PrimaLuna Dialogue Seven Tube Amp Review

[MacCali]

Isn’t this amp and pre amp that Kevin from Upscale audio always talks about and says they are highly sought legacy products that have increased in value and are more of an investment rather than a purchase

Also, maybe wrong here but isn’t he vested in that company or something. The way they push those amps on their channel is highly nauseating

 

[Mart68]

Art Dudley, RIP, was a great writer and for all I know, a good person. There was, however, an inverse relationship between measurements and his recommendations. In most cases, the worse something measured the more Art liked it. (I used to subscribe to Stereophile.)

His reviews almost always baffled me.

I have been subjected to one of these things and I can confirm there are no redeeming features like the warmth and the liquid midrange. Just awful, coarse, grungy sound and weird bass. If you need a new amp buy a class D and move on with your life.

 

[Hipster Doofus]

My primaluna was great in the winter and unbearable in summer. All because of the heat. Mood lighting was also a highlight. You could use it to weigh down a body, but it would probably be your own body as it is so heavy it may kill you trying to move it.
ps primaluna for sale .buyer must pick up (not an ad, just a joke)

Here in the Great Pacific Northwest the term is boat anchor.

 

[mhardy6647]

Isn’t that radioactive?

You know -- I don't know, so I'll have to google! There's certainly a radioactive thorium isotope [EDIT: several!], but I don't think that regular old out-of-the-ground thorium is terribly "hot" (i.e., in the sense of specific activity).

Thorium - Wikipedia

en.wikipedia.org

Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90...
All known thorium isotopes are unstable. The most stable isotope, 232Th, has a half-life of 14.05 billion years, or about the age of the universe...

huh. Thoriated tungsten in TIG welding rods... who knew?

Estimated radiation doses from thorium and daughters contained in thoriated welding electrodes (Technical Report) | OSTI.GOV

The U.S. Department of Energy's Office of Scientific and Technical Information

www.osti.gov

Sort of like uranium glass, which was also found in some vacuum tubes, although generally not in consumer radio/tv/hifi tubes.

Uranium glass in vacuum tube

("translated" Japanese site link - sorry!)

Of course out of the ground uranium isn't terribly "hot", either.

Uranium - Wikipedia

en.wikipedia.org

Uranium is a chemical element with symbol U and atomic number 92... Uranium radioactively decays by emitting an alpha particle. The half-life of this decay varies between 159,200 and 4.5 billion years for different isotopes, making them useful for dating the age of the Earth. The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99% of uranium on Earth) and uranium-235 (which has 143 neutrons). Uranium has the highest atomic weight of the primordially occurring elements...
Uranium is a silvery white, weakly radioactive metal...

Wiki-p wouldn't steer me wrong, would it?

 

[fpitas]

There does not exist one single technical reason to use tube power amps nowadays. They are poor in distortion, poor in S/N, poor in output impedance, thus sensitive to load complex impedance characteristics. Their value is only for vintage gear collectors, it is like to drive BMW 327 today, in contemporary traffic.

Agreed, but the emotional appeal to some people seems to trump any technical deficiencies. My gripe is that modern tube amps seem to be incompetently designed. They did better in the 50s.

 

[mhardy6647]

The late Art Dudley and I had pretty similar taste in sound for reproduced music, it appears. He's one of the hifi writers I wish I could've met and chatted with.
Sorry, ASR-ers!

Oh. the other thing about thoriated tungsten filaments...

source: https://audioxpress.com/article/reducing-filamentary-triode-amp-distortion

we're in light bulb territory with a white-hot filament (cathode)!

With apologies to Timbuk 3:

The cathode's so bright, I gotta wear shades

 

[fpitas]

thoriated tungsten filament

When you just have to push some electrons!

 

[DanielT]

The distortion is not drowned in that of the speakers, it is added to that of the speakers... which is always there because it is intrinsic to them.

When comparing two amplifiers, one of which has high distortion in the mid-high range, it is not at all impossible to hear it compared to the amplifier "without" without distortion...
(An analogy: if you use a scale that is unusable to weigh weights less than 2 kilograms, they will nevertheless indicate weights of 101.5 kilograms...)

In the same way, the linearity defect of an amplifier can be heard even if it is of the order of 0.2 dB... whereas the speaker has an in situ response curve which varies from + or - 5 or 6 dB... but only in comparison with an amp which would not have this defect... Because in abstracto it will not be heard.

A friend has a pair of Revel Salon powered by two 1500 watt Pascal mono blocks reputed to have a treble response varying with the speaker load... Perhaps compared to a Purifi we would hear something at the top of the spectrum, but listened to alone they deliver, connected to these Revels, a listening experience of breathtaking beauty...

