I think I damaged my amp.... for science!

[MalVeauX]

Hah, well, probably just being an idiot enjoying too much bourbon at the end of the day.

I think I damaged an amplifier. I have several of these because they're inexpensive and solid little units. It's an AudioSource AMP100. I was playing around with using both channels at the same time on it. I was reading about how to use Channel A for the loudspeakers and Channel B for high-level output to a sub with high-level inputs (as the unit lacks unbalanced RCA options) to splice in a subwoofer, without putting the loud speakers on the high-in/out terminals on the back of the sub (low quality one in this case, so the signal is not good coming back out to the speakers). Anyhow, I read you can enabled both channels simultaneously so that you could send signal to the speakers and the sub via this method. I tried it, and man, it worked. Sounded great too.

However, in doing so for a few days, I think I damaged the amplifier. I'm not keen on this, but if I have both channels outputting simultaneously, this means they were seeing my 8ohm speakers as 4ohm instead, which is fine, as the amp is rated to handle 4ohms; but it means the other channel was seeing my 4ohm sub as possibly 2ohm and that probably started to degrade the circuit from the high current and damaged it I think. Does this sound right? The amp plate on the sub was definitely getting hot. The sub is fine. But the right channel on both channel A & B on that amp now is lower output and sounds sloppy. So I think I destroyed the right channel partially, despite it still working, its definitely degraded. I tested it by using each channel separately and on different speakers to rule out speaker wires, speakers themselves, etc, and it definitely is the amplifier and definitely it's right channel side only (regardless of channel A or B).

So again, just to be clear so I don't blow up another amp, I damaged it because I used both channels together and it saw the 8ohm load as 4ohm (which is fine) but it saw the other 4ohm load as 2ohm and this is not fine, and that is how I damaged it. I think? Just looking to learn about this so I don't mess that up again.

The bourbon was good.

Very best,

 

[Pogre]

This is a little over my paygrade, but it sounds like you tried mixed mono? A wiring scheme that includes stereo left and right for the mains and a mixed mono signal powering the sub?

Iirc you'd have the sub's positive on one channel and the negative on the other channel like a bridged connection with the front left right still wired and playing in stereo?

 

[PENG]

Hah, well, probably just being an idiot enjoying too much bourbon at the end of the day.

I think I damaged an amplifier. I have several of these because they're inexpensive and solid little units. It's an AudioSource AMP100. I was playing around with using both channels at the same time on it. I was reading about how to use Channel A for the loudspeakers and Channel B for high-level output to a sub with high-level inputs (as the unit lacks unbalanced RCA options) to splice in a subwoofer, without putting the loud speakers on the high-in/out terminals on the back of the sub (low quality one in this case, so the signal is not good coming back out to the speakers). Anyhow, I read you can enabled both channels simultaneously so that you could send signal to the speakers and the sub via this method. I tried it, and man, it worked. Sounded great too.

However, in doing so for a few days, I think I damaged the amplifier. I'm not keen on this, but if I have both channels outputting simultaneously, this means they were seeing my 8ohm speakers as 4ohm instead, which is fine, as the amp is rated to handle 4ohms; but it means the other channel was seeing my 4ohm sub as possibly 2ohm and that probably started to degrade the circuit from the high current and damaged it I think. Does this sound right? The amp plate on the sub was definitely getting hot. The sub is fine. But the right channel on both channel A & B on that amp now is lower output and sounds sloppy. So I think I destroyed the right channel partially, despite it still working, its definitely degraded. I tested it by using each channel separately and on different speakers to rule out speaker wires, speakers themselves, etc, and it definitely is the amplifier and definitely it's right channel side only (regardless of channel A or B).

So again, just to be clear so I don't blow up another amp, I damaged it because I used both channels together and it saw the 8ohm load as 4ohm (which is fine) but it saw the other 4ohm load as 2ohm and this is not fine, and that is how I damaged it. I think? Just looking to learn about this so I don't mess that up again.

The bourbon was good.

Very best,

Is you sub a passive one or active? If active, speaker level should still be fine with very high input impedance so there should be no issue connecting it in parallel with you 8 Ohm speakers. As you know, you only get 4 Ohm if the sub's impedance is also 8 Ohm. If it is say even as low as just 5k Ohms, the overall impedance will still be very close to 8 Ohms.

 

[MalVeauX]

This is a little over my paygrade, but it sounds like you tried mixed mono? A wiring scheme that includes stereo left and right for the mains and a mixed mono signal powering the sub?

Iirc you'd have the sub's positive on one channel and the negative on the other channel like a bridged connection with the front left right still wired and playing in stereo?

