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Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD
Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD
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Old Yesterday, 03:33 PM   #541
TioFrancotirador is offline TioFrancotirador  Poland
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Quote:
Originally Posted by tomchr View Post
You'll get six times the idle dissipation, so on 30 V rails, you'll get ~18-20 W instead of 3ish W per channel. If you leave your MOD86 amp on at idle (no music) for a few hours and the heat sinks are more than 2-3 C warmer than the room, I'd get larger heat sinks for the MOD686.



I'm assuming 2x22 VAC @ 300 VA here. That's a wee bit underpowered if you intend to run the amp to clipping. If you're not changing your listening level by much, the 300 VA and 2x22000 uF will probably be OK.

Tom
Tom,
Thanks for explanation. I actually got 300VA,2x26VAC, so it should be fine.
As far as Guardian686
In my case I use transformers on the DAC output, so no way DC shows up at mod686 inputs.
Probability of lm3886 chip failure in mod686 is bit higher than in mod86, since mod686 uses six of them instead of one. Still the risk is relatively low in both cases.
Are there any other potential risks that mod686 has and mod86 does not, for which using Guarding686 makes sense?
Lastly is there any way one could match lm3886 to build mod686? Or this completely unnecessary?
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Old Today, 06:20 AM   #542
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by TioFrancotirador View Post
I actually got 300VA,2x26VAC, so it should be fine.
2x26 VAC is perfect. 300 VA is a bit lower than what I normally recommend, but should be fine, especially if you don't run the amp continuously at clipping levels.

Quote:
Originally Posted by TioFrancotirador View Post
Probability of lm3886 chip failure in mod686 is bit higher than in mod86, since mod686 uses six of them instead of one. Still the risk is relatively low in both cases.
I agree.

Quote:
Originally Posted by TioFrancotirador View Post
Are there any other potential risks that mod686 has and mod86 does not, for which using Guarding686 makes sense?
Not that I can think of. The LM3886 is quite rugged. That said, it is pushed to its limits in the MOD686 and there are six of them.

Some like the protection circuits for the peace of mind they provide. They may have more expensive speakers than I do...

Quote:
Originally Posted by TioFrancotirador View Post
Lastly is there any way one could match lm3886 to build mod686? Or this completely unnecessary?
You could set up a test jig to match the LM3886es by their input offset voltage. Pick two pairs of three that have close to identical offset. If the three parallel LM3886es have the same offset, there'll be no error current flowing in the ballast resistors. That'll in theory give you slightly better performance near clipping.

In practice, there's no need for matching or binning the LM3886es, though.

Tom
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