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

P

PENG

Audioholic Slumlord
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,
Seems like you just switch topic. Are you now talking about troubleshooting your power amp that you think was damaged? I thought you just want to see if for yourself that the speaker level input of your BIC sub can be connected to the same amp's binding posts in parallel with your front left/right speakers.

Again, trying to find out what's wrong with your amp is a different story. One would need to know the symptoms, what it is doing and/or not doing, and really should have a copy of the service manual on hand and you have some electrical/electronic knowledge not just a multi meter. Otherwise there isn't much you can do other than checking all connections (if it still makes sound) points, fuses (if not making sound) etc. If not, the best bet is to send it back to the manufacturer for repair especially if it is under warranty.
 
MalVeauX

MalVeauX

Full Audioholic
Seems like you just switch topic. Are you now talking about troubleshooting your power amp that you think was damaged? I thought you just want to see if for yourself that the speaker level input of your BIC sub can be connected to the same amp's binding posts in parallel with your front left/right speakers.

Again, trying to find out what's wrong with your amp is a different story. One would need to know the symptoms, what it is doing and/or not doing, and really should have a copy of the service manual on hand and you have some electrical/electronic knowledge not just a multi meter. Otherwise there isn't much you can do other than checking all connections (if it still makes sound) points, fuses (if not making sound) etc. If not, the best bet is to send it back to the manufacturer for repair especially if it is under warranty.
I think the amp is damaged (the AMP100). The sub part of this is that I think my hooking it up may have damaged it the way it interacted. But maybe not. Looks like probably not based on everything was hooked up right. The sub is behaving fine separate. All components are behaving fine except the amp's right channel, no matter what I hook up to it and with different cables. So I've narrowed it down to the amp (not the sub's amp plate, separate, the amp that was sending high-level output to the speakers and the sub's inputs, the AMP100).

I already had hooked up the sub the way I described. It worked fine. And per the manual the sub is fine. What I don't know is if the AMP100 is fine after enabling both channel A & B and how that works in terms of the load it will see and if I introduced too low of an impedance doing that, harming the AMP100.

Currently the AMP100's right channel is degraded, lower volume, muddy and it wasn't like that the previous day. It only started after I ran the sub off the high-level output from the AMP100 to the sub's high-level inputs on the sub's amp plate for a while. This is why I asked if it was a coincidence or if I had setup something incorrectly and harmed the amp.

This amp is old, and I bought it used, have had it for years. They're $125 new, so I'm not worried about it. I got plenty of my money out of it over the years. It's fine if it's dead. I just wanted to learn something from it, in case I caused its demise, or if it was just "it's time" and it was a coincidence.

So to help clarify:

I started with the AMP100 (50 watt stereo amp) hooked up to bookshelf speakers normally.
The AMP100 has channel A & B to switch between two outputs (both stereo outputs).
I had the bookshelf speakers on channel A.
I then output from channel B on the AMP100 to a sub's amp plate that has high-level inputs.
I then enabled both channel A & channel B simultaneously so that the bookshelf and sub speakers were getting signal from the AMP100 amp.
This was working well, sounded great for a few hours. The next day, I noticed the AMP100's right channel was dim, veiled, muddy. I rotated different speakers to check speakers and rotated different wires. I narrowed it down to the right channel on the AMP100 being much lower volume, dim, muddy, distorted. Figured I damaged something with my connections. Started this thread.

So earlier in this thread, it was noted that the connections were correct and it should have been ok. And so maybe the AMP100's right channel going bad is just a coincidence.

Now, since I am certain the right channel is degraded, I was curious to test it other than listening to it, perhaps with a multi-meter since I have one to see what it's doing, other than the obvious degraded, low signal that it's outputting. I have no plans to repair or fix it, it's old and used, lived it's life well. If it's dead, that's no big deal, I have several of them.

Very best,
 
P

PENG

Audioholic Slumlord
I think the amp is damaged (the AMP100). The sub part of this is that I think my hooking it up may have damaged it the way it interacted. But maybe not. Looks like probably not based on everything was hooked up right. The sub is behaving fine separate. All components are behaving fine except the amp's right channel, no matter what I hook up to it and with different cables. So I've narrowed it down to the amp (not the sub's amp plate, separate, the amp that was sending high-level output to the speakers and the sub's inputs, the AMP100).

I already had hooked up the sub the way I described. It worked fine. And per the manual the sub is fine. What I don't know is if the AMP100 is fine after enabling both channel A & B and how that works in terms of the load it will see and if I introduced too low of an impedance doing that, harming the AMP100.

Currently the AMP100's right channel is degraded, lower volume, muddy and it wasn't like that the previous day. It only started after I ran the sub off the high-level output from the AMP100 to the sub's high-level inputs on the sub's amp plate for a while. This is why I asked if it was a coincidence or if I had setup something incorrectly and harmed the amp.