It was wrongly expressed by me. Yes, it is added, but given the conditions in my fictitious example, I still maintain that you cannot hear any difference, as long as everything else is equal between the amplifiers. But of course, different load dependent amps, different FR between the amplifiers, different power levels and also speakers with lower distortion then it becomes another matter.
How much difference is needed between the amplifiers for it to be audible is another matter. Probably depends a lot on how good you are at detecting distortion.

How do you sum up distortion in the sound chain?

That's the question. Anyone have the answer? It's not as simple as just a plus, is it? For example 0,03% + 0,3% = 0,33%? Edit: After a bit of googling that it seems to be about some kind of Root Mean Square calculation ..Or...

audiosciencereview.com

 

[fpitas]

I still maintain that you cannot hear any difference, as long as everything else is equal between the amplifiers

That might be true on most music. Of course, now I have to ask why then you would burden yourself with a tube amp.

 

[DanielT]

That might be true on most music. Of course, now I have to ask why then you would burden yourself with a tube amp.

I'm not a tube dude. It was just a fictional scenario I sketched.

Good that you mentioned the fact that the music material also plays a role in a detection test, that is.

 

[fpitas]

I'm not a tube dude. It was just a fictional scenario I sketched.

Good that you mentioned the fact that the music material also plays a role in a detection test, that is.

Yes, I think on complex music you'll be able to distinguish the intermod.

 

[pma]

My professional guess is that the parameters of this amp under test are so bad that it is possible to distinguish it in a DBT from a competently designed solid state amplifier. May depend on speaker used, of course,

 

[AudioSceptic]

This is a review, listening test and detailed measurements of the PriamLUna Dialogue Seven tube monoblock power amplifier. It is on kind loan from a member and cost $2,747 when it came out in late 2000s.
View attachment 309754
Fit and finish seems excellent. My back unfortunately is not so situated and burdened under the load of 64 pounds that this amp weighs! Back panel shows high quality binding posts with a choice of impedance taps as is typical of tube amps with output transformers:
View attachment 309756

The amp has two modes of operation: Ultralinear (default) and Triode. Sadly the only way to select Triode mode is with the remote. You would think a hard button would also be provided. Since I didn't have the remote (and I didn't see a point anyway), I only tested the unit in its Ultralinear mode. Here are the specs and how that mode impacts the amp:

​

utput Power: Ultra-linear	70 watts x 2
Output Power: Triode	40 watts x 2
Inputs	1 each RCA
Outputs	2, 4, & 8 Ohm speaker taps
Freq. Response (+/- 3dB)	10Hz-100kHz
THD	< 0.25% @ 1 watt 2% at full power

S/N Ratio	84 dB
Input Sensitivity	1.1V
Power Consumption	232 watts (per amp)
Standard Tube Complement (per amp)	2 - 12AX7 2 - 12AU7 4 - KT88
Dimensions (WxHxD) (per amp)	15.2" x 8.3 " x 16"
Weight (per amp)	63.8 lbs

The unit has auto-bias and softstart which is nice.

Note: the amp has aftermarket 12AX7/12AU7 tubes. KT88s are PrimaLuna branded.

If you are not familiar with the tests that are about to follow, please watch my video on understanding amplifier measurements.

PrimaLUna Dialogue Seven Amplifier Measurements
I used the 4 ohm tap and ran our usual dashboard of 1 kHz at 5 watts:
View attachment 309757
There are ton of mains/power supply spurious tones which I could not at all impact with various grounding indicating that they are internally generated. They don't impact SINAD though as that is dominated by the sum of distortion products that have equal amounts of 2nd and 3rd harmonic plus higher ones mixed in for good measure. Notice the dual tones around our main 1 kHz tone due to power supply modulating it, i.e. kind of like digital jitter.

While not the worse we have measured, the Seven nevertheless lands in our "red" zone:
View attachment 309758

Noise performance is poor, likely due to power supply noise:
View attachment 309759
This is a problem as people tend to use sensitive speakers with tube amps so you want a low noise floor.

Multitone is disasterous showing rising distortion in low frequencies in addition to general intermodulation distortion:
View attachment 309760

As a result, 19+20 kHz doesn't look quite as bad:
View attachment 309761

Anyone thinking they are hearing more detail in music is going against the data here. And keep in mind that we are measuring the amplifier at just 5 watts.

Frequency response is highly tap sensitive and at a any rate, high enough to change the response (tonality) of any speaker you connect to it:

View attachment 309762

We see the typical gradual rise in distortion in power sweeps:
View attachment 309763

Distortion is so high that if we only allow 1% of it, the measured power goes way down, not up:
View attachment 309764

Here is the power with 8 ohm load (and tap):
View attachment 309765

I usually measure pop noise when the power on/off exceeds 1 millivolt. Here, the idle noise is at that level!
View attachment 309766
That is one messy response. Testing with my speaker (see below) I could hear a pop during power off although it was not too unpleasant.

