifier normally uses a transformer rated at 1times to 12times the maximum ClassAB output power.
A 149VA transformer could power a two channel ClassAB amplifier that is from 37W+37W to 74W+74W
For a two channel ClassA amplifier, this becomes 7.4W+7.4W to 12.4W+12.4W
Buy the correct transformer for your ClassA project.
according to Zen Mod post http://www.diyaudio.com/forums/parts/199652-transformer-two-secondaries-multiple-taps-how-parallel.html i can connect transformer in parralel
Or, you could make 2 mono amplifiers, both with their own PSUs...
Anyhow, if Nelsons amplifier draws a constant 1.3A from your 2x18VDC supply x2 channels, it makes about 94W, lets say 100W constant power consumption (for 2 channels).
As it is a Class-A amplifier this power will either be directed from the positive supply rail directly to the negative supply rail,
or from the positive rail to the speaker,
or from the speaker to the negative supply rail.
Besides the bias, your 8ohm speaker needs also a full power peak AVERAGE 18V/8R from each rail for both channels. And because it is a reactive load it is not necessarily constant so lets double that peak to be on the safe side here...
Oh and by the way - when it does that, it just left the Class-A!!! And moved to Class-B - how nice...
But still - this peak current can nicely be provided from the power supply capacitors - as the music you are playing will not be a constant sinusoidal max power flat out test signal...
So, according to my understanding, you should be able to make a quite decent low power Class-A amplifier (such as this one) also with not that powerfull transformer - but hey, I really know nothing about Nelsons designs and how much power they need from their transformers to perform at least reasonably well...
Anyhow, if Nelsons amplifier draws a constant 1.3A from your 2x18VDC supply x2 channels, it makes about 94W, lets say 100W constant power consumption (for 2 channels).
As it is a Class-A amplifier this power will either be directed from the positive supply rail directly to the negative supply rail,
or from the positive rail to the speaker,
or from the speaker to the negative supply rail.
Besides the bias, your 8ohm speaker needs also a full power peak AVERAGE 18V/8R from each rail for both channels. And because it is a reactive load it is not necessarily constant so lets double that peak to be on the safe side here...
Oh and by the way - when it does that, it just left the Class-A!!! And moved to Class-B - how nice...
But still - this peak current can nicely be provided from the power supply capacitors - as the music you are playing will not be a constant sinusoidal max power flat out test signal...
So, according to my understanding, you should be able to make a quite decent low power Class-A amplifier (such as this one) also with not that powerfull transformer - but hey, I really know nothing about Nelsons designs and how much power they need from their transformers to perform at least reasonably well...
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