This amp is old, and I bought it used, have had it for years. They're $125 new, so I'm not worried about it. I got plenty of my money out of it over the years. It's fine if it's dead. I just wanted to learn something from it, in case I caused its demise, or if it was just "it's time" and it was a coincidence.

So to help clarify:

I started with the AMP100 (50 watt stereo amp) hooked up to bookshelf speakers normally.
The AMP100 has channel A & B to switch between two outputs (both stereo outputs).
I had the bookshelf speakers on channel A.
I then output from channel B on the AMP100 to a sub's amp plate that has high-level inputs.
I then enabled both channel A & channel B simultaneously so that the bookshelf and sub speakers were getting signal from the AMP100 amp.
This was working well, sounded great for a few hours. The next day, I noticed the AMP100's right channel was dim, veiled, muddy. I rotated different speakers to check speakers and rotated different wires. I narrowed it down to the right channel on the AMP100 being much lower volume, dim, muddy, distorted. Figured I damaged something with my connections. Started this thread.

So earlier in this thread, it was noted that the connections were correct and it should have been ok. And so maybe the AMP100's right channel going bad is just a coincidence.

Now, since I am certain the right channel is degraded, I was curious to test it other than listening to it, perhaps with a multi-meter since I have one to see what it's doing, other than the obvious degraded, low signal that it's outputting. I have no plans to repair or fix it, it's old and used, lived it's life well. If it's dead, that's no big deal, I have several of them.

Very best,
If it is still making sound but just degraded, it could be just the power supply caps failed/partially failed. The thing is, for the money you paid and you said its old, it may not be worth getting it repair as it will likely cost almost, or more than the $125 you paid. I would just use it as a mono block, or leave it alone for spare parts.

As for the speaker level input, I have already commented that you did not do anything wrong because I read the manual, so I know that sub is design for the way you connected it to your amp.

When you use speaker A+B, the amp would just connect them (A, and B) in parallel, you can tell by the warning of total impedance has to be 4 ohms minimum. Since you connect the sub to speaker B binding post and the sub's input impedance would be in the order of thousands of ohms not 4 ohm (100% sure) unless the sub is defective. So again, you didn't do anything wrong except you might have overloaded the poor old little 60 W amp, and/or it's just getting old and tired so something (such as the caps) gave..
 
MalVeauX

MalVeauX

Full Audioholic
Thanks,

I think it was just its time. I won't try to repair or anything, its cheap and lived a good life. I think it was a just an extraordinary coincidence since everything was hooked up right. I mainly wanted to learn a bit, to know I didn't introduce an inappropriate load and killed it (doing what I did with the sub connection, etc). I think perhaps in reality because I was outputting both channels, it was likely demanding the power supply and the heat did the rest to finish her off. True, I could use it as a 50 watt monoblock. Not sure what application I'd ever need that for. I will tape off the bad channels to avoid plugging anything in. That said, I probably should toss the whole thing. Would hate to have it hooked up and when it does its final death throw, drag down anything else with it.

Very best,
 
highfigh

highfigh

Audioholic Slumlord
Thanks,

I think it was just its time. I won't try to repair or anything, its cheap and lived a good life. I think it was a just an extraordinary coincidence since everything was hooked up right. I mainly wanted to learn a bit, to know I didn't introduce an inappropriate load and killed it (doing what I did with the sub connection, etc). I think perhaps in reality because I was outputting both channels, it was likely demanding the power supply and the heat did the rest to finish her off. True, I could use it as a 50 watt monoblock. Not sure what application I'd ever need that for. I will tape off the bad channels to avoid plugging anything in. That said, I probably should toss the whole thing. Would hate to have it hooked up and when it does its final death throw, drag down anything else with it.

Very best,
The 4 Ohm rating for the sub is immaterial- the AMP100 never sees the driver's impedance after the input and plate amp.

Unplug the AudioSource amp, press the power switch as if you were turning it on (defeat the auto on, if you had enabled it) and look for fuses- if you see a blown fuse, replace it. I recently sold a power amp that hadn't been used in a few years and it worked fine for a while, then sounded like the outputs were blown. That one has resettable breakers that look like a plastic cap with a slot for a screwdriver, but the caps don't come out, they just make and break contact. I think they may twist internally because it was fine after resetting it.

If you wired the AudioSource to the sub as if it was just another stereo connection, I would ask if the sub was designed for 50W (or higher) input power. If that's old, it may have some internal damage that caused the power amp channel to meet its maker.

