PrimaLuna Dialogue Seven Tube Amp Review

[JayGilb]

Time to buy a panther figurine taking a dump.

 

[Multicore]

I had a box of tubes when I was a kid. As soon as transistors were even vaguely usable, I threw the tubes in a lake.

The TV we had when I was a kid was a box of tubes. It was hot, smelly, took a long time to "warm up" and wasn't reliable. TV repair shops were commonplace.

 

[Multicore]

I've wondered for awhile if the 'warm' sound some claim from tubes is caused by PSU noise and ground hum....

Amps that are designed to look like warming ovens, like these from PrimaLuna, are powerfully suggestive. I can't imagine how they could fail to sound warm while you sit there admiring the looks while listening to Dire Straits.

 

[Multicore]

looks like a bread toaster oven

PrimaLuna Dialogue Three Preamp Review

I do not understand what you mean. I think Primaluna build quality is nicer; Octave is just expensive. Just my opinion.

www.audiosciencereview.com

 

[Andysu]

Time to buy a panther figurine taking a dump.

 

[pma]

Human ears are just not very sensitive to distortion. We are much more sensitive to frequency response.

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.

 

[Michael Fidler]

I've wondered for awhile if the 'warm' sound some claim from tubes is caused by PSU noise and ground hum. Many of the tube products tested here have a problem with 60 Hz spikes and other noise at low frequencies. Hum and noise tend to be intended in a lot of these 'audiophile' electronics.

Also mains intermodulation/banding that you can see on the measurements. I'm always surprised that nobody talks about this as power supply rejection ratio in push-pull valve amplifiers degrades dramatically once the output stage starts working and shifting away from the centre of its operation so cancellation can no longer occur...

Really not great to see so much of it here so voted 'not terrible' by valve amplifier standards but still this looks like something that could be fixed with proper care and attention paid to the power supply. What they don't tell you about ultra-linear/triode outputs if that they've got far worse PSRR once the symmetry starts shifting when driven.

Maybe I'm being charitable here but it might be because this weekend I measured a Chinese EL34 amplifier with 10% THD at just 4 watts output and a whopping 180 ohms of output impedance on the 8 ohm tap at 1kHz.

 

[mmuetst]

I don't know if they are or are not replaced. I do know I measured lower distortion than the spec (although power rating is different). And my measurements agree with that of Stereophile.

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”

 

[SIY]

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.

I'd say the same about any Class A/AB amp. We choose them because of non-technical reasons since, if engineered, the sonics will be the same as any other engineered amp.

 

[Michael Fidler]

I'd say the same about any Class A/AB amp. We choose them because of non-technical reasons since, if engineered, the sonics will be the same as any other engineered amp.

I guess in this case the reviewer preferred higher distortion though. It could probably do with a bit more negative feedback although it's disconcerting to see the response peaking (if only by a dB) at 70kHz, although having said that there's probably room in there for a dominant pole somewhere too...

 

[mmuetst]

Is this not the man

That killed Prima Luna in de first place?

 

[amirm]

@amirm unless you have coined a new phrase you misspelled distortion in this graph.

Nah... It is distortion in Italian. Read it as: "dis tor tino!"

 

[mmuetst]

Not sure why 3 people voted it 'Great'!

Kevin Deal has 3 5 fake accounts (the fake accounts keep rising)

 

[mmuetst]

Not correct

 

[SIY]

I guess in this case the reviewer preferred higher distortion though. It could probably do with a bit more negative feedback although it's disconcerting to see the response peaking (if only by a dB) at 70kHz, although having said that there's probably room in there for a dominant pole somewhere too...

I will state with 99% certainty that more feedback won't help (the response curves show that stability is already questionable), the problem is in the open loop performance as well as grounding. And included in that 99% is my confidence that they made design errors stemming from a cut and paste approach. As Morgan Jones would say, "Heavily designed, lightly engineered."

 

[fatoldgit]

that is too much to ask of Amir. And is he supposed to measure the new tubes in isolation as well to ensure they are good and matched samples. There can be a relatively wide margin of error in tubes, vintage or newly made.

And what about transport? Big power tubes don’t take kindly to being shipped all over the place. Vibrations, drops and such can cause degradation even if the tube is intact and well packed.

My advice for Amir is just to not bother reviewing tube amps at all. Maybe tube preamps. But power amps. Not worth the trouble.

No... its really the responsibility of whomever sends the device in but unless there is irrefutable evidence provided by the sender as to the condition of the tubes then a review shouldnt take place.

Or if Amir wants an even playing field, he could buy some new tubes of various common types to ensure reviews are fair. And yes, get any tubes used tested.

Reviewing older gear is a slippery slope and I dont know what value it really adds. Flakey capacitors, internal corrosion and out of spec components mean any older device is at a disadvantage.

Sure it helps people have a laugh, esp when its tube based, but given this site has "science" in the name, reviewing older gear that isnt certified "as new" is kinda wrong.

Peter

 

[Spocko]

CLEARLY, @amirm should've tried exotic NOS tubes that cost $1,500 each right?

 

[amirm]

No... its really the responsibility of whomever sends the device in but unless there is irrefutable evidence provided by the sender as to the condition of the tubes then a review shouldnt take place.

Irrefutable evidence? Here are the company specs for SNR:

S/N Ratio

84 dB

Here is my measurement:

Right on the money (right).

Here is the spec for distortion:

< 0.25% @ 1 watt

I measured half as much at 0.12% at 5 watts. Their SINAD would be 52 dB whereas I measured 58 dB.

Here are stereophile power measurements (4 ohm):

Here is mine:

Note how distortion takes over with the curve flattening around half a watt in both measurements.

That should be plenty of evidence for you that we have proper measurements of this amplifier.

 

[CleanSound]

I take it that it was from the same member who loaned the 3 pre-amp.

 

[Toku]

CLEARLY, @amirm should've tried exotic NOS tubes that cost $1,500 each right?

Measurements should only be made in the original condition, and if you replace it with a completely different NOS tube as you say, then it has been modified.