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I've been running Icon Audio MB 845 II (Special) mono blocks for seven months now and although I'm sure the 845 output tubes have a fair bit of life left in them I'm starting to wonder what I should be replacing them with. Any suggestions?
http://www.iconaudio.com/portfolio-item/mb-845-mk-ii/
By the way, these things satisfy most solid state fans I've exposed to them and give thermionic lovers wet dreams.
Follow Ups:
Just picked up on this thread and see that you are a fellow Ozzie. Firstly, no need at all to be so paranoid about tube amps. I had a similar experience with ARC Ref 600s until I heavily modded them but have never had a problem with any other commercial or DIY amp since.
I'm really hard on my home brew 845s and I can tell you that it's hard (read near impossible) to kill 845s!
Some of the guys have given you good advice and unless you really want to upgrade to better tubes I would not bother paying for more of the same that will most likely sit around for many years.
You should be able to monitor the condition of your tubes by periodically checking on the bias requirements. Start to think about replacement only after you find that the idle current is continually dropping.
As for the sound of different 845s that's a subject of its own and I've tried a heap of current and NOS. PM me if you would like me to share my experiences.
Naz
My intention was to simply have spares on hand in case the graphite 845's went out of production as some manufacturers appear to be claiming the metal grid ones are superior. My suspicion is they've found they're cheaper to manufacture and would prefer to drop the graphite.
Thanks for the biasing advice . It's almost word for word the same as the blurb that came with my Icon Audio 845's. I'm not going to explore the different 'flavours' of different 845's as I'm totally in love with what I'm hearing now. I've lost track of the number of amps I've used over the decades and not one of them has given me the musical magic the Icon Audio MB 645's dish out. Thanks for the hints though. Appreciated Naz.
On a slightly different subject Eunice Kron, the owner of Kronzilla amps often claims any valve that produced a lot of light is badly designed. OK, I've heard a pair of Kronzilas and was most impressed but think she's blowing her own trumpet on this one.
I've also tried many serious amps in my system but none have compared to my 845s so I get that you are happy with yours. That being the case I honestly wouldn't worry about buying spare 845Cs, they should remain easy to get and though there is certainly nothing wrong with them there are even better ones out there. The Chinese are doing a fine job of continually advancing this tube and the W was the overall best of them IMO but even it has recently been surpassed by the Psvane T in almost every way.
Naz
SuperTNT 845 will be back soon.
Don't know if I simply don't understand the format of this forum or if the message 'SuperTNTwill be back soon' is the entire message. If so I've no idea what it means.
You may want to check out the Psvane line of tubes. http://psvanetube.com/wordpress/purchase/psvane-vacuum-tubes/
I have read positive reviews of their 845s. Not cheap though!
Michael
Thanks for the link. A very well designed site and a very expensive looking one . Unfortunaetly I can't find any 845's using graphite screens and according to Icon Audio's email I received today they must be graphite. Not to worry, Icon Audio hold spares themselves. Why didn't I try them first? DUH!
I think the advice you are getting is to use tubes with Grahite plates not Graphite screens.
I don't think they have ever been made with graphite screens because they are triodes and only have cathodes (integral with the filaments),grids, and plates. They don't have screens !
That said, most of the chinese production for the past 20 or more years has been graphite plate (the metal plates are described as metal plate 845's, sold at a premium price, and not that many were sold).
Some or all of the Czech 845's are metal plate and sell for big bucks.
Virtually all of the vintage GE, RCA, Cetron, and United 845's are graphite plates and big bucks.
As I often do I put my ignorance of the basics of electronics on public display. Googling I found this quote from a Hi Fi World Magazine review of my amp.
"Designer David Shaw told me he tried the latest model metal anode Shuguang 845's(845C0 that have higher power handling but preferred the graphite anode originals, albeit in improved 854B form as fitted to the Icon Audio MB 845 II. "
Noel keywood in Hi Fi World Dec 2010.
Yeah as far as rolling 845 tubes....from what I've used and heard.
