Are MULLARD NOS EL34s and LTA ZOTL40 REF worth the price of admission?

I'm considering giving an older Linear Tube Audio (LTA) ZOTL40 Ref amp an audition.  LTA has a factory upgrade that includes upgrading to Mullard NOS EL34s for $800 (or less with additional discounts).  I am wondering if quad set of old-stock Mullard EL34s are worth the $800 price of admission?  I don't pretend to know what anyone else's budget is but $800 for quad EL34s seems like a lot.  If I'm paying the premium, it better be across the board and not just improvements on chamber music or obscure Chinese opera (no offense intended).  Does anyone have experience with either NOS Mullard tubes or LTA ZOTL40 Ref amp?  If so, please chime in.  Thanks.
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s_k_77, appreciate you sharing your experience with the LTA ZOTL40 Reference with NOS Mullard tubes.

" If you are looking to replace EL34 tubes, Mullard EL34 and TungSol EL34B are the go-to tubes. They are step up from the OEM tubes shipped with the amp, and will provide great tone.",and%20will%20provide%20great%20tone.

My experience, I agree, new production, not pricey NOS.

In 1973 I inherited mono blocks made in 1958 with used but tested good original Mullard EL37’s in it (not EL34's), and a spare set of vintage Mullard EL37’s my uncle had ready to go,

I have bought new/collected old tubes for years, thus tried a variety of substitutes in those amps.

I also have used Fisher 500C and 800C receivers with various brands of 7591’s. There are differences, slight, and I have found, after research, the general descriptions of differences, i.e. more mids, firmer bass ... are correct.

I bought a Cayin amp, came with good 6550’s, sounded great, but, how would KT88"s sound in it? Bought the KT88’s, convinced myself I hear the expected slightly tighter bass. It could have gone the other way, came with KT88’s, try 6550’s, oh boy, those slightly better mids, .... i.e. how much do we convince ourselves?

OTOH, I have tried and hated a variety of 6sn7 tubes, clear differences, make sure your seller will allow returns after break in, like my favorite source

I think the ZOTLs need EL34 family tubes only. There's a review where they preferred new Genelex KT77.

I can’t say how NOS Mullard el34’s will sound in an LTA amp but I assure that xf2 NOS Mullards (both single and double getters) and the unicorn xf1’s are so much better than anything made today that the difference wont be subtle. $800 for a NOS quad is actually pretty fair. i wouldnt sell my xf2’s for $800.
You should call Andy at Vintage Tube Services. He'll help you figure tube related things out.
True did you convince yourself.Thats the thing with tube swapping your trying to find Oz...or Heaven.But it gives you something to do.

Have you priced out what a matched quad of NOS would cost if you bought them separately?

What kind of warranty on tubes do you get from LTA?

It's your money to spend as you like of course.I have found that I prefer new production power tubes and flavoring the presentation with small signal tubes.I can easily replace the np tubes every couple of years without going bankrupt:-)
It is worth it. I love the XF2 Mullard EL34’s and will never part with them. I also have an older ZOTL40 and have taken it in to to get the  latest mods. Check with Mark but I think for the price you will be getting more than just excellent tubes. They now have different/better resistors and Mundorf caps. The improvements from my original ZOTL40, and I do have one of the first ones, is tremendous.
IMO with my ears, no.
I bought new Chinese EL34s from a local tube matcher in Cleveland and they sound wonderfull in my RAM-9mkii.  I would just start with matched new production Chinese EL34's and see how they sound.  About 160 to 200 for the octet.  I can give you the contact info on my guy in Cleveland if you want.
Amps depend on the tubes. Tubes depend on the amp. Both depend on the system and the CBLF.

Only your hairdresser knows for sure.
I have the Linear Tube Audio Z10 and all I will say is that you should try it and prepare to be amazed. Never heard another amp play music with such clarity and power that is far beyond what the watts would suggest. It’s less Tubey by far than my Primaluna was, but the trade offs i made for the Primaluna are gone. 40 watts on the Primaluna couldn’t match the 10 coming out of this. Just try it and find out. 

So, not sure if this is of any use, but thought I would share my experience with EL34's.

Gone through a pile of them over the past 25 or so years with my amp. EH, JJ's, Psvane Phillips Replica's, Winged-C's Gold Lion KT77's (currently in amp) and some others that I don't remember??? 

Never spent the $$'s on NOS Mullards, was more than I wanted to dish out, and passed on the new production ones. However, that doesn't mean I'm not curious as hell to hear them in my amp...

The Psvanes, quite lovely sounding (open, nice extension), but my amp burned through them- two sets of quads in 18 months? Prior to those, I ran the Winged-C's for years with no problems and they sounded to me as I felt EL34's should sound. Warm, nice mids and tight bass. Would get again, but they have become a bit pricey. The KT77's rival the Psvanes as far as transparency and extension goes at half the price. 

Then there are these...

