Different/same tubes for MM/MC phono stage?

[jdandy]

Originally Posted by MisterBritt

I'm not sure if I'm following. Let me start here. Let's say you have the top off the unit and you're looking down at the tubes from the front of the unit, as if you were about to turn it on. There are six tubes. My understanding is the first two tubes to your left are the phono section. The middle two tubes are the D/A. And the two tubes to your right are the CD. Correct?

I'm on the McIntosh website and have the owners manual open in front of me on another screen. I see on page 14 what you supplied, but I don't see where it indicates which tubes are which.

Britt.......On page 14 of the C22 Anniversary preamp Owner's Manual you will see in the middle column Tube Compliment, under which is listed what each pair of 12AX7 tubes serves, you can see one pair are dedicated to the line stage amplification (High Level Circuitry), one pair are dedicated to the moving magnet phono stage (MM Phono Circuitry), and a pair of 12AX7 tubes are dedicated to the moving coil phono stage (MM Phono Circuitry). All of the C22 analog inputs signals, with the exception of the moving coil and moving magnet inputs, use the two 12AX7's for the line stage amplification. Each phono stage has a pair of 12AX7's dedicated to its specific input.

[MisterBritt]

Originally Posted by jdandy

Britt.......On page 14 of the C22 Anniversary preamp Owner's Manual you will see in the middle column Tube Compliment, under which is listed what each pair of 12AX7 tubes serves, you can see one pair are dedicated to the line stage amplification (High Level Circuitry), one pair are dedicated to the moving magnet phono stage (MM Phono Circuitry), and a pair of 12AX7 tubes are dedicated to the moving coil phono stage (MM Phono Circuitry). All of the C22 analog inputs signals, with the exception of the moving coil and moving magnet inputs, use the two 12AX7's for the line stage amplification. Each phono stage has a pair of 12AX7's dedicated to its specific input.

Yes. I'm looking at it. But how do you know which of those three pairs of 12AX7 tubes is for the line stage if you want to swap out the stock tubes? Looking at the unit from the front, is the line stage the pair farthest left, the middle or the farthest right, please?

For comparison, the C2300, which I believe is same circuit design as the 60th Anniversary C22, shows a block diagram of the tubes on page 21. As minor point perhaps but the way they have the tubes facing the reader leads me to believe they are "looking" at the preamp from the front. This would lead me to suspect the line stage tubes are the pair farthest right.

http://www.mcintoshlabs.com/Mcintosh.../c2300om04.pdf

[edward3132]

I would suspect it is the same as the C2300

Starting from the left looking from the front: MM, MM, MC, MC, Line, Line

Hope this helps

[MisterBritt]

Originally Posted by edward3132

I would suspect it is the same as the C2300

Starting from the left looking from the front: MM, MM, MC, MC, Line, Line

Hope this helps

Cool. Thanks!

[vego99]

I also have the C2300.
The Gold Lions are very nice tubes for sure...

Currently running two pairs of Yellow Tipped Medical Grade NOS Telefunken Smooth plates in the MC section and the main section.

When comparing the sonics between the two, they were both compatible sound wise but the Yellow Tippers had significantly lower noise which helped with my very low voltage MC Cart.

-e

[miketuason]

On my C2300, I have a pair of Tefunken smooth plate on the MC stage since I have MC cart and left the stock tubes in the MM stage since I don't have MM cart.

[longgone]

... well, I popped in a pair of blue tip Telefunken smooth plates in the MC stage.
Now all I need is a MC TT!
Soon.
Soon.

[jdandy]

Originally Posted by longgone

... well, I popped in a pair of blue tip Telefunken smooth plates in the MC stage.
Now all I need is a MC TT!
Soon.
Soon.

Don.......That's the way to go. You'll be happy with the performance of the Tele's.

[puresp]

Am I wrong when I think that MC pickups (cartridges) use all 4 tubes? The two middle ones (in C2500) to boost the weak MC signal to MM strength and then the two on the left also used by MM pickups. The latter is the RIAA amplifier. Otherwise how would you make the RIAA correction when using MC pickups?

Edit: Had a look at the diagram on top of the C2500 and it seems I was wrong. I guess it means the amplifier must have two parallel RIAA correction stages?

[vintage_tube]

Originally Posted by puresp

Am I wrong when I think that MC pickups (cartridges) use all 4 tubes? The two middle ones (in C2500) to boost the weak MC signal to MM strength and then the two on the left also used by MM pickups. The latter is the RIAA amplifier. Otherwise how would you make the RIAA correction when using MC pickups?

Edit: Had a look at the diagram on top of the C2500 and it seems I was wrong. I guess it means the amplifier must have two parallel RIAA correction stages?

As the top glass reflects,
2 each for Line
2 each for MC
2 each for MM

The MM & MC operate independently -- depending on cartridge type your using. There is no combining of the signal where the signal would also use the other 2 phono tubes.

RIAA is performed in the phono circuitry of the two different phono preamplifier circuits.

Best sir,

Bob