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Cambridge Audio 651A

Stereo integrated amplifier with USB input (Black)

12 Reviews | 2 questions - 7 answers

Item # 779651AB

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Our take on the Cambridge Audio 651A

Just looking at the Cambridge Audio Azur 651A, you get a little unstuck in time. Is it an exquisitely "old-school" integrated amp — everything you need for classic, analog stereo without any unneeded bells and whistles? Well, yes, but wait. The design is decidedly up-tempo and modern. And what's this USB port on the rear panel? That's the indication that the 651A is not your father's integrated amp.

Old school? Or a fresh face?

Just looking at the Cambridge Audio Azur 651A, you get a little unstuck in time. Is it an exquisitely "old-school" integrated amp — everything you need for classic, analog stereo without any unneeded bells and whistles? Well, yes, but wait. The design is decidedly up-tempo and modern. And what's this USB port on the rear panel? That's the indication that the 651A is not your father's integrated amp.

The analog features you want...

The 651A will handle analog stereo sources with the best in the field, process them without coloration, and feed them to the muscular amplifier stage. That's when things really get good: separate transformer taps and power supply units for the left and right channels manage 75 watts of robust, pristine power for startlingly quick transients and powerful, yet musical bass you can feel down to your core.

... and the digital processing you need

The Cambridge Audio Azur 651A back panel

The Cambridge Audio Azur 651A features a USB connection.

Of course, that's just what you'd expect from a Cambridge Audio integrated amp. But there's a nice surprise waiting. The USB input we mentioned before is a port to an internal DAC that processes your computer's audio files and delivers them to the analog preamp section with minimal jitter or other undesirable artifacts. And for most computers there's no need to install any new drivers. One connection and you're ready to go.

The handsome, acoustically damped chassis features a brushed-aluminum, matte-black finish. The precision volume control means the 651A will deliver even low-volume levels with impact, presence and minimal noise.

Product Highlights:

  • 75 watts x 2 channels into 8 ohms (20-20,000 Hz), 0.03% THD at 80% of rated power
  • signal-to-noise ratio: >92 dB
  • toroidal power transformer for low noise and high-current output
  • separate transformer taps for left and right channels, twin rectifiers and separate PSUs for dual mono operation of the left and right power amps
  • 5 RCA line-level analog audio inputs accommodate CD players, tuners, other components
  • front-panel minijack input for connecting a portable music player
  • 2 stereo RCA record outputs
  • 1 stereo RCA preamp output and a dedicated mono subwoofer output
  • connect a turntable with a phono preamp
  • USB input accepts 16-bit, 32/44.1/48kHz signals, no drivers needed for Mac® or Windows® computers
  • infrared control input and control bus input/output for integration into multi-room systems
  • full-size headphone jack
  • remote control
  • 16 15/16"W x 4-5/8"H x 14-5/8"D
  • weight: 18.5 lbs.
  • warranty: 3 years
  • Our 60-day money-back guarantee

After spending a little time with the unit and honing in my studio connections, I am very happy with the purchase. I was going to return the unit and purchase a NAD DAC integrated amp; however, for the price; a no brainer. I am running a pair of vintage Klipsch Heresy II with the amp. Incredible!!

Jude, North Carolina

What's in the Box:

  • Integrated amplifier
  • 6' AC power cord
  • IR remote control (RC-651A/C)
  • 3 "AAA" batteries
  • User Manual (Eng/Fre/Spa)
  • Quick Start Guide (Eng/Fre/Spa)

Cambridge Audio 651A Reviews

Average Customer Review(s):

(12 Reviews)

Cambridge 651A

Jude from North Carolina on 6/28/2015

Crutchfield Customer Review (What's this?)

After spending a little time with the unit and honing in my studio connections, I am very happy with the purchase. I was going to return the unit and purchase a NAD DAC integrated amp; however, for the price; a no brainer. I am running a pair of vintage Klipsch Heresy II with the amp. Incredible!!

Pros: Easy to use; had more of a problem synchronizing everything with my Presonus software. Once in, it's killer!!



Will from South Dakota on 5/26/2015

Crutchfield Customer Review (What's this?)

Was wanting a simple amp with CLEAN POWER. Being OLD school wanted to be able to hook it up with out a lot of problems. Has all the power needed to run four speakers with power left over. Have not had a need to go much over a quarter of the volume to have crisp ,clean music!! Was simple to hook up, and even simpler to use. Want old school ease with new school power, then this is the AMP to have. All the company reps where GREAT to work with. Not sure what your looking for, ask a Rep. They led me to this GREAT AMP. You shouldn't be disappointed with this one.

