tube guidance for MC 240, help please?

[st. patrick]

Just got a very clean McIntosh MC 240; I also just read the archive posts re some tubes preferences, most of which are more than a year old.....and somewhat inconclusive. Allan Songer, obviously very knowledgeable, references WE 350b's, Mullard EL 37's and GEC KT 66's or 6L6 variants ( is there a difference between 6L6 and 6L6CG?), but indicates the latter are very pricey. Allan, If i can find them and afford them, which would you suggest be my first choice? Input from other past or present 240 owners also most welcome.

First question: where do i go to learn the tube preface and suffix lingo?

Second question: where do i go to learn the cross reference/ inter-changeabilty of the different tubes?

Third ?: where do i go to get tubes without getting screwed? I do not mind paying for quality, along as i am getting quality.....i just prefer not getting srewed, blued and tattooed while i am still trying to learn this stuff ( in other words, i got too much "perfect" and "mint" stuff off ebay already, and am remembering the infamous words about the fool and his money soon parting company)?

Amp is on its way, with original tubes........so i plan on listening for a while, but want to start my educational process right away....and start searching for the holy grail of 240 tubes. Will be driving Cherry (Jorjen) Cornwall's, maybe going to a BB ala mode (mark, whadda ya think of ala mode for mc/mm phono plus killer headphone set-up?) , but starting with a MX 110 pre. Arcam 82 cd player and going to vinyl eventually...scoutmaster or black knight.

appreciate your thoughts, patrick

[ben.]

Patrick,

Do a search for 350B in this forum for lots of positive comments. They are expensive, but your amp is famously easy on output tubes. Some prefer NOS 6l6gc (Steve Hoffman goes for NOS GE 6L6GC. I obviously don't). Also look for Dflip's posts regarding small tube selections. These all apply to the MC30 we use, but I think they'd hold true for the 240 as well.

Congrats, BTW

Ben

[garymd]

Congrats Patrick!

Listen for a while before even THINKING about tubes. Chances are, the original tubes are fine. You need to decide if the 240 is right for you. Tubes will make a difference but not big enough to change your mind if the sound isn't what you're after. I certainly could have lived with mine but opted for something different. 240s are beasts so make sure you have a nice, sturdy shelf for it and give us a full review after you listen for a while. Pictures would be nice too.

[Dflip]

Here is a quick description of the MC-240 amp.

ELECTRICAL: 40w/ch stereo, 80w mono.

Response 16-40kHz (+0 -0.1dB).

Distortion 0.5%.

Noise & hum -90dB.

Output impedance 4, 8, 16, 125 and 600 ohms.

600 ohm center tap internally grounded.

(2, 4, 8, 16 and 32 ohms in mono).

Output voltages 25 (isolated),

70.7 (one side grounded) and 140V

(center tap grounded).

Internal impedance less than 10%

of rated impedance.

Input impedance 250k.

Input sensitivity: 0.5V

(in mono or twin amp). 2.0V in stereo.

MECHANICAL: Chrome chassis.

Line output octal socket for higher

impedances and voltages.

Barrier strips for 4, 8 and 16 ohms.

Audio inputs: stereo, twin and mono.

Gain controls: twin amp, balance and mono.

Input switch: stereo, twin amp or mono.

Can be used for 80w mono.

Line voltage switch: 117 or 125V.

TUBES: 4-6L6GC/7027A output, 3-12AX7,

2-12AU7, 2-12BH7 Solid state rectifier.

Size 8"H, 10-3/4"W and 17-1/4"D.

Weight 56 lb.

The tubes are highlighted in red. Steve Hoofman seems to like GE 6L6GC's as the favourite power tube.

From Steve Hoffman, "Good luck. Remember, the 12AU7 tube is the one I used for tweeking the sound of the 30's. On some speakers that need top end (not yours) I might use an Amperex Bugle Boy in the spot. On some speakers with too much top end I would use a Telefunken in that spot. And so on. RCA's both clear and black are good but might be a tad agressive with your horns. You can't go wrong with Mullards, the older the better...."

Try going with an older pair of blackplates for the 12BH7, probably RCA or Sylvania, 1950's would be good, at least according to Allan Songer. I have them in my MC-30.

For the 12AX7, Steve's recommendation is Telefunkens, but they are pricey.

Don

[3dzapper]

Patrick, You can download a nice tube data program complete with specs and links to other data here:

http://tdsl.duncanamps.com/

It is a valued resource to me.

Rick

[Allan Songer]

I would second the notion that you should spend a few weeks listening to the amp with the tubes it came with--providing they are the CORRECT tubes and working properly. Only then, after you really get to know the amp will tube rolling make any sense.

[scott0527]

I use an MC240 and MX110 with my Klipschorns. I love it. I didn't think my 240 was very good compared to other amps I had at the time, Dynaco, Marantz and some SS stuff. Turns out I had some pretty weak power tubes and some capacitor issues inside. I sent it to AudioClassics and have been thrilled with it ever since. Geez , I can't even remember what tubes they installed. I don't think they're anything special, might even be.. gasp.. Sovteks. I'll have to double check that tonight.

[st. patrick]

Gentlemen, you guys are aces! thanks for the guidance.

Mark, obviously my bad.....i knew the BB, and knew the cream option was the phono stage, but didn't know it already had a headphone jack/amp.....thus my ala mode comment...........best to all of you'z.

Patrick

[Dflip]

I also have 350B's instead of the 6L6GC's, but they are definitely not cheap. Excellent, but not cheap to be exact.

As others have said, listen to it first and see what you think. You may like it just the way it is and that will save you a chunk of coin. Enjoy.

Don

[Guy Landau]

I'd start experimenting with the input tubes first and go on from there.

[tillmbil]

Good idea, listen first and then upgrade. I settled on RCA 6L6GC black plates for mine. The 350B's are way to expensive. I would check into Genalex KT88's if I wanted to spend more money. They add more volume also if you are interested.