Prima Luna Findings and Questions

[Haselsh1]

Early in 2016 I bought a secondhand Prima Luna Prologue 3 preamp with built in phono stage. I was immediately impressed by the stereo sound stage of the thing. In November 2016 I then bought a Prima Luna Dialogue Premium power amp fitted with the then standard EL34's. After a year or so I swapped over the power valves to JJ EL34 II's. This provided a much more refined sound over the stock valves.

At that time I was using B&W CM8 S2's and thought that the sound was good but then domestic things happened and I had to swap those over to Spendor S3/5R2's. Domestic things happened again and by sheer chance I stumbled upon a dealer who immediately demo'd a pair of KEF R5's when requested. I went back the next day and bought them.

Now during the period of CM8's and R5's I noticed that I couldn't get over a certain hardness to the upper mid and treble. I checked and noticed that I was using the 4 Ohm taps even though these speakers do dip down slightly below 4 Ohms so I assumed all was OK, I then though swapped onto the 8 Ohm taps to see if there was a difference. Oh my, what a difference. No trace of hardness or aggression in the sound anymore making me certain that in my case the 8 Ohm taps are superior.

I now thought 'what about triode mode' ? So of course I switched it on. Playing some vocal jazz the difference is astonishing. Incredibly 'real' and natural. So much separation between instruments. The sound is noticeably drier and tighter but way more preferable to me. So on to the question. What if I swapped the EL34's to KT120's..? Does anyone have experience of these valves in direct comparison to EL34's.

Once again I thank you in advance if you come up with advice for me.

Cheers everyone. Happy self isolating.

Oh yeah, CD source, Atlas Hyper interconnects with Tellurium Q Blue cables, single wired.

[Ali Tait]

First thought is would the amp be happy running 120’s?

[mikeyb]

There's a Facebook group that I'm a member of that might be able to help. Lots of people there have changed the power valves.

https://www.facebook.com/groups/509067122811946/

I have the Dialogue Premium HP power amp, running Primaluna EL34s and 4x JJ 12au7s with two NOS Mullard CV4122s in the middle.

I've not tried changing the power valves but have certainly been tempted, although I always fancied KT150s but too expensive to try in case I don't like them.

[mikeyb]

First thought is would the amp be happy running 120’s? Hi Ali,

Can run anything up to KT150, fully auto biasing and can even run a complete mixture of types IF you wanted to


Spec ...

Output Power:
Stereo Ultra-linear

(8 Ohms, 1% THD)70 watts x 2 (EL34)
73 watts x 2 (KT88)
85 watts x 2 (KT120)
96 watts x 2 (KT150)

Output Power:
Stereo Triode

(8 Ohms, 1% THD)40 watts x 2 (EL34)
43 watts x 2 (KT88)
45 watts x 2 (KT120)
48 watts x 2 (KT150)

[Ali Tait]

Ok fine, worth a go then I’d have thought, though it’s been my experience that front end valves generally make more of a difference than power valves.

[Haselsh1]

OK you guys thanks for the comments. I have tried KT88's and the difference was akin to changing the amp. Huge punchy, tight and fast bass but lost the EL34's gorgeous midrange. Maybe it is the old story, a few quid in the bank and no rainy day worthy of it.

[Haselsh1]

Oh yeah all of the small AX/AU valves are now either JJ or Tungsol.

[anthonyTD]

I have a customer who currently run's a primaluna with KT120's in it, and is very pleased with it, he has run it with EL34's, KT88, and KT150, but always comes back to the KT120's, i would like to add that the person in question is a concert Violinist, and has been playing from the age of 5, so should have a very good handle on how things should sound!
Hope this helps. :)
PS, don't believe the negative Bull**it out there on the KT120's, in the right amp, they can sound superb, infact; i have been running them in my own amps for around 7 years now!
A...

[Haselsh1]

Thank you Anthony.

[anthonyTD]

:)
Thank you Anthony.

[Ali Tait]

Sounds like they are worth a punt then. :-)

[mikeyb]

Just remember your cage, if you're using it won't fit over KT120s.

On that Facebook group people who use 120s and 150s use little spacers or slender bars to raise the cage a few mm.

[Haselsh1]

OK Mike. My biggest worry is that it may turn out to be a waste of 200 quid. Of course I'll never know if I don't spend it. I'm looking at buying the valves from Icon Audio as they have been amazing in the past.

[mikeyb]

OK Mike. My biggest worry is that it may turn out to be a waste of 200 quid. Of course I'll never know if I don't spend it. I'm looking at buying the valves from Icon Audio as they have been amazing in the past.That's why I've never tried them, although for me I was going to 150s which are even more expensive, however I like how it's sounds with the Primaluna EL34s that I'm in no rush to change them unless I have to, I already have a set of JJs as spares

[Ali Tait]

I have tried KT77 which I like a lot.

[Hopeful]

I may be a bit late with this but here's my two penetrative.

I had a Jadis amp that came with KT 120's and eventually used it with EL 34's.

I always found the KT120's (in the Jadis) cold and analytical the EL 34's sounded fluid and musical. During the rebiasing I took all the voltages ect and dialled in the 34's.
When I looked at the graphs for the 120's I'm surprised they even worked, anode voltage and cathode current were way too low.

So although KT120's work in a lot of amps that were originally designed for EL34 / KT 88's they are run so cold they may not sound any better than EL34, KT88 ect.

[anthonyTD]

That is a very good point Philip,
Many amps that give a choice of output valve are seriously compromised on at least one version, if not all, the only way to evaluate a paticular valve in any output stage, is to give it the correct conditions, this is where i feel a lot of the negativity come's from when folk are trying, and therefore evaluating certain types, especially the KT120.
I may be a bit late with this but here's my two penetrative.

