CSD Class D Integrated Amplifier

The goal of the CS series has always been to produce an integrated amp that focuses on performance-per-dollar, not on cosmetics or bells and whistles. The focus is on the stuff that makes music: the guts, the circuitry, the power supply; not on cosmetics or a bunch of options that most people don't really need. In order to keep the price down and the design simple but functional. The chassis is aluminum not steel. The faceplate is the standard Blue Circle stainless steel.

CSD Int Amp front

There are only three single-ended line-level inputs, no tape loops or preamp outs. The front panel has only a power button, a laser-trimmed Alps volume control, and an input selector. There is just one set of speaker terminals on the back panel. But if you take a look under the hood, where it really counts, you will see that this is not a typical entry-level amplifier.

The CSD preamp section is based on the BC reference-quality BC107 line stage preamp. This precision-biased class A/B single-ended parallel topology was developed by Gilbert Yeung and is exclusive to Blue Circle Audio. The output stage is derived from a unique class D design that he developed for the new 2K series of power amps. It produces a conservative 145 watts into 8 ohms and 290 watts into 4 ohms. As with all Blue Circle components, power supply filtering is best described as very serious overkill. There is plenty of gas in the tank of this little hot rod.

GDC Int Amp back

Optional features

  • USB input with built-in DAC for playing music and movie audio from computer
  • RF remote volume control
  • JAFBP binding post
  • Tape loop
  • Phono input feature 60dB and 38dB user adjustable gain.
  • Stainless steel and wood control knobs
  • Stainless steel faceplate
  • Retail price

    Standard unit: $2495.00 E-mail us for optional feature pricing.

    TLP Audio says...

    "I recently had the pleasure of auditioning the production version of the new CSD class D integrated amplifier. Gilbert told me it had already been running for a week straight prior to its arrival here and I believe it because I listened immediately after power on and again several hrs later in the afternoon. There was no discernable difference to me. After being powered on for 6 hrs and running continously, the amp was barely warm to the touch. It sounds UNlike any other solid state amp that I've heard....warm, "toasty", comfortable, expansive, and detailed. I thought sure there was at least 1 tube hiding in there someplace BUT nope! For a retail price of $2500 and short lead/build time of 30-45 days, this should be a good seller for us. It brings back fond memories of the halcyon days of CS integrated.

    During its hayday, we sold a ton of the original CS (50 wpc) integrated amplifiers and the CSD replaces it with better sound, more power in a lightweight package. What a great way for high-end audio fans to get started in the Blue Circle realm."

    Standard Features

  • 145 watts into 8 ohms and 290 W into 4 ohms
  • 3 line level inputs
  • Laser-trimmed Alps attenuator
  • Stainless steel faceplate and wood knobs
  • Optional features

  • Black Plexiglas, black aluminum, or custom wood faceplate
  • Stainless steel knobs
  • Custom cover colors
  • Processor bypass loop
  • RF remote volume control
  • Onboard DAC and/or phono stage in a larger chassis

    Technical Information

  • Residual noise referenced to full output power, volume control at zero: >-105dB within audio band
  • Tracking error: < +/- 0.2 dB
  • Frequency response (10W into 8 ohms): 10Hz to 35kHz +0.00 dB, -0.2 dB; - 3.0 dB at >100kHz
  • Distortion at 10 W into 8 ohms: < 0.3 % Voltage gain: 38.5 dB
  • Input sensitivity (reference to 10 W) with volume control fully open: 0.1 V
  • Input impedance: 100k ohms
  • Shipping Weight: 15 Lbs

  • DAR Integrated Amp

    Sparkling highs that make music come to life, a sweet inviting midrange, full-bodied palpable presence, and a rounded controlled bottom end are the hallmarks of the DAR's sound. The DAR will produce stunning, musical bass performance even when driving small stand-mounted monitor speakers but will also tame the overloading often associated with large woofer designs. All of these features combine to present the listener with an enjoyable musical experience.

    The DAR, a hybrid integrated amplifier with a 6SN7 tube at the input stage, produces 100 watts into 8 ohms and 150 watts into 4 ohms. The innovative design of the DAR presents a number of technical firsts for Blue Circle Audio. It uses a "pancake" style torodal transformer that has high current, high power, and high-speed capacity without the noise that is typically associated with transformer design. Its dual power supply allows the tube and output stages to function independently for better imaging and soundstage creation.

    DAR Int Amp

    The DAR's discrete circuitry creates smooth sparkling highs and a powerful-controlled bottom end. The circuitry utilizes two ultra high power bi-polar transistors for each channel to ensure that phase coherence is at its best . The over sized heat sink makes ensures that the output devices run at their optimum operating temperature.

    DAR Int Amp

    Most interestingly, the 6SN7 tube, seen in the following picture, is configured as a unity gain at the input stage. This innovative design feature optimizes the 6SN7 to take full advantage of its sonic signature. The DAR's circuitry is so transparent, it shows off the best of the 6SN7 and allows the seasoned audiophile to roll tubes and fine-tune this exceptional design to their personal preference.

    DAR Int Amp

    The DAR runs so cool that you can install it in confined space. It needs a scant 5 inches to breathe *. Its multiple protection circuits including DC offset, thermal overload, and short circuit at the output make it safe and easy to use while driving the most difficult loads to satisfying volumes. The DAR also includes a power-on muting delay to avoid turn on transients.

