Hi Rick! I love mine. The new ones are actually 90+ watts/ch (180+ in mono) so I think one amp should be sufficient for all the EMIT's and EMIM's. And though having two separate power transformers is nice, the one in the new model is 490V (the old was 420V I think.)
Speaker cable choice is very important with stats and planar electrodynamic drivers like yours. They should have very low capcitance (< 40pF per foot) and inductance, and they should actually have a little resistance.
The only cautionary note for the 275 is: Lose the OEM tubes immediately! (Save them for resale;-) The McRussian power tubes blow up regularly (and sound crappy) and the McChina signal tubes can go gassy and blow up a power tube (and they also sound crappy ;-)
If you need more info, let me know.
Neil
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My (moderate priced) tube recommendation would be a quad of the new reissue Gold Lion KT88 (about $200) and some NOS Telefunkens for the 12AX7's and 12AT7's. If you'll send me your email address, I'll give you more details when I have some time. |
If you go to and search the McIntosh forum on AudioKarma, you'll find lots of 275 info and owner experiences. McIntosh used to provide the finest tubes with their new equipment such as Telefunken and (English) Gold Lion/Genalex, etc. For one thing they were plentiful and not particularly expensive.
Today, companies that make tube equipment have to favor price and availability over quality -- so of course NOS is absolutely out on both counts. The KT88 power tubes Mac uses are Electro Harmonix made by the American-owned New Sensor Co. in Russia. They have bought the rights to many old brands like Mullard, TungSol, Genalex, Svetlana, and would like you to think they are re-issuing the genuine article(s) but they aren't (mainly because they don't know how to make them:-) BTW, you can still get real Svetlanas from the S.E.D. company in St. Petersburg, now sold under the Winged-C logo after their company name was sold out from under them!
The Mac signal tubes (12Axx twin triode-types) are Chinese, made for them probably by Shuguang. If you have a new Mac power amp with OEM tubes, my advice is to run it for 5 hours or so without any power tubes, so you can find out if the little signal tubes are going to hold up (I even do this with NOS/vintage tubes too) If a little tube dies, it dies (no problem, and certainly no problem in a preamp) but in a power amp, it could take out a power tube (again, not a problem if it's a cheapie power tube ;-) BUT, a shorted or runaway power tube can damage bias and plate resistors, and even power transformers, and that's where the repair hassles and expense begin -- and unfortunately, the fuse doesn't always pop fast enough (which is why I keep my finger on the trigger when I'm using tubes with reported reliability issues!
On the positive side, tube problems usually show up very soon (1 hour to 1 month) and once they're past that, you shouldn't have to worry (but I NEVER leave tube equipment on when I leave, not even a tuner!) Also, problems usually occur during turn-on/warm-up, so once things are stabilized they're OK - usually ;-)
The thing to remember is that tubes have been used reliably for the last 85 years, and often in critical locations (like ICBM's) so don't discount their quality. The problem is that tubes aren't tested and then burned-in the way they used to be -- certainly not by manufactures (they are by many online tube sellers such as Upscale Audio)
I'm using a quad of NOS Genalex KT88's ($800) and a quad of GEC/Genalex 12AT7's ($250) in my 275 and never a hiccup; plus they last twice as long as the reissued tubes. |
Lapierre -- The reissued GL KT88's are a good choice from what I hear, and cost about $200+ for a matched quad. The PentaLabs/Shuguang KT88SC's which I tried (and liked) are just as good according to many, and about half the price. Try Doug's tubes http://www.dougstubes.com he's very nice, has reasonable prices, and he sells both. For the AX's and the AT's, NOS Telefunkens are the minimum place to start. THE 12AX7's AFFECT SONICS THE MOST. There are three of them (V-1, V-2, and V-5) If you are using balanced interconnects (which you should be, with the C46) then the first 12AX7 (V-1) is not in the signal path and so it can be any ol' 12AX7, just to complete the filament circuit. The first tubes I substituted (for the OEM tubes) were a pair of ratty old TFK 12AX7's (in the V-2 and V-5 spots) and the difference was really amazing in all respects -- air/ambience, detail, dynamics, soundstage/imaging, good hi and lo freq. response. Then came the TFK 12AT7's, and finally a quad of the Penta KT88SC's. The total should run about $300 - $500 depending whether you buy the TFK's on eBay or through an online tube seller. It's hard to beat NOS Telefunkens, but you can. Particularly by substituting Sylvania or RCA 5751's (triple mica black plates) for the 12AX7's. But the price/value ratio starts to go down as with all things audio ;-) (A pair of Sylvania 5751 TMBP goes for $150 or more these days -- but boy do they sing!) You might want to read the 12AX7/5751 sections of Joe's Tube Lore, if you haven't: http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html. |
Gavetti, it's the EH's that Mac now uses as their OEM power tube. They are both unreliable and crappy sounding -- one getter, low vacuum/thin bottle, yuk! I can honestly say I have experienced these attributes first hand! Back in the day, when the MC230,40,60,75 etc. established their great reputation(s) Mac was using genuine english Gold Lion and Gold Monarch KT88's from England and American Richardson KT88's. Along with original GE and Tung Sol 6550's. Of course they only cost Mac a few bucks a tube back then ;-) At least Audio Research uses the (fairly decent) SED (formerly Svetlana) Winged "C" tubes.
