Linn Intek Stereo Amplifier Review

Originally known as a manufacturer of fine record-playing components, Linn Products, based in Scotland, has expanded its line to include speakers, preamplifiers, and power amplifiers. The Intek is its first integrated amplifier.

The Intek is rated to deliver 50 watts per channel into 8-ohm loads or 80 watts into 4 ohms. Although the instruction booklet’s specifications page lists input sensitivities, impedance levels, and power-output capabilities, it does not mention distortion ratings as required by the Federal Trade Commission for home audio products advertised for sale in this country.

The Linn Intek’s front panel presents a clean, uncluttered appearance, with full-size knobs, large rectangular control buttons, and clear, legible white markings. The case is finished in black.

The amplifier’s circuitry, including the front-panel controls and back-panel connectors, is all on one large circuit board. Unusual for an integrated amplifier, the Intek has separate power supplies for its power and preamplifier sections. In fact, the only parts of the unit common to both sections are the primary winding of the power transformer and, of course, the AC line cord.

According to Linn, the output transistors used in the Intek are identical to those in its more expensive LK280 power amplifier. The output devices are protected by a sensing circuit that shuts down the power supply instantly if the transistors draw excessive current. Unlike the current-limiting protection circuits used in some other amplifiers, which can degrade the sound quality under certain conditions, the Linn system simply turns off the amplifier before the output transistors can be damaged. To restore operation, it is necessary to switch off the power for a few seconds. There is also a thermal-protection system that shuts down the amplifier if its internal temperature reaches 70° C (158° F).

The front panel, machined from an aluminum extrusion, contains separate program-selector knobs for the listening and tape-recording outputs. The available sources are identified as phono, tuner, CD, video, tape 1, and tape 2. Volume is controlled by a concentric pair of knobs for the two channels. Normally operated as a unit, the knobs can be adjusted relative to each other for channel balancing. A slip clutch maintains their relative setting during normal operation.

The other front-panel controls are five bar-shaped pushbuttons. Two of them connect the front-panel headphone jack and the rear-apron switched speaker jacks to the amplifier outputs. A second set of speaker jacks, permanently connected to the amplifier, is normally used for the primary speakers. Another button mutes the audio outputs, and the fourth parallels the two channels for mono operation. The last button is the power switch, with a green LED pilot light above it.

The rear apron of the Intek contains standard RCA-type phono jacks for the signal inputs and tape-recording outputs. There are separate gold-plated jacks for moving-magnet (mm) and moving-coil (MC) phono cartridges. A small switch beneath these routes the preamplifier to the appropriate input and changes its input termination and gain to match * the cartridge type (the switch merely changes a control voltage in the phono stage and does not actually handle the signal). A grounding post is located near the phono inputs.

A pair of pre-out/power-in jacks can be used to drive an external power amplifier. In order to drive the Intek’s power amplifier from, say, an equalizer or surround-sound decoder fed from its preamp stages, however, internal jumpers on the main circuit board must be cut. Although instructions are given for doing this, it is recommended that the modification be done by a qualified dealer.

The speaker-output jacks on the rear apron are compatible with standard single or dual banana plugs, but Linn furnishes connecting plugs of a slightly different design that make a very positive contact with the jacks. The socket for the detachable line cord contains a replaceable fuse.

The Linn Intek measures 17 x 3-1/2 x 13-3/4 inches, and it weighs about 16-1/2 pounds. Price: $995.

Lab Tests

The Linn Intek’s top cover, over the heat sink and the power transformer, became moderately warm in normal operation and not much hotter during our high-power measurements, but the bottom plate, immediately below the power transformer, became uncomfortably hot to the touch.

With both channels driving 8-ohm loads at 1,000 Hz, the outputs clipped at about 55 watts per channel. Into 4-ohm loads, the clipping-level output was 100 watts. The respective clipping-headroom figures were 0.25 and 1 dB. Clipping-level power could not be measured into 2 ohms (for which the amplifier is not rated) because the protection circuit operated before the clipping point was reached. The dynamic power outputs were 90 and 100 watts into 8 and 4 ohms, respectively, corresponding to dynamic-headroom figures of 2.55 and 1 dB. The 2-ohm dynamic power was an impressive 264 watts, and the protection circuit did not trip during the 20-millisec-ond tone bursts (although it frequently shut down the amplifier during steady-state tests into 2 ohms).

