A long road traveled with the McIntosh MC-30

[Chicago_Pete]

Warm and clean makes sense to me. That is how I would describe Dean's crossovers. No taps to mess with, perfect from the get go. At least for me, I like easy set-ups.

[NOSValves]

Thanks for the offer Nectar? I guess I will never get used to using screen names.

Dont see a road trip anytime soon though. I plan on keeping these so I dont have a problem throwing some money into them. My biggest problem would be if they ended up sounding bright. Some people refer to this as detail, to me its listener fatigue big time. I could buy some Adcom or Rotel SS and get those results. If Mac's signiture sound is to roll off the highs, I guess thats what I'm used to. Did that make sense? No offense to the SS camp. Pete

With your above statements I highly suggest you find the time to visit with Dave. I really would rather not work on your amps until you actually hear what they might sound like or at least a similar example. I truly believe to many people are stepping over each other guessing, estimating and assuming what the intended McIntosh sound really was when these amps were built some 45+ years ago. The McIntosh reputation that is rampant today thoughout audio circles is not the true McIntosh sound. Find a modern McIntosh dealer and go listen to the reissued version of the classics today. They sound nothing even remotely like one of these still 100% original 45 year old version with the imfamous "Brown Sound" or like on stuffed with 50 cent IC capacitors. I'm not saying you will like the amp more after better caps are installed. I am however saying you should absolutely go listen to a pair before you have me do yours. The last thing I want to hear is "Craig ruined my wonderful McIntosh amps" You may prefer them just as they are we all have are own independant audio preferences. No ones wrong or right in this game. The last thing I want to end up hearing is "Craig ruined my McIntosh amps".

Craig

[scott0527]

Craig, if you don't mind, it's time to post a picture in this thread. Here is one of the 30's Craig refurbished for me. My instructions were to simply do a straightforward rebuild. They sound so much more lively than my other pairs which are in original condition. I haven't put in nearly the amount of critical listening time some of you have, but I certainly prefer the newly refurbished pair to either of my original pairs. Not even close for me.

[scott0527]

Another view. Incidentally, what do those 12K resisitors do? In the 6 MC30's I have inspected, I've found 5 (out of 12) of those resistors to be bad.

[Audible Nectar]

I don't know circuits like Craig and Joe, but I have been told that those 12K resistors are critical to the performance of these amps by several techs. It is required to match those resistors within 1%, or thy listener will have distortion up the wazoo....at least that's the word from those in the know......

[NOSValves]

That was the frame off resto job!! Those are the chassis Scott reproduced and did a wonderful job every single hole was right where it belonged (except the one he oops and missed all together.) I actually thought you missed two holes but the other day when Dave was here I think I found out why you missed the second hole. Some of the amps did not have that hole near the fuse and AC cord for the terminal strip. One of his amps had it but the other did not I bet the chassis you used for a sample did not have the hole in that spot. No big deal the trusty cordless made short order of both. Did you end up running more of those chassis at the your shop Scott?

Craig

[NOSValves]

I don't know circuits like Craig and Joe, but I have been told that those 12K resistors are critical to the performance of these amps by several techs. It is required to match those resistors within 1%, or thy listener will have distortion up the wazoo....at least that's the word from those in the know......

Yup and that is why they are replaced on his amps. But the 1% thing is a little anal. 1% resistors did not exist in the 1950's and the AB's the MC used were surely far from 1% resistors. You just do not want them wildly off. In fact if one really wanted to be anal about it a pot could be installed to really balance things out. The tube that those resistors supply is not a 1% tube.

[scott0527]

That was the frame off resto job!! Those are the chassis Scott reproduced and did a wonderful job every single hole was right where it belonged (except the one he oops and missed all together.) I actually thought you missed two holes but the other day when Dave was here I think I found out why you missed the second hole. Some of the amps did not have that hole near the fuse and AC cord for the terminal strip. One of his amps had it but the other did not I bet the chassis you used for a sample did not have the hole in that spot. No big deal the trusty cordless made short order of both. Did you end up running more of those chassis at the your shop Scott?

Craig

I made them all for Joe who was forever patient and forgiving of my inevitable first time miscues when recreating these things with no drawings. I think we have it down now.

[Audible Nectar]

I would say so, Scott - those look really good!

[NOSValves]

If it wasn't for the transformers having some marks from age those amps looked like brand new. Scott said he was going to tackle the transformer touch up work. Did you do that Scott? If so lets see the top side.

