Tube Rolling | Luxman CL-38uc

Update :
to start. I am using Legacy audio Studio HD monitors in near/midfield in a small 10’x12’ room.    
I just purchased a vintage but restored v-fet Yamaha B-2 amplifier. 
The amp is smooth yet unforgiving. But the soundstage is huge

jvc/victor QLY-77f turntable    Hana SL cartridge 

for digital just a Wiim pro and Spotify 

3 x RCA clear top 12au7 in the linestage made a big difference. 
The 1950’s RCA’s smoothed out the sound a lot.    Listening fatigue is gone  without blurring the details    I spent an evening pulling out sibilant 80’s punk records and cranked it like I was 20yrs old 

I also tried a few 12ax7 in the phono stage 

new gold lions and a pair of vintage mullard

the Mullards won out but the phono stage tubes did not make near as big of a difference to my ears.  I honestly have never been in love with this Hana cart ( I have a few others but haven’t set them up in the spare arm)

comparing the same tracks on vinyl and Spotify  

new Gold Lions were still better than digital or stock JJ 

a vintage pair of Mullard with 1 gold lion in the 3rd spot was better than all

but not a big subjective leap like the linestage tubes 

@oimuller , try the Psvane Horizon 12AU7. They are not warm though.

I ended up with Genalex Gold Lion 12AU7 for all the input tubes. Sounded the absolute best of all the ones I tried. Smooth yet detailed, superb depth and width.

I'm going to bump this thread up as I'm looking for some new tubes.  

I actually want easy on the ear & forgiving of bad recordings types 

I see a few responses here and it seems to be the biggest thread I can find on this model pre

I would stick with 12AU7.   It was voiced with those and they are easier to find  NOS .  And usually cheaper than same vintage nos 12ax7....

RCA 12au7 from the late 50's / early 60's is what I used in my last preamp and they sounded great and measured super strong .   

From the illustration and description of @acefactory above, my understanding is that tube 7 is the balanced input, but is input 1 tube 2 or tube 6?

always good to experiment - enjoy the music 

@brubin, as of now I’m not looking for anything. I got lucky to obtain a quintet of absolutely mint Amperex tubes (1965), so I’m all set, but thanks for your post, even though it’s 5 months old.

it depends what you are looking for.  I have some extra 12AU7 set,  items,  otherwise can recommend some sellers.  What are you looking for?

@brubin where do you get Mullards for $25 and TFs for $80?

For me my favorite 12AX7 has been the Telefunken Smooth Plate NOS or even the ribbed plate. For the 12AU7 I've been happy with the Telefunken ribbed plate or a Mullard NOS. 

Mullard 12au7 are great sounding smooth tubes $25 USD ea.

Telfunken ECC82 12au7 $80 each 

I removed that horrid sounding 12au7 JJ tubes, and put Genalex Gold Lions instead. Much better sound. Very smooth. The only drawback is the cost.

So does the EQ have 2 tubes, the phono stage has 3, and the line stage has 3, ecc82 tubes? 

wow this is a lot of help.   I wasn't sure about tube position either.

If anyone has done some rolling please post it up

Wonderful!! This is really helpful. Looking forward to hearing back on some rolling results. 

Thank you so much @acefactory ! you just saved me ton of time trying to figure that out! :) ... I'll report back on how the tube rolling goes, will try a set of Telefunken and Mazda tubes.

@jjss49 thanks for the picture, comments and your initial remarks regarding tube differences. You are absolutely right, better to stick with 12AU tubes in this case as intended (that's what I ended up doing).

well done @acefactory -- here is a pic to accompany your excellent description

so the tubes op wants to roll are three of the four middle ones (leaving aside the one single middle one with the white spring loaded tube damper/cage)

Hi @jfandr147 and all - I have the CL-38u and CL-38u-SE models, the tubes of which are laid out the same as in the 38uc. 

I don't know how to post an image, but I've spent some time under the hood of the 38u, traced out tube signal flows, and can describe for you the location of the tubes in question.

With the faceplate facing you, there are two rows of four tubes; a front row and a back row. For purposes of this description we'll call the back row tubes 1 through 4, from left to right. The front row holds tubes 5 through 8, from left to right. For reference, the phono tubes (with cages) are positions 3, 4, and 8. Tube positions 1 and 5 are for the EQ section. The tubes not involved in phono or EQ sections are in positions 2, 6, and 7.

I haven't done much in the way of tube rolling but can assure you with confidence the above is accurate.

I hope this helps - I'd love to hear back on any experiences with the tube rolling.

my 2 cents

i don’t have this particular luxman pre... so this is from general knowledge and a lifetime of tube rolling

12au7 and 12ax7 are usually NOT interchangeable... vastly different gain characteristics (that is why those three tube types were designed and made in the past, despite the common 12v heater dual triode small envelope designs -- 12au7 vs 12at7 vs 12ax7 - very different gain profiles from one to the other -- 1x 3x 5x gain, thus applicable for different circuits)...you can bet that putting in a 12ax7 with 5x the gain of a 12au7 in your nice luxman will create problems

you would need to contact luxman, or a knowledgeable dealer or tech to confirm specifically which three 12au7 slots are for main amplification, not tone control buffering circuitry (what is drawn on the circuit diagram is idealized, the actual circuit board may not be laid out in exactly the same fashion)... you CAN safely swap in different 12au7 tubes in those 5 positions, but without knowing for sure, you won’t be able to assess what you are hearing in the attempt to tube roll

here is a fairly complete discussion and listing of 12au7 equivalents (these are different names for the same tube, from different parts of the world, or very very similar variants made over time i.e. improved ruggedness etc etc - with identical or very similar gain profiles) - you would be well served to read it carefully and completely

http://www.audiotubes.com/12au7.htm

Hi!

Yes, those are the right tubes :) ... only 3 would be needed if you are not using phono input or tone controls.

The only caveat is that they are placed a bit differently inside on the actual unit, so a "best guess" would be needed unfortunately on picking which ones to replace. The phono input ones are clearly distinguishable, but the others not so much :(

Haven't taken the time to do that quite yet, but will try to report back when I do.

Hope that helps!

Hey, did you try rolling those tubes? I have the same amp and have been tempted to try something similar. I actually had the same questions as you regarding just changing the ones you highlighted. let me know!

You can change out the 12AU7s with another brand, and you might even be able to substitute a 12BH7a, but the 12AX7 has a lot more gain than a 12AU7 so I don't think those are interchangeable in that application. 

I changed all of the tubes.

If you are only using certain tubes and they are the only ones you hear, then it should work.

I don't know enough technical stuff to comment on your diagram, etc.

Thanks for the quick reply @jperry :)

Was wondering, did you change all tubes?

What do you think about just changing the 3x 12AU/ECC82 on the center section? (see my initial post)

Let me know,

Thanks!

I got good sound with RCA cleartops, and better sound, for a higher price with NOS Telefunken tubes in mt CL-38uC