Tube rolling question.

I'm lucky enough at the moment to have both solid state and valve power amps, and have been doing endless A/B comps as I wish to sell one of them.

Tranny: Pace and attack and a bit louder.
Valve: More detail, better soundstage, quieter, slightly boomy bass and they sound slightly "veiled".

If I could get round the flabby bass on the valves I'll keep them in preference to the S/S power amp.

Question: My monoblocks are using 4 x EL34 2 x 12AX7 2 x 12AU7.
To make the system slightly brighter, which tubes do a i need to swap, and can anybody make a specific reccommendations?
Amps are PrimaLuna ProLogue 6 monoblocks.
Thanks.

 

Based on the Prologue 2 I have the first tubes to play with are the 12AX7s which are apparently the phase splitters - a good cheap option are Sovtek 12AX7LPS, they hold up well to many NOS tubes in my experience, certainly much more 'full range' and punchy than the stock tubes. They take a while to break in though, give them a couple of weeks.

Tony.

 

imo "it's yer power pentodes, sir" which are probably contributing most to boomy bass (esp. if the EL 34s have a good few hours on them). I'd try Svetlanas or possibly JJ Tesla. Tubedepot have good matching service and ship to UK. you could also try www.hificollective.co.uk/valves/octal_output_valves.html or more traditionally go to www.watfordvalves.com or http://www.chelmervalve.co.uk/index.htm

 

I'd agree with Tony, and go for the 12ax7's and 12au7's for max bang for buck sonic-change.

 

Always start with the pre-tubes. For a bit brighter try some Brimars if they're around. They lifted mine quite a bit

 

Electro-Harmonix pre-tubes often have a tighter, slightly more forward sound IME. Keep away from Mullards, probably, great musicaility IMO but not for putting more 'zip' into the sound.

Pre-tubes are cheapest to replace - but power tubes (especially el34) are also worth swapping out.

 

I think that if you have 'flabby' or 'boomy' bass then tube rolling will not deliver the cure. Rolling is a useful tuning tweak but it won't overcome transformer limitations or fundamentally change the design of the amp. Transformer phase errors, saturation and distortion will not be altered by changing small signal tubes. Output impedance will also affect bass quality. All transformer coupled amps suffer these problems to greater or lesser degree so I'm not picking on your particular amp.
All of these effects are level and speaker dependent. In many systems they are not important, in others they can make the amp completely unsuitable.

 

Minority view ;-) obviously but as far as bass is concerned I've always experienced the greatest difference when power tubes are changed. As Rob says transformers are important I have these - http://www.sowter.co.uk/specs/9015.htm in my Kit88. I'm not familiar with the Prima Luna monos so don't know what they're equipped with in that dept.

 

Well I don't know anything about tube rolling but I know about Valve rolling.!!
To get the brightness get some Telefunkens or Siemens pre valves. Siemens are generally cheaper than Teles. and avoid Mullards if you want a brighter sound.

I don't know about EL34s, but I've now got Winged C Svetlana KT88s

Get them from a vintage Audio jumble for best price

 

Exactly! We don't even know what your speakers are yet. If they are not receiving enough current then bass will be under-damped, subjectively sounding like bigger bass, albeit softer and flabbier. The amps need to be properly matched to the speakers (and speakers to room) before tube rolling is even considered.

 

I agree with that too, having tried a bit of tube rolling to rid myself of woolly indistinct bass as well (unsuccessfully btw). I did manage to achieve slightly improved mids and highs (IMO) by swapping input valves though. I've now got a hybrid amp, and am very happy with the bass, and everything else for that matter .