Pros: Nothing hard to use about it. Hook it up and enjoy great ,clean music.

Cons: NONE......

Good Deal Good Experience

MartinR from Philadelphia on 3/5/2015

Crutchfield Customer Review (What's this?)

I'd been looking for an amp to place in a small to medium space. Didn't want to spend a ton of dough because its not my critical listening area but I wanted quality performance. I looked at a lot of amps and settled on this one. Happy with the choice and the price. Plenty of power for my application (2 bookshelf speakers and a powered sub) . sounds very good when sourced by a computer and an audio engine d-1 dac. I wouldn't bother with the internal DAC unless you're forced to. its just OK. Solidly built and handsome to look at in an understated way. (well I think so). You should consider this one if its in your price range. Also I was very pleased with the purchasing process and quick shipment. kudos to Crutchfield!

Pros: Very Good performance / value at this price Well constructed feels solid Plenty of power

Cons: Internal DAC is meh. Indicator lighting could be better but I really don't spend a lot of time looking at it.

Best Amp

Antonio from New York on 2/17/2015

Crutchfield Customer Review (What's this?)

The best amp I've ever owned, The moment I plugged in, I knew that was a special thing, the sound was just unbelievable. It made my speakers sound like heroes.

Pros: Great sound at great price, it is all you need, to have proper audiophile sound



Matthew from WI on 1/19/2015

Crutchfield Customer Review (What's this?)

This is a great amp! I previously had the NAD T758 and that sounded.. ok.. it had amazing hi's and midrange however the bass seemed like it was missing something. Kind of doggy, sliggish, boring. This system out of the box sounds like a real hi-fi system. The simplicity of the design is what makes the difference. The bass is tight and punchy, Hi's are crisp and clean not harsh, and the mids sound mellow with a little bite here and there during rock music all the way to the piano guys and enya. Imaging is clear and thats something the NAD completely missed compaired to this system. Its driving my Monitor Audio Silver 10's without a problem through audioquest oval cables. I couldn't be happier! Very impressed Cambridge very indeed!

Pros: Crisp Hi's clean mids punchy and straight forward bass. plenty of power!! im not biamped yet! The Imaging!

Cons: Non to be found yet. maybe the fact the only way to use the DAC is by usb and not coax or optical. but the sound may be cleaner without those two.


kjj from Massachusetts on 12/15/2014

Crutchfield Customer Review (What's this?)

I've had this integrated amp for two weeks now and I am very happy with it. I have Polk LSi7 bookshelf speakers with a powered sub and they were hooked up to a Onkyo receiver that I was happy with but wondered if an integrated amp would be an improvement. I have to say I'm amazed at the difference. More detailed highs and more powerful bass, more overall detail and dimension in the sound. I read some reviews that said some amplifiers were "fatiguing" to listen to and didn't understand until I compared this to my old receiver. A volume that I would only listen at for one song with the receiver I listened at for two hours with the 651A. The 651A also places instruments more precisely and made my small den seem much bigger than it is, and the DAC makes streamed music sound great too.

Pros: Terrific clean full sound

Cons: no outlets on the back, not a big deal to me but worth mentioning. the only way to select A or B speakers is with the remote, not sure what happens if the remote quits.

I have no words to express

nprathap from California on 12/7/2014

Crutchfield Customer Review (What's this?)

I have been doing a lot of research for finding a best amplifier which will do justice to my listening choice and sources I have and finally I have my hands on CA Azur 651A. Elegant and it pairs very well with my KEF LS50 speakers and both european brands and what more to say it is an awesome combination which is joyful and musical! its been few days I have them connected and both the AMP and speaker is burning in and I will feel the true and even more sweetest musical treat in coming days. I am so thankful to crutch field team getting my AMP what I was looking for from last 2 years... for an awesome price during the holiday. I got Nancy from crutchfield who helped me to have my faith more stronger in this product. We work, spend time with family and friends and there could be moments where you needs your own time and space, where you might be bound my emotions, feelings and as we say "You enjoy the music when you are happy and you listen to the lyrics when you are sad" and CA 651 can make you happy - the clarity of the sound you get from it is Amazing, and more over the mid and the high frequency signals are very well engineered and you can feel the music as you hear the artist perform live. My setup when I plugged it to the speakers I experienced the true sense of disappearance. It was the most joyous moment which I will ever remember! The support was excellent and I received my order as promised and a safe delivery with great problem free package over all no complaints!