So the exact setup is:

Source (stereo) -> AMP100 -> AMP100 Channel A (enabled) with both R/L terminals (+/-) output to 8ohm speakers & simultaneously Channel B (enabled) with both R/L terminals (+/-) output to an active power subwoofer's plate amp which has high-level inputs & outputs and the sub itself is 4ohm. I'm not sure what the high-level inputs impedance is. But I'm sending two channels, stereo, to the loud speakers and to the active sub. I'm mostly curious if the circuit is seeing the two channels operating at the same time the way bridging works and so the impedance on the sub end might have went too low and caused damage. But I'm not sure.

Very best,

 

[MalVeauX]

Is you sub a passive one or active? If active, speaker level should still be fine with very high input impedance so there should be no issue connecting it in parallel with you 8 Ohm speakers. As you know, you only get 4 Ohm if the sub's impedance is also 8 Ohm. If it is say even as low as just 5k Ohms, the overall impedance will still be very close to 8 Ohms.

The sub is active, with an amp plate that has high-level input/output terminals. The sub itself is 4ohm. I'm not sure what the high-level inputs are in this situation or how they effect things in terms of what the amp will do there.

The AMP100 has channels A & B with switches but both can be enabled at the same time for simultaneous output to two separates with their own R/L terminals (+/-). So I was running Channel A to the loudspeakers (8ohm) and running Channel B to an active powered subwoofer's plate amp's high-level inputs and using the crossover on the sub. The sub's impedance is 4ohm. But again, I'm not sure how the high-level inputs effect this.

I'm curious how the circuit works internally. The AMP100 can be bridged. But there's no documentation that I could find about what happens when you use both Channel A & B at the same time. But logically, I figure, if I am splitting the signal or basically connecting the speakers in a parallel circuit, then basically I'm dropping the impedance I think? So while the 8ohm speakers are fine, I'm mainly thinking the sub at 4ohm on this circuit might have been seen as 2ohm and that damaged it? Or does the high-level input change this?

Very best,

 

[PENG]

The sub is active, with an amp plate that has high-level input/output terminals. The sub itself is 4ohm. I'm not sure what the high-level inputs are in this situation or how they effect things in terms of what the amp will do there.

I don't understand what it meant by "The sub itself is 4 Ohm". I guess you meant the driver itself? If it is an active subwoofer, the 4 Ohm thing does not make sense. May be I am missing something, please clarify. What model is that anyway? Then I can read the manual, or even service manual, with any luck.

 

[Trebdp83]

Well, whatever you did, at least you did it... for science!

 

[MalVeauX]

I don't understand what it meant by "The sub itself is 4 Ohm". I guess you meant the driver itself? If it is an active subwoofer, the 4 Ohm thing does not make sense. May be I am missing something, please clarify. What model is that anyway? Then I can read the manual, or even service manual, with any luck.

Sorry, I may be assuming incorrectly. I was playing with a BIC F12. I was testing on a junk sub that I didn't care if I blew it up too. I assumed it was a 4ohm speaker like most subs. It has a plate amplifier with high-level inputs/ouputs. I'm not sure what resistance they have or what they precisely do on a circuit when high-level inputs are applied. I did that to extract signal for the sub to play and used the manual crossover to limit it to a range of frequencies. So I'm not sure what the AMP100 saw, as load, when connected to the high-level inputs on the sub's amp plate. I may be totally incorrect, which is why I'm asking to learn more about how this works in case I caused the damage. My amp maybe also just failed from sheer chance, as the right channel is definitely degraded at this point and it happened at the same time that I started doing this practice with the amp and the sub with each channel active. From this, I assumed the load the amp saw was likely out of its spec and so maybe it damaged it?

Very best,

 

[Pogre]

So the exact setup is:

Source (stereo) -> AMP100 -> AMP100 Channel A (enabled) with both R/L terminals (+/-) output to 8ohm speakers & simultaneously Channel B (enabled) with both R/L terminals (+/-) output to an active power subwoofer's plate amp which has high-level inputs & outputs and the sub itself is 4ohm. I'm not sure what the high-level inputs impedance is. But I'm sending two channels, stereo, to the loud speakers and to the active sub. I'm mostly curious if the circuit is seeing the two channels operating at the same time the way bridging works and so the impedance on the sub end might have went too low and caused damage. But I'm not sure.

Very best,

I understand. I thought you were working with a passive sub. I've never used high level connections for an active sub before. Oops. Carry on!

 

[MalVeauX]

I understand. I thought you were working with a passive sub. I've never used high level connections for an active sub before. Oops. Carry on!