I had a Jadis amp that came with KT 120's and eventually used it with EL 34's.

I always found the KT120's (in the Jadis) cold and analytical the EL 34's sounded fluid and musical. During the rebiasing I took all the voltages ect and dialled in the 34's.
When I looked at the graphs for the 120's I'm surprised they even worked, anode voltage and cathode current were way too low.

So although KT120's work in a lot of amps that were originally designed for EL34 / KT 88's they are run so cold they may not sound any better than EL34, KT88 ect.

[Haselsh1]

Hmm... Interesting !

My power amp as with other Prima Luna power amps has a switch on the right side for EL34 operation and a.n.other KT types. So the switch is either set for EL34 or other KT types which sounds a bit vague to me. I did try it with KT88's and they sounded good but my current EL34 II's by JJ sound excellent in all but the bass. The borrowed KT88's were I think by EH and I think were also faulty as on switch off there was a consistent crackle through the speakers resulting in me putting the original EL34's back sharpish. Everything was then OK.

I am not too sure I believe that an amp designed with EL34's in mind is totally compatible with any KT type just by flicking a switch. If all there is to it is bias then maybe yes, but I doubt it is really that simple.

[Jac Hawk]

I've been reading this thread with great interest as i've just bought a new Prima Luna Evo 400 integrated, it's not arrived yet but i was told they are well suited to the KT88 and KT120

[Haselsh1]

I've been reading this thread with great interest as i've just bought a new Prima Luna Evo 400 integrated, it's not arrived yet but i was told they are well suited to the KT88 and KT120

My own finding Mike with KT88's was that the low end was far punchier and more solid than with EL34's whose bass tends towards the classic warm and fat kind of expression.

[Jac Hawk]

Well out of the box it runs 8 EL34’s giving me 70wpc into 8 ohms so power isn’t an issue and I can imagine 8 KT88’s or 120’s isn’t going to be cheap, I think it might be something I do later on in the year

[Slawts]

Ran a VTL with EL34's for years and found them weak for my speakers. Tried Svetlanas, JJ's and Tungsols with the latter being the best and middle being worst by a margin.

Thought it was because EL34's weren't very good. Went round to a friend who has a Radford with EL34's and a Trilogy with KT88's driving Tannoys. I much preferred the EL34's!

I think it depends what speakers you are driving.

The Prima Lunas are very good and you are lucky you can try different types so I would keep on going until you are happy.

[Haselsh1]

At this moment in time I am considering Genalex Gold Lion KT88's. I have used Gold Lion valves in the past and been seriously impressed by the sound and quality of finish.

[Jac Hawk]

Like many electrical and electronic components and i imagine valves are no different, a particular model will have it's designed operating window, so matching valves so they are as similar as possible is important, in my case i'll have 4 EL34's per chanel so when i come to try experimenting i'll need 8 valves that all perform similarly to get the best out of them and the amp, or am i just talking crap?

[Hopeful]

Like many electrical and electronic components and i imagine valves are no different, a particular model will have it's designed operating window, so matching valves so they are as similar as possible is important, in my case i'll have 4 EL34's per chanel so when i come to try experimenting i'll need 8 valves that all perform similarly to get the best out of them and the amp, or am i just talking crap?

That’s where biasing comes in, matching the current draw of each valve. If your amp is auto bias it is recommended to start with reasonably matched valves.
You get more leeway with manually biased amps.

[Haselsh1]

Prima Luna claim that their amps use adaptive auto bias so there is no need to match any valves. They also claim that their amps work perfectly with a whole host of KT/6550/EL34 and others. Jack of all trades, master of none..? I don't have the knowledge to answer that one.

[mikeyb]

Prima Luna claim that their amps use adaptive auto bias so there is no need to match any valves. They also claim that their amps work perfectly with a whole host of KT/6550/EL34 and others. Jack of all trades, master of none..? I don't have the knowledge to answer that one.Upscale Audio on YouTube [emoji6]

[southall-1998_mk2]

That Kevin from Upscale Audio is nothing, but a charming sales man. Never trust them.

S.

[anthonyTD]

Tend to agree, Unfortunetly, like many people in this industry, Kevin will seemingly promote what he has, when he has it, hence my earliar quote concerning the KT120/150, nothing wrong with being a salesman, as long as you can do it with honesty, and integrity.
That Kevin from Upscale Audio is nothing, but a charming sales man. Never trust them.

S.

[Haselsh1]

Prima Luna claim that their amps use adaptive auto bias so there is no need to match any valves. They also claim that their amps work perfectly with a whole host of KT/6550/EL34 and others. Jack of all trades, master of none..? I don't have the knowledge to answer that one.

The info in the quote was from Prima Luna as stated on the tech sheet when I bought the amp. The preamp I bought secondhand so I had no spec sheet with that one.

[Jac Hawk]

Now i'm no expert on tube amps but in the videos Kevin does say the reason apart from the adaptive biasing why Prima Lunas can work with a range of tubes is that they run at a lower voltage than others, like i said i'm no expert and their amps do sound nice.

[Elephantears]

I've tried many different power and input valves with the Dialogue Premium, so happy to answer detailed questions but first, just one or two brief comments. First, every time you change power valve type, you need to try 4 and 8 Ohm taps again. With my speaker, EL34s only really worked on the 4 Ohm tap. KT120s work best on the 8 Ohm tap, and KT88 is a tricky decision between them. Gold Lion KT88 are probably the best compromise between grip and mid-range richness. However I did borrow some KT77s recently and on a very brief listen I was very impressed. KT120s do have the most grip and extension, but I think the mid-range performance will be a bit speaker dependent. They are excellent, but can be liable to a little upper mid-range hardness in the wrong context.

[mikeyb]

There is also a switch on the later PL amps to tell it which valve you're using [emoji6]