Is it possible to remove the protection relay out of a home audio amplifier?

HappyTorrent

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So I have this TEAC SA-200 amplifier, it works good and I'm guessing it pushes out at least 150w per channel because I have been able to blow 100w rms speakers easily. My issue is that I have in total four subwoofers hooked up to it. Two Cerwin Vega Mobile Hed 150w subs in a sealed box and two Audiobahn special Editions in a sealed box. Sounds great especially when watching movies, I have the subs wired up at 8ohm in series. When I turn the amp up loud the protection relay kicks in, which really sucks. I was wondering if there's a way to remove the relay so that wouldn't happen? I won't be doing this to the TEAC since I am going to start using it to power a different set of speakers, but I plan to get another amplifier to power the subs and my Fisher DS-825 towers, I have a feeling it will do the same thing as the TEAC with such a load put on it.
 

BFG-9000

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That is exactly how such amps were used in car audio. For home audio though the intention isn't to cheat but flexibility--you could wire your speakers in 8Ώ for best damping factor, or get 4x the power at the expense of less control and more THD by wiring subs in 2Ώ--after all distortion is less audible with subs. Keep in mind the limit is ~1500w total per 15A outlet so to exceed this you'd need to go to dual mono amps on separate breakers.

I was suggesting a much more powerful amp because it's actually easier to damage speakers using an underpowered amp because you don't hear the drivers bottoming from over-excursion. Speakers are designed to handle the thermal load from their rated wattage but no speaker is designed to handle sustained DC current. When you overdrive an amp the first thing that happens is the peaks of the waveforms gets clipped off which means momentary DC at the maximum possible amplitude. You must have heard OEM car radios that detect clipping and cut the signal momentarily to prevent blown speakers and thus warranty repairs. Well the protection circuit in your old 1980s $10 thrift store Teac does no such thing and only cuts power on thermal overload of the amp. That's why it's not much use to bypass it (as suggested, point a fan at it instead).

This thermal overload circuit is what shuts the amp down even at modest volume if say, you wired the speakers at a 2Ώ load. It detects only the temperature rise from the excessive current.
 

asven1

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It is not a relay that is doing the over drive clamp down to prevent the amp from blowing up. Put a fan on the amp blowing directly on it if you are trying to push it to the limit. otherwise buy a better amp.
 

BFG-9000

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Well sure, but that circuit is designed to protect the amp, not the speakers.

The power transistors themselves in that amp are only rated 150w on each channel when used as relays--so that's @ 100% THD. Don't laugh but it sometimes can be difficult to hear fairly severe, even speaker-blowing distortion or clipping from a sub!

The amp is only rated by the manufacturer at 25w per channel @ 8Ώ with 0.04% THD. To give you an idea of how ill-suited this amp is for high-current operation, it's only rated 2w more--27wpc at 4Ώ with 0.15% THD. A decent sub amp would double or at least nearly double the output wattage if dynamic resistance is halved so this should be a big clue that amp isn't designed for that much wattage or at least to dissipate that much heat.

I've got an amp that doubles in wattage from 8 to 4Ώ and then again to a 2 ohm load and nearly again to 1 ohm.
 

nukemaster

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That is just ohms law. If you cut the resistance at the same voltage the output(load in the form of speaker) is doubled. Not all amps are designed for this and may be damaged. This is why they have rating.

If you have actual relays you can bypass them, but you may damage the amplifier or speakers by doing so.
 

HappyTorrent

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I've already damaged some speakers with it lol. Besides, the speakers that I have the amp powering are cheap speakers. Ones that have been damaged in the past and aren't all that great. So if I blow them then it's not that big of a deal.
 

HappyTorrent

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So if I am understanding this correctly what you have is essentially a "cheater" amp. I know that with car audio you could get amps that would increase in power with the smaller impedance. They are called cheater amps because you could essentially use them to "cheat" in car audio competitions.
 

BFG-9000

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Sep 17, 2016
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That is exactly how such amps were used in car audio. For home audio though the intention isn't to cheat but flexibility--you could wire your speakers in 8Ώ for best damping factor, or get 4x the power at the expense of less control and more THD by wiring subs in 2Ώ--after all distortion is less audible with subs. Keep in mind the limit is ~1500w total per 15A outlet so to exceed this you'd need to go to dual mono amps on separate breakers.

I was suggesting a much more powerful amp because it's actually easier to damage speakers using an underpowered amp because you don't hear the drivers bottoming from over-excursion. Speakers are designed to handle the thermal load from their rated wattage but no speaker is designed to handle sustained DC current. When you overdrive an amp the first thing that happens is the peaks of the waveforms gets clipped off which means momentary DC at the maximum possible amplitude. You must have heard OEM car radios that detect clipping and cut the signal momentarily to prevent blown speakers and thus warranty repairs. Well the protection circuit in your old 1980s $10 thrift store Teac does no such thing and only cuts power on thermal overload of the amp. That's why it's not much use to bypass it (as suggested, point a fan at it instead).

This thermal overload circuit is what shuts the amp down even at modest volume if say, you wired the speakers at a 2Ώ load. It detects only the temperature rise from the excessive current.
 

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