MC75 Tubes

Swanny88

Swanny88

AK Subscriber
Subscriber
Good morning everyone,

I recently picked up a pair of MC75 amps that are currently getting serviced.

These will be paired with a C20 that is being serviced as well. Two questions that have come to mind.

1. Are there suggested tube brands for the MC75s?

2. Are there suggested tube brands for the C20?

All of these units are the original versions and I have several weeks to explore for the tubes.

Mitch
 
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quite the wide range of options. May be a bit much for an AK post. For the MC75 you can go from NOS US tubes, to Russian to Chinese KT88s.

For the C20 would be similar. NOS US or UK tubes, new Russian re-issues, Chinese PSVANE ART series.

Not sure anyone can say these are the tubes to get. May have to do some experimenting to find what you like.
 
mcgjohn said:
quite the wide range of options. May be a bit much for an AK post. For the MC75 you can go from NOS US tubes, to Russian to Chinese KT88s.

For the C20 would be similar. NOS US or UK tubes, new Russian re-issues, Chinese PSVANE ART series.

Not sure anyone can say these are the tubes to get. May have to do some experimenting to find what you like.
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Thank you. Being relatively new to tube gear, my goal is to try and avoid those tubes folks have been having problems with. Any tips are appreciated
 
I rebuilt my MC30's about 4 years ago. A complete set of NOS tubes for your MC75's, as for my MC30's, is quite expensive. I bought cheap new issue tubes at first to make sure everything was working. I didn't want to damage expensive tubes if there was any issues such as biasing. Today, they have all vintage tubes bought as I found and could afford them. I kept the new issues to be used for trouble shooting if need be. I have also collected many spares as I find good deals. Bartertown here on AK is an excellent source for tubes. There is no shortage of advice on what tubes to use for your amps here on AK. Good luck with them Mitch. Would love to see pictures when you get them back. Paul.
 
prww said:
I have also collected many spares as I find good deals. Bartertown here on AK is an excellent source for tubes. There is no shortage of advice on what tubes to use for your amps here on AK. Good luck with them Mitch. Would love to see pictures when you get them back. Paul.
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Great tips Paul. For my Sansui 500 tube receiver, I purchased tubes from AK members and they were very good.

On the service being done on the units, Bob the Tech is working on the MC75s and the C20 is with Audio Classics. It will probably be late summer before I receive the gear back from them due to their workload, which is worth the wait. Pictures of the finished products will be posted then
 
I echo what @prww said.

Beyond that, what tubes are currently on them and work well when returned to you, are probably great.

There are favorite small tubes out there, Mullard and Telefunken 12AU7 & 12AX7A, GE, RCA, Sylvania, all very popular and reasonably inexpensive, fun to play with. The output tubes are going to be the biggest expense, especially because you will be buying them four at a time, again there are favorites whether you go with the KT88 or spend more for the original-era 6550A (not 6550) tubes, where you can spend a lot, and I’m not sure that there’s enough difference to justify it from perhaps a good quality current production KT-88.

My 75s were last running ~1960 GE 6550As, a mix of NOS smaller tubes, Tele 12AX7As. I also ran Gold Lion KT-88 on the same amps, and didn’t notice a difference.

One size DOESN’T fit all in these choices IMO, enjoy “tube rolling” as part of the hobby, or pay out for the most-favored NOS tubes (and there are a LOT of counterfeits as well as used tubes masquerading as NOS) and presume that it will be the best sound for you, your choice. I recommend starting with what’s on the amps and preamp and see where it goes from there.
 
My one recommendation will be regarding the 12BH7. Use ONLY old stock North American (Canada or USA) or Asian (Korea or Japan) tubes for this one.
They are readily available, although they may cost a little extra. This tube works very hard in all of the McIntosh amplifiers that use them.

12BH7's of modern manufacture do not survive in this application, regardless of the marketing hype or the pretty box they come in. Hell, they don't even meet the type specs..
 
Swanny88 said:
Thank you. Being relatively new to tube gear, my goal is to try and avoid those tubes folks have been having problems with. Any tips are appreciated
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A lot of good suggestions from other folks.

if you are new to tubes, maybe stick with a quartet of the Russian re-issue 6550s or KT88s, and opt for some used but good US input tubes.
Quite a selection from sylvania, RCA, tungsol, GE, Raytheon, etc.
 
BNR_1 said:
I also suggest your search is not specific to MC-75. Its cousins can also reveal good information (MC-275, MC-60, MC-240, etc.).
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Great idea. Thank you to everyone who has provided suggestions. They give me some ideas once the techs work their magic on the gear.
 
BNR_1 said:
I also suggest your search is not specific to MC-75. Its cousins can also reveal good information (MC-275, MC-60, MC-240, etc.).
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a good idea. But one has to be careful at the same time. Before you know it the MC75 will invite its relatives to your locale and all of a sudden you will have a whole family of MAC amps that have somehow shown up.
 
mcgjohn said:
a good idea. But one has to be careful at the same time. Before you know it the MC75 will invite its relatives to your locale and all of a sudden you will have a whole family of MAC amps that have somehow shown up.
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One big happy family.
 
Only thing I can offer is V1 in the MC-75 will impact the sound the most. I use Telefunken in my 75’s and 30’s. Some of the current production 12*** have smaller pins too.
 
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