Sugden IA-4 Flagship Integrated Amplifier by John Hoffman

Sugden IA-4 Flagship Integrated Amplifier

I have wanted to hear a Sugden amplifier in my listening room for years. I am a big fan of Class A amplification, which excels in producing a warm midrange and fast, controlled bass. My Class A amplifier journey includes building two Nelson Pass-designed Amp Camp Amps and owning two other Pass Labs Class A models. My current solid-state reference amplifier is a rebuilt Plinius SA-50 that offers both Class A and A/B modes, which is a great feature when running the AC in the summer heat. The amp runs cool in A/B mode, which reduces stress on the amplifier. I also use my system for two-channel movie watching, so no need to have it in Class A.

J.E. Sugden & Co Ltd.

Sugden Audio has been designing and manufacturing audio products in the UK since 1967. The IA-4 is their flagship integrated model from their “Master Class” series. It provides 33 watts per channel, has three line-level inputs, a tape input, an MM phono input, a balanced variable pre-out, a fixed out, a loudspeaker out, a monitor and record button, and a decent plastic remote that works well. Retail price is $7,495 as of this writing. The review model was sent to me by Jonathan Halpern, the owner of Tone Imports, and arrived in a cool Kermit-green ionized front panel, a pleasant change from the audio-orthodox black or silver.

The fit and finish are high-quality. The front features a symmetrical design, with a center-volume knob flanked by an on/off button to the left and an input selector to the right.  A “Monitor on/off” push button and a power on LED on the left, and the eye for the remote and “Record on/off” to the right. The back is laid out nicely, with “Phono in” at the top, “Tape in” at the bottom, and three RCA source inputs in the middle. The IA-4 also has one set of balanced inputs.

Outputs include a “Pre-out” for use with other amplifiers and a “Tape out”. Speaker posts are high-quality and large, making it easy to see the red/black indicators. The main power switch is on the back, lower left area, while the front power switch puts the amp in standby mode.

Sugden offers other integrated models at lower prices, so what do you get from the Flagship IA-4 upgrade?  According to Sugden, “the Class A power output circuit has been upgraded from the A21 product series with a larger power supply and improved smoothing and output capacitors. Also included in the move to the flagship IA-4 are gold-plated circuit boards, full relay switching, and a precision input selector switch, which offer further detailing. Sugden continues, “The IA-4 is a bespoke design, with surprising clarity and detail.” 

Sound Characteristics

This is a stunning-sounding amplifier. The first thing I noticed was the broad and deep soundstage. Images were holographic and clearly separated in space. Tonality was warm, with lush midrange, natural timbres, and extended decay, all bursting out of a black background. The IA-4 produced controlled, clear bass and had no problem driving my Devore O/96, which are 10-ohm and 96 dB efficient, and the Qualio IQ speakers, which are 4-ohm and 89 dB efficient. What came to mind while listening to the IA-4 was tube warmth and solid-state dynamics.

Sugden states, “The most noticeable feature of the IA-4 is the ability to create a large performance with depth and height on any type of music,” and I agree. No matter the genre of music, the IA-4 delivers depth, detail, and width in the soundstage, making for an engaging listening experience.

While the tonality was similar to my reference Plinius Class A amplifier, the IA-4 had a bit more detail and nuance. At the same time, the Plinius presents a leading-edge, sharper, and less natural sound, especially with piano.

Listening Tacks:

Billy Strings “Gild the Lily” on the Album Highway Prayers

Let’s start with something different that has become of interest to me: Bluegrass. Billy Strings is leading a Bluegrass revival and has gathered a cross-genre following. Gild the Lily was recorded with the full Bluegrass band of Mandolin, Guitar, Double bass, Fiddle, and Banjo. This track has a contemporary/psychedelic feeling more than a traditional Bluegrass sound. The IA-4 allows me to hear the subtle Banjo and mandolin playing in the background, and the weight of the Double bass comes to life with clear, room-filling sound. The sound-staging qualities Sugden described really shine in this recording.

Thelonius Monk “Epistrophy” on the album Monk in Tokyo

The IA-4 presented a very realistic layered instrument separation and natural tone and timbre, engaging and bringing the live show into my listening room. Charlie Rouse’s sax was crisp, clear, and warm with plenty of detail. Frankie Dunlop’s drums had fast transients and realistic-sounding symbols with long decay. Together with the rest of the band, the IA-4 delivered a weighty, thoroughly engaging experience at the venue.

Kronos Quartet “Rambling Boys of Pleasure” on the album Folk Songs

The Kronos Quartet performs far beyond the traditional classical genre. I highly recommend them. “Rambling Boys of Pleasure” begins with Olivia Chaney’s soulful vocals, accompanied by a Harmonium and other instruments. The IA-4 gave her voice a realistic quality, fully engaging me. The previously mentioned qualities of the Sugden IA-4, such as soundstage width and depth, combined with its Class A lush midrange, make for an excellent listening experience.

If you are in the market for an integrated amplifier, I recommend hearing the Sugden IA-4.

Specifications: 

Price: $7,495

Line Input Sensitivity: 125mV​​

Phono Input Sensitivity: 2mV (mm)​

Power Output: 33 Watts per channel into 8 Ohms

​​Frequency Response: +/-1dB 14Hz-200kHz

Bandwidth: 6Hz- 300kHz

Signal to Noise: >84dB

Gross Weight(packed): ​20kgs

Dimensions: 165 x 430 x 440mm (hwd)

Features: Three line level, tape, MM phono, balanced

Variable pre-out, fixed out, loudspeaker out

Remote control RC5 Compatible

Monitor and record off​​​​​

Website: www.sugdenaudio.com/ia-4-integrated-amplifier

John’s Associated Equipment

Grimm MU2 Music player (Streamer/DAC/Preamplifier)

Plinius SA-50 Power Amplifier

Audio Note Kit EL 34 Amplifier

Pine Tree Audio ISO-Twist SPC (Silver Plated Copper) RCA interconnects

Pine Tree Audio Visceral Speaker Cable

Devore Fidelity O/96 speakers