Amplifier Question!

[eduardokbb]

Hello! First of all, I'm not very used with english so, perhaps you'll find some errors in my post, I'll do my best to make you understand what I'm asking here!

I'm in the process of building an audio amplifier. It'll be a huge stereo amplifier capable of delivering 500w RMS 8R, 800w RMS 4R and 1200w RMS 2R.

My setup will have a preamplifier with asynchronous usb DAC, that will receive all music from my computer and will output it for my amplifier that, will amplify the signal and send for my speakers. My preamplifier has a volume knob that controls the signal that's sent for my amplifier.

Since I spent quite a bit of money buying my preamplifier and lots of money to build my stereo amplifier (I'm not a millionaire or something like that, I earn 500USD/month), I'll have to wait sometime to build my speakers. With everything I said in mind, my speakers are some cheap Philips that work with 26w RMS 6R and I won't be able to replace them for at least 8 months.

Will the preamplifier volume control be enough to make my amplifier don't burn my cheap Philips' speakers? Or I would better install a volume knob in my amplifier? Just to clarify, my preamp is an Oppo HA-1.

Any help will be very appreciated.

Thanks for your help and I'm really sorry for bad english.

Peace,
Eduardo Barth.

 

[PENG]

Hello! First of all, I'm not very used with english so, perhaps you'll find some errors in my post, I'll do my best to make you understand what I'm asking here!

I'm in the process of building an audio amplifier. It'll be a huge stereo amplifier capable of delivering 500w RMS 8R, 800w RMS 4R and 1200w RMS 2R.

My setup will have a preamplifier with asynchronous usb DAC, that will receive all music from my computer and will output it for my amplifier that, will amplify the signal and send for my speakers. My preamplifier has a volume knob that controls the signal that's sent for my amplifier.

Since I spent quite a bit of money buying my preamplifier and lots of money to build my stereo amplifier (I'm not a millionaire or something like that, I earn 500USD/month), I'll have to wait sometime to build my speakers. With everything I said in mind, my speakers are some cheap Philips that work with 26w RMS 6R and I won't be able to replace them for at least 8 months.

Will the preamplifier volume control be enough to make my amplifier don't burn my cheap Philips' speakers? Or I would better install a volume knob in my amplifier? Just to clarify, my preamp is an Oppo HA-1.

Any help will be very appreciated.

Thanks for your help and I'm really sorry for bad english.

Peace,
Eduardo Barth.

The HA-1 volume control will be limit the power output of your hugh power amplifier and is all you need. It does not matter whether the volume control is on your preamplifier or amplifier. The danger is that if the volume is turned high accidentally by you or anyone without being noticed, then when you first turn your system on the 26W rated speaker could still be damaged, unless you are quick to turn the volume down. If you want to have on the safe side, you can protect them with fuses too.

 

[markw]

That's like asking if the gas pedal on a Jaguar XJ220 is adequate for it to be able to cruise legally in a 25 mph speed zone.

Like Peng said, the level control on the Oppo is up to the job. It's up to you to not turn it up to such a level that the speaker gets hurt.

 

[Speedskater]

Never test your project with your best speakers (even if they are budget speakers). Find some old speakers to test with until you are sure that everything is operating correctly. That includes some turn on/off cycles and several hours use.

 

[eduardokbb]

Thank you all for your replies. Since there's no kids or pets here, I assume my speakers will be safe for the time I won't be able to replace them!

The HA-1 volume control will be limit the power output of your hugh power amplifier and is all you need. It does not matter whether the volume control is on your preamplifier or amplifier. The danger is that if the volume is turned high accidentally by you or anyone without being noticed, then when you first turn your system on the 26W rated speaker could still be damaged, unless you are quick to turn the volume down. If you want to have on the safe side, you can protect them with fuses too.

@PENG:
How can I use fuses to protect my speakers? Sorry for such a dumb question, but I'm not an electrician and I don't really know much about that world. The only thing I'll have to protect my speakers are loudspeaker protection boards installed directly in my amplifier boards, that'll avoid any DC offset of being sent from the amplifier, in case it fails, for the speakers.


Peace,
Eduardo Barth.

 

[PENG]

Thank you all for your replies. Since there's no kids or pets here, I assume my speakers will be safe for the time I won't be able to replace them!



@PENG:
How can I use fuses to protect my speakers? Sorry for such a dumb question, but I'm not an electrician and I don't really know much about that world. The only thing I'll have to protect my speakers are loudspeaker protection boards installed directly in my amplifier boards, that'll avoid any DC offset of being sent from the amplifier, in case it fails, for the speakers.


Peace,
Eduardo Barth.

This link https://www.trueaudio.com/st_prot1.htm should give you some idea and you can search for more information. Basically you connect suitably sized fuses of the right type (typically slow-blow type) in series with the speaker. To calculate the exact size and type is not easy as you do not know the exact characteristics of the speaker. Fuses are cheap so you can do it by trial and error but start from the size calculated base on the most basic formula and make an assumption of the average impedance of your speaker.

In my opinion, if the speakers are also cheap (you said that yourself), why not just be careful with the volume knob and before you turn it on, make sure you turn it down first.

 

[markw]

Keep in mind that fuses take a bit of time to blow. You still have to very, very careful with that volume control because with those low power speakers and that gigunda hulk of an amp, it won't take much time to fry the delicate voice coils of your tweeters.

 

[PENG]

Keep in mind that fuses take a bit of time to blow. You still have to very, very careful with that volume control because with those low power speakers and that gigunda hulk of an amp, it won't take much time to fry the delicate voice coils of your tweeters.

Agree, woofers can be protected by suitably sized time delayed (aka slow blow) fuses quite effectively but tweeters could be protected better with faster acting fuses. The whole thing is easier said than done, or can be easily done but not all that effective. For argument sake, it may be possible to find circuit a breaker that can trip fast on high value spike and trip slower following a current/time curve that are similar to that of the woofer's damage curve. We do that all the time in high power industrial systems. Again, that's just for argument sake, no one with a normal mind would spend that much time, money and energy to do such silly thing.

I still think the OP should just be extra careful with the knob.

 

[eduardokbb]

Thanks, guys! I do really appreciate your patience and time. I'll probably just try to be careful with the preamp volume knob in a first moment, but I'll do my lesson about that, because my future speakers will probably need a little care when amplified with this huge little monster I'm building, haha!