Blown Adcom 555 II

[BMWCCA]

that last piece of news is damn scary

Somehow Emerson and Pass in the same breath does not seem natural

Hey! Emerson Electric used to make a damn good ceiling fan! I think my brother had a summer job with them in St. Louis about fifty-years ago. Do they still make anything here in the USA?

[grumpy]

Emerson Electric
Emerson Radio Corp.

quite different animals as far as I can tell.

So what's going to happen with the blown Adcom?

[BMWCCA]

Emerson Electric
Emerson Radio Corp.

quite different animals as far as I can tell.

You are correct, sir. A look at their product offerings and maybe it is the electric motor company that should be making amps!

[Ducatista47]

I labored over an amp for three weeks, ordered all kinds of parts, went through and replaced anything that looked even questionable. I turned it on and it ran for 10 minutes before popping. Really disheartening. I feel once a SS amp takes a dive the cost and trouble of repair is not worth it. There is a lot of energy in there and when things get weak they die in a spectacular manner

As to eventually death, MOS-FET and other thick film outputs are sensitive to static, and can also develop "holes" in the substrate over time. Add to that dirty heat sinks and dry silicone compound on the transistors and it's possible they can just go out. Although we all romance over how things were made better back then, I think quality has greatly improved today when it comes to transistors. Objective sound quality aside, it's a reasonable argument that a modern amp for 300-400 dollars would do just fine and come with a warranty to boot.

I agree, and it is a shame but true that repair prices, complexity and difficulty render most transistor amps Kleenex products - throw away.

MOSFETS can be very reliable when designed and put together with skill. Note the startling failure record of Nelson Pass amps. Startling because some of the designs have never had a failure in the field.

Well I 've owned many tube amps over the years and I would not give two cents for one now.

The new SS amps built today are quite good and reasonably prices; old electronics are just that - old.

And the new SS amps will later become throwaway pieces too. Compare that to replacing a tube. Way down the road, eventually perhaps a few caps, on a tube amp easily accessible with simple tools; usually just removing a cover.

Class A tube amps tend to be very simple circuits. My favorite amp is wired point to point. I have never seen more open and easy access.

The hifi shop I use has a tube tester. I look for 5000 hours for my power tubes and at least 20000 for my preamp tubes.

Notice that where heat is the enemy of transistors, tubes and MOSFETS need to be hot to work best, and their amps are designed to run hot and not be bothered by it. No fans, either. Heat rises so the hot parts or their heat sinks are outside or on top. Heat rises, what a concept! In a Nelson Pass authored amp, the heat sinks are designed to regulate the temperature of the output devices to a range, not to keep them cool.

Clark

[opimax]

I am not an expert or trying to cause trouble, just adding observed info, really

My Perreaux 6000b, (300/c mid 80's vintage, are mosfet and do have fans and run very cool. The smaller 3000b 180/c does not have a fan, not noticeably hot, you can tell it is on, but not hot at all.

I originally ran them with fan disconnected but they got hot when pushed so I reconnected them and in the basement away form the listening room. Heck maybe they should be hot, I thought they are well respected amps.

Mark

[Ducatista47]

maybe they should be hot, I thought they are well respected amps.

Mark

I will go with the flow. Everyone says they sound great and I won't argue.

I am sure they were designed to run at whatever temperature they reach when used as intended. I could have added that hot is relative and applies to the part, not the heat sink.

Nelson feels his First Watt F1 and F2 are most of the way there after a five minute warm up, but better after an hour. Cold, they never make it to where they should be. I notice that when people build them from scratch they sometimes use too much heat sink and they never get hot enough.

Like so many things, while it sounds un-American, more is not better here.

Clark

[opimax]

I leave mine on. Currently I would rather pay higher electricity then repair is my theory. so they always warmed up then too.

the adcom 555 I and II, they are mosfets too?

