PrimaLuna Prologue Two tubes upgrade

Hi,

I am wondering to upgrade my PrimaLuna Prologue Two's stock tubes. They seem to be cheap chinese (don't be surprised, the amp is assembled in china) ones. The amp utilises 4xKT88, 2x12AX7 and 2x12AU7.
I am looking for especially a better bass-response. Could you please advice some tube brands? Somebody said to me Electro Harmonix.

Thank you

Enjoy music

 

I've got a PL2 myself. My feelings are the supplied KT88s are not bad at all though the smaller tubes are far less good. The first to ditch are the 12AX7s, and surprisingly the best I've found to date despite working through many NOS tubes is the Sovtek 12AX7LPS. Make sure you get the LPS as it's a whole other thing to the other Sovteks, it's very 'full range' with really deep tight bass once it's run in. I've compared it to GE, yellow-shield Mullard, Brimar, Mazda and several modern tubes and whilst the Mullards are beautiful at the top nothing touches the LPS at the bottom. I'm using a selected cryo'd pair.

The 12AU7 changes the sound a lot too, I'm currently using a pair of 60s RCAs with grey long-plates which are again full-range, clear and tight. Mullards are nice hear too and Brimars a good cheap alternate NOS.

I've not played round with KT88s at all, I'm running my amp with EL34s at present, the Groove Tube E34LS which is a great sounding tube based on a Mullard design. I prefer them to Svetlana Winged 'C' EL34s, they are tighter and more detailed, but not quite as grippy or forward as the supplied KT88s, I prefer their mid though.

Tony.

 

Hi!

Thank you for your advice.
I have Sovtek 12AX7EHs at the moment, how good or bad are they? What does this mean: "I'm using a selected cryo'd pair." The 12AX7EHs must be matched pairs?

Thanks again

 

The 12AX7LPS is a completely different tube, the LP stands for 'long plate' and the 'S' refers to a spiral filament, i.e. the tube is of a different physical construction to the EH. I don't know why but the PL seems to really like tubes with long plates!

I'm using a pair of Black Sable cryogenically treated 12AX7LPS, details here. I'm not sure how much difference, if any, this makes, but I can vouch that they are a damn good tube and marginally better than a stock pair I've got as well, though they are different ages so how much is down to the selection / treatment and how much is other factors is anyone's guess. I suspect you will be surprised how much the bass definition and articulation improves. The 112AX7 is in a critical position in the PL as it's the phase splitter, i.e. it's the tube that splits the signal +/- to feed the two output tubes. It's the tube that makes the most difference to the sound of the amp IME.

Tony.

 

I actually have the Prologue One. This amp has 2x12AX7's, 2x12AU7's and the only difference is that it comes with 4xEL34's.
I treid the Winged 'C' EL34's and the 6CA7's but then tried the 7581A's. To my ears a huge improvement. Don't know if you can use these in your amp. If unsure Herman at Primaluna will advise you.
12AX7? I use Tungsol after trying JJ Tesla's. Tightened things up considerably. 12AU7's? Tried Tungsol but prefer Radiotechique (French Philips).

 

Oops. Forgot to mention if you can use 7581A's you MUST go for the Phillips. World class valve. Hard to get but I have a source. If you fancy them pm me and I will give you the number.

 

I am wondering to get these:

http://cgi.ebay.com/12AX7LPS-Sovtek...intage_Electronics_R2?_trksid=p3286.m20.l1116

and

http://cgi.ebay.com/12AU7-ECC82-JJ-...hZ018QQcategoryZ64629QQtcZphotoQQcmdZViewItem

Could you please comment those tubes Tony?
What do you think Tony what is a good choice for a pair of 12AU7 from Tubedepot?

Thank you

 

When you have done with the smaller tubes (enormous fun and reward can be had) the KT88's are worth playing with.

I've got 6SN7's in my amp so can't help you with the 12's.

I've had three different sets of KT88's.
1. Svetlana's - good all round sounding tubes - meaty sounding but well balanced. Quite aggressive on power. We had to add an extra PSU (one per each channel of two KT88's as a single PSU kept failing). Once that was done all was well but they never balanced up and stayed put as nicely as the others I've tried.
2. Tesla's - Bit drier sounding than the Svets. Would suit over warm sounding systems. My amp is not a warm cuddly valve amp BTW. Easier on power requirements.
3. Electro Harmonix's - I've only tried the non cryo (does -300deg F for 24hrs make a huge difference?). These are more emotional sounding and somehow deeper than the others I've tried. Not deeper as in bass (they do that very well and nicely controlled) but more depth of sound, timbre or whatever words...
They do everything well in my amp. Quite a bargain - I got a matched set of 4 from an Ebay dealer. Plugged straight in hardly needed any balancing changes from the Tesla's.

Both the Tesla's and the Electro's hardly drift out of balance at all. I check em once ever 6 months and there's a few mV in it.

The be all and end all are supposed to be GEC KT88's. At about as much each as a Quad of the others I have not gone for these yet...

The splitters and drivers can shape the sound. My 6SN7 experience is you can have warmer bassy (Kenrad), Pacey Sylvainia brown base, fairly dull GEC's, Exciting Sylvania white labels, fairly balanced Sylvania Greens. Great midrange from the NU's. Never got a quad of top flight Tung Sol's (the ordinary ones are just that, ordinary IMO!).
Good NOS stock or nearly all of the used tubes I've bought off ebay are not microphonic at all and all work well. Buying and selling tubes is fun.
I have cheap Chinese tubes in a headphone amp and boy do they ring...

So tube rolling is def worth it and fun. If you change your speakers or room you can tailor/optimise the sound to suit.

Let us know how you get on.

 

The cryo'd Sovtek 12AX7s look like a really good deal, though I'd go NOS for the 12AU7s. Tubestore have quite a few RCAs, the cleartop is meant to be a stunner. I'd also recommend the Brimar ECC82 (12AU7) from Tube-Shop, I'd be very surprised if there was a current production tube that will beat a pair of these and they are only £12.50 each. I've also got a pair of the Brimar E83CCs (12AX7) listed on that site, they are good, but I still prefer the Sovtek LPS to them.

Tony.

 

Some closer to home http://www.watfordvalves.com/product_detail.asp?id=1724

 

You could also have a chat with Ian Large at Alium Audio. Really nice guy. I have had some excellent results with the new Tung-Sol valves. Power and signal valves but not any of the ones you need.

I tried comparing an old Tung-sol 6sn7 to the modern(much better than the old IMHO). I also use 5881 new Tung-Sol valves very good and much better than any el34's i have tried.

Regards D Louth