Article · Published 2026-10-18

Hi-fi terms explained: a glossary of audiophile words, from soundstage to tube sound

Audiophiles in every language share a vocabulary that is vivid but not always precise. Some words describe what we hear, such as soundstage, resolution or warmth; others name circuits and parts, such as single-ended, output transformer or R-2R. This glossary explains the terms that come up again and again on forums, in reviews and on our own product pages, each in one or two plain sentences, with links to the guides that go deeper. If you have ever wondered what soundstage means, what reviewers mean by resolution, or what forum regulars call tube sound, the answers are below.

A word of caution first. Listening terms describe perceptions, and two listeners may use the same word for slightly different things. Many of them relate to measurable properties, such as frequency response, distortion, noise and timing, but none maps neatly onto a single number. They are most useful when comparing two components in the same system and room.

Listening terms

  • Soundstage — the imagined space in which the performers seem to stand, between and beyond the loudspeakers, with width, depth and sometimes height. It depends first on the recording, then on loudspeaker placement and the room; see The stereo image.
  • Imaging — how precisely each voice and instrument is placed within the soundstage, from left to right and from front to back.
  • Image focus — how solid and sharply outlined each source sounds within that space, rather than vague or smeared. Symmetrical placement and careful toe-in usually sharpen it.
  • Resolution (detail) — the ability to reveal fine information: reverberation tails, the texture of a bow on a string, separate lines in a dense passage. Resolution is not the same as bright treble, which can sound detailed at first and tiring later.
  • Transparency — the sense of hearing through the system to the recording, with little veiling and little character of the system’s own.
  • Timbre — the tonal colour that tells a violin from a viola, or one singer from another. “Real timbre” means that instruments sound like themselves.
  • Tonal weight (density) — the body and substance of notes, especially in the lower midrange. Its opposite is a lean or thin sound.
  • Dynamics — the contrast between quiet and loud passages, and the ease with which a system moves between them, as in an orchestral crescendo.
  • Micro-dynamics — small changes of level within a phrase: the pressure of a bow, an accent in a voice, the shading of a piano note. They are what keeps music alive at low volume.
  • Transients and speed — how cleanly a system starts and stops a note, such as a plucked string or a piano hammer. Systems with clean transients are described as fast.
  • PRaT — pace, rhythm and timing, a term from British reviewing for how well a system conveys the rhythmic drive of music. It has no single measurement.
  • Warmth — a slightly full, rich balance in the upper bass and lower midrange, often with a gentle treble. Pleasant in moderation, it turns into muddiness in excess.
  • Air — the sense of space around instruments and of the ambience of the hall, carried largely by the upper treble.
  • Black background — silence between the notes. Low noise lets quiet sounds and decays emerge from nothing.
  • Colouration — any character added by the system that is not in the recording, described with words such as boxy, nasal, bright or hollow.
  • Tube sound — the character commonly attributed to tube amplifiers: a rich midrange, dense harmonics, smooth treble and a sense of body. Part of it is explained by low-order distortion, the output transformer and the interaction of a higher output impedance with the loudspeaker, and a well-designed tube amplifier can also sound neutral; see When a tube sounds better than a transistor.

Amplifier terms

  • Single-ended — an output stage in which one tube, or several in parallel, amplifies the whole waveform, always in Class A. With a triode it is called SET (single-ended triode); see Tube amplifiers: the logic behind the sound.
  • Push-pull — an output stage with two tubes, or two groups, working in opposite phase and combined in the output transformer. It gives more power per tube and cancels even-order distortion; it can run in Class A or Class AB.
  • Class A — the output devices conduct over the whole signal cycle and never switch off. This avoids crossover distortion, at the cost of a high idle current, heat and low efficiency.
  • Class AB — Class A at low levels; at higher levels each device switches off for part of the cycle, which raises efficiency and power. Bellerophon is our Class AB amplifier.
  • Class D — an amplifier whose output transistors switch on and off at a high frequency, with the audio recovered by an output filter. It is efficient and compact, but not “digital” in itself. Hades is our Class D amplifier.
  • Negative feedback — returning part of the output, inverted, to the input, which lowers distortion and output impedance. Many single-ended designs use little or none; “no global negative feedback” means no loop around the whole amplifier.
  • Output transformer — the transformer that matches the high impedance of the output tubes to the low impedance of a loudspeaker. Its quality largely sets bandwidth and bass, and taps for 4, 8 or 16 Ω suit different loudspeakers.
  • Directly heated triode (DHT) — a triode whose filament is itself the cathode, such as the 45, 2A3, 300B, 845 or 211; see Power triodes for single-ended amplifiers.
  • Rectifier (kenotron) — the part of the power supply that turns alternating current into direct current. Owners often describe a supply with a tube rectifier, or kenotron, as softer than a solid-state one; in our amplifiers the 6D22S is chosen for a darker tone and the 5C3S for a brighter one.
  • Headroom — the reserve of power above the average listening level, needed to reproduce peaks without clipping.
  • Transformer volume control (TVC) — a volume control that switches taps on a transformer instead of dividing the signal with resistors; see Passive or active preamplifier.
  • Tube rolling — swapping tubes for other makes or compatible types to fine-tune the sound. Use only the types the maker approves for that socket.
  • NOS tubes — new old stock: tubes made decades ago and never used. Not to be confused with NOS in DACs; see our guide to NOS tubes.