Craig

[Audible Nectar]

Time for an update......

Until just recently, I kept the MC-30s in similar "state", not changing much, save for an older vintage 1950's Amperex 12AU7 that I rolled in (that Ben was so kind to share here on forum), bumping a newer vintage out of that phase splitter slot. I have pretty much settled into thier "sound", allowing sufficient time for the amplifiers to burn in, as well as my familiarity with the sound of these builds.

The primary output tube used since the last post has been the SED Winged C 6L6GC. I figured it a decent tube, and would allow for an inexpensive current production tube while the break in took place, and to allow for some other minor adjustments to be made elsewhere (cables and networks, primarily). The SED is a balanced tube, and while doing no one thing exceptionally, it is predictable and consistent. I also spent limited time with the RCAs, but the SED has been the primary tube for the past three months or so.

The overall performance has been very good: The 30s extend better now on both ends, the bass deeper and better defined.....while yet retaining that tube rectified "roundness". They are still not a "bass head's amp", ideal for instrumental and generally good enough on most material, even the classic rock and most modern offerings. For King Crimson, Tool, and "heavy" guitar stuff, the 30 isn't your amp anyway, and that hasn't really changed (unless you are bi-amping). The highs are much improved and offer a clarity and cleanliness that is very much welcome. This is the "new side" of the MC-30......those who are used to vintage caps will find this a surprise. But it is a welcome surprise, especially when you tube this amplifer properly. And then there is the midrange, of course[]

Having discovered the goodness of the newly reborn MC-30, it was time to revisit some experiments that on the old stock builds went.......poorly. Many will recall my posts regarding the old builds, where the results I was getting weren't lining up well with other results posted here. Now that the new builds are in place, time to try some of these again.

Enter the GEC KT66 (clear glass version), now on loan and in my amplifers for audition.

WOW what a warm and beeeeeeuuuuutiful MIDRANGE!!! They have a richness and a
harmonic complexity that is difficult to describe other than it takes the term "lifelike" to a new level. The fuller bottom is also very welcome.....no longer does they come off as "bloated" like they did in the stock builds.....

The highs are a very neat trick: they extend nicely, yet warmly, with that smidge of crunch when appropriate. Snare drums and cymbal sound very "right", again it seems a part of that "harmonic complexity" that makes this a very special tube.

And of course the added authority and boldness tha the KT66 brings to the table......instead of being, as recording engineer Steve Hoffman said "like pushing the loudness button", it is now a warm, liquid and authoritative sound that is most welcome. No longer thick or heavy footed in the new builds, it is reassuring, bringing a total body to the sound that envelops and invites you.

An interesting aspect of this tube is the longer warm-up time. It seems to take a while before they really begin to liquefy and "sing" to thier optimum. Once this occurs, they really "bloom" and stage, without exaggerating.....where the RCAs are really good at certain things (like guitar, for example), the GECs are a complete tube, seeming to do everything right with a complete and balanced presentation. Quite frankly, this is "uncharted territory" for me......performance like this has never been experienced in my home. Those cap upgrades (in amps as well as the V-Cap OIMPs in the crossovers) are really paying dividends now.

Miles Davis never sounded soooooo good!! Ohhhhhh, the air.......the timbre.....it's juuuuuust reeeeeeeediculous[]. Not to mention the "breath of life" you get from these on classic rock recordings like the Beatles, Moody Blues, and if you really wanna have the hair on the back of your neck stand up, try Roy Orbison on for size......it's just spooky. On Jazz, these amplifiers are perfect.

But now I have a problem........with my wife.

Now many of you are well aware of the phenomena of hiding boxes of tubes, caps, components, and other audio goodies to keep the peace at home......many write of shielding the wifey from too many incoming boxes from the post office. And of course, WAF issues. That's not really an issue here.....the system resides in "her room", where besides the audio system she has free reign over the deco (with system specific "requirements", of course), and we do work this as a team project.....it is a part of our home, and we both value the music and systems here in our home. But I'm sure many are aware of the "angle" that the wife usually imparts on our sonic travels and journeys.

But fellow forum members, I have a different problem.

She of course knows that the tubes are on loan, and she asks me a question. "How much does it cost to get a set of THOSE????" Not as an interrogatory question, but as a desire to get some.

