audience banner


sheng ya


banner ad


You are reading the older HTML site

Positive Feedback ISSUE 56
july/august 2011


blue circle audio

BC 507/509 DAC

as reviewed by Gary Lea



blue circle dac






Von Schweikert VR4 MKIII, Odeon Elektra Horns, Compact WZSE Collector's Edition, Usher 6311 and AAD Silver Reference 1.

Tube: Jolida Music Envoy 211 tube monoblock amps and preamp (main reference). 
Solid-State: ShengYa PSM-600 monoblock solid-state amps and matching CS6 tubed preamp.

Digital Front End: Grant Fidelity Reference Tube 1000 CD player (main reference), Cary Audio DVD 6 used as a CD, Wadia i170 iPod Deck and 160Gig iPod.
Analogue Front End: Consonance Droplet 5.2 MKII with ST600tonearm (main reference) Nottingham Analogue Hyper Space and Arm with Wave Mechanic. Montegiro Lusso with DaVinci Noble and SME 5009 tonearms.
Cartridges - Koetsu Azule Platinum(main reference), Koetsu Urushi Vermillion, Goldnote Baldinotti, Dynavector 17D3 cartridges. Phone Stages: Goldnote Pamphili (main reference), Blue Circle Fon Lo Thingee, Musical Fidelity V3, and Koetsu Step up transformer.

XLO Signature 3 interconnects speaker cables and power cords (main reference cables currently). Furutech DIY interconnects. Kimber Kable Monocle XL speaker cables and Select Interconnects. And a bunch of cables I am too lazy to list.

Grant Fidelity RPF-120 MKII Reference Power Conditioner. Misc doodads and tweaks and loose parts like all audiophiles.


So here I find myself again reviewing one of Blue Circle Audio's bits. Albeit a more conventional piece than the Fon Lo Thingee that I last reviewed a year ago.

For a bit of history on this iconic company and its founder Gilbert Yueng, check that particular review or the website. Suffice it to say that those of us who know Gilbert are never surprised by anything he produces; be they quirky items like the Music Pumps and Purse (affectionately called Mary Lou), the Thingee group or the more esoteric, if somewhat pedestrian by comparison, 200 Series. Whatever Gilbert designs and produces, one thing is assured; it is well thought out, is as fine a quality as you are bound to find anywhere and it will sound great. So the mystery of this review ends here. As with all the Blue Circle products I have encountered the BC 507/509 is no exception.

What is a bit disappointing about the DAC is that it lacks anything visually entertaining or intriguing; a simple black box, black plexi front plate with a rotary selector knob, and the backlit Blue Circle logo. (Perfect match to the rest of my room lighting!) Of course not everything can be as visually entertaining as Mary Lou or the BC301FY preamplifier.

A Few Words from the Designer

The BC 507and 509 digital to analog converters share the same decoding engine. The difference, according to Gilbert, is in what size fuel tank and what kind of fuel they use.

The Digital to Analog Section...

The digital to analog part of the machine will support anywhere from 16 bits to 24 bits - 30KHz to 216Khz and anything in between. Every signal trace on board has been carefully designed and tested. It features a complete DC path to ensure ultra low jitter performance. Another feature that adds to the signal performance is that the microprocessor is not used in the control circuit. The less the clock contaminates the signal the better. The The unique analog output stage uses a design similar to those in our best solid-state preamp, the BC109.

So what about that fuel issue? Well, according to Gilbert, the power supply, AKA the fuel tank, is the latest of his Blue Circle "IAOE" designs. The BC 509 has a power supply filtering capacitance of over 200,000uF. To put it in perspective, that is more than the typical 100-watt stereo amplifier. Ultimately this ensures a very stable power supply. However, for the ultimate goal of a silent running power supply, the BC507BA has a 1,000,000uF (1 million micro Farad) additional battery power supply. When running off the AC power line, there is no ground hum or any sort of noise caused by the power line that can be detected by the audio circuit. The result is a blacker than black background which has a major impact on the micro detail of the musical presentation. Gilbert claims that this is one of the major factors which contribute towards that elusive sense of effortless and dynamic, yet relaxed musicality.

One additional note from Gilbert... "We have designed a circuit that will transfer between battery and ac power with complete silence. When the ac power is taken off, the battery will gently take over without making any noise. It is the same going back onto ac. And what happens if the battery runs low? It will simply turn off the DAC without any complaints or any noise.

