Patiently, gently, and mindfully, I removed the Mullards, then, even more carefully, I inserted the JJ 12AT7s. Voila, a new amp was born.
The sound-character change was significant, as Luca had predicted. The Levante…
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When I unpacked the Levante, I noticed two pairs of boxed ECC81 tubes and thought oh nice, they sent spares. Not so: The pairs were different brands. The Mullard boxes were empty; the JJ tube boxes were full (footnote 2). Before turning on the Levante, I removed its top cover and verified that, yes, only two tubes are required, and the Mullard pair was installed.
Sidebar 1: Specifications
Description: Hybrid (tube-BJT-MOSFET) stereo integrated amplifier with no global feedback, output switchable between class-A and class-AB. Analog inputs: 1 pair balanced (XLR), 4 pair unbalanced (RCA). Outputs: 1 pair 3-way loudspeaker binding posts; one ¼" (6.3mm) unbalanced headphone output. Output power: 30Wpc into 8 ohms (14.8dBW) in class-A, 120Wpc into 8 ohms (20.8dBW) in class-AB, 200Wpc into 4 ohms (20dBW).
Dimensions: 17.3" (440mm) W × 5.1" (195mm) H × 19.3" (490mm) D. Weight: 66lb (30kg).
Finish: Metallic Sand Gloss/Gold or Dark Titanium/Silver…
Sidebar 2: Associated Equipment
Analog sources: Dr. Feickert Analogue Blackbird turntable with Schick 10.5" tonearm, Koetsu Rosewood Signature Platinum, My Sonic Lab Ultra Eminent Ex moving coil cartridges; EMIA, Koetsu, and Lundahl LL1931Ag SUTs, EAR Phono Classic, Sutherland Engineering Little Loco phono stages.
Digital sources: Roon Nucleus+ music server; HoloAudio May (Level 3) D/A processor; Mola Mola Tambaqui DAC, dCS Bartók DAC/Streamer with Mosaic control app.
Integrated amplifiers: Pass Labs INT-25, Rogue Audio Sphinx V3, RAAL-requisite HSA-1b.
Power amplifier:…
Sidebar 3: Measurements
When I unpacked the Riviera Levante amplifier and lifted it onto the test bench, it struck me that this is actually eight amplifiers in one. It has balanced and single-ended line-level inputs. Its output stage can be operated in class-A or class-AB. It was supplied with two choices for the two input stage ECC81/12AT7 tubes: vintage Mullards or modern JJs. Add to those variations that the Levante has a headphone output and an optional phono stage (not fitted to the review sample), and it became clear that I had a lot of testing ahead of me.
I decided to…
There has not been a conventional preamplifier in my main audio system for quite a while, because no multichannel preamp is available that's of high enough quality. Instead, I use the high-precision digital volume controls in my players and DACs and choose sources with a relay-based multichannel analog switch. Plus, I tell myself that no preamp can be more accurate and transparent than no preamp.
However, I recently installed Dirac Live 3, which effectively reduces the available system gain by almost 20dB! In my salad days, I would have designed and built a balanced driver with gain for…
Moving to a larger ensemble—10 voices and players—L'Escadron Volant de la Reine (The Queen's Flying Squadron) offers a stylish program of music in the French style by Giovanni Girolamo Kapsberger (Il Tedesco, Harmonia Mundi HMM 902645, 16/44.1 PCM download). The opening a cappella of "Lunge da voi ben mio" is lovely and airy with realistically rounded voices spread across the front within a moderately deep acoustical space. The full ensemble soon joins; the instruments fill that space, front to back and side to side, even as all the voices and instruments remain distinct.
…
Sidebar 1: Specifications
Description: Stereo line-level preamplifier with remote control and relay-selected resistor arrays for level control. Inputs: 1 pair RCA (unbalanced), 1 pair XLR (balanced). Input impedance: 2k ohms. Input sensitivity: 9.2V @ 0dB. Outputs: 1 pair RCA (unbalanced), 1 pair XLR (balanced). Output impedance: 20 ohms (RCA), 40 ohms (XLR). Gain: –99dB to +10dB (RCA output), –93dB to +16dB (XLR output). Maximum output level: 25V (RCA), 50V (XLR). DC offset at output: <1mV RMS. Frequency response: 20Hz–100kHz, ±0.1dB. Channel separation: >130dB (1kHz). THD+N (1kHz…
Sidebar 2: Associated Equipment
Digital sources: Oppo Digital UDP-105 universal disc player, custom , exaSound s88 streaming DAC and Okto DAC8 PRO D/A processors. QNAP TVS-873 NAS.
Preamplifiers: Coleman Audio 7.1SW for source switching, Pass Laboratories XP-32.
Power amplifiers: Benchmark AHB2, NAD C 298.
Loudspeakers: Revel Ultima2 Studio with IsoAcoustics Gaia I isolation feet. Revel Performa3 f206 for surrounds. Two SVS SB-3000 & one SB-2000Pro subwoofers.
Cables: Digital cables: AudioQuest Coffee (USB). Analog interconnects: Benchmark Studio&Stage XLR-XLR,…
Sidebar 3: Measurements
I measured the Topping Pre90's performance with my Audio Precision SYS2722 system (see the January 2008 As We See It), repeating some tests with the magazine's higher-performance APx555 system.
The Pre90's volume control operated in accurate 0.5dB steps. The maximum gain at the unbalanced outputs was the specified 10dB for both the balanced and unbalanced inputs; the maximum gain at the balanced outputs was the specified 16dB for both types of inputs. The preamplifier preserved absolute polarity (ie, was noninverting) with both balanced and unbalanced…
I'm deep into audio power amplifiers because they remind me of race car engines. Both power sources are wildly inefficient, converting only a small percentage of their stored energy into work while dissipating the rest as heat and vibration. Mainly though, I love how race car engines sound. How they shake the air. Just like amps and speakers.
Audio-frequency power amplifiers take a small input signal—usually less than 1V—apply it to an input impedance of (typically) no less than 10k ohms, and make this tiny eye-blink of power (0.0001W) into a waveform that's many times more powerful,…