| cpemma |
I've a dual 50V secondary, 300VA toroid bought years ago for a project, I'm wondering if it will make a reasonable stereo amplifier with a pair of LM3875s, using the datasheet circuit with some gainclone techniques like minimum feedback path and a relatively light reservoir (2000uF?).
Should be about 70V DC supply.
1 secondary per amp or a common supply?
Influence of size & type of output cap?
Any suggestions? Or what are the disadvantages of single-supply amps, if cost of the output cap is offset by a "free" transformer?
:confused: |
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| phn |
| The "standard" Gaincard configuration is a single 340 W C-core trafo. But it's only 28 volts, if I remember. Won't 70 volts fry the chip? Sorry for answering with a question, but I'm not sure about the last one. |
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| cpemma |
| quote: | Originally posted by phn
Won't 70 volts fry the chip? Sorry for answering with a question, but I'm not sure about the last one. |
Datasheet says 84V max between rails. Some caps will need to be 100V. |
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| Bazukaz |
| It should work from 70V rails without damage , but you should expect Spike protection response due to increased output power , especially while driving a 4 ohm load at higher levels. |
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| leadbelly |
| quote: | Originally posted by cpemma
Or what are the disadvantages of single-supply amps, if cost of the output cap is offset by a "free" transformer?
:confused: |
The reason the output cap is avoided is not cost, but how it affects the sound. So making an economic argument to justify the output cap is pointless to most. IMHO, this is one of the areas where DIY is pointless, because if you take shortcuts like this, you are essentially building a consumer grade amp for more $$$ than you could have just gone out and bought one. |
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