| MtBiker |
| I rarely see many (if any) fuses on chip amps. I can find tons of schematics for large solid state amps that have a fuse before the transformer and one on each rail within the amp, but I never see more than a single fuse in a gainclone? Is the short circuit protection on the LMxxxx so good that fuses are not necessary? |
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| digi01 |
| I think fuses and circuit protection is necessary,I do not hope the expensive loudspeaker is risky. |
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| Mr Evil |
| I think a fuse before the transformer primary is assumed to be there, and thus not necessarily shown. You should most definitely not build anything mains powered without a fuse! |
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| peranders |
| The primary fuse is mainly for the protection of the transformer. Secondary fuses help better to protect things after the fuses. I have fuses in both locations, but that's me. |
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| kmj |
Same here, one primary, two secondarys.
OT
PA
Du nämnde en trådleverantör i göteborg på hififorum, var det månne en trafolindare?
om så, har du lust att berätta vad företaget heter? |
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| MtBiker |
| Secondary fuses between the transformer's secondaries and the diode bridges, or after the bridges on each rail? |
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| scone |
| quote: | Originally posted by MtBiker
Secondary fuses between the transformer's secondaries and the diode bridges, or after the bridges on each rail? |
I've seen both. I have one on the AC mains and two after the PS board on the +V and -V rails... reasoning is that I'm protecting my amplifier boards from my PS just in case something shorts near the opamps. (Perhaps not a problem in most cases, but my PS can do 15A at 31V on paper and I'd rather not take the chance.) |
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| skyraider |
best fuse is no fuse at all. Ceramic fuse 'mellows' the sound, but silver fuse can make the sound 'thin':bawling: :D :D :D hehehe...
Not using fuse is breaking the law from another point of view. I just use the fuse in the 3-pin plug for protection purpose. I didnt use secondary fuse for cost and simplicity reason. But if your chip is the last piece you have on earth, you better use it. |
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| peranders |
| quote: | Originally posted by kmj
OT
PA
Du nämnde en trådleverantör i göteborg på hififorum, var det månne en trafolindare?
om så, har du lust att berätta vad företaget heter? |
You have got email...:) |
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| scone |
| quote: | Originally posted by skyraider
best fuse is no fuse at all. Ceramic fuse 'mellows' the sound, but silver fuse can make the sound 'thin':bawling: :D :D :D hehehe... |
Only if you fuse the audio signal. ;) :D |
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| demogorgon |
never used them, never gone wrong without..
have a few though.. maby i'l do it, but then again thats just empty talk..
never cared to think longer than my nose stretches really :clown: |
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| AudioFreak |
| Well for starters, operation without a fuse is illegal in many parts of the world and will certainly do less than wonderful things for your house insurance. To properly protect your device, you should use correctly rated fuses on each of the primary and secondary windings. |
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| chipco3434 |
Here's what I have gathered over the years regarding secondary winding protection on transformers...
On US machinery, it is was uncommon to see secondary fuses 20 years ago. Typically, that fuse will not protect the transformer in a short condition and it was thought that the secondary windings are going to burn anyhow. I am guessing that it was not a NEC (National Electric Code) requirement. Secondary protection may have been a requirement of the more stringent NFPA (National Fire Protection Association) or city codes like Los Angeles and Port of Portland among others.
Over the last couple decades, European machinery (and particularly machines complying to CE safety requirements) were either fused or OL breaker equiped on the secondaries. It's interesting to note that the CE standard control voltage is 24VDC compared to US standards of 110VAC.
So it is a world market, and we see secondary protection as standard construction feature on most industrial equipment today.
I have not used secondary protection on my GC's. Don't know if I'm right or wrong, it's just my observations.
If somebody has NEC 2005, I'm all ears.
My 2 cents. |
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| runer |
If I use fuses on the secondaries, what would happen if I blow a fuse on only one of the rails?
Would that generate a full rail voltage across the speaker from the remaining rail, or would the chip protection prevent that?
I'd rather protect my very expensive speakers first, and the cheap chipamp second. |
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| chipco3434 |
| A circuit would no longer exist... |
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| Peter Daniel |
| quote: | Originally posted by runer
If I use fuses on the secondaries, what would happen if I blow a fuse on only one of the rails?
Would that generate a full rail voltage across the speaker from the remaining rail, or would the chip protection prevent that?
I'd rather protect my very expensive speakers first, and the cheap chipamp second. |
Even with one rail missing, there will be no DC offset at the output. The circuit will not be damaged either.
Happened to me at least two times.
Without the load, the circuit will show DC offset (with one rail missing), in presence of the load the offset disappears. You can experiment with it using 8 ohm power resistor instead of a speaker. |
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| budwiser |
So,, are fuses recommended between the rectifier board and amp boards? If so V+ V- ?
Thanks,
Pete |
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| peranders |
| I have secondary fuses when I'm using "big" transformers and none for small like < 20VA. |
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| ransom peek |
I have read the posts in this listing and conclude 1 primary and 2 secondary fuses are a good way to go for the brian gt lm3875 rev3.
What rating is appropriate (using a 330va avex toroid) for:
a) primary
b) each of the secondaries
For a 3 prong plug 110vac, where does the center ground connection go? This is for a wood enclosure.
Does polarity matter for the other two 110vac leads? No difference on the primary connectino for these, right? |
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