Angela-Gilbert Yeung - C312 Preamplifier & SP CP36 Cap Pack Review
Angela-Gilbert Yeung C312 Preamplifier
Besides the obvious duty of a preamp, there also comes the matter of personal preference and finding the sound that makes you happy. Isn’t that the main goal in this subjective hobby? Despite this not many manufacturers offer any sort of control or adjustment outside of digital or DSP based applications. Tone controls and equalizers have been mostly phased out with the exception of pro audio and without modification, contouring of the sound typically isn’t possible for the end consumer unless you can roll the tubes in your preamp. Like all things, there isn’t one answer in audio, so I’ve always been opposed to a “one size fits most” type of solution that you tend to receive with even the upper echelons of audiophile offerings. I enjoy adjustment that allows for individual preference and considers the complexity of different rooms, speakers, and synergy, so when I was offered a chance to review the C312 from Angela-Gilbert Yeung, I was thrilled at the opportunity.
Gilbert Yeung Audio
The C312 is a bit of a departure from the "budget" side of audio and is built for the involved audiophile or music enthusiast, being priced to reflect the years of knowledge and the craftmanship that goes into every component. Whereas budget and high end components are typically built to a price point for mass production, components from AGY are built solely for the performance, considering every detail that affects the sound without over engineering the signal path or devoting a great deal of budget into aesthetics. The sound and music take center stage as the components are described as a serious investment that provides real audio performance and musical enjoyment that you can live with for years without spending thousands on "side step upgrades" in the struggle against diminishing returns. The C312 is considered a production model unit, where more affordable options include equipment upgrades and modifications, or the Funky series built from recycled, non-working components. Each unit is built in house by Angela Gilbert-Yeung who draws from over 30 years of audio electronics knowledge and expertise, most of those years as the owner and inspiration behind Blue Circle Audio founded in 1988.
A Look At the C312
The C312 is a two chassis system including the external power supply. The main unit has an iconic multi-layer acrylic faceplate with a centered glowing blue circle and dim red back illumination. The external power supply has a matching acrylic faceplate with just a splash of red and blue color in the two inset sections and is connected to the preamp by an braided 1m cord. There is no power or on switch, as this is meant to be left on for best sound and performance. A small RF remote for volume control is included, mounted to a Blue Circle metal keychain.
As I came quickly to find out, it is difficult to take a good photo of a reflective surface, so enjoy my sleeping cat in the background.
Even though the C312 is considered a production model, every unit is built to order by hand allowing for different options and connections at request. There are three single ended inputs as well as two balanced inputs for a total of five input connections. The balanced inputs double as unbalanced connections as well with RCA jacks mounted to the chassis alongside the XLR ports.
Each input is manually selectable by the front panel only for the most direct path, using no relays or auto switching inputs that can add noise, interference, or simply more solder connections and resistance in the audio path. The two balanced inputs are selected by the first two positions of the left most dial, where single ended requires you to turn on the appropriate input, and the others off.
The three smaller knobs are the fun highlight of this preamp. From the left there is Warm, Tube S (Sim) and SS (Solid State) adjustments that allows you to adjust your system's tonality. That being said the distinction has to be made that these are not tone controls, but carefully constructed circuits to tailor the sound to your own preference without degradation to the signal or the sound. They are also independent gain stages, so they must be operated in tandem, raising and lowering to reach your desired sound.
I am sure there is a mathematical equation to calculate the number of different possible sound signatures and combinations possible, but I didn't even keep track of how many I tried over the few months that the C312 was in my system. There truly is no "right" or "wrong" setting and that brings a lot to the table for a great number of systems. The controls were very helpful in comparing different power amplifiers, giving me the ability to fine tune the presentation and how the two components paired. I was easily able to set the gain levels to match the variances of input sensitivities which is something else some manufactures don't offer or account for, my NAD 218 being a great example of this. Great amplifier, but no gain levels makes preamp selection critical as it only requires 1.5v to max output. The C312 had absolutely no issue and sang with anything I paired it with. Solid State amps, Class D, full tube, each of them performed better than I had heard before because I was in control. If I didn't like something, such as a slight edge of harshness in the treble from a Class D amplifier is easily remedied with a couple dial adjustments, injecting a bit more warmth and tube sound into the mix while pulling back slightly on the SS.
The Sound
After having had plenty of fun seeing how close I could get two amplifiers to sound alike, I decided it was time to dig in and really get to know this preamplifier. I swapped my NAD 218 back into the system and let them both sit for the week, connecting the CP Cap Pack as well so that it would be ready for comparisons over the weekend. I then went about my work week, taking a few opportunities to listen through the week but without any impressions until I could really spend some time with the preamp.
