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Gain & pain

Reviewer: Srajan Ebaen
Financial interests: click here
Main system: Sources: Retina 5K 27" iMac (4GHz quad-core with Turbo, 32GB RAM, 3TB FusionDrive, OSX Yosemite. iTunes 14.4), PureMusic 3.02, Audirvana 3, Qobuz, Tidal, Singxer SU-6 USB bridge, Sonnet Pasithea DAC; Active filter: icOn 80Hz/4th-order hi/lo-pass; Power amplifiers: Kinki Studio EX-B7, Enleum AMP-23R; Headamp: Kinki Studio THR-1, Cen.Grand Silver Fox; Phones: HifiMan Susvara; Loudspeakers: sound|kaos Vox 3awf + sound|kaos DSUB15 on Carbide Audio footers, Audio Physic Codex, Cube Audio Nenuphar Cables: Complete loom of Allnic Audio ZL; Power delivery: Vibex Granada/Alhambra on all source components, Vibex One 11R on amps, Furutech DPS-4.1 between wall and conditioners; Equipment rack: Artesanía Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands; Sundry accessories: Acoustic System resonators, LessLoss Firewall for loudspeakers, Furutech NCF Signal Boosters; Room: 6 x 8m with open door behind listening seat
2nd system: Source: Soundaware D300Ref SD transport clock-slaved to Denafrips Terminator +; Preamp/filter: icOn 4Pro SE; Amplifier: Goldmund Job 225; Loudspeakers: MonAcoustic SuperMon Mini or Acelec Model One + Dynaudio S18 sub; Power delivery: Furutech GTO 2D NCF; Equipment rack: Hifistay Mythology Transform X-Frame [on extended loan]; Sundry accessories: Audioquest Fog Lifters; Furutech NFC Clear Lines; Room: ~3.5 x 8m
Desktop system: Source: HP Z230 work station Win10/64; USB bridge: Singxer SU-2; Headamp/DAC: iFi iDSD Pro Signature;  Headphones: Final D-8000; Active speakers: DMAX SC5
Upstairs headfi/speaker system: Source: smsl Dp5 transport; DAC: Auralic Vega; Integrated amplifier: Schiit Jotunheim R; Phones: Raal-Requisite SR1a; Active DSP speakers: Fram Midi 120
2-channel video system: Source: Oppo BDP-105; All-in-One: Gold Note IS-1000 Deluxe; Loudspeakers: Zu Soul VI; Subwoofer: Zu Submission; Power delivery: Furutech eTP-8, Room: ~6x4m

Review component retail: n/a

A recent hardware not wardrobe malfunction meant a temporary reshuffle – uh, downstairs. That prompted experiments which could be useful to share. For starters, my regular amp fronting ~93dB sound|kaos Vox 3awf is an Enleum 25wpc AMP-23R; and a Kinki Studio 225wpc EX-M1 integrated on the passive 2×15-inch companion sound|kaos sub. The Enleum packs 22.5dB of voltage gain, the Kinki 26dB. I don't have the sub's sensitivity spec and suck at math but the correct volume balance between mains and sub amp sets the latter at ~200/255 on its ¼dB-stepped attenuator. That leaves some 10dB+ of potential bass gain on reserve. Having refused to power up even after a mains fuse replacement, the Enleum was in Seoul for repair. What to drive the monitors with in the interim? Complicating my question was an outboard fixed active filter box for a 80Hz 4th-order split into high/low-pass signals. It lacks an attenuator or balance control of its own. Arriving at correct bass balance thus relies on an attenuator built into mains or sub amp; whichever happens to play too loud on a given mains speaker.

When I tried Kinki's 250-watt EX-B7 monos on the monitors and left its stablemate integrated on the sub, the latter wouldn't go loud enough even fully open. Yes I could have preceded the monos with a dedicated preamp to cut them instead. No I didn't think that hulking amps on bandwidth-restricted small monitors of higher efficiency were a package I wanted to promote when the 1/10th-power Enleum had been perfectly sufficient and would be again on its return. I next tried Crayon's 64wpc CFA-1.2 on the monitors, Kinki monos on the sub. Now I achieved correct balance when I lowered the Crayon's voltage gain in its menu. Great. I thought myself done. Alas, I was to soon find that on certain tracks, the Metrum DAC's 2Vrms RCA outputs ran out of puff when their R2R ladders' variable reference voltage was at max. To cover all software eventualities, I needed the Crayon dragon at its max gain mated to a sub amp of higher gain than the Kinki twins. If that sub amp was too hot, I'd precede it with Wyred4Sound's STP II SE preamp to trim its output by remote.

