Hello.
If I have a stereo amp with 4 KT88 and 6 Ecc83, how to I calculate the right amount of the VA for the secondary ?
Let's say I need 500V B+, and I use a bridge rectifier.
If I want full volume music peak without any sag, I know it's easy just over spec, but the transformers are already very heavy. Is there a way to have the perfect amount ?
I know there is also the transformer winding resistance to not forget but I am really lost.
And guys I don't have a schematic and I am just a beginner, thank you.
If I have a stereo amp with 4 KT88 and 6 Ecc83, how to I calculate the right amount of the VA for the secondary ?
Let's say I need 500V B+, and I use a bridge rectifier.
If I want full volume music peak without any sag, I know it's easy just over spec, but the transformers are already very heavy. Is there a way to have the perfect amount ?
I know there is also the transformer winding resistance to not forget but I am really lost.
And guys I don't have a schematic and I am just a beginner, thank you.
I expect you will not know many of the answers to my questions, but we need to start somewhere.
What are the target specifications of your amplifier, like maximum undistorted power out?
Are you going to operate the KT88s at their maximum power rating, or at a more conservative and cooler operating level, for example?
How much current will will each KT88 stand?
Will the KT88s use self bias (the self bias subtracts from the 500VDC B+, so there can be more current at the maximum dissipation limit)?
Using a solid state rectifier bridge:
1. Cap input filter: 500VDC/1.414 = 354VAC B+ secondary (probably more like 375V is needed to make up for more losses in the B+ filter (choke, or resistor to the 2nd capacitor).
A Cap input filter causes the most heating of the secondary winding, so the required ampere rating is higher than for a choke input filter with the same DC load current (below).
And the voltage regulation of a cap input filter is worse than for a choke input filter (below).
2. Choke input filter: 500VDC/0.9 = 556VAC B+ secondary (probably more like 575VAC needed to make up for more losses in the B+ filter (1st resistor, and 2nd resistor to the 1st and 2nd caps that follow after the choke).
A Choke input filter causes the least heating of the secondary winding, the required ampere rating is lower than for a cap input filter, for the same DC load current (above).
And the voltage regulation of a choke input filter is better than for a cap input filter (above).
I am sorry, but as you can see, it is best to start with more knowns, such as an example schematic with parts values, voltages and currents, to be able to specify the power transformer needs.
Or at least tell us your desired power output from push pull KT88s.
Any power supply design that looks to trade off weight for required current output, is not going to last until your grandkids are adults.
Those KT88 amplifiers are Hernia Makers (the surgeons hope you will build a stereo KT88 amplifier).
Reduce the need for surgeons, build 2 KT88 Mono-Block amplifiers.
Set a target for an amplifier, and hit it.
No target, the amplifier will be hit and miss (mostly miss).
Or, did I miss-understand your question, you already have a stereo push pull KT88 amplifier, and you want a replacement power transformer. In that case, what is the make and model of your amplifier?
All the above are just my opinions.
What are the target specifications of your amplifier, like maximum undistorted power out?
Are you going to operate the KT88s at their maximum power rating, or at a more conservative and cooler operating level, for example?
How much current will will each KT88 stand?
Will the KT88s use self bias (the self bias subtracts from the 500VDC B+, so there can be more current at the maximum dissipation limit)?
Using a solid state rectifier bridge:
1. Cap input filter: 500VDC/1.414 = 354VAC B+ secondary (probably more like 375V is needed to make up for more losses in the B+ filter (choke, or resistor to the 2nd capacitor).
A Cap input filter causes the most heating of the secondary winding, so the required ampere rating is higher than for a choke input filter with the same DC load current (below).
And the voltage regulation of a cap input filter is worse than for a choke input filter (below).
2. Choke input filter: 500VDC/0.9 = 556VAC B+ secondary (probably more like 575VAC needed to make up for more losses in the B+ filter (1st resistor, and 2nd resistor to the 1st and 2nd caps that follow after the choke).
A Choke input filter causes the least heating of the secondary winding, the required ampere rating is lower than for a cap input filter, for the same DC load current (above).
And the voltage regulation of a choke input filter is better than for a cap input filter (above).
I am sorry, but as you can see, it is best to start with more knowns, such as an example schematic with parts values, voltages and currents, to be able to specify the power transformer needs.
Or at least tell us your desired power output from push pull KT88s.
Any power supply design that looks to trade off weight for required current output, is not going to last until your grandkids are adults.
Those KT88 amplifiers are Hernia Makers (the surgeons hope you will build a stereo KT88 amplifier).
Reduce the need for surgeons, build 2 KT88 Mono-Block amplifiers.
Set a target for an amplifier, and hit it.
No target, the amplifier will be hit and miss (mostly miss).
Or, did I miss-understand your question, you already have a stereo push pull KT88 amplifier, and you want a replacement power transformer. In that case, what is the make and model of your amplifier?
All the above are just my opinions.
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