Digital terms

  • NOS (non-oversampling) — a DAC that converts at the recording’s original sample rate, without a digital oversampling filter. The trade-off is a gentle treble roll-off and ultrasonic images that a steep filter would remove; see NOS multibit DACs explained.
  • Multibit — a converter that builds each sample’s value at once from many weighted elements, one per bit, as in the TDA1541 or the PCM1704.
  • R-2R — a multibit design based on a ladder of resistors with the values R and 2R. A “discrete R-2R” DAC builds the ladder from separate resistors instead of a chip.
  • Delta-sigma — a converter that uses one or a few bits at a very high rate and shapes the resulting noise out of the audio band. Most modern DAC chips work this way; the Cirrus Logic CS4397 in Hyperion is a multibit delta-sigma chip.
  • Oversampling and upsampling — raising the sample rate inside the DAC chip (oversampling) or before it, in software or hardware (upsampling), so that filtering can happen far above the audio band.
  • Jitter — small timing errors in the clock that decides when each sample is converted. They add low-level distortion and noise; an external master clock such as Charon is one way to address them.

Loudspeaker terms

  • Sensitivity — the sound level a loudspeaker produces at 1 m with 1 W (or 2.83 V) of input. Every 3 dB more sensitivity halves the amplifier power needed for the same level, which is why low-power tube amplifiers pair with sensitive loudspeakers; see Loudspeakers for single-ended amplifiers.
  • Impedance — the AC load a loudspeaker presents to the amplifier, which varies with frequency around a nominal 4, 8 or 16 Ω. Deep dips make life hard for amplifiers with a high output impedance.
  • Full-range driver — a single driver that covers most of the audio range without a crossover, valued for coherence and high sensitivity; Perseus MkII is built around one in its single-driver form.
  • Horn — a flare in front of a driver that couples it to the air more efficiently, raising sensitivity and controlling dispersion. Cassandra MkII uses a horn-loaded tweeter.
  • Field coil — a driver whose magnet is an electromagnet fed with direct current from a separate supply; see Field-coil loudspeakers explained.
  • Electrostatic — a loudspeaker whose diaphragm is a thin charged film between two perforated stators that carry the signal, with very low moving mass; see our guide to electrostatic loudspeakers.
  • Open baffle — drivers mounted on a flat panel with no box, so the rear wave radiates freely. It needs space behind the loudspeaker and a large panel for deep bass; Atreus is a fully electrostatic open-baffle design.
  • Crossover — the filter that divides the signal between the drivers of a multi-way loudspeaker. The frequency where it hands over is the crossover point.

Setup terms

  • Burn-in — playing new equipment for some time before judging it. Loudspeaker driver suspensions are known to change in their early hours of use; claims for cables and electronics are debated; see Common audiophile misconceptions.
  • Warm-up — the time after switch-on for tubes and circuits to reach a stable temperature. Owners of tube amplifiers commonly allow 20–30 minutes before serious listening; see the setup FAQ.
  • Toe-in — angling the loudspeakers towards the listening position. It changes the treble balance and the focus of the centre image; see Getting the most from your loudspeakers.
  • Room modes — standing waves at low frequencies, set by the room’s dimensions. They create peaks and nulls in the bass that change from seat to seat, and moving the loudspeakers or the listening seat is the first remedy to try.
  • Ground loop — a loop formed when components are grounded through more than one path, heard as mains hum. A ground lift switch, fitted to several of our DACs and amplifiers, can break it.

Which Demograf Audio piece fits

If these words describe what you are looking for, here are a few starting points:

Every Demograf Audio piece is made by Dmitriy Gubchenko. Each is made to order and covered by a one-year warranty (extra warranty available: +1 or +2 years). Tell us which of these words matter to you, and we will suggest where to start.

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