I've used high-level input on subs in the past. It works fine. The intention is to have the output from the stereo amp to the sub's high-level inputs so the sub can get the signal, and then it outputs the signal onto the high-level outputs to the speakers and then set the crossover on the sub. A very basic analog way to splice in a subwoofer with a stereo amp.

However, I did it slightly differently. Instead of running a set of L/R high level output to my sub and then speakers from the high level terminals from the sub itself, I did it with my two channel amp and basically gave it two sets of speakers to output to. On channel A I gave it two bookshelves at 8ohm and on channel B I gave it the high-level inputs on the sub amp plate (I don't know what they are, resistance wise). I enabled both channels at the same time, and it outputs to both of those, with high-level output to both channels A & B, and both channels are receiving R & L +/- high level signal. I assume to do this, it can't just put 50 watts into both, since its a 50 watt amp. So I assume it see's the loads and either see's them at a lower impedance or something and so it will have a different behavior, so this is where the impedance of the sub came into question as I don't know what the amp see's with those high-level inputs on the sub.

Very best,

 

[PENG]

Sorry, I may be assuming incorrectly. I was playing with a BIC F12. I was testing on a junk sub that I didn't care if I blew it up too. I assumed it was a 4ohm speaker like most subs. It has a plate amplifier with high-level inputs/ouputs. I'm not sure what resistance they have or what they precisely do on a circuit when high-level inputs are applied. I did that to extract signal for the sub to play and used the manual crossover to limit it to a range of frequencies. So I'm not sure what the AMP100 saw, as load, when connected to the high-level inputs on the sub's amp plate. I may be totally incorrect, which is why I'm asking to learn more about how this works in case I caused the damage. My amp maybe also just failed from sheer chance, as the right channel is definitely degraded at this point and it happened at the same time that I started doing this practice with the amp and the sub with each channel active. From this, I assumed the load the amp saw was likely out of its spec and so maybe it damaged it?

Very best,

Thank you, I read the manual of the BIC F12 and it says:
"HIGH LEVEL INPUTS FROM AMPLIFIER – If your receiver does not have a SUBWOOFER or LFE output, use these color coded binding posts to run speaker wire from your receiver’s main left and right speaker terminals to these HIGH LEVEL INPUTS."

So you did the right thing according to instructions. The subwoofer obviously has to convert (internally) the high level signal from the AVR speaker output binding posts to much lower level suitable for the plate amp and the plate amp will have very high impedance, like thousands of Ohms. That means your amp most likely failed for other reasons than just by connecting it to the sub.

One important point to keep in mind, you can only assume 2 parallel 8 Ohm speakers being equivalent to one single 4 Ohm speaker if the two speakers being parallel are identical. Impedance specs are not reliable to begin with, as they don't always follow the same rules/standards to determine the so called "nominal" impedance. On top of that, the phase angles of two different speakers are also going to be different. It doesn't mean it will always result in higher risk, but it just might.

 

[MalVeauX]

Thank you, I read the manual of the BIC F12 and it says:
"HIGH LEVEL INPUTS FROM AMPLIFIER – If your receiver does not have a SUBWOOFER or LFE output, use these color coded binding posts to run speaker wire from your receiver’s main left and right speaker terminals to these HIGH LEVEL INPUTS."

So you did the right thing according to instructions. The subwoofer obviously has to convert (internally) the high level signal from the AVR speaker output binding posts to much lower level suitable for the plate amp and the plate amp will have very high impedance, like thousands of Ohms. That means your amp most likely failed for other reasons than just by connecting it to the sub.

One important point to keep in mind, you can only assume 2 parallel 8 Ohm speakers being equivalent to one single 4 Ohm speaker if the two speakers being parallel are identical. Impedance specs are not reliable to begin with, as they don't always follow the same rules/standards to determine the so called "nominal" impedance. On top of that, the phase angles of two different speakers are also going to be different. It doesn't mean it will always result in higher risk, but it just might.

Thanks,

I knew the connections were appropriate with the sub, its' an ancient safe way to do it after all.

The main thing was figuring out how the AMP100 behaves with this configuration. Normally, it would be AMP100 -> L/R high-level output to Sub's high-level inputs -> L/R out from sub's plate to L/R speakers. But the way I configured it, based on the AMP100 having channel A & B, I figured something had to be going on since you can enable channel A or B to switch between speaker sets or zones basically, or you can push them both and have them both active with the same signal sent to both. So I did that and treated the bookshelves as a set of L/R speakers with high-level output to them on channel A and sent another set of L/R high-level output to the sub's high-level inputs L/R posts on channel B.

