[HT cOz]

I'm trying to figure out how my tube amp works.  It is an Onix H6550 AKA Genesis I60 or Melody H88, they are all basically the same amp. 


"As delivered, every tube is tested for linearity and low noise, then pair matched. Milspec versions of the 6SN7 are used for their reliability and durability as the phase splitter and driver tubes for both the I60 and M60. Each amp unit is burned in for 100 hours and the tubes are biased and rechecked before shipping."

I cut this out of the 6 Moons review of the Genesis I60.  http://www.6moons.com/audioreviews/genesis3/i60.html

So if I am looking at Tube Rolling the 6SN7 tubes does this mean I have to buy matched pairs?  Is the fact that one of the tubes is used for Phase Splitting and the other as a driver tube make any difference?  Or is the phase splitting and driver action occurring within one tube making it necessary for them to be matched?

As I have been reading up on the 6SN7 it has become obvious that certain NOS tubes do different things better than others and hence my question. 

I also emailed Melody to see if they would send me a schematic of the amp so maybe these answers could be nailed down if they send me it.

Any help is appreciated.

Cheers,
Robert

[woodsyi]

I am no sage -- I derive most of what I know audio wise from the mighty internet.  Having said that, I believe one tube (dual triode) will do both for each channel.  You want them matched to get LR even.  Here is a good example of how a push-pull amp works.

http://www.dogstar.dantimax.dk/tubestuf/4x4howit.htm

[JoshK]

Truth is the statement is vague.  There are numerous different topologies this could imply.  I see two 6SN7's per channel, so I have a guess as what it might be, but its just a guess.  Is one labeled differently then the other?  Like one phase and one driver?

Phase = phase splitter.  There are a number of ways to do this, examples include long tailed pair and cathodyne as some of the more common ways.  I'd hazard a guess that they are using gain > cathodyne > differential gain (driver).  If this is the case, then really the only matching you really need is the matching of the two triodes within the driver tube's envelope.  Then again, the loop feedback does a lot to mitigate any differential.

You wouldn't happen to have a schematic, so we wouldn't have to do so much guessing?

[HT cOz]

You wouldn't happen to have a schematic, so we wouldn't have to do so much guessing?

I've asked Melody for a Schematic.

If you think about the tubes 1, 2 - 3, 4 and look at the pictures from the review, you can clearly see that 1,4 and 2,3 are having a similar function for each channel.  I guess the question is which sets are driving and which sets are splitting?  To a laymen like me the pic looks like 2,3 are splitting.  Lol

The other puzzle in the equation is at what voltages, a Schematic would help with that too.  In reading about the different kinds of 6SN7 tubes, it appears that different tubes are more sutable given all these variables.  Which begs the question, how do you know without the technical data about its construction?


I'm bringing it in for service in a few weeks and will ask the tech if he knows any of these answers.

Cheers,
Robert