Different McIntosh MC 30 models

Discussion in 'Audio Hardware' started by Henry Love, Jul 11, 2005.

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  1. Henry Love

    Henry Love Senior Member Thread Starter

    Location:
    Chicagoland
    I've seen a set of MC 30's for sale.One was older without the barrier strip and McIntosh logo and the other amp had the strip and logo.Looks like they might've been at different ends of the model run.Does anyone think there could have been enough changes that they might not match up good?Thanks.
     
  2. Stax Fan

    Stax Fan Forum Resident

    Location:
    Midwest
    There were production models and there were kits (MacKit) toward the end of the product life cycle.

    Output transformers from different production runs can sound different. In a perfect world, you'd want transformers that sourced iron from the same batch.

    There might've been circuit updates over the life of the MC30 too, which could result in a slightly altered sound. I don't know if there were any changes, though.

    Maybe the plain example you saw was just one where the logo had come off at some point.
     
  3. Joe Nino-Hernes

    Joe Nino-Hernes Active Member

    Location:
    Chicago, IL
    As far as I know, the MC30 circuit did not change. However, Arin is right, you do want to find two which have consecutive, or at least close serial numbers
     
  4. Stax Fan

    Stax Fan Forum Resident

    Location:
    Midwest
    I just looked at Roger Russell's McIntosh site and it looks like later examples of the MC30 had a variable damping control of some sort.

    I guess that would be to adjust for a better *grip* on the low end.

    Hey, why's the bass all flabby? :D
     
    russk likes this.
  5. Henry Love

    Henry Love Senior Member Thread Starter

    Location:
    Chicagoland
    Thanks,Arin and Joe.It makes sense.
     
  6. Steve Hoffman

    Steve Hoffman Your host Your Host

    Buy your Mac pairs as close together as you can. The circuit did indeed change over the years. Not radically much, but according to the schematics, there were over 10 changes in 10 years..
     
    nm_west likes this.
  7. Henry Love

    Henry Love Senior Member Thread Starter

    Location:
    Chicagoland
    Thanks Steve.That confirms my hunch.
     
  8. McLover

    McLover Senior Member

    Hi all and Steve,

    FYI, the early McIntosh MC 30's didn't have the barrier strip/McIntosh logo in the front. I have a friend with a 1956 MC 30 (he purchased new in Oak Ridge, TN) with same. That didn't come until later. The MacKit version was made in 1960 only (very limited run)
     
  9. Henry Love

    Henry Love Senior Member Thread Starter

    Location:
    Chicagoland
    If I remember correctly the old 30 had a sticker instead of a logo.
     
  10. Steve Hoffman

    Steve Hoffman Your host Your Host

    This 1960 pair that I still use have never had any maintenance whatsoever; amazing build quality. Heck, it's only been 45 years without a tune-up..
     

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  11. Henry Love

    Henry Love Senior Member Thread Starter

    Location:
    Chicagoland
    A thing of beauty.I've got this picture stashed in my pictures.
     
  12. MisterBritt

    MisterBritt Senior Member

    Location:
    Santa Fe, NM, USA
    I think I remember seeing a picture of these beauties in Stereo Review a couple of years ago -- in a cabinet chock full of gorgeous McIntosh gear. I've got a pair myself and was wondering, based on a comment you made in another thread, about the viability of plugging the WE 274B into them. It seems like you alluded to the idea that the surge when one turns on the amps might be too hard on the tubes, wearing them out prematurley. My tube gear is in storage just now -- but I bought a pair of WE 274Bs and a quad of WE 350s for the Mc30s. Just curious if you had an opinion about it. (Got the Telefunken ecc802s and ecc803s for the same purpose. Do you use the RCA 12BH7 or other, please? Maybe I'm "gilding the lilly" but these are my favorite McIntosh amps.)
     
  13. Steve Hoffman

    Steve Hoffman Your host Your Host

    Welcome!

    Actually I never thought about using a WE274B in a MC-30 only because a new example of the tube could be worth more than the amp. Actually the 5U4 seems to work well. I've tried Tung-Sol's and all different types of 5U4's and the sound seems to hold constant. So, I would advise against the WE unless you have very deep pockets. Fred Volz of Emotive Audio likes the RCA 5R4GY in that spot as much as the 274B...

    I have never found the MC-30's to be hard on tubes. Indeed, my oft told story about the Mac 30 we had at our college radio station in the 1970's which still had the same tubes in it since 1960 and had been in the "on" mode constantly since 1968 was no exaggeration!

    I use either RCA or GE 12GH7's but my faves of the moment are Brimar.

    Below is a shot of that vintage system from around the time of the Stereophile article but several pieces have changed since then...
     

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    SandAndGlass likes this.
  14. MisterBritt

    MisterBritt Senior Member

    Location:
    Santa Fe, NM, USA
    >I never thought about using a WE274B in a MC-30 only because a new example of the tube could be worth more than the amp.<

    Good point. I follow what you're saying ... but you only live once. I've yet to plug them in, but it's amazing how distance can make the heart grow fonder. I've got RCA 5U4s in there now. 12GH7s, eh? I'm not familiar with those so I appreciate the thoughts.

    I've looked at this site before but the more I seach around, the more I think I can glean from previous posts. A unique thread on MC-30s -- this is my kinda place. Thanks for your kind reply.
     
  15. Steve Hoffman

    Steve Hoffman Your host Your Host

    I meant 12BH7. My finger slipped!
     