Pros: Crisp and clear. It takes a while to burn in, once you have the right cable, speakers and power supply its phenomenal. More value for money and it is really a premium amplifier. I was lucky that I got the holiday price discount and its worth the buy! I have a monitor headphone and the headphone out on the AMP makes it a treat too, if i have to use it just for myself when there are people around. You will start listening to the musical notes which you might have missed, music is so detaile

Cons: None. I wish the DAC was 24 bit.

Cambridge Audio 651A

RichardK from Raymond, Ms on 3/25/2013

Crutchfield Customer Review (What's this?)

After purchasing a pair of high end floor standing speakers, I wanted an integrated amp that would fully take advantage of the incredible sound capabilities of these speakers. After some helpful, expert advice from Norm, my Crutchfield advisor, I selected this Cambridge unit. I am amazed the diffference this amp makes to truly make these speakers "sing" at their best.

Pros: Ability to create incredible sound from your stereo components.

Cons: Pricy, but worth it if you want high quality sound results. Wish it had a phono input.

Cambridge 651a .....My 2nd REVIEW

Franklin O from New kensington ,PA on 3/16/2013

It`s been 3 weeks now since i got the 651a it was a little bright when i first hooked it up useing the polk tsi200 bookshelf speaker`s since then it has got better more bass.this is a fantastic amp if you buy this you won`t regret the purchase at 75 watts its enough to drive most speakers fine .I hope this helps the buyer who reads this review

Pros: nothing bad or negative all good for this amp ,sound is superb with all music etc....

Cons: i agree with the other reviewer you hear a thump when other sources are hooked only time i hear it is when the powered subs turn on at start up which all amps do this one day they will get this fiquered out to stop the thump

Cambridge 651a

Franklin O from New kensington ,PA on 3/5/2013

I bought this based on the 2 reviews i sure am happy i did wonderful sound hooked it to my polk tsi200`s and i have to infinity subs it only has 1 sub output so i split the channels it sounds like a $3,000 system thanks CHAD for your advise on getting this amp also thanks crutchfield for putting up with all my questions through chat you all are wonderful and very helping even though i did not buy everything i chatted about with thoughts on purchasing again all my thanks to you all FRANKLIN O-

Pros: it has everything ill ever need for my setup

Cons: none here just a great amp sounds clear and punchy i cannot say enough to express how nice this amp is

Cambridge Audio 651A

JonzDad from Tucson, AZ on 12/21/2012

Crutchfield Customer Review (What's this?)

Excellent amplifier for home. Delivers clean and clear sound with even power distribution across the entire audio spectrum. No discernable bias to bass, mid-range, or treble results in full audio presence. Result is very satisfying full and natural sound.

Pros: Great sound. Easy installation. Intuitive controls. Connections fool-proof and solid.

Cons: A difficulty that all amplifiers have, and no resolution yet: a very smart electronic control to suppress speaker "thump" when other connected devices are turned on and off. Not doable yet, but I can always hope.

Lovely Integrated Amp

JamesW from Brooklyn, NY on 1/17/2012

Crutchfield Customer Review (What's this?)

Wonderful component, lush warm crystal clear sounds with paired Cambridge 651CD player, fantastic value, drives my high-end speakers loud and fine




Hands-on research

Features and Specs

Performance Specs
Watts RMS per Channel (8-ohms) 75
Watts RMS per Channel (6-ohms) Not given
Watts RMS per Channel (4-ohms) Not given
Frequency Bandwidth 20-20k
THD 0.03%
Minimum Impedance 4 ohms
Signal to Noise Ratio 92
Digital Music Features
Built-in DAC (Digital to Analog Converter) Yes
High-resolution Audio Playback No
Bluetooth ---
Total Analog Inputs 5
Phono Input No
Optical Digital Inputs No
Coaxial Digital Inputs No
USB Input Type-B
Preamp Outputs 3
Headphone Output 1/4"
Dimensions and Warranty
Width (inches) 16-15/16
Height (inches) 4-5/8
Depth (inches) 14-5/8
Weight (pounds) 18.5
Parts Warranty 3 Years
Labor Warranty 3 Years

Product Research

Add-On Devices


High Quality Sound Reproduction: The Cambridge Audio Azur 651A integrated amplifier has been designed and engineered to deliver the purest, most realistic sound reproduction possible; free from interference or distortion.