Most modern chineese 845 all sound about the same, if you want real
sound from an 845 you have go with vintage grade 845's..ie. RCA or
Amperex, GE or the like. The other alternative is Cetron, if they are
still making them. Either case you gonna pay , they are not cheap.
Now I'm sorry I got rid of my Cetrons a few years back. For my
upcoming Low power 845 build, I've got a couple of early 2007 Chineese
845's and a pair of metal plate 845's, I'll use for testing and
breakin before I get serious about investing in better sounding 845's.
JMHO !!!
Have fun
Willie
What 845s do you have in them now?
If you are thinking of swapping tubes, you may get better results by swapping the small signal tubes instead. What tubes do you have in there now? What sound are you looking for?
Jack
I not looking to improve the sound I'm already getting I was simply wondering where to start looking when I eventually need replacements. I haven't run valve power amps for decades due to a terrifying experience with an Audio Research power amp a long time ago that made me utterly phobic about valve power amps until what I heard from the Icon Audio's made me overcome my fears. I still cringe though every time I turn them on.
The input valves ( maybe they're power supply valves? I'm too ignorant to know) are labelled on the chassis itself as '6SN7 & 6SL7. I can't properly read the wording on the valves themselves but they appear say "Treasure Se?????? Sh????????" or something like that. As the output 845's themselves are labelled 'Shaguang 845C I guess the input valves are also Shaguans .These amps are giving me more goose bumps than anything I've ever owned so I'm not looking to fiddle with a successful design until it's time to replace aged valves. The only solid state amps I remember as anything like the Icon Audio's equal were Nelson Pass mono blocks whose model number I've forgotten - - Aleph? ( they were driving very different speakers than my present Usher BE10's though so it's hard to be sure.)
Edits: 08/01/12
Those are common tubes. Since you are down under, I can't really tell you where to buy tubes in your area. Ask where you bought the amp. You shouldn't have any problem finding the tubes you use, Aussies seem to like tubes too. :-)
Jack
I bought the amps in Hong Kong and have heard some horror stories about some of the suppliers in Australia.
Those 845's should last for several years at least.
Alan
I wouldn't worry about wet dreams when you seem to suffer from premature replacement syndrome. 7 Months is not a long time unless they are run really hard 24/7 which most tube amp owners are smart enough to avoid. The lifespan of an output tube is several thousand hours. Some like the WE 300B are thought to have very long lives indeed.
Steve
Thanks Steve, I understand about life-spans but I"m mad enough to want to have spares to hand. I keep spare MC & MM cartridges even though I know the suspension ages without use. Call me nuts or a spoilt brat if you want but the thought of being without music from my main system for even a short length of time horrifies me. I suppose having had a disastrous history with exploding output valves/tubes on power amps and managing to wreck far too my cartridge cantilevers over the decades has something to do with this. Hope that makes some kind of sense.
There is nothing wrong with back up tubes. For example, I have one pre amp and one integrated ampo wich use 2 6SN7s each. I got a thrill out of rolling the tubes. So much so that I bought as many different ones as I could that were affordable, and very few that were expensive. When I liked the sound of one type/brand/vintage etc. I bought extras. There is no way I can use all of these 6SN7s I have over 100. I am not speculating BTW, these are not true collector style mint NIB tubes for the most part. It is a compulsion I share with you.
What is different is -is that I don't stock more than one or two extra outputs because they are current production except I keep one quad of Philips EL-34s and some 7868s.
Steve
It appears I have no idea how this forum operates as I can make no sense of "RE: 845 replacements - ahendler 07/31/1218:04:39 07/31/12 (0)" Sorry.
Funny how a minor difference manages to confuse my tiny brain - I used to the abbreviation being expressed as Re - - not RE.
k
It means reply
Thanks for the 845 replacement suggestions but I forgot to mention in my original post that the HK retailer warned me not to replace the output valves with anything other than those using graphite plates. I'm showing my ignorance again but I remember something about the Icon Audio running it's 845's at higher than usual voltage making metal plate 845's a risky proposition.
I've no idea if that's true but I'm averse to experimenting with output tubes on this thing as the thought of having to replace transformers fills me with horror.
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