I have a big main transformer, out of an Fostex PA-amp.
Without load, I measured 2x60V and on a second secondary 2x16V.
Any idea to build a great amp around this stuff?
Franz
http://mypage.bluewin.ch/gysiaudiophil/fostextrafo.JPG
Without load, I measured 2x60V and on a second secondary 2x16V.
Any idea to build a great amp around this stuff?
Franz
http://mypage.bluewin.ch/gysiaudiophil/fostextrafo.JPG
"Have you checked LM4780 ?
Supply Range ± 20 - ± 84 V
It's on National's web site."
That is an error, it should read 84V total swing, or ±42V.
A 2X 60V transformer will give ±85V rectified and filtered. This is consistent with the pair of 18,000µF 100V filter caps in the photo. The filter caps are big enough for a two channel amp running on 50hz (or higher) driving a 4 ohm load (or higher) per channel.
My guess is that with typical construction what you have would give 250W X 2 at 8 ohms and about 400W X 2 at 4 ohms, with about 3dB of dynamic headroom.
The dual 16V windings are intended to drive opamps, relay circuits, etc. They would normally be rectified, filtered and then regulated to ±15V.
I could recommend a circuit if I knew the intended use.
Supply Range ± 20 - ± 84 V
It's on National's web site."
That is an error, it should read 84V total swing, or ±42V.
A 2X 60V transformer will give ±85V rectified and filtered. This is consistent with the pair of 18,000µF 100V filter caps in the photo. The filter caps are big enough for a two channel amp running on 50hz (or higher) driving a 4 ohm load (or higher) per channel.
My guess is that with typical construction what you have would give 250W X 2 at 8 ohms and about 400W X 2 at 4 ohms, with about 3dB of dynamic headroom.
The dual 16V windings are intended to drive opamps, relay circuits, etc. They would normally be rectified, filtered and then regulated to ±15V.
I could recommend a circuit if I knew the intended use.
no project yet
Your guess is perfect: this is an transformer, out of an Fostex 2x350W amp!
Actually, I have no big intention or special application for such high power, specially not with my Coral Beta 8 Speakers, normally driven by my 300B SET.
So I think, I will put this transformer in my box, for a later project.
Many thanks!
Franz
P.S.
The power from the chipclones is already to high to try them with the Corals. To much risk for this gems.
Your guess is perfect: this is an transformer, out of an Fostex 2x350W amp!
Actually, I have no big intention or special application for such high power, specially not with my Coral Beta 8 Speakers, normally driven by my 300B SET.
So I think, I will put this transformer in my box, for a later project.
Many thanks!
Franz
P.S.
The power from the chipclones is already to high to try them with the Corals. To much risk for this gems.
Choke-input filter.
If you use a choke-input filter, once you have more than a certain minimum load, the dc voltage will sit at 0.9x the transformer voltage, i.e. +/- 54vdc. At zero load it will go up to the peak voltage though, so some kind of preloading is necessary for anything other than a class A amp.
If you use a choke-input filter, once you have more than a certain minimum load, the dc voltage will sit at 0.9x the transformer voltage, i.e. +/- 54vdc. At zero load it will go up to the peak voltage though, so some kind of preloading is necessary for anything other than a class A amp.
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