    DAR Int Amp

    All parts used in the DAR are RoHS (lead-free) compliant. The DAR uses less energy than a 5 watt tube amp during idle. When the power switch is off the unit is disconnected from the power source and draws zero power. The high efficiency output stages are efficient and therefore generate very little heat.


  • 100 watts into 8 ohms, 150 watts into 4 ohms.
  • 3 line level inputs
  • tape or processor loop
  • 1 preamp output
  • Ground lift swtich
  • Earth Ground post

  • Specifications

  • Residual noise referenced to full power output, volume control at zero: >- 110 dB or <75 uV non-weighted
  • Residual noise referenced to full power output, volume control at zero: >- 115 dB or < 35 uV within audio band
  • Tracking error: < +/- 0.2 dB-Frequency response (10W into 8 ohms): 10Hz to 35K +0.00db, +/0.0dB, -0.2dB; - 3.0db at >100kHz
  • Distortion at 10W into 8 ohms: < 0.3 %
  • Voltage gain: 23.5dB
  • Input sensitivity (reference to 10W): 0.6V -input impedance: 100K
  • * at 25 degrees C room temperature

    Read the Reviews

    Affordable Audio: February 2008 issue

    SoundStage: September 2008 issue


    The even better news is that you can order the Shallco attenuator and remote volume control options. Yes, you can have both. Plus, you can choose to have either a balance control or dual Shallco attenuators.

    MSRP for standard unit and available options:

  • DAR standard price: USD3299.00
  • Single Shallco attenuator price: USD419.00
  • email us with questions.

    KATLAS Integrated Amplifier

    The Katlas is a 145 wpc integrated amplifier that shares it's sonic heritage with the GDC. With its extra wattage and power supply storage capacity, the Katlas has a more authoratative bottom end while retaining the overall balanced presentation of the music. Its quick and transparent quality lets you hear through the performance and the venue acoustic*. The Katlas strikes that perfect balance between delicacy and authority that will make you simply want to spend more time listening to music.

    Katlas Int Amp front

    TLP Audio says.... We here at TLP audio spend a lot of time doing live recording, mixing and mastering music, as well as listening, of course. When we listen to our live recordings, we hear the space that separates each instrument along with definition. We hear none of that "lost in spaceness" that is typical of today's integrated amplifiers. The music simply sounds more live!

    Katlas Int Amp rear

    Standard Features

  • 3 Line level inputs
  • Ground Lift switch
  • Single Shallco attenuator with high/low level switch
  • JAFBP binding posts
  • Black metal faceplate
  • KATLAS prototype shown with optional stainless steel faceplate.

    Optional Features

  • processor bypass loop
  • remote volume control
  • various colours and materials for faceplate, cover and control knobs - some options at additional cost.


    Not all options may be installed in one unit.
  • USB input with built-in DAC for playing music and movies from a computer
  • remote volume control
  • tape loop
  • processor loop
  • phono input feature 60dB and 38dB user adjustable gain.
  • Stainless steel faceplate
  • various wood control knobs
  • Specs and Measurements

  • 145 wpc into 8 ohms, 220 wpc into 4 ohms
  • Tracking error: <+/- 01dB
  • Frequency response (10W into 8 ohms): 10Hz to 25KHz +0.00dB, -0.1dB; -1.0dB at 50kHz
  • Distortion at 10W into 8 ohms: <0.15%
  • Voltage gain: 38.5dB
  • Input sensitivity: 0.5V with volume control at full clockwise
  • Input impedance: 100Kohms
  • Dimensions (basic black faceplate model): 19" wide x 3.875" high x 15.5" deep
  • Weight: 42 Lbs
  • Retail price

    Base unit: $4285.00

    E-mail us with questions and optional feature pricing.

    FtTH2 Hybrid Integrated Amplifier

    FTth2 Int Amp front

    The Details
  • 100 watts / channel into 8 ohms and 135 watts / channel into 4 ohms.
  • hybrid integrated amplifier using 1 6992 tube for both channels.
  • true balanced output stage.
  • Shallco attenuator with level switch.
  • heavy-duty binding posts.
  • separate power supply to elminate hum and mechanical noise from the transformers. separate power transformers for the input stage, output stage and control circuitry to reduce noise and interference between each stage.
  • total power supply filtering is over 210,000uF.
  • soft-start circuit to prolong tube life.
  • controlled-time turn-on to elminate turn-on/off transients between stages.
  • 3 ft standard DC power cord between the power supply and integrated amp.
  • longer cord lengths available - maximum 5 ft for optimum performance.
  • FTth2 Int Amp back panel

    Optional Features

  • preamp output
  • dual Shallco attenuators or balance control
  • processor bypass loop
  • remote RF volume control
  • various colours and materials for faceplate, cover and control knobs - some options at additional cost.
  • KQ power box (an additional 450,000 uFof power supply filtering)

    Specs (measured w/matched tubes)

  • Residual noise ref to full power output: >- 95 dB or < 480 uV non weighted
  • Residual noise ref to full power output: >- 108 dB or < 100 uV within audio band
  • Tracking error: < +/- 0.05 dB
  • Freq response (10W into 8 ohms): 10Hz to 50K +0.00db, - 0 dB; - 0.2 db at >100kHz
  • Distortion at 10W into 8 ohms: < 0.35 %
  • Voltage gain: 29.4 dB
  • Input sensitivity: 0.94 V
  • input impedance: 100k
  • Weight: 22 lbs integrated amp; 23 lbs power supply; 9 lbs KQ power box

    Retail price

    Base unit: $6155.00

    E-mail us for optional feature pricing.