Line Magnetic LM-170IA
Line Magnetic LM-170IA, the KT170 push-pull integrated amplifier
Four KT170s lined up in push-pull, 45 kilos on the scale, and 2x130 watts in class AB: the format sets the tone. Line Magnetic pushes its tube integrated amplifier into the realm of power, where most tube amps throw in the towel. The KT170 is the most robust power tube in production today, and the LM-170IA uses four of them to drive speakers that demand substantial current.
The KT170, the most powerful power tube
The KT170 is a beam tetrode from current production, the most powerful in its category. Its high plate dissipation and higher transconductance than the KT150 and KT88 give it the reserve needed to deliver 2x130 watts in class AB. The LM-170IA uses four of them, two per channel, mounted in push-pull. This configuration explains the rare power output for a tube amplifier, capable of competing with many transistor power amps in terms of control and dynamics.
An all-tube signal path
Before reaching the KT170s, the signal passes through three types of double triodes. Three 6922s handle input amplification, renowned for their low noise. Two ECC82s and two 6SN7EHs form the driver stage that controls the power tubes. Nothing leaves the tube domain between the input jack and the speaker terminals, which preserves the texture sought after in this type of design. Line Magnetic wires its amplifiers point to point, a manual method that takes longer than printed circuit boards, a guarantee of longevity and ease of maintenance.
Three output taps for a variety of speakers
Where many tube integrated amplifiers are limited to two impedances, the LM-170IA offers outputs at 4, 8, and 16 ohms. The 16-ohm tap is valuable for vintage or high-efficiency speakers, an area Line Magnetic knows well since the brand was born from the restoration and replication of Western Electric, Altec, and Jensen loudspeakers. Choosing the right tap according to your speakers’ impedance determines the output transformer’s efficiency and bass control.
Balanced input and home theater integration
The LM-170IA accepts a source via balanced connection (XLR) in addition to standard RCA inputs, with a sensitivity of 0.5 volt versus 0.36 volt unbalanced. A dedicated PRE input allows it to be integrated into a home theater setup by taking over the front left and right channels at fixed gain, without going back through its volume control. A SUB/PRE output, at 1.8 volt, sends the signal to a subwoofer or an additional power amplifier. These connections go beyond the scope of stereo listening alone.
A 45-kilo chassis and matching power consumption
The weight tells the story: oversized power and output transformers, essential for sustaining 2x130 watts from tubes. At 45 kilos, installation requires a stable support and a solid shelf. Power consumption reaches 750 watts, heat included: four KT170s generate a lot of heat, and it requires sufficient clearance around it, away from enclosed furniture. The frequency response extends from 20 Hz to 35 kHz at -3 dB, with a signal-to-noise ratio of 89 dB and distortion of 1% at 1 kHz, values consistent with a tube push-pull amplifier of this power.
Technical specifications
Overview
- Model: LM-170IA
- Type: integrated tube amplifier
- Configuration: Push-Pull KT170
- Power: 2 x 130 W
Tube complement
- Preamplifier tubes: 3 x 6922, 2 x ECC82, 2 x 6SN7EH
- Power tubes: 4 x KT170
Audio performance
- Output power: 130 W + 130 W in class AB Push-Pull
- Frequency response: 20 Hz to 35 kHz (-3 dB)
- Total harmonic distortion: 1% at 1 kHz
- Signal-to-noise ratio: 89 dB
Inputs and outputs
- Input sensitivity
- RCA: 0.36 V
- BAC: 0.5 V
- PRE: 1 V
- SUB / PRE auxiliary output: 1.8 V
- Input impedance: 100 kΩ
- Output impedance: 4 Ω, 8 Ω, 16 Ω
Power supply
- Power consumption: 750 W
Dimensions and weight
- Dimensions (W x D x H): 43 x 49 x 24.8 cm
- Net weight: 45 kg
Frequently asked questions
Which speakers are best suited to the LM-170IA?
With 2x130 watts and 4, 8, and 16 ohm taps, the LM-170IA drives a wide range of speakers, including low-sensitivity models that many tube amps struggle to power. High-efficiency speakers remain a natural match, especially via the 16 ohm tap. Compatibility depends as much on the speaker’s sensitivity as on its impedance curve.
Does the LM-170IA include a phono preamp for a turntable?
No. The LM-170IA does not include a phono stage. To connect a turntable, you need to use an external phono preamplifier, then connect its line output to one of the LM-170IA’s RCA inputs.
Should the power tubes' bias be checked?
A KT170 push-pull operates with a bias current that must be checked and adjusted periodically to keep the tubes within their operating range. The procedure is described in the supplied manual and should be followed after a few minutes of warm-up. Regular checking extends tube life and preserves sound quality.
Are KT170s expensive and time-consuming to replace?
The KT170 is among the most expensive power tubes on today’s market, pricier than a KT88 or an EL34. In return, a set of tubes lasts several thousand hours under normal home use. A full replacement is therefore fairly infrequent, but its cost is worth anticipating at the time of purchase.
Does a balanced connection provide a real benefit?
It rejects interference better over long cable runs, which makes it useful when the source is far from the LM-170IA. Over a short connection, the audible benefit remains slight: the choice depends mainly on the source and the installation, not on any automatic superiority of the balanced signal.
Should the amplifier be warmed up before listening?
Yes, a tube amplifier benefits from warming up before critical listening. About ten minutes is generally enough for the sound to stabilize. This warm-up also affects both the texture and the bass control.
- Eco-contribution included in the sale price.