When my wife starts making tube decisions based on sonics, I know the landscape here at home is really changing. Now she has always been a good compass on my system tweaks and changes......her ears and thoughts have been a good guide and affirmation of my audio decisions. But now, she's making requests. As in "I want a set of those for our system. Do we really have to give those back? Those aren't for sale????"

"No, honey, they are only loaners."

Even after dropping the proverbial "price bomb" on my wife as to the current value of such NOS (and even used) gems, she's already doing out-loud mental budgeting......they have made THAT much of an impression here. It isn't me who is discussing how we want these tubes in house.......it's HER. I've deliberately not said much about them (even though she knows damn well what I think).....but she has mentioned it daily since install. It's that obvious.

It's a nice problem to have. It could also be an expensive and time consuming problem to solve. But at least we now know. The GEC KT66 in these builds are certifiably the BOMB, and I can think of few other amplifers so deserving. These truly did bring down the house! And we are just giddy with joy over what is happening sonically here. Even my wife is on the bandwagon[]

What is most satisfying, however, is to finally "see the light at the end of the tunnel" with these amplifers. It is even better than I ever hoped for. I've played around with the MC-30 for several years now (with the invaluable help of many here), and am finally wintessing the return on that invested time, money, forum reading, and patience. It's even better than I ever imagined could be. I thought they were good before........but WOW.

I feel like Chief Brody in "Jaws": "HEY, I GOT IT!" And now it's a helluva ride!!!!!! And as for the wife, I'll coin another old line: "How ya gonna keep 'em down on the farm, after they've seen Par-eeeee?????"

[Allan Songer]

Told you so!!

LOL!!

I wish I still had the extra quads I sold in the last few years so that I could send you a quad. I had TWENTY FOUR of these that I bought from a Aussie military surplus dealer back in the mid-90's and now I only have eight tubes left and I just can't part with any more of them. I sold them for $75 per tube NOS--what a DUMMY!

You're going to have to pop about $150 to $200 per tube for them NOS today.

By the way, if you like the GEC KT-66 just wait until you hear the WE 350B in your MC30s!!!! They might not have the same bottom end extension as the KT-66, but they provide and even MORE lifelike and glorious midrange!!

You can get used WE350B one at a time on ebay for about the same price as NOS KT-66--around $200 per tube.

One nice thing is that you might well NEVER wear any of these out in an lifetime of MC-30 operation!!!

[Audible Nectar]

You bet you told me so, Allan. And the fact that you DID tell me so was a key reason that I never gave up on these amplifers. I knew something better was in there, it was a matter of having them restored properly and completely. Admittedly it seems that my original examples weren't the best.....at least capwise. Once redone, a completely different story. The ensuing cap experiments, trials, and tweaks REALLY paid off.

[Joe Auwen]

Dave, Just don't get toooooo attached to those KT66s...... []

[dp1954]

Audible... I was wondering if by chance you had tried the VA kt66's back in the amps? The reason I ask, is because I have been in the process of rolling tubes on an mc240 and an mx110. I tried all kinds of 6l6gc tubes in the 240 plus a quad of Groove Tube kt66's. None of these compared to the fullness of the VA's. They really have impressed me. I even went to the extent of ordering a pair of VA 350B's which I put about 6 hours on. Granted, I only played with the 350b's for 6 hours which I know is not enough for complete breakin, but they didn't hold a candle to the VA kt66's. At least not in my setup. I have not heard a quad of the GEC's and am curious if they are that much better than the VA's. Both the mc240 and the mx110 have been rebuilt by Terry in the last 3 months so I know the amps are up to snuff.

Dave

[Audible Nectar]

Dave, Just don't get toooooo attached to those KT66s...... []

Hehehehe.....we won't get too attached.....but those should come with a government warning.....that when properly used are very habit forming. Usually, anything that pleasurable and addicting is illegal....or at least heavily taxed........[] Oh, and thanks, BTW for the look-see!!

Regarding the Valve Arts: I may research doing another trial with those.....but one thing bugs me: reliability, particularly when it involves self biasing amplifers. I have read some complaints about those tubes holding up for the long haul........but by all indications sound quite good. Maybe I've just read the worst of the "flameouts" regarding these.......but one desire is to find reliability. The GECs will bring that, and in an MC30 a good quad or two might well last me a lifetime.