I have read folks saying nice things about the EH KT88's too, but I can't help wondering about their hearing!. At least the damn things didn't blow up on them! |
Bosrt, I pasted the following from my AK post:
I was curious why some folks didn't find tube changes had much effect with Mac amps and others like myself (and friends) were astounded at the improvement. I'm a natural detective, so I couldn't just 'let it go' After asking everybody lots of questions, I realized that most, if not all of the people who were 'underwhelmed' had changed their power tubes first (or only!)
I changed my 12AX7's first. Not because someone with prior experience had given me a hot tip. But because one night right after I got my amp, a (vintage gear) friend came by to hear the new toy, and brought some old Telefunken 12AX7's 'just for fun' and we were both blown away! Only later I read where Ron C. (I think) said that in order of sonic importance, it would be the AX's, AT's, and last the KT88's.
You will definitely hear subtle sonic differences in power tubes if you change the little ones first. But the biggest difference between power tubes will be in power (duh!) and the EH's (when they work) are the weakest. They have transconductance values around 4500-5000. The Pentas and (I'm assuming) the reissued Gold Lions as well, are much stronger 6000 +/_. The strongest, are the NOS Gold Lion, Gold Monarch, and GEC KT88's which, when new, are 10,000-12,000.
McIntosh also declares that it doesn't matter that much to have matching pairs of power tubes (or even the little signal/driver tubes.) Strictly speaking, that's true. And just to prove it, they make no provision for adjusting the bias if they don't match! However, if you're concerned with tube life (power tubes), or with precise channel matching (signal tubes) then you'd like to have tubes that match. No, they don't have to match within 5%, or even 10%. I'd say 20% or better is reasonable. Except if you're using the single ended inputs, I'd recommend that V-1 should have its two internal triodes matching within 10% or better. |
12AX7A's are simply 12AX7's with a filament center tap that allows them to be run in series or parallel. Not an issue with the Mac amp. |
Greg, the fastest way to answer that question would be to call McIntosh. While you're at it, order a service manual/schematic -- that's what I did.
You can also find out by 'naming' the phono input something else (on the menu screen) if you do that, the phono tubes won't light up when you turn the amp on -- at least that's the way their preamps work ;-) (It's a way of saving tubes and reducing heat if you don't have a turntable.) |
Rick, first I want to add some information about the new 275's you may not have encountered:
The two latest MC275's have 490V (vs. 420V) power transformers. They put out almost 90w/ch (180 mono) even with the stock power tubes. With the better current manufacture tubes (PentaLabs, 'new' Gold Lions) it's more like 95w/ch. And even higher with vintage tubes from the GEC family -- which even lightly used, have transconductance values upwards from 9500 mMHOs!
Second, the few (but real) attributes you noted using two amps, are largely due to having a separate (and huge) power supply for each channel. If you were driving full-range speakers, you'd notice improved bass control immediately.
And last, every hour that goes by using the stock tubes is an hour of audio bliss wasted. You can't know this now of course, but the sooner you put in some decent tubes, the less you'll be kicking yourself later ;-) Any any sonic evaluations you might make now, no matter how well intended, you'll have to completely scrap later on, so why delay the inevitable?
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Rick, I won't speak for the others, but I don't understand what you've got running what ;-) Are you running the 275 on the main panelsand the (what?) driving the woofer towers? And you want to know why that should result in (apparently) better bass performance than when you were driving the mailn panels with the ASL's? |
The short answer is: the ASL's are 200w/ch and the 275 is 100w/ch (and the Perreaux is 200w/ch.)
Since the preamp is driving the Perreaux with the same volts as it's driving either of the tube amps, naturally the bass will sound louder relative to the panels driven by the 275 than driven with the ASL's. |
Rick, I'm glad you're happy with the TFK's, (and that's ALL I'm going to say about that!) And the rest of your plan I think represents the most bang for a *sane amount* of bucks. I just hope you can stop there; I couldn't. (But then, I only have one amplifier to feed ;-) |
