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.
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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:
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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:
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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:
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Noise performance is poor, likely due to power supply noise:
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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:
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As a result, 19+20 kHz doesn't look quite as bad:
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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:
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We see the typical gradual rise in distortion in power sweeps:
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Distortion is so high that if we only allow 1% of it, the measured power goes way down, not up:
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Here is the power with 8 ohm load (and tap):
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Edit: forgot to post this initially:
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As bad as 1 kHz distortion was, it gets even worse at higher frequencies.
I usually measure pop noise when the power on/off exceeds 1 millivolt. Here, the idle noise is at that level!
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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:
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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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She's got a hummmmm. One of these days... 