[Diamond Dog]

Let the games begin! I've just done the first tube roll on my Manley 300B preamp and I must say the outcome was startling. The first swap was to yank the OE Sovtek 5AR4's and replace them with current production Shuguangs. I wouldn't imagine this would have had much impact on the sound but they certainly give off a lovely glow and I worry a little less about these than those Sovteks.

Next, on the advise of Chris at PartsConnexion, I replaced the OE Sovtek 6SL7GT's with a matched pair of NOS JAN RCA 5691 Red Specials...SHAZAAM !!!! Everything I love about this preamp just got super-sized! Better detail and definition, tighter bottom end, bigger soundstage, more overall impact. Can't wait to see how these sound with some time on them... I don't know a lot about the 5691's other than the fact that they are a military-spec version of the 6SL7GT and are rated for a very long 10000 hour service life. Can anyone tell me more about them? One thing's certain - they sound mighty fine!

I'm gonna let these work their magic for a while before I do my next roll- I'm looking at you, EH 300B Gold Grids. Get ready to hit the showers 'cuz the A-team is gettin' ready to take the field...More to follow.

D.D.

[Berndt]

While I don't have a manley piece, I have noticed a rectifier swapping to be very productive in my amps, Phono stage, and line stage.
My Phono stage uses 6sl7's and I never found the Gucci red base rcas.
I am using both the blackburn mullard 6sl7 and the Russian metal base 6sl7 equivalent. The Russian tube is more forward without being bright, and is still available relatively cheaply.

[Diamond Dog]

While I don't have a manley piece, I have noticed a rectifier swapping to be very productive in my amps, Phono stage, and line stage.
My Phono stage uses 6sl7's and I never found the Gucci red base rcas.
I am using both the blackburn mullard 6sl7 and the Russian metal base 6sl7 equivalent. The Russian tube is more forward without being bright, and is still available relatively cheaply.

Hi : Interesting comment about the rectifier swap. I spoke with Paul Fargo at Manley about the effect of rolling different  tubes on this unit and he felt that the money should go to the 300B's and the 6SL7GT's because his opinion was that changing out the rectifiers and 0D3 regulators wouldn't have much effect. I'm gonna have to try re-installing the OE 5AR4's and see how much of the improvement might actually be coming from rolling the rectifiers. I never gave in to the urge to tube-roll on my last Manley preamp ( Jumbo Shrimp ) but I sure like what I'm hearing right now.

D.D.

[Diamond Dog]

Put the original Sovtek 5AR4's and 6SL7GT's back in and after a listening session, replaced the 5AR4's with the Shuguangs. Another listening session ( same material ), then replaced the 6SL7GT's with the 5691's...Oh yeah, that's the stuff ! Little discernable difference between the two different 5AR4's sonically ( in this unit at least ) but those 5691's are a big and positive change across the board.

More to come.

D.D