Tube Rolling in my Pathos

It sounds like those are vintage tubes. The Mullards have a reputation for having a warmer sound and the Siemens from the mid 60s on for being bright. But depending on your amp and system, you may not find those descriptions apply to your system.

I’m not sure what the readings mean because different tube testers use different scales for their measurement. Those are probably measurements of transconductance, one measurement used to test how strong the tube is, how much life it has left.

To answer your questions,

1. Tubes sound their best for a long time and then slowly deteriorate. If you get a new pair of the tubes you like, you can swap them in and see how the sound compares to your old tubes. If the same, the old tubes are still good. If the new tubes sound better, your old tubes are running out of life and you can leave the new ones in when you feel the difference is significant to you.

2. New tubes of the same brand, construction and measurements should sound the same.

3. Tubes can sound different in different amps and systems. Recommendations from people who own the same amp are more useful than those from people who own different amps. Still, you may not agree with the recommendations from people who own the same amp.

Sometimes the manufacturer will give you recommendations on tubes to try. If not, talk to a good tube dealer and they can probably help you find what you want.

Two tube dealers that most people find helpful are:

Andy Bouwman at Vintage Tube Services

Vintage Tube Services – Tubes you can trust! Providing vintage audio tubes (new old stock) to audiophiles around the world. Celebrating 28 years of technical knowledge, experience, expertise, and tubes you can trust. For a free phone consultation call 616.454.3467.

Brent Jessee

BRENT JESSEE RECORDING HOMEPAGE (audiotubes.com)

That is about all I can help you with. There is a lot of information about tubes on the web and in threads on this forum and others. Some searches should provide some useful information for you. Good luck!

@tomcy6 - I don't know for sure.  I purchased them from a fellow Pathos owner that likes in the UK.  He said the EC88 Mullards are UK Blackburn's.  He measured them and here are the numbers:

Tube #1: 15.0/19.0 and 13.7/16.5
Tube #2: 15.0/17.5 and 13.0/15.0

He also offered me a pair of 70's Siemens Berlin ECC88 tubes.  They measured:

Tube #1: 15.2/15.0 and 14.3/16.0
Tube #2: 13.8/15.5 and 13.9/16.0

I have no idea what the measurements mean.

I opted to go for the Mullards based solely on his recommendation of them being his favorite in his Pathos Classic One MkII and Pathos CinemaX amplifiers.

I just wanted to say I think Tube Rolling IS My Pathos would have been a much cooler title. ;)

Are your Mullard tubes new production or vintage (pre-1980)?

Buy NOS vintage tubes from reputable sellers who can actually test each tube (matched pairs if needed). New JJ tubes are junk compared to vintage tubes from the brands like Sylvania, RCA, Telefunken, Mullard etc. Reputable sellers do not sell fake tubes. They know a lot about tubes and can answer your questions. Some NOS tubes are expensive, some are not expensive. 

Do not buy used tubes (those that test bad). 

New tubes will not last forever, turn off your equipment wheb you are not using it. 

What you hear using tube audio equipment is tube, this is why tube rolling is so popular.