[Massimoo]

Hi everyone,

Following my introduction, I’d love to get your advice on optimizing tube combinations for my VTL IT-85 MK2

My goal is to match or even surpass the sonic qualities of my Pass Labs INT-60 (other amplifier)— especially in terms of soundstage depth, resolution, and overall realism — while maintaining that magical tube midrange.

I currently have the following tubes on hand:

12AT7 variants: Mullard M8162 CV4024, JJ ECC81
12AU7 variants: Mullard ECC82 (Parasol getter), JJ ECC82
Power tubes: Genelex Gold Lion KT77 (current stock), and vintage Phillips XF2 EL34
I’d appreciate any input on:

Best tube combination for imaging, depth, and holography
Tube choices that bring out tighter bass and dynamic grip
Any recommendations for alternative NOS or current production tubes to explore
I know synergy matters a lot, so I’m happy to share more about the rest of my system if needed.

Thanks in advance for your suggestions!

System Overview: Blumenhofer FS2 MK2 speakers, Pass Labs INT-60, VTL IT-85 MK2, Holo Audio May KTE DAC, Transrotor Zet1 turntable with Hana ML.
Supporting Gear: Magna Mano Ultra 3.5 streamer, Primare R35 phono stage, Furutech DPS 4.1 cables, SR PowerCell 8, IsoAcoustics Gaia II, and SR Master/Purple fuses.

Best,
Massimoo

[Tyson]

Oh, I might own a few tubes, so I might be able to help . These are the 12at7's I have:

Amperex 12AT7
International Servicemaster 12AT7 (E180CC/7062)
JJ 12AT7 (ECC81)
Mullard 12AT7 (CV4024)
Penta Labs 12AT7
Philips (Beckman) 12AT7 (7062)
Philips JAN 12AT7 WC
Philips Miniwatt (Dario) 12AT7WA
RCA 12AT7
Siemens 12AT7 (ECC81)
Sylvania 12AT7 (5965)
Telefunken 12AT7 (ECC81)

The Telefunken's and the Amperex's are the best, IMO.

Here are the 12AU7's I have:

Amperex 12AU7 Orange Globe
Amperex 12AU7 Bugle Boy
Electro Harmonix 12AU7
JJ Electronics ECC82 (12AU7)
Psvane 12AU7-S
Raytheon 12AU7 Black Plates
RCA 12AU7
Siemens 12AU7 (E82CC)
Sylvania (Baldwin) 121AU7
Sylvania 6350 (12AU7)
Toshiba (Baldwin) 12AU7
Tung Sol 12au7 Black Glass
Westinghouse 12AU7 Black Plates

The Bugle Boy's and the Tung Sol's are the best of this group, IMO.

For power tubes, I have:

Philips 6L6GC (7581A)
RCA 6L6GA(2)
Russian 6N3C-E (6P3S-E)

Electro Harmonix EL34
GE (Amperex Bugle Boy Holland) EL34 DD getter
Mullard (Amperex & Philips labels) EL34 xf4
Mullard new production EL34
Psvane EL34PH metal base
Svetlana EL34

Black Treasure 6CA7
Psvane 6CA7 grey glass
Shuguang WE6CA7 Plus

Gold Lion KT77 (2) 

Gold Lion KT66
Shuguang Black Treasure KT66

Gold Lion KT88
Penta Labs KT88-SC
Psvane KT88 grey glass
Shuguang Black Treasure KT88
Shuguang Nature Sound KT88-T
Sovtek KT88

Svetlana Winged C 6550
Tung Sol (Sylvania) 6550

Tung Sol KT150

IMO the KT77's are the worst sounding power tube I have, it's very easy to do better than the KT77.  In fact Shuguang KT66's are my favorite tubes.  After that EL34's made in Holland.  And then the NOS Tung Sol 6550's. 

[Massimoo]

@tyson, thanks a million for the answer.. i'm doubting the split phase tubes in this set up is a weak point,, not sure though.. do you think adding amperex bugleboy too the XF2 (phillips EL34) combined + the Mullard M8162 will improve the qualities of this amp ?

To be honest, I gave up on my VTL after just one month of use (it was bought new from a dealer last october). I had high hopes and even invested in quality NOS tubes from a reputable seller in the Netherlands. But in my system, the sound lacked some essential qualities — especially in the bass and lower midrange, where it felt like a few layers were simply missing.

When I switch back to my Pass Labs INT-60, the difference is striking: more layering, depth, and realism across the board. With the VTL, I also struggled with fatiguing highs, especially from horn-loaded tracks — at times even "screechy." The Pass, in contrast, brings musical coherence and a more relaxed, natural presentation.

That said, my goal isn’t to sell the VTL — I genuinely want to improve it. I’m wondering whether, with the right combination of tubes, fuses, and perhaps cabling, this amp could match or even surpass the performance of the Pass Labs in my system.

[Markwatkiss]

What’s that expression ? You can put lipstick on a pig but it’s still a pig.

[Massimoo]

Hi Markwatkiss.. this is fair enough.. alot of trial and error (and money) in this hobby.
Just wanted the confirmation to understand the real limitations (is it me or the gear), then can make a decision accordingly.

Rgds, Massimoo

[JakeJ]

<Snip>
Just wanted the confirmation to understand the real limitations (is it me or the gear), then can make a decision accordingly.

Rgds, Massimoo

Both! 

[SteveFord]

I have the ST-85 so the basic sound should by similar.

Try Electro-Harmonix 6CA7 EH power tubes (the fat ones), Sylvania for the little guys.

I like Kimber 12TC for the speaker cables.

[rotarius]

I have tube and SS amps, enjoy both, but your tube amp will not have the bass quality of a good SS amp, particularly an El34 based amp.  But you can try JJ 6ca7 if you want more bass heft and perhaps the EH 6ca7 for a more "solid state" sound.

[Massimoo]

that should be fun to try different tube class. I understand that the amp will accept El34 / K77... is it ok to use the 6CA7 as well ?

[Tyson]

Yes should be fine with other pentodes.  IME the KT66 is the best tube.

[rotarius]

Yes 6CA7 is in the same family, no issues there.  The KT66 is not, it is a 6L6 sub and unless VTL manual says it can take it, don't use that one!

[SteveFord]

I don't know what the preamp section is like in the integrated model, I'm using a Conrad-johnson preamp with my little VTL.
It's a good match.
To give credit where credit is due, the EH recommendation came from AVNerdguy, he knows his stuff.