Just a strange coincidence to get a problem after doing this for a few hours. So I figured something had to have happened due to the configuration. So then I got to thinking about what happens with parrallel speakers on a circuit and how it effects impedance and started thinking of the internal bridge option in this amp and went into the realm of silly with it thinking maybe I induced too low of an impedance and the current output was just too demanding and the thermal damage was induced and the result was the degraded right channel somehow. But maybe it truly is just a coincidence.

Very best,

 

[PENG]

However, I did it slightly differently. Instead of running a set of L/R high level output to my sub and then speakers from the high level terminals from the sub itself, I did it with my two channel amp and basically gave it two sets of speakers to output to. On channel A I gave it two bookshelves at 8ohm and on channel B I gave it the high-level inputs on the sub amp plate (I don't know what they are, resistance wise). I enabled both channels at the same time, and it outputs to both of those, with high-level output to both channels A & B, and both channels are receiving R & L +/- high level signal. I assume to do this, it can't just put 50 watts into both, since its a 50 watt amp. So I assume it see's the loads and either see's them at a lower impedance or something and so it will have a different behavior, so this is where the impedance of the sub came into question as I don't know what the amp see's with those high-level inputs on the sub.

Very best,

I know what you are doing, there is no issue and I have done it before too without any issues. The so called high level speaker outputs on the sub is just an option for you to use the sub plate amp's cross over filter. It is you choice! Obviously if you choose to use your AVR to set the crossover, then say if you set it to 80 Hz, then you would be limiting the low frequency response of the sub (the BIC F2) as the AVR's crossover setpoint will affect it too.

Yes it is just coincidence. If it was in fact the problem, your amp would have been damaged much sooner, instead of after a few days unless you only use it for a few minutes each day.

 

[MalVeauX]

Sounds good,

I'll throw it up to chance then. I'll test the amp some more to see if it's pretty much going to be considered dead. Would hate to keep using it for any application and it's death throw drag a good speaker down with it in a catastrophic melt down. They're cheap anyways.

Maybe I'll enable its bridge and see what it does and how it sounds. Otherwise, probably just need to retire it.

Very best,

 

[PENG]

Sounds good,

I'll throw it up to chance then. I'll test the amp some more to see if it's pretty much going to be considered dead. Would hate to keep using it for any application and it's death throw drag a good speaker down with it in a catastrophic melt down. They're cheap anyways.

Maybe I'll enable its bridge and see what it does and how it sounds. Otherwise, probably just need to retire it.

Very best,

If you have a multimeter you can try measuring the resistance across the speaker level inputs to see for yourself. Make sure you disconnect everything and unplug it (the sub) first if you are going to do it.

 

[MalVeauX]

If you have a multimeter you can try measuring the impedance across the speaker level inputs to see for yourself. Make sure you disconnect everything and unplug it (the sub) first if you are going to do it.

I have one, I'll do that!

Very best,

 

[PENG]

I have one, I'll do that!

Very best,

You can't measure impedance with the meter, just resistance but it should still tell you the story. Set it to highest range first, like 1M, 100 k (likely the right range for this experiment) or something and then lower it to 10 K, even 1 K depending on the reading you get. I would be shock to see a few ohms as that would only be possible if it bypasses the plate amp, I am not aware of any active sub with speaker level inputs operates in such manner.

 

[MalVeauX]

You can't measure impedance with the meter, just resistance but it should still tell you the story. Set it to highest range first, like 1M, 100 k (likely the right range for this experiment) or something and then lower it to 10 K, even 1 K depending on the reading you get. I would be shock to see a few ohms as that would only be possible if it bypasses the plate amp, I am not aware of any active sub with speaker level inputs operates in such manner.

So should I test the output of the amp on its terminals to see if they're different within a range of tolerance? And then hook it up to the sub plate amp and measure it there too?

Very best,

 

[PENG]

So should I test the output of the amp on its terminals to see if they're different within a range of tolerance? And then hook it up to the sub plate amp and measure it there too?

Very best,

There is no need to measure the output terminal of the amp. You can do a lot of thing just to play but again be sure to unplug everything first to avoid damages.

 

[MalVeauX]

There is no need to measure the output terminal of the amp. You can do a lot of thing just to play but again be sure to unplug everything first to avoid damages.

So what do you think is the simplest best way to use the multi-meter to evaluate the channel differences (be it voltage, resistance, etc), either at the amp, or at the sub. I'm happy to leave the sub out of it. After I noticed the right channel acting up, I simplified the total circuit and rotated speakers and cables and consistently the only thing that remained constant was the right channel no matter what was plugged into it, had problems. Audibly, it sounds dimmer, muddy and distorted and significantly lower volume than the left channel.

Very best,