Full Metal Chassis: The 651A integrated amplifier features an acoustically damped, low resonance full-metal chassis with a thick, brushed aluminum front-panel.

75W x 2Ch Integrated Amp: The Cambridge Audio Azur 651A delivers an impressive 75 watts per channel into 8 ohms, at 20-20kHz, with 0.03% THD at 80% rated power.

Fully Discreet Amplifier Circuitry: The 651A integrated amplifier has separate transformers for left and right channels, twin rectifiers, and separate PSUs for dual mono operation of the left and right power.

ALPS " Black Box" Volume Encoder: The 651A integrated amplifier uses a high end ALPS "Black Box: volume encoder that all of the signal goes through this at all times, so this is a very key component. Benefits include perfect channel balance at all volume levels and improved and stereo separation.

Toroidal Transformer: Unlike a lot manufactures who use cheap laminate type transformers, the 651A use an audiophile grade toroidal transformer offering minimal electro magnetic interference and delivering superior audio performance.

Heat Sink: The 651A integrated amplifier features substantial extruded heat sinks, allowing the amp to deliver incredible power and control.

Polypropylene Capacitors: New low inductance resistors and polypropylene signal capacitors are used for superior audio performance.

Buffered Input Circuitry: The 651A features buffered input circuitry for superior audio performance, including lower crosstalk and improved stereo imaging. It also uses new low dissipation polypropylene signal capacitors and custom made electrolytic capacitors in critical positions.

Redesigned Output Stage: The 651A integrated amplifier uses completely redesigned output stages with new Sanken output transistors, improving bass response and dynamics even further.

5-Way Protection System: Cambridge Audio has developed a proprietary protection system to ensure reliability and long life of its amplifiers. This proprietary protection system is known as "CAP5 protection circuitry". This protection system comprises five main protection methods:

  • DC Detection: CAP5 offers loudspeaker protection if the output of the amplifier goes to a high constant voltage (DC).
  • Over Temperature Detection: AP5 includes temperature detection which constantly monitors the heat generated by the output transistors. If the monitored temperature reaches a high level (suitably within the limits of the output devices) the amplifier will automatically switch into a fault mode.
  • Over Voltage Detection: CAP5 offers V/I protection by constantly monitoring the output transistors to keep them working inside their Safe Operating Area (SOA). The SOA is a set of limits given by the output transistor manufacturer to ensure reliability. V/I also protects the amplifier against short-circuits on the speaker terminals during use.
  • Short-Circuit Detection: During power up from Standby, CAP5 performs a check on the loudspeaker terminals to see if a short across the terminals has been accidentally introduced. If the resistance measured across the loudspeaker terminals is too low, the unit will remain in Standby mode until the fault has been removed and power up is re-attempted.
  • Intelligent Clipping Detection: CAP5 has the ability to detect when the amplifier starts to clip or overdrive at its output, which can damage loudspeakers and degrade the sound. Clipping distortion is caused at high volume levels when the output signal briefly goes outside the maximum voltage that the amplifier can provide, causing the tops of the signal to flatten off. When CAP5 detects clipping, the volume will be automatically nudged down until CAP5 detects an undistorted output.

Standby Circuit: This innovative new circuitry design allows 651A integrated amplifier to consume less than 1 watt of power when in Standby, but itself remains totally isolated and non-detrimental to the sound quality when the amplifier is in operation.


Main Power Switch: The 651A integrated amplifier's main power on/off switch is located on the rear-panel.

Standby/On: Once the amp's rear-panel main power switch has been turned On, you can switch the 651A On/Off using the front-panel Standby/On button.

Volume: Use the front-panel rotary volume control to increase or decrease the level of the sound from the outputs of the amplifier. The volume control affects the level of the loudspeaker output, the preamp output, and the headphone output. It does not affect the Rec Out connections.

A/B Operation: The Cambridge Audio 651A integrated amplifier lets you play A speakers only, B speakers only, or A and B speakers together.

Direct: This control gives the audio signal a more direct path to the power amplifier stage of your amplifier, bypassing the bass and treble control circuits for the purest possible sound quality.

Bass and Treble: The 651A integrated amplifier has independent Bass (20Hz) and Treble (20kHz) controls which can be adjusted from +/-7.5dB. The Bass and Treble controls only effect the speaker and preamp outputs; they do not effect the record outputs.

Balance: This control allows you to adjust the relative output levels of the left and right speaker channels. The Balance control only effects the speaker and preamp outputs; it does not effect the record outputs.