Uff. Let's backtrack to unpack this. In audio amplification, we have listening levels influenced by room size, sitting distance and personal preference. We have recorded levels. We have voltage gain in our hardware chain. We have voltage sensitivity on our speakers. These variables must meet up just right to give proper control over our playback levels. With player software like PureMusic, we can see not just our digital files' recorded dynamic range—the flicker width between quietest and loudest sounds—but where the max value sits. Always-loud Pop sets its peaks at virtually 0dB. If seriously compressed, it may not flicker broader than down to -6dB. That means just 6dB of recorded dynamic 'range'. Pathetic. Anyone who there invokes 'lifelike' dynamics to need 500-watt amplifiers to reproduce them has lost their mind. What happens instead is that our DAC's standard 2Vrms outputs dispatch close to full voltage to our amp's inputs; typically twice the dose on XLR. If our amp requires rather less voltage for full power and our speaker sensitivity is an average 88dB, we must cut our DAC's output voltage by 20-30dB for normal listening. Enter a variable DAC, preamp or integrated amplifier for the necessary attenuator. Done. We clearly don't need extra gain so a passive preamp or amp with a simple pot is sufficient.

Premium recordings without deliberately compressed dynamics like ECM will flicker across up to 30dB of range. Just one of mine, plain Redbook at that, does 50dB! What's more, their peaks may never get close to 0dB. They remain at -10dB, even lower. It's obvious that for such tracks, we must make up by turning up our volume control. Easy with sufficient gain in the chain. By now you may appreciate why my Crayon/Kinki-mono scenario was off. When the sat/sub balance was right by cutting the main amp's gain by 10dB in its clever menu, tracks which never make it higher than -15dB on PureMusic's DR meter wouldn't get loud enough. For those I had to re-up Crayon's voltage gain to max. For compressed music now average playback SPL mean ~30dB source attenuation as is normal. ECM-type fare requires perhaps a 20dB cut, super-purist tracks a 10dB cut. With my sub not going loud enough, I had to pad out its amp's gain. At 35dB of voltage gain, Goldmund's 125wpc Job 225 circuit was tailormade though without trim now too loud. Music grew bassy and love-handle portly. Preceding it with EJ Sarmento's preamp which operates passive until 63 on the dial then kicks in 17dB of active gain to 80, I now set it below 63. It puts plenty of headroom in my pocket and remote control over bass level in my hand. I can goose the LF on certain ambient fare, compensate the Fletcher-Munson effect at whisper levels or set things to neutral for purist classical. Happy days.

This whole tattletale only came about because of my sub/sat division of labor, losing the mains amp to a temporary refusal to power up, then using a passive subwoofer which needs its own outboard amplifier. Unless the sub amp is an integrated to add discrete bass volume, I need to add an attenuator to the bass leg via preamp. That's if the bass leg has excess gain. If it's the mains leg because I changed speakers, that's where the attenuator must go. Into this chanciness steps a proper variable active outboard xover. It not only handles signal splitting for sub and mains but adds attenuators on either leg; or a master balance to either cut bass or mains signal by up to 20dB. That accommodates divergent voltage gain in mains/sub amps; and mismatched sensitivities of their attached transducers. Active subwoofers obviously include plenty of extra gain plus their own attenuator. They render my extra hardware redundant. On the flipside, I get to use premium outboard electronics without being stuck with generic class D plate amps, DSP latency and cheap variable-state filters. Once Pál Nagy's pending Gradient Box 2.5 drops, I'll extricate the Wyred4Sound preamp from my downstairs equation to instead enjoy variable filter freqs separate for high and low pass, variable gain plus infrasonic shelving all in one remote-controlled chassis. Until that smart crossover arrives, I'm piecemealing it for peacemaking on today's pain/gain axis.

So is the subject of hifi gain really a pain? Generally not at all. It's just sensible to give it a basic think on what we really need and consider not just amplifier power in watts but voltage gain aka amplification factor. Otherwise we may buy too much which then just sits there never used but paid for. That, I suggest, would be unnecessary pain not just financially. Excess gain also tends to inject noise and distortion whilst making a volume control's usable range too narrow. It's a subject I covered here. For today, I'll leave you with what's already implied above. An amp with twice the power rating may, for the same volume setting, play noticeably quieter than a lower-power amp whose voltage gain is rather higher. In my case, the 125wpc Job 225 out-louds the 250w Kinki monos by a fair margin. It's not watts but amplification factor that make it so. Over and out.