The amplifier’s frequency response, through the CD input, was flat within +0, -0.5 dB from 20 to 10.000 Hz and down 2 dB at 20,000 Hz. When the gains in the two channels were matched at a typical volume-control setting, the channel balance varied less than ±0.3 dB over a 40-dB adjustment range.

The maximum power delivered into 8 ohms with no more than 1 percent distortion was 55 to 57 watts between 20 and 2,500 Hz, decreasing to 50 watts at 5,000 Hz and dropping at higher frequencies to 18 watts at 20.000 Hz. These figures do not mean the amplifier cannot deliver its full power over the audio range— merely that its distortion exceeds 1 percent at high frequencies.

The total harmonic distortion (THD), including noise, was fairly constant with frequency from 20 to 1.000 Hz but rose at higher frequencies regardless of the power level. At 5 watts output, it was typically 0.06 percent below 1,000 Hz, reaching a maximum of about 0.5 percent between 10,000 and 20,000 Hz. At 50 watts, however, the distortion measured about 0.2 percent up to 1,000 Hz, 1.25 percent at 10,000 Hz, and 3.5 percent at 20,000 Hz. Spectrum analysis showed that these readings reflected a large number of distortion components (up to at least the twentieth harmonic) whose individual levels were typically between -45 and -60 dB.

The RIAA phono-equalization error was -1 dB at 40 and 10,000 Hz and - 3 dB at 22 and 20,000 Hz. Input sensitivity, for a reference 1-watt output, was 22 millivolts (mv) through a high-level input, 0.265 mv through the mm phono input, and 0.0245 mv for MC phono. The respective A-weighted noise levels were -80.2, -78, and -78 dB.The mm phono input impedance was 47.000 ohms in parallel with 80 picofarads, as rated. The phono input overloaded at 104 mv at 20 Hz, 75 mv at 1,000 Hz, and only 17 mv at 20.000 Hz (where the overload was gradual and evidenced largely by the appearance of third-harmonic distortion rather than clipping).

We made limited frequency-response and distortion measurements at the pre-out jacks, where the frequency response was perfectly flat from 20 to 2,000 Hz and down 0.9 dB at 20,000 Hz. Distortion was 0.01 to 0.02 percent at output levels less than 7 volts, and the output clipped at about 7.5 volts.

Comments

The Linn Intek is an excellent illustration of the fact that the worth and sound of an amplifier cannot be judged solely by its measured performance. Some of the measurements of this amplifier were, frankly, well below what we would expect from Linn. Although the preamplifier section was very good, the power-amplifier section’s frequency-response and distortion characteristics were unexpected.

Nevertheless, nothing we heard from the Intek suggested that it was anything but excellent. Although the measured distortion rose at high audio frequencies to levels that would probably have been audible a few octaves lower, it had no discernible effect on the sound quality. The amplifier’s noise levels were very low, but the phono preamplifier overloaded (at high frequencies) at a surprisingly low input level.

Although the Intek met its power specifications easily at low and middle audio frequencies, the increased distortion at the top end of the audio range suggests either that a power rating following the FTC standard would be unrealistically low or that its distortion rating should be correspondingly high. Since both channels gave essentially identical test results, we can only assume that our measurements were valid.

As always with high-fidelity components, however, the ultimate proof of quality is in the listening. When we played various CD’s through the Linn Intek into a pair of good speakers, the sound was flawless, even at levels that would certainly have revealed any meaningful deficiency in power or excess of distortion. Furthermore, the simplicity and clarity of its front panel made the Intek amplifier a pleasure to use.

The Linn Intek is not inexpensive, but, like other Linn products, it is a handsome, carefully built, and fine-sounding component. I did not hear anything from it that was not commensurate with its appearance, price, and heritage.

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