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What could cause this amp to fail?

Hi Everyone,
Apologies if this is the wrong forum for this question. I just got into serious speakers (been into headphones most of my life). I picked up a pair of Thiel CS1.5’s that have blown me away. Anyways, I also bought a used Perreaux EX-120 (circa 1994 MOSFET Class AB 100wpc) Integrated amp on ebay for pretty cheap (seller had no feedback and I decided to take a chance) which is the subject of this question.

For the first few days after plugging it in it sounded great: warm, smooth, powerful until on around the fifth day, I noticed the sound cut from the amp and what sounded like a click. I powered it down and let it rest. The next day I heard the same thing but it started to happen more and more frequently. It would start about a minute after starting to play music and then quickly increase to the point where it would be clicking and cutting out multiple times per second (it doesn’t happen if no signal is running through). There was also a noticeable clicking coming from within the amp itself. The problem now starts happening immediately after putting signal through it and doesn’t stop.

I took it to a local audio repair who thought it was a relay issue but was unable to fix it after several tries. He referred me to another repair shop who has now told me that 8 Mosfets in the amp are blown and the input selector has ’aged out’. To repair it would cost about $450 dollars as he would have to replace many components in the amp and that it would end up as a just a power amp since the selector is a custom component that Perreaux doesn’t sell anymore.

I’m trying to get my money back from the seller, but he’s pretty much refusing saying that this is impossible and suggesting that I must have overloaded it since it worked when he sent it out. One thing to note is that I have carpet (not deep, quite short) and the binding posts on the Thiels are at the very bottom where I imagine it’s possible that the carpet could come into contact with the connectors. I have 2 other amplifiers (an entry level Cambridge Integrated and a B&K receiver which is a MOSFET design) and neither have had this issue.

My question is: could static electricity or contact between the carpet and the binding posts/cable connectors cause the amp to fail? If so, how come it took 4-5 days? If not, what is the possibility that it is my fault?
joezuu
mickeyb
546 posts
 
*1 atmosphere. Can’t handle the load. Like someone else I know. 
stevea11757's avatar
stevea11757
128 posts
 
Sorry about your issues with the Perreaux. I still have a 3150 that I bought in the late 90's, I hold onto it as a spare....just in case kina thing. By and large they are built like tanks and rarely need repair, although with age comes failures in caps and such as they have a fixed life span.

They do tend to use some odd parts as I have an On/Off switch that has long given up the ghost, I managed to get it on and now shut the amp down by killing the power in my conditioner.

If I were to start using it for any period I would be definately looking at a re-cap before putting it back into service...always liked their products...

Good Luck

PS, You should email Perreaux, they were very helpful when I was looking to replace the switch even though they no longer had them, they gave me several alternatives that they had been recommending.

Couldn't hurt..
gs5556
1,218 posts
 
A clicking sound to me is a relay not latching. It’s possible that an overload or dc offset protection circuit has a bad holding/charging capacitor that feeds a transistor holding a speaker protection relay closed.
ozzy62's avatar
ozzy62
2,922 posts
 
What would you consider 'legendary'?

Here are amps I would call legendary.

Music Reference RM9
CJ Premier 11a
McCormack DNA-1 deluxe
Marantz 8B (although this one put me to sleep)

Adcom amps could be called legendary because they were the gateway for the uninitiated into what was possible in the high end world. The first really good system I heard many, many years ago was using a GFA-555 and a pair of Vandersteen 2cs. I guess that got the ball rolling for me.

Oz


8th-note
376 posts
 
Here are several points which I hope are helpful.

1. Your Thiels are difficult speakers to drive. They dip below 4 ohms for part of their frequency spectrum and they aren't very sensitive. If your amp were going to fail on any set of speakers it would be the Thiels. It is entirely possible that the amp was working fine when the seller shipped it to you. It's a 25 year old amp that you put under very stressful conditions.

2. Due to its age the amp needs to be rebuilt including new capacitors. That's going to be expensive - probably well north of $500. In the future you should figure that any amp, preamp, or integrated of over 20 years old needs new capacitors and a thorough tune up. You should figure this cost into your buying decision.

3. I live in central Washington state and I take my electronics to two different shops in the Seattle area that I can personally vouch for. The first is Gig Harbor Audio near Tacoma. They have a very skilled tech who has recapped and repaired my Krell electronics but I think they work on just about anything. Erik (owner) and George (tech) are great to work with. The other option is Condor Electronics in Seattle. They specialize in recording equipment (sounds boards, tape decks, amplifiers, etc.) some of which is quite old with the manufacturer out of business. In other words they are up to the challenge of working on a piece of gear that may not still have OEM parts available. A switch shouldn't fail unless there is a chip that fritzed. I suspect that Condor could fix it.

4. IMO it won't be worth it to repair the Perreaux because even if it is completely refurbished it won't be the proper amp for your Thiels. It's power is not rated below 8 ohms and it only weighs 18 lbs. You really need an amp or integrated that doubles its rated power into 4 ohms. A good example is the Denon PMA 2000IVR (there are several iterations of this amp but all would work). This integrated is a monster (60 lbs) that was made to drive low impedance speakers. A used one in good condition goes for between $500 and $800. The advantage to this amp is that it is new enough so that you won't have to worry about recapping it for another 10 years. Another option is a Krell KAV 300i integrated. These go for around $1000 but if it has not been recapped you will have to figure that into the cost ($700 or so). A third option is to go with Adcom separates like a GFA 555 and an Adcom preamp. Again, depending on the age you should factor in recapping if it hasn't been done already.

5. Finally, I don't think it's a problem to put your speakers on your carpeted floor. I have a pair of Thiel CS6 speakers and they have a similar setup for the binding posts. I have mine sitting on carpet and they have worked just fine.
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