Mark

[Ducatista47]

According to this review, transistors, not MOSFET.

http://www.stereophile.com/solidpoweramps/678/

But they ended up leaving them on all the time anyway (next review). The review goes on about how it does not suffer the ills of previous transistor amps, but we have all heard that before. As have the tube haters about tube amps. (If you want to hear a tube amp solid state lovers would actually like, try Rogue.)

Clark

[Ducatista47]

My Perreaux 6000b, (300/c mid 80's vintage, are mosfet and do have fans and run very cool. The smaller 3000b 180/c does not have a fan, not noticeably hot, you can tell it is on, but not hot at all.

I originally ran them with fan disconnected but they got hot when pushed so I reconnected them and in the basement away form the listening room. Heck maybe they should be hot, I thought they are well respected amps.

Mark

Looking at your post again, I realize the magic phrase is "300/c." That would be too much power for any home use solid state device to dissipate without forced air or advanced (seen a CPU cooler with copper pipes and a radiator?) conductive cooling. What follows gets a Rant Warning and is not about you, Mark.

High power has always come at a high price in all departments. In the high efficiency speaker era when small tube amps ruled (and were all there was), things were quite different. When transistor amps appeared, low efficiency speakers like the AR3 were possible. Transistor amps, when pushed, produce speaker killing clipped waveforms and odd order harmonics. Tube amps do not clip like that and are pretty much second order harmonic distorters. MOSFETS can be designed either way.

That is when the famous JBL white paper (Danger - Low Power) came out. It was all about transistor amps. Push a 20 watt tube amp and it will not kill a speaker with distortion and is generally incapable of sending DC (I suppose nothing is impossible, but I don't see how). Plus, 20 tube watts through a large blue face monitor will set off car alarms out on the street. Like I said, a very high price was exacted for this "progress" in amplification and speaker technology.

Stick with high efficiency speakers (most of us here do), use tube or MOSFET amps, and bury that old "high power needed" idea in the nearest landfill where it belongs. Or save it for Home Theater. I swear if I read one more guy announcing a new project to tri- or quadamp a high efficiency speaker and drive it with 3 x 200wpc I am going to stop reading that forum. I have only been here 3 1/2 years, not a long time, but I am burned out on this particular brand of fiction. A guy needs to know the difference between A) trying to justify complicating a system beyond reason, making it sound inferior and cost too much, and B) admitting that it makes no sonic sense but is really a mine-is-bigger-than-yours quest. Or an "I have this stuff lying around, I have time on my hands, I am bored and don't know when to leave well enough alone and look for real improvements elsewhere" thing. And don't even start to talk about needing more power because 19KZ sounding a little fuzzy. We can't hear it and it takes .01 watt up there anyway. Stick to how the music sounds. By all means biamp if you can get a good enough active, but dividing amplification more ways is killed by exponentially diminishing returns and increasing complexity.

Buy the best first watt you can afford. It is 99% of what you hear with the speakers we like. Sorry to kill another popular plan of action, but Japanese receivers generally have a terrible first watt. They are designed to put watts into low efficiency mediocre speakers typically found in households that buy receivers. The great big models from the Seventies and Eighties were sold to power bookshelf speakers, not floor standing big woofer units. Also know that it is nearly impossible to design a high watt amp with as good a first watt as a smaller amp.

And leave the sound reinforcement systems outside. They have their place and it is not in living rooms. You can't afford the room treatment needed to even attempt to make it work in a home. Besides, Bo knows SR and you do not.

Room treatment - if your system is not bad, dollars much better spent than buying power and/or triamping.

Clark

[sourceoneaudio]

New Power Amp Info:
http://www.adcom.com/prod/shopdispla...sp?prodid=1322


Trade in Info:
You can call to find out what they will give for old Adcom gear. They do take it in on trade even though it is not listed.
http://www.adcom.com/tradeins.aspx

GFA-5802 MOSFET:
http://www.adcom.com/prod/shopdispla...=0&prodid=1151

[Ducatista47]

Nice. I see the GFA-5400 and GFA-5500 are MOSFET output designs.

"ASI participates in the Rethink Initiative and will recycle your trade-in in an ecologically sound manner." I wonder what that is... Scrap to China?

