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Upgrading tube for a MAC 275 mk5 what are you using?

I have a MAC 275 mk5 new this year and I'm looking to re-tube it as i don't like the factory tubes. I find they are too bright and lack midrange tone. I'm using Spendor D9.2's that are rather unforgiving on the top end, supper detailed but lack some midrange tone as well when driven with the current tubes.

What tubes are others using, NOS? new production? KT88's or 6550. I'm personally leaning towards the 6550's.

What about the driver tubes? I've never owned an amp that used the 7AT's what are people recommending for them? 

I drive the 275 in balanced mode with my Mac C2700 preamp. 

thanks for your experiences 

128x128glennewdick
stereo5's avatar
stereo5
6,405 posts
 

Most of the Mac people I have spoken with prefer the KT88 Gold Lion tubes.  The consensus is that they make the amp sound its best.  I haven't heard the amp in that configuration, but I did not care for the Gold Lions in my C2500 tube preamp.  I like the McIntosh branded tubes (JJ) better in the pre.

glennewdick's avatar
glennewdick OP
1,690 posts
 

I'm personally thinking NOS tubes, I've tried the gold lions in other tube types (300b,12 series small signal tubes, kt66, etc) and yes, they can be good.

I'm really wondering what NOS tubes people have tried, I've not used 12AT7 before so i'm not really sure which are great specially for the money ( i'm not paying $300 each for telies for example). I still want over all good sound from top to bottom but i'm looking for more midrange tone and sound stage depth and width. I find the JJ's if that's what Mcintosh is still using to be lacking in midrange tone and sound stage they are quiet, decent bass and decent up top if not a bit bright. But not like many of the NOS tubes I own. 

Also, anyone using 6550's opposed to the KT 88's? I find the KT series to be overall leaner in the midrange compared to other NOS types. 

dekay's avatar
dekay
5,598 posts
 

RCA black plate 12at7 and 6201 offer a harmonically richer sound (I use 12at7 to drive 2A3's).

Mullard Blackburn production is also good for such.

Avoid Sylvania and Eastern European 12at7's as they are leaner/brighter (I also include Mullard box plate CV4024/12at7's from the Mitcham factory in this group).

For input/gain "12ax7's" (which your amp uses) I seem to always end up preferring Amperex Holland (the less expensive 60's short plates are still reasonably priced and their sound quality is up there with the older Holy Grail versions).

Google "Brent Jessee" to view his current inventory/pricing and specifically check out his damaged and rebranded label offerings if you do not require pretty tubes.

 

DeKay

 

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