Lab12 Melto 2 - tube rolling

@lewm and @billstevenson 

​​​​​@lalitk reached out to lab12 and posted their answer in his response on this thread

I’ll repost it again

 

“Please be informed that Melto2 is equipped with a pair of E88CC / 6922 tubes as well as a pair of 6N2P NOS (New Old Stock) tubes. For the 6922/E88CC tubes that are placed in the output stage you could use any brand you prefer according to your sound taste. However, make sure it is a strictly matched pair of tubes. 

Regarding 6N2P NOS tubes we are not sure if there is anything better out there. These tubes are special selected in our factory for melto2 design, from specific date lots and after critical listening tests.”

To add, I have borrowed NOS Siemens from my friend and a pair of NOS Russian 6H23P EB tubes I can test in place of the Electro Harmonics. 
I will report back after hearing these tubes. 
 

My thought process is because I bought this phono amp used I don’t know how many hours are on the tubes thar are currently installed. Seller said low hours. In several years even at 1hr per day average that would be 300+ hours per year. I will assume the tubes have between 2000 and 3000 hours. Not a lot of people buy this level of phono stage to have it sit around. 
The sound is absolutely spectacular. I am running it at 58db gain and 240ohm load which in my system is a good match. I will fit this unit with a fresh set of tubes just as a piece of mind. Which tubes…will see. 

“I have borrowed NOS Siemens from my friend and a pair of NOS Russian 6H23P EB tubes”
@audphile1 

Good call, that’s really the only way to find out how responsive the Melto2’s tube circuit is to tube rolling.

The tubes in output stage in theory has no voltage gain as @lewm pointed out but in real world, they behave quite differently.  A cathode follower has no voltage gain, it’s there to lower output impedance, provide current and buffer stages. So on paper, it shouldn’t influence the sound much, right…lol! 

But in real world, it still does. Tubes differ in transconductance and behavior under load, which affects microdynamics and low-level detail. They also shape the distortion profile, influencing tone, texture, and decay. Since a cathode follower is about current delivery not gain, how a tube handles dynamic current impacts attack, ease, and overall musical flow. 

If one is averse to tube rolling, you might as well buy a solid state component and call it a day. IMHO, you don’t tube roll or buy a tube component to change the sound or add coloration….you buy them to make the music bites feel more human. 

@lewm ​​​​@billstevenson 

There’s definitely a difference. And it isn’t small.

With the Siemens 6922 the sound is bigger and warmer without the sibilance (albeit very minor) I noticed on female vocals with the EH tubes. 
Dire Straits “Calling Elvis” from On Every Street album sounded bigger than ever with the drums and the bass laying a massive foundation. The drums hitting harder and weightier. 
Took several hours for the tubes to settle. At first they were a bit tipped up in treble. Once warmed up…Biggest delta in bass, overall warmth of the presentation and size and weight of instruments. Vocals are honey. No noise. Dead silent by the way, just like the EH. 

Next up is the NOS Russian 6H23P EB. 

 

Very interesting.  I am learning all the time and appreciate the update.  @lalitk thank you for your comments as well.  I almost makes me want to tube roll on my ART Phono...nah.