So I spent some time with it, months actually, and I have to say this is probably the most difficult review I have had to do. This isn't because of the amount of options here, or the different settings you can try. In a typical review I would try to pick the component apart in some way, to find any fault or shortcoming, make head to head comparisons to other products to give you some idea of how it stacks up in the audio world. The C312 doesn't care about any of that, only about getting the music right. Any time I tried to sit in front of my QLS with my notebook and pen in hand to write down my thoughts and observations I only found myself captivated in the music. Next thing I know its been a couple of hours and Ive run out of time for the day. Repeat this countless times through the 3 months of the preamp being in my system and only in the last week of the review was I able to actually pull it from my rack to take my last photos and gaze upon the internal circuits that have captivated my senses so. For anyone that knows me personally would recognize that as a compliment in itself as I have taken everything apart ever since I was a child, leading me to be a repair and modification tech myself. As curious as I was after having only seen photos or videos of Angela-Gilbert's work, I had an example sitting in my living room to admire in person, yet the blue circle glow never faded because I sat down to listen instead.
As fun as the controls were at first, after having found my happy spot I never really moved them from there. The process for finding this "happy spot" was simple, I would make slight adjustments until my happy spot became the couch as I made a dent in the seat cushion for an hour having realize I quit experimenting. The included remote gave lend to this being able to adjust the volume on the fly. Ive had or listened to equipment that has had remotes before, but I typically didn't use them, usually because of how finicky they could be aligning the IR through the glass door of my stereo cabinet. The C312 remote is RF or radio frequency so you don't even have to point the remote at the unit, having great range as well. There were many weeks I would have background music playing in the living room and I could control the volume from my office over 20 feet away.
Critical listening sessions were a very similar experience as what I described earlier where I would just find myself lost in the music. For a review or even just forming my own personal opinions when listening to a piece of equipment I try to pinpoint and pull out what this component does differently compared to others, what it lends to the sound and the music. Sure I could go into a bunch of audiophile descriptors, but I will just say this preamp gives life to the music. It just feels natural, making you want to listen for hours on end. Sometimes when you listen to a wide variety of equipment on a weekly basis you crave a sound that is familiar to you, your own personal reference that has been honed and tuned to your preferences. The C312 really allows you to zero in on that sense and sound, melding itself perfectly into the background leaving only the music and emotion. I can honestly say this preamp has brought me the levels of enjoyment and satisfaction that I felt first starting out in this hobby learning what a proper sound system can do. The C312 showcases what a proper preamplifier can do, with no corners cut, designed and built by someone who cares about the music with the in depth knowledge of circuits and electronics to bring it all out.
CP36 Capacitor Pack
The controls on the front were fun and transformational, but the Cap Pack brings a whole new level to the sound that truly was addicting. This is the SP Cap Pack which is a carefully designed capacitor array that adds a mass surplus of capacitive energy to both the input and output sections of the preamplifier. This essentially supercharges the power supply giving all of the components abundant headroom for current demands, while also ensuring an extremely steady and quiet input voltage from the sheer size alone. The "36" in the name stands for the 3.6 Farads of energy storage contained in the chassis that is connected to the rear of the preamp, or 3.6 million micro-farads. For those less technical, that is a huge amount of energy as most amplifiers only boast 10s of thousands of micro-Farads, let alone most preamps that have much less.
So what does this do to the sound? The best part about the cap pack is once it is charged, you can do instant a/b comparisons just by unplugging the unit from the back of the preamp. Plug the unit back in and you start to notice everything has more body and density as if the "image" became clearer. This was no small effect, being a very impactful difference in the musical presence in the room, making every performance absolutely captivating. Every note was smoother, carrying the sustain and being able to clearly hear the resonance of the recorded venue of live recordings. The preamp is already remarkably quiet but the addition of the Cap Pack really showcased these minute details in the music, bringing me better realism with an effortless presentation that I haven't heard in systems costing many multitudes more, let alone in my own. This effect only got better with time as the capacitors continued to burn in over the course of a couple months. I did the A/B comparisons by unplugging the unit from the rear in the first week and the last week of testing the preamplifier combo, other than that the Cap Pack remained plugged in and an integral part of the system.
Final Thoughts
I have to say that I have been honored to be able to audition this preamplifier, and this isn't because of the aesthetics or the cost, or the fact that this is honestly the best preamplifier I have ever heard even put head to head against ARC or other offerings in the same market. My time with the C312 and the conversations I have had with Angela-Gilbert opened my eyes (and ears) to new concepts, as well as given me a new perspective on true high end audio. Those of us who are truly passionate audiophiles always chase something greater from our systems and honestly there are some brands who don't have that best interest at heart. How much do we pay for aesthetics when sometimes the internals are lackluster at best in terms of sonic performance, or something that wont be serviceable in the future?
Anything that makes you ask questions always pulls more intrigue from me compared to something that tries to convince you of a fact. The C312 truly makes you ask these questions and more, redefining what you truly want out of your system. It doesn't pretend to be anything its not, enticing you to get closer to the music and tailor it to your own preferences leaving you couch locked for hours tapping your feet. The pitch black background really allows all of the details to come through but is extremely musical without any sense of the analytical nature that something this resolving can be. Then again this was my own personal preference I was easily able to find by adjusting the 3 front controls. Any tonal issues perhaps from a poor pairing with an amplifier I was able to accommodate for with the “flavor enhancement” while also giving me a greater ability to match gain levels between the source and amplifier. The Cap Pack only added to the entire experience by adding a real weight and density that is easily noticeable in A/B comparisons, though once you hear it with, its going to stay as something you don't want to go without. In finally removing the C312 from the audio rack it had resided in for the past couple of months and reconnecting my reference system, this is the first thing I notice and begin to miss. Everything has less body and density, immediately making me want to overcompensate with tubes just to bring a sense of this back. While tubes can bring a similar effect, it is not the same as the Cap Pack retains perfect clarity of the music, only filling it the gaps and details of the soundstage you didn’t know you were missing.