We realize not everyone wants batteries in their system so we've come up with something that approaches the performance of the BC507BA without the batteries. It's called the BC507NB. Instead of batteries, we add an additional 1 Farad of capacitance, resulting in a total of 2.2 Farads of capacitance. This gets you close to the performance level of the BC507BA without batteries to periodically recharge and replace. 

blue circle dac

Both the BC509 and BC507 are upgradeable in the future. The BC509 can be upgraded to BC507BA or BC507NB.

What brand of chip set, someone may ask. (Only someone that doesn't know us, of course.) As usual, we would prefer our customers to audition the product instead of reading specs and comparing them to the latest buzz words or trendy parts on the net to make their decision. We don't make our decision based on how popular the parts are, and we believe you shouldn't make any decision based on the latest fashion trends."

Some of the features of the BC507/509 are a combination of one Toslink, one SPDIF and one AES/EBU input that accept 16 bit to 24 bit, from 32kHz to 192kHz and anything in between. You can also spec an optional USB 24/96 or USB 16/44. Mine came with the optional USB. My unit also came with the standard configuration of a pair of RCA and XLR outputs. You can also get manual or remote volume control and a BNC jack (replace RCA jack) for SPDIF input at no additional cost. (Mine did not have these options)

The BC509 unit is very tidy at 8 x 8 x 3 inches and right at five pounds. The 507 is about twice the size in depth and all other dimensions remain the same.

This has been a rather long term evaluation as I have been using this unit for approximately a year, and I have used it in many different configurations. The one application that the 509 saw the most action was being paired with my Wadia iDock in a number of different systems. Since my Jolida preamp is not equipped with balanced inputs, any time another preamp came through my room that had XLR inputs, the 509 immediately went into balanced output mode.

I found the BC509 worked wonderfully in my system. The bulk of the time I played music either through the Wadia and iPod combo or through my computer using the USB connection. There were a few times that I utilized my CD player and no matter what device I was using the BC509 did a great job of delivering the audio signals in a totally transparent way.

"Bite My Tongue" from Mind Walk Blvd.'s self-titled release (available directly on their site or on iTunes) just seemed to come alive with the BC509. This is not an audiophile recording by any stretch and thus I find it perfect for reviewing as it represents that vast majority of recordings in the hands of the masses. The soft vocal harmonies and delicate twelve string guitar work were really brought to the front and made it easy to actually catch all the lyrics. Not so easy to do while listening to an iPod directly. There is a certain dissonance in the vocal harmonies that becomes progressively more enjoyable depending on the device being used to listen. My favorite way of hearing this recording easily became the BC509/iPod combo.

"Keith Don't Go", from Nils Lofgren's Acoustic Live (Vision 820761101422), took my breath away especially when sourced out of my laptop. His guitar seemed to explode into the room, (imagine a more explosive rendering of an explosive rendering and then tell me a more flowery way to say that), and the crowd seemed to surround me rather than being projected from the two speakers. I could sense people standing to applaud at some of the guitar wizardry throughout the song. I think for all of us audiophiles, and especially those of us that fancy ourselves musicians, this is the critical WOW factor that we are striving for.

On Roger Water's "Dogs" from Live in the Flesh (Columbia C2K 85235) the normally holographic imaging rose to completely new heights. While the barking dogs in the interlude are normally quite obvious and the imaging is stellar through the BC509, they were in the back of the room and not in the backyard. The improvement to the detail of imaging was even more astounding when playing through the iPod on the Wadia iDock. So much so that I dare say that it not only rivaled the CD but actually may have sounded just slightly more focused.

Sometimes I think we, as writers anyway, spend more time looking for fancy and/or superlative words to simply state the most basic and obvious truths. I have spent a great deal of time and effort battling this particular affliction, and to be as straight forward as I can be, Gilbert has simply done it again. Here is an honest and direct DAC that performs well beyond its price point. No pretentiousness. Easy to set up, flexible and attractive. I am not sure what more any of us can expect from our gear. The older I get the more I appreciate value and, more importantly, exceptional value. I have found that Blue Circle Audio provides that in all their products that I have experienced to date. The Blue Circle BC509 is no exception to the rule. Now if we could only make it as pretty as Mary Lou…

Blue Circle Audio BC 507/509 DAC
Retail: $1250 (varies with specs)

Blue Circle Audio
web address: