Retubing the McIntosh MC-30.....let's play "20 questions"

AN: Outstanding!

Glad to hear that 2 more amps now live again operating the way the engineers at Mac intended.

I've learned the same thing with my MC-225. Without a good going over, you cannot really know how they can sound.

May they live another 40 years in your care.

Cheers,

David
 
Question: Were all of the caps changed?

I'm tempted to get a pair myself at one point, but as Ron-C has said many times here before, they need a very good going over. Some people have the philosophy that you only need to swap out ony the "bad" caps. But given its age, and the desire to not always having it go back to the workbench, I would be tempted to swap out all the caps. Is this what Terry do for you?

BTW ... Alan Songer on the Klipsch forum vexes poetically about the GEC KT-66s while Steve Hoffman says the GE 6L6GC is just as good and a lot cheaper. Are you also going to try the tube rolling thing (after your wallet recovers)?
 
Not all the caps, filter caps, bias supply, phase inverter grid cap, and a few others, the main signal path are still black beauties. Changing the black beauties is a quick way to change the sonic signiture of a MC30, paper foil keeps it sweet sounding.
 
Originally posted by Number 9
Question: Were all of the caps changed?

BTW ... Alan Songer on the Klipsch forum vexes poetically about the GEC KT-66s while Steve Hoffman says the GE 6L6GC is just as good and a lot cheaper. Are you also going to try the tube rolling thing (after your wallet recovers)?
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Allan actually quite prefers the 350B over any other output tube. Not by a slim margin, either. I believe his second choice is the GEC, followed my Mullard EL-37. He's been through it all, and always comes back to the 350B.

I have been running the supplied 6L6GC (RCA Blackplates in one, International Servicemaster in the other) in mine (newly acquired) for the past week or so, and will be rolling in some 350B, as well as some Sylvania 5U4G.
 
Would not the old caps left fail at some point? Why not change all of them and be done with it?

Sorry for harping on this, but I just want to understand the reasons why.
 
Yes some caps will eventually fail, with regular use and a dry enviornment a black beauty will last longer than I will. I have had amps with them all changed out and was very disapointed in the final sound, no improvement or too hard and SS sounding. If one is going to fail it is easilly found when I do my testing on the bench, I do replace critical path components but am not a believer in a 100% rebuild if an amp sounds right, meets power with margin, makes power band width, and has low distortion that is better than 1/2 of the original spec.
I think in the long run my 42 years of experience helps a bit, though the customer is allways right, if they insist on a 100% rebuild and want to pay who am I to say no.

Off of my soap box now ...........
 
Originally posted by dewickt
Yes some caps will eventually fail ... I think in the long run my 42 years of experience helps a bit ...
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Hey, that's why I was asking. Just wanted to know why - the rationale.
:dunno:

I wonder if Audible Nectar has been able to come up for air yet. Time for another status report.
:rolleyes:
 
First, a question:

I am getting some blue glow from the 12bh7 (Raytheon), from the base of the plates. Is this normal? No sonic problems here, just a visual observation.

As far as tube rolling goes, I'm really in no hurry here, as I want to settle into the sound of the amps as they are. I find that only extensive listening reveals the true ramifications of a component change. I am certainly curious, however, so let's begin by listing what is in there.

1st 12AX7: RCA silver top grey short plate
12AU7: Sylvania on one side, RCA on the other
12BH7: Raytheon on one side, RCA on the other
2nd 12AX7: GE with long grey plate
Rectifier: GE on one side, Hitachi on the other.
Outputs: RCA black plate 6L6GC

There are a few small tubes that are mismatched, but seem to be similar looking and seem to not affect the sonics between amps. Apparently there is enough matched up that the amps sound the same.

Other than 12AX7's (4 mullard CV4004 and 2 Tesla ECC803S), I do not have much for tube options for swapping. I would be curious what results or opinions you folks have. I'm not itching to make changes, but certainly wonder what changes would come about from swapping.
 
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Here is a good read on "blue glow"
http://members.aol.com/larrysb/blue_glow.html

It looks to me like you already have quality so there won't be a
whole lot of differences rolling, and a big YMMV applies here.
You are already experiencing tube rolling it looks with your
signal tubes. The black plate 12BH7's are the nice ones to use,
you won't improve there, they are black plates? I believe you have those anyway.
Glad you really enjoying your MC30's!

Carl
 
I once owned an amp with a tube rectifier. The GE 5U4 was OK, also had a Tung Sol, but I also tried a Mullard CV378/GZ37 along the way from Angela Instruments which really was much better. It did make an audible difference!

Nice tighter bass, and quieter. Not too sure why, but my understanding is that the GZ37 works a little differently, resulting in a slow startup (which extends the life of the other tubes). The GZ37 is supposedly compatible with a 5U4GBs on most amps. It may be worth checking out.

The Telefunken 12AX7s are the ones everyone seems to be willing to pay big $ for, but I've seen Ron-C mention here a few times he prefers the GE 12AX7s.
 
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I rolled all my preamp tubes at the same time, including a stock Chinese military 5Z4G to a NIB '50s Mullard GZ30 equivalent...I wonder how much of a sonic improvement the Mullard rectifier alone made to the preamp's overall tone? With the included NOS RCAs rolled in as well, my preamp sounds way more detailed than with the no-name tubes...
 
I've swapped out Telefunken 12AX7s with GE 12AX7s and think the GE tube sounds better too.

I did not have the Telefunkens tested however, and the GEs were NOS.

BTW, the output tubes on my MC240 fluoresce blue and it's so beautiful I could charge admission.
 
I know this is an old thread, but i have to say that I had a similar experience with my MC30s. I was wondering what the fuss was all about and found them weak sounding, dull and smeared. So, in anticipation of selling them, I had them overhauled by a local guy with experience going back to the 70s. He recapped them, etc., and swapped out a few of the tubes. I brought them home, hooked them up and was completely flabbergasted. I should mention that I'm an audio engineer and have heard master reels of classic recordings in amazing sounding rooms on awesome gear and the MC30s are among the most magical components I've ever heard. The first thing I played was a jazz album and I could hear the shape and size of the kick drum, as well as all the air and resonance under the ride cymbal. After that, I was curious how they did with funk, and put on Peace Beyond Passion by MeShell N'Dgeocello. Unbelievable sound. The snare was slamming and the bass deep and strong. I was playing through a pair of B&W DM330s. Not the greatest speakers, but for $25 they were a good score. Now the speakers are Avalon NP2s. An upgrade in some respects, maybe not in others.

My tech had a quad of McIntosh labeled GE 6LGs which I bought, which sounded pretty good, but the output tubes I absolutely love for these amps are the NOS Philips 7581As. Much smoother high end and mids. They are also my favorite tubes for my 67 Fender Showman. Great, great tubes that last forever (MTBF is 5,000 hours). I sold the GEs. In general, the MC30s seem a little less sensitive to tube rolling than a lot of tube amps I've used, getting them up to spec with good caps is a lot more important. Now I get the hype. They are all that and more.
 
WOW - what a blast from my past.

This thread was only the beginning. I have traveled soooo much farther with these since I posted in this thread - hard to believe it was over ten years ago.

Yes, rebuilding them yields results. I now have two pairs of these beauties, extensively rebuilt with specially selected parts, thanks to help from a couple of dear forum friends who post here.

One such friend did a trade with me - he wanted my "MacKIT" version so I traded my pair for another matched pair, and he took me through a whirlwind tour of different recapped MC30s, in an attempt to ascertain which caps gave the best sonic results. We ended up with a pair of 30s stuffed with Sonicap Platinums - a boutique teflon formulated cap that adds just a bit of richness versus other teflons. These amps also had extensive top grade resistor work. The end result after significant break-in is a pair of MC30 like no other - superb clarity while yet smooth - they are a prized pair in my collection.

I tubed them with Tele 12AX7 smooth, Amperex 12AU7, RCA blackplate 12BH7, and GEC KT66 outputs. Got a matched set of 13 of those KT66, and after 5K hours on one quad they test just like the day I installed them. The amps are incredible.

I also have a second, consecutively numbered pair that were rebuilt mostly with the Russian K40 PIO caps, for a sound reminiscent of a vintage amp yet with the reliability of a new build. I use RCA 6L6GCs in these primarily.

I also liked the SED Winged C 6L6GC, but like a dummy I failed to stock up on those before the factory closed down (a mistake I did not make with other tubes I use). I assumed that they were still being made so I would focus on the harder to get NOS stuff, then the Winged C's went out of production before I stocked up.

But I am still an MC30 guy through and through - I also own a pair of NOSValves VRDs, which is my favorite modern tube amp pair, but the 30s are still here and used frequently.

(Shaking my head) I'm still amazed this was 10 years ago:nutz:
 
Its a proven fact that we hear things differently from day to day. What we like one day we might not like the next. I might love a 2301 one day and find it questionable the next. So lets say on Monday you like your MC30's and you wake up Wednesday and you don't and you spend the next month rolling tubes try to get the sound you liked on that Monday or improve upon it. You will waist all your time and loads of money instead of enjoying the music. Been there done that. And with out test equipment to make sure your not throwing bath water on the sound you are just playing a game. So listen to your sound system for hours and hours and get to know its personality be fore changing anything and recognize the sound you will learn to love. Because until you do your just taking chances. And like the gentleman says I would rather invest in a good graphic EQ, to touch up a thing hear or there, but you'll have to train your self to know what need s to be changed and what doesn't.