If the power amp was always used with only the speaker A terminals and the B switch was never pressed, the switch may be faulty/dirty, although I don't remember if these use a relay for that function. Have you ever moved the level control on the power amp? If not, rotate that several times and if it comes back, the control needs to be cleaned.
 
highfigh

highfigh

Audioholic Slumlord
If it is still making sound but just degraded, it could be just the power supply caps failed/partially failed. The thing is, for the money you paid and you said its old, it may not be worth getting it repair as it will likely cost almost, or more than the $125 you paid. I would just use it as a mono block, or leave it alone for spare parts.


When you use speaker A+B, the amp would just connect them (A, and B) in parallel, you can tell by the warning of total impedance has to be 4 ohms minimum. Since you connect the sub to speaker B binding post and the sub's input impedance would be in the order of thousands of ohms not 4 ohm (100% sure) unless the sub is defective. So again, you didn't do anything wrong except you might have overloaded the poor old little 60 W amp, and/or it's just getting old and tired so something (such as the caps) gave..
Power supply caps failing make that fairly obvious in most cases- they can go off sounding like a firecracker, leak from a small hole or just bulge, but if they do the first two, it usually smells bad. In any of these cases, the amp would shut off, but if the output transistors fail, it may sound like the description in the original post. Fortunately, the sub's input is resistive and has no wild impedance swings, so even if using A and B, the load isn't particularly difficult.
 
MalVeauX

MalVeauX

Full Audioholic
The 4 Ohm rating for the sub is immaterial- the AMP100 never sees the driver's impedance after the input and plate amp.

Unplug the AudioSource amp, press the power switch as if you were turning it on (defeat the auto on, if you had enabled it) and look for fuses- if you see a blown fuse, replace it. I recently sold a power amp that hadn't been used in a few years and it worked fine for a while, then sounded like the outputs were blown. That one has resettable breakers that look like a plastic cap with a slot for a screwdriver, but the caps don't come out, they just make and break contact. I think they may twist internally because it was fine after resetting it.

If you wired the AudioSource to the sub as if it was just another stereo connection, I would ask if the sub was designed for 50W (or higher) input power. If that's old, it may have some internal damage that caused the power amp channel to meet its maker.

If the power amp was always used with only the speaker A terminals and the B switch was never pressed, the switch may be faulty/dirty, although I don't remember if these use a relay for that function. Have you ever moved the level control on the power amp? If not, rotate that several times and if it comes back, the control needs to be cleaned.
Hi,

I'll check for the fuse and any other caps. But its still working and the right channel is still playing on both channel A & B, and both channels exhibit the lower volume, distortion, dim veiled treble and muddy sound on the right channel. I think if a fuse was popped, it wouldn't play at all? So maybe it's a cap going bad?

I have used speakers on all the terminals in channel A & B over time with two sets of speakers. I've used it in bridged mode (not a lot, mostly just to experiment). The only thing new was using the sub with high-level inputs, the classic way of introducing a sub to a stereo amp.

The documentation on the sub doesn't have a specific range listed that I noticed. I would think 50 watts, especially low level since the attenuation pre-amp knob never went past around 33% of max to hit listening levels, probably never got 50 watts. But I'm not sure how they interact here since I don't know what's on those circuits in the amp plate; but if they're likely high impedance, then it shouldn't matter.

Very best,
 
highfigh

highfigh

Audioholic Slumlord
Hi,

I'll check for the fuse and any other caps. But its still working and the right channel is still playing on both channel A & B, and both channels exhibit the lower volume, distortion, dim veiled treble and muddy sound on the right channel. I think if a fuse was popped, it wouldn't play at all? So maybe it's a cap going bad?

I have used speakers on all the terminals in channel A & B over time with two sets of speakers. I've used it in bridged mode (not a lot, mostly just to experiment). The only thing new was using the sub with high-level inputs, the classic way of introducing a sub to a stereo amp.

The documentation on the sub doesn't have a specific range listed that I noticed. I would think 50 watts, especially low level since the attenuation pre-amp knob never went past around 33% of max to hit listening levels, probably never got 50 watts. But I'm not sure how they interact here since I don't know what's on those circuits in the amp plate; but if they're likely high impedance, then it shouldn't matter.

Very best,
It's possible that a cap failed internally and one function of power supply caps is to filter AC from the rectified DC voltage- however, only testing and inspection will reveal the problem.

Have you connected the amplifier's right channel to the left channel speaker?
 
P

PENG

Audioholic Slumlord
Power supply caps failing make that fairly obvious in most cases- they can go off sounding like a firecracker, leak from a small hole or just bulge, but if they do the first two, it usually smells bad. In any of these cases, the amp would shut off, but if the output transistors fail, it may sound like the description in the original post. Fortunately, the sub's input is resistive and has no wild impedance swings, so even if using A and B, the load isn't particularly difficult.
I think you missed the part that its an active BIC sub that has speaker level inputs. So the impedance should be very high.
 