Clark

[sourceoneaudio]

that last piece of news is damn scary

Somehow Emerson and Pass in the same breath does not seem natural

Mark

http://www.adcom.com/news.aspx

[hjames]

Emerson Electric
Emerson Radio Corp.

quite different animals as far as I can tell.

So what's going to happen with the blown Adcom?

Dunno - seems the tales here are going to be legendary ...
Doesn't seem that hard to put it on ebay, mention that it cooked and the seller is not an engineer and doesn't know exactly what that means, but it won't power on now ... and just sell the darned thing!

[robertbartsch]

Do they make tube amps with >200 WPC?

[Ducatista47]

Do they make tube amps with >200 WPC?

First of all, Robert, I am sorry to have ranted away on your thread. I was considering posting on a new thread and should have gone with the instinct.

The short answer is, yes they do, and they are beasts, and I don't recommend them! They do not sound as good as lower powered units and cost way too much to buy, to retube and to run. And they are huge!

If you really don't like tube amps, from experience, perhaps you would still not find them to your liking. But the fact is that no one using high efficiency speakers needs 200 tube watts. The JBL paper recommended, if I remember right, a ten to one safety margin for headroom over the continuous draw during music playback. Say a speaker is a 92dB/watt/meter, not really very efficient for a large speaker but way better than the average bookshelf. Put six watts through such a unit and it would be damn loud, uncomfortably loud. Times ten, sixty watts. So who needs a 200wpc tube amp? No one who plays JBL's or Altecs, that is for sure. I can guarantee that if you put six continuous watts through a large JBL you would not be able to get to the volume control fast enough to turn it down.

If a speaker needs only six watts to blast you out of the room, the only reason so much power is recommended is not headroom for clean music but headroom so a transistor amp does not enter a mode of operation where it will destroy the drivers. Even so, why recommend so much power? Most people would never turn it up that high. I think JBL was counting on some of their monitors and home speakers being turned up insanely loud by, frankly, fools. Fools still qualified for the free replacement guarantee for drivers, so I'm sure the recommendation was based on financial as well as engineering reasons. Given a clean signal, it says right in the literature, a JBL monitor will hurt you before it will hurt itself. But never underestimate the stupidity of some humans who nonetheless have money. (I remember a post on this very site where a fellow complained that when he turned up his system, he loved the bass but it caused him pain and made him sick.) In other words, it is a rare circumstance where a high efficiency speaker would need a high powered tube amp.

Perhaps if I knew what you were driving I might be able to figure out how much power you would need in a tube amp. You would be astounded what a ten or twenty watt tube amp will drive. Good tube amps, classic or new, are known for having outrageously great iron. The reserve power available is beyond the experience of the uninitated.

I found a sixty watt push-pull tube amp to be enough by plenty to power the woofers of my 4345's. Overkill, really. If I had not biamped them, a couple of watts more than the modest signal I was actually feeding the woofers would have been required to power the whole box. I am sure twenty watts would have been plenty.

Another great opportunity here is to go Class A for the top drivers when biamping. Ask Widget if you don't believe me. A little Class A amp has the best sound in the world. Whereas a six watt Class A tube amp is perhaps a grand for the best there is (not the most expensive, but the best), a 200 watt Class A tube amp would cost a fortune, literally. And not sound as good.

Class A MOSFETS are, if well designed and built, as good as anything. You might investigate the build it yourself designs of Nelson Pass. Ian has built a few and is way ahead of the curve. He sure is great about helping me out, and the resources and help available on the web are almost unlimited. The Aleph J, for instance, is supposed to be astonishing.

Tube or MOSFET (or JFET - Nelson strikes again), any chance to get away from bipolar transistor output will eliminate the need for high power and yield much better sound. Remember, quality for quality smaller amps sound better than bigger amps, and the exception rate to that is close to zero. And no wonder, if you use efficient speakers the first watt is everything, nearly. "What good are the next 199 watts if the first watt sucks?"

Clark