Manley Chinook SE MK2

There are two tubes that would make a difference so far as "matching" goes. Those are the tubes that provide gain in the L and R channels, respectively. In the Steelhead these provide the "top half" of a cascode where the bottom half is probably an FET. The other two tubes are used to create an output stage that is very low in output impedance; in effect they form an unusual type of cathode follower (a stage that turns voltage into current). There is no added gain in the output stage, so the sound of tubes in a cathode follower is generally thought of as not a prominent factor in the overall presentation. I think tube matching is overrated, because tubes are aging as we use them, and no two tubes will age in exactly the same way or rate. So what "matches" today may not match tomorrow. And yet, I am guilty of perceiving that some tubes of any type sound better than other tubes of the same type. In my Steelhead, I use Siemens CCa, I think. I would not shed a tear, however, if some day I had to use some other brand.

By the way, as regards the autoformers in the Steelhead, I get the feeling that my Steelhead sounds best through its MM outputs, where there is no autoformer in the signal path. Interestingly, in the Steelhead, I have read (never tried it) that you can get up to the max 65db of phono gain via the MM outputs.  To me that suggests the autoformers are more for impedance matching to MC cartridges than for their potential to step up voltage.  Also, if you look inside, you can see that for each input R setting available via the rotary switch, there are discrete pairs of resistors whose values match the choices offered via the rotary switch. (If the autoformers were used like SUTs, you would think that the different input impedances would be mostly the product of what pair of primaries is selected.)  It's a bit of a mystery to me.  Manley are very secretive and certainly will not provide a schematic; I have asked.

By the way, as regards the autoformers in the Steelhead, I get the feeling that my Steelhead sounds best through its MM outputs, where there is no autoformer in the signal path. Interestingly, in the Steelhead, I have read (never tried it) that you can get up to the max 65db of phono gain via the MM outputs.  

This has been widely reported-that the MM input with MC often sounds best-by various reviewer and owners. I have tried it and agree. 

I did replace some of the putative MC load resistors in my Steelhead with TX2575 resistor equivalents. (TX2575 are the best most transparent phono load resistors I have ever heard and by general consensus.) That may have improved SQ in the MC circuits; I would not swear by it.

I stand by my suggestion that experiencing a Valve Exchange, could prove to be all that is necessary to discover the sonic that is more of an attraction to yourself, and even possibly an attraction that comfortably fends of other Phon' Models. I am not seeing where the method fails to be a experience that could prove to being cost effective, as a means to make a change. 

For myself to have my E88CC Phon' superseded, it took a Bespoke Built Valve Input/Valve Output design to achieve this. The E88CC is still used and has proven to be my most preferred with a Head Amp coupled to it. It is not one that is a relegated to being a 'sell on' item or to being a 'storage' item either.

The CCa referred to earlier was a Matched Pair demo'd in my DAC, but the Siemens & Halske early 60's E88CC's were the ones selected over all Tubes offered as a loan for the Tube Rolling experience.

Early 60's Mullard E88CC's were selected for the Phon' over the ones used in the DAC and all others loaned.    

Pindac, in what phono stage are you experiencing the benefits of tube rolling? The Steelhead and probably the Chinook use a hybrid cascode (FET/6922) for gain at the input. In that topology it’s not surprising that differences among 6922s would be muted if not inaudible.