PlasticDoc
Member
Advertisements based on selective snippets of subjective client reviews should be posted in the appropriate place, which, if I am not mistaken, is either the vendor's website or the "Desperate Dealers Forum" thread on this forum.
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"Micro Bamboo Project" : 3E Audio 260-2-29A Stereo amplifier + Micro-Audio PSU
How about something other than anecdotal claims. It's definitely going to be hard to convince anyone of anything if it is just based on stories.
This thread has inspired my to give the 3E Audio board a try too. I ordered two boards, and two PSU's from Micro Audio. I noticed the post about good results with a cheaper PSU, which is obviously interesting in this price range, but I went for the Micro Audio option mainly because of the build quality. Whether there's a notable impact on the sound of the amp or not, I trust the better build quality to last a while longer.
I went for 46V versions, slightly under the max rating of the 3E boards.
Can anybody comment about the built-in speaker protection of the 260-2-29A? There's supposed to be speaker protection, but I find it tough to determine if it's adequate for all failure scenario's and I don't want to blow up someones expensive speakers trying to impress them with a cheap amp. I'm considering adding a couple of Guardian-86 boards by Neurochrome just to be sure, but that means a pretty big part of the total budget on such a cheap amp.
I went for 46V versions, slightly under the max rating of the 3E boards.
Can anybody comment about the built-in speaker protection of the 260-2-29A? There's supposed to be speaker protection, but I find it tough to determine if it's adequate for all failure scenario's and I don't want to blow up someones expensive speakers trying to impress them with a cheap amp. I'm considering adding a couple of Guardian-86 boards by Neurochrome just to be sure, but that means a pretty big part of the total budget on such a cheap amp.
Roland68
Major Contributor
I wouldn't rely on that, at least not with expensive speakers.
The protection is only integrated in the chip. I've already lost expensive speaker chassis to DC twice in my life, once even large and resilient woofers because an amplifier broke. If things go really badly, the power supplies deliver 36-48 volts DC at several amps.
@jwdevos
In the diyaudio forum I've seen several projects on SSR protection circuits, I particularly liked the one by xrk971.
Personally, I would only go to that trouble with expensive chassis. These amplifier ICs are really good and it happens much less than with normal amplifiers.
somebodyelse
Major Contributor
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It would be good to have some clear documentation of the failure modes that the protection covers, and the modes it doesn't. This isn't specific to 3E - many other manufacturers miss it too. This would let people make a more informed decision about whether to add extra protection for their speakers.
From my understanding of the TPA3255 datasheet section 9.4.1 most of the built in protection is to protect the amp from various conditions that may damage it. Only the 'DC Speaker Protection' (section 9.4.1.3) is to protect the speaker, and even that seems to be limited in what protection it offers. Nominally it is there in case one speaker terminal is accidentally connected to ground when the amp is in a bridged mode, which would lead to DC on the speaker. This is detected by an imbalance in current in the bridged channels, not by detecting DC at the output terminals, so doesn't protect against other sources of DC offset. It also doesn't protect against an output transistor failing short, although that _might_ at least trigger fault indication due to current mismatch - @3eaudio can you confirm or deny this? The fault signal could be used to disconnect or power down the power supply if this happens.
From my understanding of the TPA3255 datasheet section 9.4.1 most of the built in protection is to protect the amp from various conditions that may damage it. Only the 'DC Speaker Protection' (section 9.4.1.3) is to protect the speaker, and even that seems to be limited in what protection it offers. Nominally it is there in case one speaker terminal is accidentally connected to ground when the amp is in a bridged mode, which would lead to DC on the speaker. This is detected by an imbalance in current in the bridged channels, not by detecting DC at the output terminals, so doesn't protect against other sources of DC offset. It also doesn't protect against an output transistor failing short, although that _might_ at least trigger fault indication due to current mismatch - @3eaudio can you confirm or deny this? The fault signal could be used to disconnect or power down the power supply if this happens.
Thanks everyone for helping me understand speaker protection in relation to this particular circuit a little bit better. I think I'd rather add 200 bucks to each build, grab a pair of Guardian-86's (https://neurochrome.com/products/guardian-86) and sleep much better. My DIY amps might end up at friends places over time and preventing speaker damage and pops is the must crucial safety factor for me with these DIY projects, besides personal safety of course.
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