When I went back to Mac power from Crown I immediately recognized the warmer Euphonic sound of the the Macs, partly because of the lower damping factor on my tri-amped woofers and the beautiful clarity and accuracy of the highs above 6,000 hz. The overly warm was corrected using my Parametric EQ's in the 50 to 63 hz region. and reducing the output of the bass amps about 1.5 db. The highs were even more pronounced than with the previous amps but the quality was so muchbetter I chose to leave things alone. The area of the lower midrange from 1,000 hz down to 250 hz measured just as before, but was much clearer and defined. Just the personality of the amps. All the variables haven't changed in the last 4 years. But from day to day I hear the system differently and yet the same. How can you know if something is seriously wrong with your system if you are always chasing the illusive ghost of perfection with an imperfect tube amplifier. Make it the best it can be as Ron has suggested and if that's not good enough, bet a new 275 or 2301, for the quality of sound not the quantity. Remember a 2301 is quieter at 1watt than your Mc 30 and has lower distortion and higher accuracy. If that isn't good enough get your self a pair of 301's and be done with it. Unless you like direct coupled amps like I do. You haven't discovered their sound yet.
 
twiiii said:
Its a proven fact that we hear things differently from day to day. What we like one day we might not like the next. I might love a 2301 one day and find it questionable the next. So lets say on Monday you like your MC30's and you wake up Wednesday and you don't and you spend the next month rolling tubes try to get the sound you liked on that Monday or improve upon it. You will waist all your time and loads of money instead of enjoying the music. Been there done that. And with out test equipment to make sure your not throwing bath water on the sound you are just playing a game. So listen to your sound system for hours and hours and get to know its personality be fore changing anything and recognize the sound you will learn to love. Because until you do your just taking chances. And like the gentleman says I would rather invest in a good graphic EQ, to touch up a thing hear or there, but you'll have to train your self to know what need s to be changed and what doesn't.

When I went back to Mac power from Crown I immediately recognized the warmer Euphonic sound of the the Macs, partly because of the lower damping factor on my tri-amped woofers and the beautiful clarity and accuracy of the highs above 6,000 hz. The overly warm was corrected using my Parametric EQ's in the 50 to 63 hz region. and reducing the output of the bass amps about 1.5 db. The highs were even more pronounced than with the previous amps but the quality was so muchbetter I chose to leave things alone. The area of the lower midrange from 1,000 hz down to 250 hz measured just as before, but was much clearer and defined. Just the personality of the amps. All the variables haven't changed in the last 4 years. But from day to day I hear the system differently and yet the same. How can you know if something is seriously wrong with your system if you are always chasing the illusive ghost of perfection with an imperfect tube amplifier. Make it the best it can be as Ron has suggested and if that's not good enough, bet a new 275 or 2301, for the quality of sound not the quantity. Remember a 2301 is quieter at 1watt than your Mc 30 and has lower distortion and higher accuracy. If that isn't good enough get your self a pair of 301's and be done with it. Unless you like direct coupled amps like I do. You haven't discovered their sound yet.
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Your first paragraph carries a lot of good advice. I learned long ago that the best way to evaluate system changes is over time. When I got the MC30s finished with that final rebuild, I rolled a few different combinations, each "roll" was left for several weeks and listened to for multiple sessions across a wide variety of music and sources. Once I arrived at the tube set I liked, I left them - I haven't rolled my 30's in years, and have no need to. I also made sure that those tubes chosen operated properly in the amps by having them inspected on the bench.

The MX110>MC30 setup is a kit that imparts a certain sonic package that I really like - and have squeezed about all I can get from it. I quite simply listen, enjoying the fruits of the long road to restoring them to make them the best they can be.

I ended up choosing the NOSValves VRDs as that "modern" solution, about as perfect a match for my Belle Klipsch as I have heard in a newly built, linear, "best sonics" choice. I effectively use two "front ends" on the same set of speakers, giving me everything I ever wanted sonically for 2 channel use. The vintage Mac setup is the tonality king, the VRD based setup more technically accurate. I don't pine for anything else in terms of electronics. I do have plans for a restoration of my Belle Klipsch cabs but have pretty much achieved what I set out to do. Being out of the electronics upgrade game due to being pleased with the current is a good feeling. It took a lot of time to find it, but worth the effort, and thanks to a lot of people helping me along the way.
 
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