IR Remote Control: The 651A is supplied with an Azur Navigator IR remote control that operates both this amplifier and Cambridge Audio Azur-series CD players. The Azur 651AC Navigator remote control can also control the basic functions of Apple devices, such as Apple TV and Apple's iPod/iPhone/iPad when docked in a Cambridge Audio or Apple dock (sold separately).

Note: The remote operates off of three "AAA" batteries (supplied).


Analog Audio Inputs: The Cambridge Audio 651A integrated amplifier is fitted with five pair of gold-plated analog audio inputs (RCA) to connect your external audio sources; such as your Blu-ray/DVD player, AM/FM tuner, CD/SACD player, or Network Player.

Note: The 651A integrated amp is not equipped with digital inputs/outputs or video inputs/outputs. There is also no Phono input.

Analog Audio Outputs: The 651A integrated amplifier features two pair of gold-plated analog audio outputs (RCA) that can be connected to a CD recorder, MiniDisc recorder, or tape recorder.

Front-Panel Aux Input: The Cambridge Audio 651A integrated amplifier features a front-panel Auxiliary (3.5mm) input to connect your portable MP3 player or other portable audio device.

USB Port: The 651A integrated amplifier is fitted with a rear-panel USB (type-B) full-speed 1.1 port allowing USB audio streaming from your Windows PC (XP, Vista, 7) or Mac computer (Mac OSX 10.5 or higher). The USB port supports 16-bit/32kHz, 44.1kHz, or 48kHz audio.

A-B Speaker Terminals: The Cambridge Audio 651A integrated amplifier is equipped with two sets of gold-plated, binding-post speaker terminals (labeled A and B). The use of A and B speaker terminals allow you to hook up speakers in another room.

Note: When using two pairs of speaker, use only speakers with a minimum nominal impedance of 8 ohms.

Subwoofer Output: The 651A integrated amplifier is equipped with a mono subwoofer output to connect a powered subwoofer for added bass response.

Preamp Output: The Cambridge Audio 651A is equipped with a pair of RCA preamp outputs to connect the integrated amp to an external power amplifier.

Record Outputs: The 651A also features two pair of gold-plated analog audio record outputs (RCA) that can be connected to a CD recorder, MiniDisc recorder, or tape recorder.

Headphone Output: The 651A integrated amplifier offers a front-panel 1/4" headphone output to connect a set of headphones for private listening. When headphones are connected, the output to both A/B loudspeakers is muted. Use headphones with an impedance of between 32 and 600 ohms.

IR Emitter: The 651A features a IR Emitter input (3.5mm) which allows modulated IR commands from multi-room systems or IR repeater system to be received by the amplifier.

Control Bus: The 651A features a Control Bus Input and Output (RCA), which allows un-modulated commands from multi-room systems or other components to be received by the amp and loop out to another unit.

AC Power Cord: The Cambridge Audio 651A operates off of standard household AC current using the supplied detachable 6' AC power cord.

Add-On Devices

Azur Series CD Player: The Cambridge Audio Azur 651C Compact Disc Player (779651CB, sold separately) is the perfect companion to the 651A integrated amplifier.

DacMagic: Get even better sound from your computer's stored music and Internet radio, as well as add optical/coaxial digital inputs to the 351 A integrated amplifier, with a Cambridge Audio DacMagic external digital-to-analog converter (779DACMPLB, sold separately).

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

Q & A

Customer Q&A

2 questions already asked

We use the additional chanels for bi wire by designating them. Yes you can tell a difference in the low end by bi wiring. [ JAY  Jan 31, 2014 ]
Yes A and B can bd used to bi wire ..but to be honest with u ..u wont gain anything unless your bi amping that is where u will see a diffrence [ FRANK D  Jan 20, 2014 ]
Yep, worked fine. [ Floyd  Dec 15, 2014 ]
115V. [ Ronald  Dec 14, 2014 ]
The back of my unit says Power rating: 115volts AC - 50/60Hz. Maximum power consumption 600W. Definitely works on USA power outlets. [ Leigh  Dec 14, 2014 ]
I got mine two weeks ago and yes, it is 120 volt. [ KEVIN  Dec 14, 2014 ]
I do not recommend the 651A. I was dissatisfied with the sound and returned it. Instead, I purchased a Rogue Sphinx and was thoroughly impressed with the difference in quality. I'm a tube man and will never go back to solid state. [ John  Dec 14, 2014 ]