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In Reply to: RE: McIntosh 275 MKVI Tubes posted by mps2002@comcast.net on January 14, 2025 at 10:32:45
Are you using the stock tubes for 12at7s and 12ax7s? When I got my 275 vi I was very disappointed with the sound. I thought I had made a very expensive mistake. The sound was grey and lifeless, no jump factor. The unit was not supplied with JJ 88s, which have three large round holes in the plates, like a traffic signal. The stock 88s had three small oval holes in the plates, like oval racetracks. I replaced them with JJs. This improved the sound, but it still didn't sound like a premium amp. Next I replaced all the small signal tubes with Psvane, which improved the sound, making it much more holographic, with individual instruments nicely separated when appropriate, but they were a little polite. Then I replaced the at7s with NOS Sylvanias. The sound started to be good , but still not enough dynamic jump. I replaced the ax7s with os Telefunkens. It sounded like a different amp, much more powerful with a very good sound stage, more like I expected. BUT, the final touch was to replace the 88s with winged C 6550s. After this it finally sounded the way I expected, slightly laid back in the McIntosh way, but clear and powerful. I said all of that to say this - I doubt you will get all there is to be got from the amp without a complete re-tube, expensive as it might be. I suggest you start with 6550s first, then see what you think.
LowIQ
Follow Ups:
If you like tube rolling for better sound, try the 5751 GE 3 mica blackplate tubes - VERY dynamic and laps better (IMO) than the Tele 12AX7 tube. BTW, the 5751has a gain factor 30% less than a 12AX7 - but greater focus and much quieter too! The gain factor results in volume difference of around 2 DB
I used the GE 5751s you mention in a CJ PV 8 and they did sound good. Some os RCAs also sounded really good. However, I tend to shy away from using a tube not specified by the manufacturer. Just me.
LowIQ
Understood.
The 5751 is a tube developed by the US Military as a high performance, low noise tube. 12AX7 can be a good tube - it was developed back in the day to replace the 6SL7, but it can sound a bit unfocused and undefined. The 5751 is a vastly superior audio tube that is a drop in replacement for the 12AX7 - but as always, call you manufacturer to confirm compatibility.
Hello and thanks for your reply. I have changed all the small tubes and it did make a nice improvement. I was considering 6550 but wasn't sure if they were a good fit for the 275 MKVI. I know some people put them in the older 275s but you are the first one I found that is using them in the newer MKVI version. This looks like a good way to go.
Thanks
Good luck with tubes on this amp. I talked to Ryan at AC about the stock 88s. He said that with the tube availability problem that McIntosh was getting tubes wherever they could find them. They still test them before sale as in the past, but that doesn't mean they sound good enough to show the amp's true colors. As for 88s vs 655os, I've had three other amps with a choice between the two, ARC D 70 II, ARC VT 100 II, and a pair of Mc 275's IVs. In each case I've preferred the 6550s - they've been clearer and more dynamic than the 88s, and a bit cooler in their sound. I haven't heard Gold Aero 88s or some of the really expensive os tubes so I can't make any recommendations as to how they will sound in any of the amps I have owned. I have noticed MC 275 VIs going for less on the used market than I would have thought. I wonder if the owners were disappointed in their sound with the stock tubes and weren't interested in expensive tube rolling.
LowIQ
Just a quick follow up, McIntosh says I can use either the KT 88 OR 6550. I wanted to ask them since one tube dealer recommended not to so I felt I would go to the source and was pleased with their answer. Thanks again for all your feedback.
I sent a note to McIntosh to ask about using the 6550 and will see what they say. I know Ryan very well since I have purchased a number of items from him over the years and even toured the McIntosh plant with him.
Some people feel the older 275s have a better sound and that the 275 MKVI leans a little more to the SS sound. I had a MKIV and feel the MKVI is better but it's all a manner of taste.
Post another follow up when you've gotten more tubes in place.
LowIQ
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