As in all things audio, a review is just one individual's opinion and to truly understand or form your own opinion, you need to hear it in person. I cannot highly recommend enough that you do so if you get a chance as recordings don't do justice to each of the effects offered in this component.
A Deeper Look
As I had briefly mentioned earlier or as some of my readers may know, my main profession is as an audio tech for new and vintage equipment, so I see and hear a lot of different pieces from month to month. This allowed me to try a great number of components with the C312 to form my opinion. Being that I work on electronics daily, I also have an intense appreciation for equipment that is well built and thought out as I will have to reverse engineer equipment that lacks proper schematics or documentation. Getting the chance to audition the C312 also presented the opportunity to take a look inside and see the craftmanship firsthand. Angela's quality and reputation precedes her, but I haven't ever seen the inner workings of any of this equipment except what is shared on Facebook or YouTube. I wanted to keep myself impartial as possible when reviewing the preamp so I waited until packing to remove the covers to see the work within. Talk about saving the best for last...
What I saw inside each of these chassis leaves me without words and a tear in my eye. I have never seen a more purpose built component laid out with such care. There is only one set of hands building each and every unit, every part installed with precision and pride. Every part of the signal chain has been considered, points of noise or interference carefully laid out.
Power Supply
To the untrained eye, this can just look like a mess, when in reality it is very well thought out without being overly complicated. Transformers are properly separated, typical glass fuses have been replaced with a resettable fuse. Everything within the chassis has been well braced with silicone to reduce the tendency of vibration or resonance of the chassis and components, such as the transformers, capacitors and the front panel of the unit that would otherwise be just plain metal. That isn't something normally considered, let alone just at the power supply level. Notice also that every solder connection that could hold any weight or transfer of energy is supported by silicone as well, not just the solder joints. A good example of this would be the IEC plug in the rear completely covered and where wires interconnect such as the top of the capacitors. These wires aren't going to move or transfer any mechanical energy or stress to the critical solder joints.
SP CP36 Cap Pack
The cap pack did not disappoint either. Rows and rows of capacitors, all mounted and braced at perfect levels by silicone. This many parts each hand placed and soldered you would expect to find some sort of human error but there was none, each solid core 14 gauge copper wire perfectly parallel to the other, with all of the capacitors perfectly spaced and straight. Nothing within this chassis will move in the slightest, all vibrations being absorbed by the carefully layered silicone. Note from the top view there are layers of silicone on top as well, this comes in contact with the top of the chassis, so that it too is perfectly braced against resonance.
The C312 Preamplifier
This is where all of the true audio magic comes together, the main chassis that contains the circuitry for the actual audio signal. This is a true art form and masterpiece.
Again symmetry is impeccable here, individual PCB boards perfectly mated together without any gap, perfectly square in relation to everything around it. As is the AGY custom, everything is thoroughly braced throughout with silicone, but also separate. This is very different than just potting the entire component, each addition has a specific purpose and doesn’t run together where it isn't needed, further reducing any possible transmission of resonance or vibration, including the "table" to the left that braces the top panel of the chassis without restricting component breathing room.
The loose red and blue wires throughout are the signal wires, carefully laid out for EMI. From the rear inputs on the left the signal is ran through the center of the main capacitor bank, directly on the base of the chassis keeping them close to the ground plane.
From there you can see your selection switches being led to the 3 circuits for the 3 respective attenuators on the front for sound contouring, with the main preamplifier circuit off to the far side. Combining or bundling wires can cause issues of interacting electrical fields that lead to crosstalk or noise, so notice how each of the signal wires here have separation, but are not loose and moving about the chassis. Every single connection is soldered, no quick connects here. .
All DC paths through the circuit are the same 14 gauge solid core used in the capacitor pack for low inductance and resistance with large gauge used for ground paths as well. See here that even the signal wires coming from the volume knob are carefully tucked within the spiraled ground wire to protect against interference and to ensure the cables do not move.
The entire circuit is bristling with op amps that are carefully chosen for their sound and what they do in that particular part of the circuit. This careful placement and internal "seasoning" is evident by Angela's use of color codes with the painted top of each IC.
Seeing the inside of each of these cases was truly a beautiful thing, and for everything that I noticed there is sure to be other details I did not. Every piece of equipment I’ve owned or spent time with has various aspects in the design that are there because of parts cost, or cost of assembly. This means there is always a bit of room for improvement. While there are some great brands and equipment that are built this way, it is a breath of fresh air to see truly every aspect considered and done in a way because that is the best way to do it and truly meant it. How many designs are “cost no object” to be just an assembly line piece full of quick connectors and machine assembled PCBs? This level of detail and craftsmanship you won’t get from even a full engineering team.
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