Κώστας Φ.
Truth hurts. Here's a teddy bear.
- Μηνύματα
- 8.978
- Reaction score
- 895
Αντιγράφω απο enjoythemusic.com:
"The ProLogue Seven is billed as a classic Ultralinear circuit based on a quartet of KT88 beam power tubes (70 wpc) used in push-pull topology. Chinese new production copies of the venerated Genalex KT88 are standard. As with other PrimaLuna amplifiers, a soft-start circuit extends tube life and an Adaptive AutoBias circuit monitors and automatically adjusts tube bias current for improved performance and reduced distortion. Hence, there are no messy adjustment pots and burnt fingers to contend with. And best of all, forget about matching output tubes. PrimaLuna even gives you a green light to experiment with a variety of power tubes. The following types may be substituted for the stock KT88s: 6550, EL-34, 6CA7, 6L6GC, KT66, or 7581.
Some feedback is used both inter-stage and globally to reduce both harmonic distortion and output impedance. The power supply incorporates a toroidal transformer and rectifiers are fast-recovery solid-state diode types for reduced noise. The output transformers are said to be custom designed for wide bandwidth. Impedance taps are provided for 2-, 4-, and 8-ohm loads. Wiring is high-quality point-to-point, and in general, parts quality is excellent featuring Nichicon and Solen caps. The chassis is made of heavy gauge steel and finished using a five-step automotive finish. A removable tube cage is included at no extra charge. In terms of parts and build quality, what more could you ask for at a $2,695/pr price point?
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The Three would have easily gotten thumbs up as a good value even with a price tag of $3K. But at $1,395 it represents an amazing value (an optional moving magnet module is available at $179). Note its weight. At 23.5 pounds this is one beefy line preamplifier. The weight is a result of an ambitious dual mono layout featuring independent power supplies. That's right, there are two toroidal power transformers, choke filters, and two 5AR4 rectifiers, one per channel. Throw in premium caps, point-to-point wiring, an Alps Blue Velvet pot, DC tube heaters, and wideband no-feedback circuitry and you have a serious sonic contender at any price point.
There is no balance control. Given the dual mono layout, I would have preferred to see dual pots, one per channel for independent tweaking of the volume level. On purist grounds, no cathode followers are used at the output stage, which for this circuit translates into a high output impedance of about 3.5 kOhm. I would recommend a matching power amplifier input impedance at least a factor of ten higher to minimize treble rolloff. Since the Seven's input impedance is 100 kOhm, this criterion is easily satisfied.
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Conclusion
Be sure to experiment with the various impedance taps, and I would not be in any rush to substitute alternatives for the stock Chinese "Genalex" KT88. Undeniably, the Three brings out the best in the Seven and you should give serious consideration to auditioning both components as a system. In my book, and in the context of budget tube amplification, the ProLogue Seven and Three add up to a perfect 10."
Full Review
ProLogue Seven
Type: Vacuum tube monoblock amplifier
Power Output: 70 wpc
Tube Compliment (per amp): two 12AX7, two 12AU7 and four KT88
Frequency Response: 20Hz to 85kHz (+/- 0.5dB)
S/N Ratio: 101dB
Input Sensitivity: 911 mV
Input Impedance: 100 kOhms
Power Consumption (per amp): 225 watts
Weight (per amp): 37.5 lbs.
Outputs: 2, 4, & 8 Ohm speaker taps
Price: $2,695/pr.
ProLogue Three
Type: Vacuum tube preamplifier
Inputs: 4 pair RCA
Outputs: 2 pairs of pre-amp outputs + tape monitor out
Frequency Response: 4Hz to 85kHz (+/- 3dB)
Gain: 11.5dB
S/N Ratio: 109dB unweighted
Input Sensitivity: 200mV
Input Impedance: 100k Ohms
Output Impedance: 3.5k Ohms
Power Consumption: 48 watts
Weight: 23.5 lbs.
Price: $1,395