The nice thing about LTA is that, in that amp, those tubes should last you a life time... I have the ZOTL10 not the 40, but upgraded to vintage 6085s and 7062 in place of the 12AU & AT Xs in the line stage (from the two suppliers mentioned above, in fact--I second their recommendation): wonderful improvement that I do not regret paying for--about half what you would pay. It's a terrific amp either way: I simply wanted to give it the best.
I have used the Genalex Gold Lion KT-77 and thought that they were better than most all EL-34s
the mullard issues do not resemble the old stock ones in sound... whether the SQ difference is worth the extra cost is a function of one's wallet and system

but be sure, the difference is undeniably there
I agree with edi retro.
I bought a octet of NOS Mullard EL34 XF2s from Andy at Vintage Tube Services and I couldn't be happier. He is a wealth of knowledge when it comes to tubes and is glad to share his experience.

I agree with edi retro.
I bought a octet of NOS Mullard EL34 XF2s from Andy at Vintage Tube Services and I couldn't be happier. He is a wealth of knowledge when it comes to tubes and is glad to share his experience.

I just bought the LTA z40 integrated with the NOS Mullard EF2 tubes. Will let you know my impressions shortly.  
a LTA is on my wishlist.  Great to see the discussion. I'm excited to hear how it goes!
Appreciate all the responses and recommendations. I will contact Andy at Vintage Tube Services to get his perspective on the matter.
Sometimes you have to adjust the bias to work with the new tubes.  That makes them sound as close to NOS tubes without the high prices.  Changing a cap or two can even take you past the NOS tube sound.

I bought the LTA Reference 40 earlier this year.  It came with the NOS Mullards.  It is the finest amp I've heard.  A true giant killer.  It is just stunning.  As for the tubes there isn't a current production tube that can compare with the NOS Mullard EL34, which is one of the finest sounding audio power tubes to be produced.  Those, combined with that David Berning circuit in the LTA, is just a match made in heaven.
@ ghasley &  jjss49 

@ OP
Have accumulated > 80 NOS EL34s over time, ever since my first tube amps ( back in the day, Marantz 2s), Mullards, Philips & Telefunkens. For beauty of tone I go with the Mullards especially the earlier 6 much more expensive Xf1 series. The winged Telefunkens being more neutral and extended with tighter bass are great also but missing those meaty mids. Philips appeares to me somewhere in between.

If $ 800 seems too steep look into NOS Ultron brand EL34s, made in East Germany in the late 70´s/early 80´s and considerably cheaper.

I have NOS Mullard EL34’s and a quad of Sophia Electric EL34ST. The Sophia’s are as close to Mullard EL34 as you can get which makes them the best new production EL34 tubes made but they are expensive.

For you guys that have a new Z10 or ZOTL40, give those caps some time to break-in properly. It gets better.
Andy is fantastic and has the real deal test equipment ;-) an alternate for new and equally of better computer matching is RAM tubes. Roger ( RIP ) a true genius. I run an octet of his matched EL-34 in his RM9 amplifier....awesome sound.

You can pick up the amp used. There is one on USAudio Mart now. 

I bought mine used at a pretty decent discount. I'm seeing that the resale price of the LTA integrated amps is not that great probably because the company isn't know well. I can also tell you that I love my amp. I did replace all of the tubes to get the sound I wanted but now its audio nirvana for me. 

i concur these are outstanding amplifiers, unique in how they present the music, a precise yet very beautiful sound, certainly not your granddaddy’s rose colored, rolled off, smoothed over tubey sound

but at over 8 grand new, 5-6 grand 2nd hand, there are a lot of options out there, many of which have more impressive published power figures

i, like most owners of these big zotl’s love em, hang on to them, they need to be heard to be appreciated, and then they become beloved (of course, as always speaker matching is important to get right)

pre and post covid, these zotl reference amps have driven speakers in some of the nicest sounding rooms at a number of hifi shows

I bit the bullet by recently replacing the tubes in my REGA ISIS VALVE cdp/DAC with NOS MULLARDs.

Were they better ? Yes. No surprise here.

Were they worth it ?
(1) That is a personal value judgement, because they are comparatively expensive. (2) In short …. “YES” for me, because it’s for a $13,000+ unit wherein

(a) the added outlay for NOS MULLARDs is a very modest percentage of the sum total , and

(b) the added performance improvement quotient in a highend unit actually capable of the added resolution in NOS MULLARDs is clear and unambiguous.

Would I spend the cash for NOS MULLARDs on a modestly built and modestly priced unit? No…it’s a very risky poker shoot at best for units in this pricepoint strata , and a highly likely disappointing outcome in a common sense approach for failures …for the same reasons highlighted above. They alone won’t be a silver bullet fix providing a Jesus moment here.


I have to mention that the latest (+) plus mods are a very big improvement in sound. If you have an older ZOTL40 the cost of the plus mods are well worth the price and the bump is bigger than that of pricey NOS tubes.