2. amps-preamps
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I think I just smoked my Amp

Ummm… yeah… what the title says…

Just received a new pair of speakers, Thiel MCS1. I got them hooked up, powered up my pre and my amp, started playing a test track (a progressive house song), I immediately noticed a slight crackle in the right channel, and as soon as the song got to the part where the bass beat dropped, the amp went into protect mode. It stayed in protect for about five seconds, then the “operate” light came back on, but the audio did not return. I powered the amp down, tried powering back up, but the protect light immediately returned, but it was extremely dim. Now, the power switch does nothing; nothing lights up. I smelled the vents in the top, and nothing smelled burnt or out of the ordinary.

My uneducated guess is that the lower impedance (4ohm nominal, 3ohm minimum), strained an aging cap which then gave up the ghost, but really I have no idea. My previous speakers were a much easier load (10ohm) and the amp handled them just fine.

 

I really don’t know what to do now, but I’m bloody devastated.

My system: 

ARC LS25 MKII

ARC D400

SMSL M400

Auralic Aries

rfnoise
curiousjim's avatar
curiousjim
4,214 posts
 

New, the D400’s came with two extra 8amp slo blow fuses.  Maybe there was a reason for that.

Hopefully that’s all it is.

gs5556
1,218 posts
 

Crackling sound, DC protection engaged, plus blown fuse is very likely a shorted output transistor. Replacing a fuse is not going to help in that situation. Also, to make matters worse, those Sanken output transistors are no longer manufactured. A substitute may work or it could cause stability or distortion issues. SS amps are  finicky.

rfnoise OP
153 posts
 

Well I managed to locate two fuses

the first, in the obvious place next to the power cable was one of these:

Due to the opaque nature of the cylinder, I can’t see whether the filament is intact or not.

The second fuse was on the main board. It was in a really awkward spot, but I managed to get it prised loose with a long wooden skewer. It’s one of these:

It looks to be intact, but I’ve had fuses on my bike that looked good, but actually needed replaced.

 

I’m going to go ahead and order both, and cross my fingers.

If it was the fuses, I’m curious to know what would cause that. Could there be something wrong with the new speakers that could cause that? Or just bad luck?

 

@gs5556 

I’m guessing those are the metal devices lining the sides of the case against the heat sink. If it is a failed transistor, I’m guessing that’s game over for my amp?

rfnoise OP
153 posts
 

Well, nothing amiss with these speakers. My CODA amp is driving them fine. Too bad it’s such a lousy match for my pre.

yoyoyaya's avatar
yoyoyaya
623 posts
 

Fuses can fail randomly from thermal/mechanical stress, but also, alternatively, from component failure.

If the amp has failed transistors, it's not necessarily the end, depending on whether replacement transistors are available.

However, on an older amp, you're probably looking at a full refurb including the power supply caps at least.

Ultimately, the cost benefit ratio may be negative depending on how much you like the amp and how much work needs to be done.

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