McIntosh MC275 VI preamp tubes


I can tell that one or more of the preamp tubes (12ax7 and 12at7) are starting to get weak...the music is starting to sound a bit muddled and not quite as clear as it used to be.  I need to replace one or some or all.  I am looking for suggestions for tubes.  I love NOS RCA tubes, but they are getting harder to find and a bit pricier than they used to be.  Has anyone tried the Golden Lion, and/or the newer black diamond telefunken?  I think I tried Tung-Sol, but didn’t care for them much.  I’m open to suggestions, I’d like to keep the price roughly around $50/tube.  
I have golden lion KT88 that still seem to be going strong.  My system is:

CD Player : Marantz SA8005
Preamp:  Krell KSP 7B
Streamer:  Cambridge Audio CXN (V2)
Speakers:  B&W683

Any suggestions would be helpful.  Thanks !!!
jbeckley42
Post removed 
+1 @tomcy6 .
I agree, don't expect these tubes to sound like NOS Tele's.
The risk in trying them is that JJ manufactures them, not known to be very durable tubes.

Prices for 12AX7 RCA's have really increased. Take a look at Brent Jessee's stock of GE tubes, about $50 each.

I should have known I couldn’t recall correctly. It was Ei in Yugoslavia that bought the Telefunken equipment according to this web page:
12AX7 Tube Gems - Tubes for Amps

Which is kind of odd, in a tube nerd kind of way, because Ei was owned by Phillips who owned many brands like Mullard, Amperex, Siemens, Valvo, etc. but not Telefunken. Maybe Phillips cut Ei loose when demand for tubes began to drop. Anyway here’s a quote from the link above:

"Ei was a tube factory that operated in Yugoslavia. Ei had close ties with Dutch Phillips. They even coded their tubes just like Phillips did.

Ei also supplied OEM tubes to companies such as Telefunken when they shifted their focus away from vacuum tubes. In fact, Ei built their small tubes on tooling supplied by Telefunken.

Now, although Ei got their tooling from Telefunken and tutelage from Phillips, their quality control tended to be minimal. So Ei screened their small signal tubes and labeled the good ones as Elites and sold at a higher price. They also offered gold plated pin version as Elite Gold."




From another forum...

Telefunken Elektroakustik is the company name, a partnership with JJ tubes. The Telefunken Elektroakustik Black Diamond tubes are essentially JJ tubes that have been cryogenically treated, silk screened in black with the Telefunken logo, tube designation, and sold in Telefunken packaging. They are definitely not Telefunken old stock tubes made in Germany. These tubes are being manufactured in Slovakia.