Is my amp worth fixing?

[TLS Guy]

No, I disconnected the speaker wire and touched the probes to the speaker terminals themselves.

Then you had better do the next test.

 

[TLS Guy]

Then you had better do the next test.

I have just done some posts for another member who has the same amp as you.

The posts are about adding speaker protection to your amps.

http://forums.audioholics.com/forums/showthread.php?t=39567&page=6

 

[AcuDefTechGuy]

I have just done some posts for another member who has the same amp as you.

The posts are about adding speaker protection to your amps.

http://forums.audioholics.com/forums/showthread.php?t=39567&page=6

So an in-line fuse (Radio Shack) between the speaker and the amp won't be sufficient?

 

[TLS Guy]

So an in-line fuse (Radio Shack) between the speaker and the amp won't be sufficient?

You can't protect speakers with fuses. There is not enough margin between the fuse blowing in normal listening and not protecting the speakers. All this is explained in the article to which I posted the link yesterday.

 

[orAgon]

You can't protect speakers with fuses. There is not enough margin between the fuse blowing in normal listening and not protecting the speakers. All this is explained in the article to which I posted the link yesterday.

I respectfully disagree. You may NOT WANT to use fuses for protection because of perceived audible or some such side effect that may or may not matter but if the sole purpose is to protect speakers from being damaged by a defective amp, then an appropriately rated fuse will do just that.

 

[TLS Guy]

I respectfully disagree. You may NOT WANT to use fuses for protection because of perceived audible or some such side effect that may or may not matter but if the sole purpose is to protect speakers from being damaged by a defective amp, then an appropriately rated fuse will do just that.

I lived through the era of the introduction of direct coupled amp. The problem is that an audio signal is a complex AC signal, and the speakers voice coil is a reactive load. So they handle complex audio signals up to their power rating fine. As soon as the speaker is presented with DC there is no back EMF and the voice coil heats VERY quickly, just like fuse wire. What happens is that an appropriately rated fuse is going to blow at around the same time as the voice coil. They are both wires burning up and from the heating effect of the current and it takes time. Voice coils are destroyed quickly.

So what happens in practice is that if the fuse does not blow now and again during your favorite CD or movie, it in fact does not protect the speakers.

We all found that out fast in the seventies.

Speaker protection is only achieved by circuits that either instantly disconnect or short the speaker output or disconnect power to the power transistors. And that is why any decently designed amp produced in the last 30 years or so has one of these types of circuits.

 

[orAgon]

...What happens is that an appropriately rated fuse is going to blow at around the same time as the voice coil. They are both wires burning up and from the heating effect of the current and it takes time. Voice coils are destroyed quickly...

If the fuse does not blow before the voice coil does then, in my mind, it is not appropriately rated. I won’t get into fuse properties and characteristics here so, if I may, suffice it to say that there are fuses out there with specific properties to protect certain loads, speakers included. Now it isn’t easy for the average person or even the average Radio Shack clerk to identify but, albeit difficult, it can be done with due diligence.

 

[TLS Guy]

If the fuse does not blow before the voice coil does then, in my mind, it is not appropriately rated. I won’t get into fuse properties and characteristics here so, if I may, suffice it to say that there are fuses out there with specific properties to protect certain loads, speakers included. Now it isn’t easy for the average person or even the average Radio Shack clerk to identify but, albeit difficult, it can be done with due diligence.

Due diligence! How are you going to test it. The end point is does the fuse fry first or the voice coil! If it's the voice coil big trouble.

I can tell you sure, that the reason fuses were abandoned is not because they affected the sound, although they do, but because they do not work. Fuses heat near the limits, and when they heat their resistance rises significantly, and it compounds the problem of thermal compression from voice coil heating. Fuses are just the wrong devices for this application. It is a crude unreliable fix. And definitely not a solution to use with a high end amp and good speakers. If it was a good solution then reputable manufacturers would do it because it's cheap. That don't do it for the reasons I have given you.

 

[AcuDefTechGuy]

...definitely not a solution to use with a high end amp and good speakers...

I love my Acurus Amps. They sound fantasic. I want to keep them. At the same time I don't want to take any chances. I just paid $300 for a 10 Year Full Replacement Warranty for my Def Tech speaker system!

I guess I have 10 more years to think about getting SAFER amps for my speakers.

Which amps are 100% safe for speakers?

I take it all McIntosh amps?

What else?

 

[TLS Guy]

I love my Acurus Amps. They sound fantasic. I want to keep them. At the same time I don't want to take any chances. I just paid $300 for a 10 Year Full Replacement Warranty for my Def Tech speaker system!

I guess I have 10 more years to think about getting SAFER amps for my speakers.

Which amps are 100% safe for speakers?

I take it all McIntosh amps?

What else?

If you you are talking 100%, its the MACS. DC won't pass a transformer.

I'm glad you bought the warranty. I would still use the Vellemans. That is an easy fix. Even with a warranty, failures are a frustrating nuisance. Are you able to accomplish that job?

 

[orAgon]

Due diligence! How are you going to test it.

You don’t. Instead, do the math right (again, not for the average Joe) and cross your fingers. Hey, I didn’t say it was easy!

 

[TLS Guy]

You don’t. Instead, do the math right (again, not for the average Joe) and cross your fingers. Hey, I didn’t say it was easy!

It isn't easy it's impossible! You don't even know the DC behavior of the of the woofer speaker voice coil wire. And every woofer will be different. I suppose you are going to tell me your guardian angel angel will whisper the DC current heating curve of the woofer voice coil in your ear. Just stop this, you don't have the first clue.

 

[orAgon]

...Just stop this, you don't have the first clue.

Yep, I can sense where this is going so I'll stop now.

 

[AcuDefTechGuy]

If you you are talking 100%, its the MACS. DC won't pass a transformer.

I'm glad you bought the warranty. I would still use the Vellemans. That is an easy fix. Even with a warranty, failures are a frustrating nuisance. Are you able to accomplish that job?

Yeah, I think will do that as well. Thanks.

 

[TLS Guy]

Yeah, I think will do that as well. Thanks.

Sounds like a good plan.