The amp kept improving its performance as I left it on. I waited a half hour and it kept going:
View attachment 309767

I didn't like the spike patterns in there.

PrimaLuna Dialogue Seven Amplifier Listening Tests
I tested the amp using my lab Infinity Reference 253 tower speaker. As I have heard before (with high impedance tube amps), the bass was flabby and overloaded. It was quite annoying and obvious artifact. Whether your speaker will do the same depends on its impedance curve. Ignoring that, I cranked up the volume. Up to medium listening level if was "OK" but above that high frequency distortion started to increase proportional with volume control. This was a super annoying effect where at limit it sounded like the tweeter shouting at you.

To be sure I had not forgotten what my speaker/room sounded like, I swapped in the Topping L90 amplifier. Bass instantly tightened up and clarity improved in high frequencies. The sound was so solid and sure-footed in contrast to the Seven. There was no change in response as I turned up the volume.

Conclusions
There is nothing to hang one's hat on here other than the packaging. In every other respect, performance is cringeworthy whether we are talking measurements or listening tests. All of which makes stereophile reviewer Art Dudley's comments seem completely out of line:

"From my experience, the DiaLogue Seven succeeds at everything PrimaLuna set out to do: It's an apparently reliable, obviously wonderful-sounding amp that offers higher-than-average value—and a lovely opportunity for you to discover the playback approach that suits your ideas about recorded music while, at the same time, having fun. Very strongly recommended."

Fun is not what I had. Even within the context of tube amplifier architecture, there are design errors leading to artifacts that have no business being there (such as copious amount of noise and rising low frequency distortion).

I can't recommend the PrimaLuna Dialogue Seven amplifier. I implore you to get a proper solid state amplifier so that you can hear music without the limitations of the box in the middle.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Amir, you don't make it clear if the price is for one or a pair. Are we talking >$5k for adding so much distortion to a system?

 

[calugg]

The engineer, the CEO and the salesman for PrimaLuna.

Bwhahahahaha! Thanks!

 

[AudioSceptic]

Yes, but this amp isn't a good performer even amongst its valve-peers!

I'd be more interested in seeing how a now vintage E.A.R power amp does (509?) which deliberately used TV line-output valves to help the end user save money come replacement time, perhaps a Manley, Radford Revival or whatever.

Agree. I'd like to see the late Tim de P's best on the bench.

 

[multisport4me]

I love tube amps. I play all of my guitars through tube amps (e.g. Marshall, Fender, Music Man, etc.). However, I cannot for the life of me figure out why anyone would want a tube amp driving their hi-fi system.

 

[DanielT]

My professional guess is that the parameters of this amp under test are so bad that it is possible to distinguish it in a DBT from a competently designed solid state amplifier. May depend on speaker used, of course,

With good speakers so absolutely there can be a possibility of hearing differences. Amir heard it.
PrimaLuna Dialogue Seven vs Topping LA90:

"I tested the amp using my lab Infinity Reference 253 tower speaker. As I have heard before (with high impedance tube amps), the bass was flabby and overloaded. It was quite annoying and obvious artifact...... Up to medium listening level if was "OK" but above that high frequency distortion started to increase proportional with volume control. This was a super annoying effect where at limit it sounded like the tweeter shouting at you."

Edit:
Solution, let a sensible solid state amp take care of the bass and the highest frequencies. And when you're still on the move, let the same solid state take care of mid as well. Thus, the tube amp problem was solved in a smooth and simple way.

 

[AudioSceptic]

Thanks for the subject and object review! It is also a mystery to Mr John Atkinson . Maybe if he reads your review now that he understands that it was his colleague's fault

“When I measure amplifiers like PrimaLuna's DiaLogue Seven, my eyebrows always rise because the things they do wrong must be balanced against the possible sonic befits of the other things they do. Certainly, the designer's decision to use very high output impedances will drastically affect sound quality for reasons that are well understood. The DiaLogue Seven's measured performance in triode mode was notably worse than in ultralinear mode, yet Art Dudley ultimately preferred triode mode. A puzzle.—John Atkinson”

John A has always managed to be schizophrenic* in this way. Could it be to retain a certain type of readership and associated advertising revenue?

*I know it's not the correct term but it's what most people say when they really mean Dissociative Identity Disorder.

 

[fpitas]

Solution, let a sensible solid state amp take care of the bass and the highest frequencies. And when you're still on the move, let the same solid state take care of mid as well.

I took that advice and went a step further with SS for the horn section. I leave all the glowing to the room lights.

 

[AudioSceptic]

My professional guess is that the parameters of this amp under test are so bad that it is possible to distinguish it in a DBT from a competently designed solid state amplifier. May depend on speaker used, of course,

Didn't 0.1% (-60 dB) use to be the "gold standard" for amps in 50s/60s? If so, this one would fail such a test, and obviously so in the bass.