Regarding the 350B: I've been told by some more technically inclined than myself that they don't feel comfortable running 350B in MC30s (1.6A per tube current draw vs. 1.3 for KT66 and .9 for 6L6GC). It does seem that there is a sufficient body of users doing just that with no apparent problems here. Since I am not a "circuit genius" - I fall into the category of "reasonably experienced and trying-to-be-educated appliance operator" - I am reserving that decision for when I understand more about this. Those successfully doing this here serve as some comfort that it can in fact be done safely, but maybe the engineer types have been getting the best of me on this issue.....which they have been often known to do, especially when I am NOT a circuit genius. I can read specs and apply those on a limited basis, but when it comes to making changes from spec and schematic, I get lost. So I tend to stay within what the engineer types deem "safe". They tell me that the KT66 offers greater "margin of safety/reserve" vs the 350B (1.6A for 350B, 1.3 for KT66).....less work for the tranny with the KT66. And given the rarity of 350B, I wasn't TOO worried about it anyway.....but am open to more technical "schooling" or explanations on this issue.

[Allan Songer]

I've run the 350B for HUNDREDS of hours in my MC30s with ZERO problems. Who told you that the 350B would stress the McIntosh transformers? I would be interested to hear who told you this and if they have lots of experience with McIntosh tube amps. In my experience the 350B is a DIRECT replacement for the 6L6GC in just about ANY amp that was designed to run 6L6GC.

http://www.westernelectric.com/spec_sheets/350B.pdf

http://www.guitaramplifierblueprinting.com/Tube/KT66.pdf

Personally I wouldn't worry too much about the 1.3 vs the 1.6 heater current specs on the two tubes when used in the MC30. Maybe Craig should weigh in here . . .

[ben.]

Audible, your detailed report is useful as always.

Check your email in a few minutes.

[NOSValves]

Well if looking from strictly a tecnical standpoint yes the added heater current demands of the 350B would be stressing the MC30 power transformer a bit more but I seriously doubt McIntosh didn't design in plently of headroom. Heck a little old company like NOS Valves designs in over double capacity on these windings. The extra 1/2 amp should be no real worry at all.

Craig

[Audible Nectar]

Well, since I was advised not to get TOO attached to the GECs, I thought it might be a good time to roll in the RCAs and see what changes. The GECs are really easy to get used to[]

The RCAs do have one thing: the MIDS.....smooth, creamy midrange that is very easy to get used to. They "project" those mids in a way that allows them to "float" into the room......very smooth, yet lively, and doesn't really sound "veiled" or shrouded like the current production tubes do. I can see why the guitar guys use them, and they make for a good flavor, especially for the guitar folks, who are primarily interested in the midrange anyway. A very nice, sweet, "vintage" tone.

But for high fidelity applications, the GEC is not only good in the mids, it ROASTS the other 6L6s in every other area. The total presentation of the GEC is big and lifelike - so much so, it's SCARY. The "kinkless" aspect (flatter response across the midrange, instead of the midrange "peak" of the 6L6GC) takes some getting "used to" in the MC-30's because they were designed around the 6L6, which does emphasize the midrange. The GEC KT66 puts no emphasis on any one thing......it emphasizes the TOTAL presentation. It extends the "life" known to exist in the MC-30 mids to a broader region of the spectrum. Any regular 6L6 seems "small" in comparison to the GEC....the depth and authority is missing with the 6L6GC in these amplifiers. And compared to an RCA 6L6GC it's NO contest.....the RCA bass is loose in comparison (that was no surprise).

There's a lot to like with the RCAs, especially if you are a "midrange" guy like I am. It's one reason I bought the MC-30s. But then I also have to ask myself if the "bigness" of the KT66 would be "redundant" with the soon-to-arrive pair of VRDs. After all, that's what I'm getting VRDs for.....the pure power and guts that the MC-30s do not have. I'll bet VRDs are KILLER with GEC KT88...........[] So I could still see the RCAs being good in 30s in a "vintage system environment", with the VRDs doing the function that the GEC KT66 does well in my MC-30s. Then again, I have a second set of MC-30 too, so maybe do one with 6L6 and the other with KT66........

Oh, but then there's that other "big dog" in town, the 350B. After doing some additional digging for information (and people who could make sense out of it for me), it seems my "worry" about running 350B isn't really much worry (granted, the three here running them should be sufficient proof, but I was seeking more technical info, which I believe I have found). Since my results here are now matching up with Allan and others, I have a hunch they're really good.......

And did I mention......this is FUN!!! Again, it seems redundant to say so, but it's really nice to sample these different flavors in a properly restored system...and hear what these tubes really sound like......may I say it again, caps and tubes DO matter......[H]