P

PENG

Audioholic Slumlord
Hi,

I'll check for the fuse and any other caps. But its still working and the right channel is still playing on both channel A & B, and both channels exhibit the lower volume, distortion, dim veiled treble and muddy sound on the right channel. I think if a fuse was popped, it wouldn't play at all? So maybe it's a cap going bad?

I have used speakers on all the terminals in channel A & B over time with two sets of speakers. I've used it in bridged mode (not a lot, mostly just to experiment). The only thing new was using the sub with high-level inputs, the classic way of introducing a sub to a stereo amp.

The documentation on the sub doesn't have a specific range listed that I noticed. I would think 50 watts, especially low level since the attenuation pre-amp knob never went past around 33% of max to hit listening levels, probably never got 50 watts. But I'm not sure how they interact here since I don't know what's on those circuits in the amp plate; but if they're likely high impedance, then it shouldn't matter.

Very best,
You can't go by that 33% of maximum as it depends on the preamp's design. For some preamps, at 33% you could have reached the rated output and could overload the power amp its driving, especially when the power amp is only rated 60 W 8 Ohms, 75 W 4 Ohms.

If you know your speaker's sensitivity, your distance and spl you typically get then you can estimate how hard you have been driving that amp instead of relying on the volume position. Or you can measure the preamp output with a multimeter but then you need to know a few other things to do it right, such as using the right kind of test signal and the right formula to use to calculate.:)

Did the amp ever run too warm to the touch, after using it for say an hour?

By the way, last time it was available at Parts Express, it was on sale for just under $100 brand new.
 
MalVeauX

MalVeauX

Full Audioholic
Have you connected the amplifier's right channel to the left channel speaker?
Yes, I've swapped several speakers in to rule out the speakers. I've swapped cables to rule out any potential issue there with the terminations and connection to terminals. And I've done this on both channel A & B, so whatever it is, it's always the right channel on both channel A & B so its occurring before that point, which is likely the amp.

Very best,
 
MalVeauX

MalVeauX

Full Audioholic
You can't go by that 33% of maximum as it depends on the preamp's design. For some preamps, at 33% you could have reached the rated output and could overload the power amp its driving, especially when the power amp is only rated 60 W 8 Ohms, 75 W 4 Ohms.

If you know your speaker's sensitivity, your distance and spl you typically get then you can estimate how hard you have been driving that amp instead of relying on the volume position. Or you can measure the preamp output with a multimeter but then you need to know a few other things to do it right, such as using the right kind of test signal and the right formula to use to calculate.:)

Did the amp ever run too warm to the touch, after using it for say an hour?

By the way, last time it was available at Parts Express, it was on sale for just under $100 brand new.
Hi,

Yea, wasn't trying to correlate the position on the amp to its wattage, but you're right, to be correct that knob doesn't determine total output in watts. My speakers are 83.Xdb, inefficient, but they're close proximity (1 meter in this situation, only temporarily as I was testing in my office). Realistically I was using less than 1 watt as I was measuring it to 75db SPL with my UMIK-1 when testing just so things were matched in some way instead of it being chaos and "by ear."

The amp never ran hot or overly warm and is not stacked or anything, well ventilated.

Yup, I got a few of them from P.E., it's a good basic amp for the money. I'm not worried about this one, just learning from what happened with it as an opportunity.

Very best,
 
P

PENG

Audioholic Slumlord
Hi,

Yea, wasn't trying to correlate the position on the amp to its wattage, but you're right, to be correct that knob doesn't determine total output in watts. My speakers are 83.Xdb, inefficient, but they're close proximity (1 meter in this situation, only temporarily as I was testing in my office). Realistically I was using less than 1 watt as I was measuring it to 75db SPL with my UMIK-1 when testing just so things were matched in some way instead of it being chaos and "by ear."

The amp never ran hot or overly warm and is not stacked or anything, well ventilated.

Yup, I got a few of them from P.E., it's a good basic amp for the money. I'm not worried about this one, just learning from what happened with it as an opportunity.

Very best,
Only 1 meter? That's not much different that my desktop system. So we can rule out overloading.

I am so curious about this amp now and want to see the service manual. Without that, there really isn't much more to learn from the failure. :D
 
Last edited:
MalVeauX

MalVeauX

Full Audioholic
Only 1 meter? That's not much different that my desktop system. So we can rule out overloading.

I am so curious about this amp now and want to see the service manual. Without that, there really isn't much more to learn from the failure. :D
Hah, yea that's where I'm at, truly just interested in how this can come about, be it just it's time (thermal degrading soldering points or things in the pathway) or if I induced it.

Very best,
 

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