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  16. jt1stcav

    jt1stcav Say It With Single-Ended Triodes

    Those Mac 30s are so sweet! All tubed McIntosh power amps are still the best IMO (and others seem to think so too, it appears)! Though I never owned a tube Mac (yet), I did have a few transistorized examples back in the day, and by far my favorite SS McIntosh was my classic MC250...love that classic Mac chassis! :righton:
     

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  17. MisterBritt

    MisterBritt Senior Member

    Location:
    Santa Fe, NM, USA
    >Though I never owned a tube Mac (yet), I did have a few transistorized examples back in the day, and by far my favorite SS McIntosh was my classic MC250...love that classic Mac chassis!<

    That's a great looking MC-250. I started with an MA-5100 and MR-71 tube tuner. Got a pair of nasty-looking MC-30s and an MC-225 in one foul swoop from a recording studio. Sold the MC-30s and got darn near whole on the package purchase. Kept the MC-225 for many years (I would still have it but for space premium). Went through another MA-5100 somewhere along the way, C-26, C-28, an MX-110, MC-240, another pair of MC-30s, which I had refurbished and still have, a C-11 (came to discover that lit up white instead of green behind the black glass so it had to go) , a C-15 (when you used the remote volume it actually turned the knob -- I thought that was great) etc. -- then got a new C-2200. Had a couple of Mac CD players along the way. And the thing is ... like others have discovered, I made money on every single piece except and MCD 7010 that "cost" me about $200 bucks after a couple years of enjoyment.

    So, as an aside, that's another great thing about the McIntosh line. It pays you to own it when you want something different. And the folks who work there are so great. Sometimes I pop in this DVD called "This is McIntosh: Elegance, Strength, Commitment," just to watch them putting these things together and talking about how they wind the transformers and such. Then you can play around with tubes just to keep the experience fresh. It's a great hobby because it doubles as an investment, too.
     
  18. PakProtector

    PakProtector New Member

    Location:
    Dearborn, MI
    Hey-hey!!!,
    There are two basic circuits for teh MC30( that I know about anyway). One has its negative rail supplied from the main HV, yeilding ~400 volts negative. The other has a tap in the HV for a lower voltage negative rail.

    I have had great success with some blueprinting of that amp. First is to use an IDH rectifier, like a 5V4GA. One must put a diode into the main PS so as not to draw the power supply 'lytics negative.

    Next is to get rid of the nasty 12AU7 and substitute a 6CG7. I'd put in a 6SN7 if I could justify cutting an octal sized hole.

    next is to remove the plate resistors, install matched value ones of your favourite flavour, and replace the 18k tail load with a cascode MOSFET CCS.

    I also like the russian 6H6Pi in place of the 12AU7( once the socket is converted to 6CG7 pin-out ). It is far more comfortable with a 30k plate load. It is a bit more heater current...

    I also substitute 12AT7 for the cathode follower valve. Its gm is nearly 10x the factory specified 12AX7's. Matched sections are easy to come by in the GE-made 6201/12AT7WA style. Also change the 220k tail loads to 180k for a little bit more current and lower output Z from that driver stage.

    The 12k 12BH7 plate loads should match well. I personally prefer Dale or Mills wire-wound, but a 2-3Watt carbon film is also quite good.

    I like these amps enough that I have contemplated a full-on power supply. Choke input, 866's for rectification, motor-run Oil filled caps for the filtering. Inductor Iron in the negative rail. special selected resistors and caps for the signal path...

    All this amounts to blueprinting the amp. No basic change is done to the circuit. I suggested this set of mods to the MC family of valve amps untried about 2.5 years ago. I finally got a pair of 30's from a friend to modify( all the rest got sold to support/augment my grad student income). The 75's have a slightly more complex CF circuit, and are the ones to use the 12AT7 driver.

    As always, for additional info, drop me a line and ask any question.
    cheers,
    Douglas
     
  19. munot

    munot New Member

    Location:
    munchen GERMANY
    Hi! I will buy a pair of MC 30 very well looking, but the man who sale them can't give the series no .Is it normal? Is it possible that there are imitations, like rolex?
    Thank's.
    munot
     
  20. munot

    munot New Member

    Location:
    munchen GERMANY
    to buy a REAL MC30

    :goodie:
     
  21. DrJ

    DrJ Senior Member

    Location:
    Davis, CA, USA
    The seller could definitely still be legit, maybe just not all that up on where to look (same with the guy I bought mine from, and me for that matter until I started frequenting the SH Forums!).

    The serial numbers are not easy to see, at least on the MC30s I have. On my units, they look kind of like a rather faded ink stamp (though they don't rub off with gentle cleansing of the unit) and are at the very bottom of the chrome area on the "right side" of the units (with the side having the McIntosh chrome logo being considered "front"). Actual numbers are 7E418 and 7E422 (I provide these in case it helps you tell the guy what type of number/letter sequence he might look for).

    I'm still not sure what vintage these serial numbers would indicate the units are, but based on all the documentation the guy I bought them from had (purchased from original owner!) I would guesstimate 1960-1 range.
     
  22. Henry Love

    Henry Love Senior Member Thread Starter

    Location:
    Chicagoland
    Hello Munot.Some MC30's don't have the serial number on the outside.You need to take the bottom plate off and look on the bottom of the top of the unit.Hope this helps.
     
  23. Steve Hoffman

    Steve Hoffman Your host Your Host

    That way you can see what the inside of the things look like. Sometimes it's not pretty...
     
  24. Henry Love

    Henry Love Senior Member Thread Starter

    Location:
    Chicagoland
    Aren't all MC30's a thing of beauty?
     
  25. Steve Hoffman

    Steve Hoffman Your host Your Host

    On the outside..
     
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