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CharterOak ProAudio - Microphones, Signal Processors, Headphones

acoustic operating principle
Pressure Gradient
Dual 1.22" 6 micron thick gold sputtered Mylar
16mV/Pa 94dB=1V/Pa@1kHz
Cardioid, Omni, Figure-8
< 200 Ohms
> 200 Ohms
17dB A weighted IEC651
125dB for 0.5% total harmonic distortion @ 1000Hz
+ 48V
| CharterOak E700 Microphone |

The CharterOak E700 is a dual diaphragm solid state condenser microphone which employs two 1.22" center terminated, gold sputtered, Mylar diaphragms and pure class A head amp electronics. While this microphone is excellent for universal applications, its rich sound, extremely low noise floor, and build quality make it a particularly excellent choice in the broadcast and voice over environments. The E700 offers cardioid, omni and figure-8 pickup patterns and a two-step sensitivity switch.

The CharterOak E700 is designed, built, quality tested, and delivered to the customer, with the intention of providing the quality condenser microphone. This has been achieved through an extended period of research and development, together with a period of beta testing performed by a select group of musicians, engineers and producers. The end result is an extremely high quality, distinctive sounding microphone. This high standard of quality extends beyond the microphone to the cables, shock mount and protective case of the E700. Whether you are in a recording or broadcast environment, a CharterOak E700 gives the discerning producer, engineer or recording artist an attractive option.

The microphone is delivered with a lifetime warranty on all parts and labor and easy access to factory technical support.

On Test : CharterOak E700 Multi Pattern FET Microphone
By Paul White | May 2008

Building in China, then disassembling in the US and replacing parts seems a long-winded way to go about building a mic... but there might just be some sense in the approach.

Charter Oak were founded in 2002 by engineer Michael Deming, who is currently operating his business from Enfield, Connecticut. His microphones are built to his specification in China, but he disassembles them in the US, changes some of the parts, rebuilds each one and checks each mic's performance.

During development, Deming beta-tests his designs with the help of industry professionals, to ensure that he's producing something that will deliver in real-world situations — and while this approach means that they're priced higher than the majority of generic Chinese mics, they still sell for rather less than a traditional European microphone.

A number of people have discovered worthwhile upgrades and tweaks for imported microphones, so making these the basis for an 'improved' product range with a recognisable name makes a lot of sense, and seems to have paid off because the name Charter Oak has won a lot of respect over the past few years.

The Charter Oak E700 is a multi-pattern FET capacitor microphone with a capsule based around a pair of 1.22-inch, centre-terminated, gold-sputtered Mylar diaphragms. The internal preamp electronics are pure Class A, as one should expect for mic preamps (in fact, it would be more of a novelty if the circuitry wasn't Class A!). Apparently, this particular model now incorporates a US-built output transformer and the internal wiring uses PTFE-coated wire because of its high insulation characteristics. Small slide-switches on opposite sides of the microphone body are used to select the pickup pattern (omni, cardioid or figure-of-eight) and one of three pad settings (0dB, -10dB and -20dB). The mic I tested was serial number 0016 but I understand that after serial number 0040, Charter Oak replaced the pad and pattern switches with three-way miniature toggle switches. All the circuitry is accommodated on glass-fibre circuit boards, and the stock polystyrene and polypropylene capacitors have been replaced by premium brands such as WEMA.

Mechanically, the mic isn't dissimilar to many other Chinese models, and that extends to the shockmount and metal case that come with it, but there's nothing wrong with that — they're all solidly engineered and functional. Cosmetically, the mic looks very businesslike, with its slightly squat shape and its glossy, black-finished brass body with the distinctive Charter Oak logo. The familiar, heavy locking ring secures the mic body 'sleeve' in place and the output is on a standard three-pin XLR, which also supplies 48 Volt phantom power.

One factor that may influence your purchasing decision is that this mic has a lifetime warranty on all parts and labour. The technical spec is pretty good too, with a 25Hz to 20kHz frequency response, and a sensitivity of 16mV/Pa (Click here to email). The Equivalent Input Noise is 17dB A-weighted, which is not exceptional but is typical of this type of microphone, and in normal applications circuit noise is not an issue. The maximum Sound Pressure Level is 125dB for 0.5 percent total harmonic distortion at 1000Hz, and although there are mics on the market that can take more level, I've seen reports on various forums that this mic delivers excellent results when used to record kick-drum, and it doesn't get much louder than that!

Studio Test
As a vocal mic, the E700 has a definite character that flatters the sound of most singers by adding a sense of density, warmth and air, but without becoming too brittle at the high end. Some users have likened it to a warmer, less toppy-sounding AKG C414, which may be true to some extent, but then I've never actually owned a C414 so that isn't a comparison I feel that I can make with any degree of accuracy. What I would say is that the E700 is on the flattering side of neutral, although not so flattering as to be obvious. In comparison with the SE 2200A, a popular and attractively priced mic (typically costing about a third of the price of an E700) with which many readers will be familiar, the E700 has a rather more open sound on vocals, tending more towards the natural character of an omnidirectional model (even when set to cardioid mode), but at the same time it has a smoother high end and more apparent low end.

The figure-of-eight pattern sounds very similar to the cardioid, but switching to the omni pattern delivers a very different result, because, of course, there's no proximity bass boost with omnidirectional mics, and all that warmth that was generated from working up close just falls away. Once you've mentally adjusted for this, the omni pattern delivers pretty much what you'd expect, and although a dual-capsule, large-diaphragm mic is never going to be as accurate as a dedicated small-diaphragm, single-capsule omni, the omni pattern nevertheless does the job pretty well — and it certainly extends the versatility of the mic.

The E700 is also a very accomplished acoustic-guitar microphone in any of its pattern modes, although (as always) you do have to search for the sweet spot. The results I achieved varied from somewhat brash and over-assertive to smooth and silky, depending on where I put the mic. Hand percussion also came over solidly, and with plenty of depth, so the manufacturers' description of this mic as an all-rounder that's primarily intended for vocals is accurate.

Judging by the tonality of the E700, I would say that it should work with a wide spectrum of voice types, as long as users position the mic to achieve the best tone, rather than relying on equalisation afterwards. It is probably best suited to singers who feel their voice sounds a bit thin or congested when using other cardioid-pattern capacitor mics, but its top end, which manages to be both smooth and airy, also works in its favour.

Although there's plenty of very strong competition for this sort of microphone at this price, the Charter Oak E700 is versatile and classy. It is well suited to vocals but also gives good results on a wide range of instruments. What's more, it offers great performance for its price and is certainly worth auditioning if you're looking for a studio workhorse.

There are plenty of mics competing in the same market area as the E700, and, as always, you should try to audition them if you plan to use the mic mainly with one vocalist, because everyone tends to suit a different mic. Some alternatives you might try are the Audio-Technica AT4050, SE Electronics' 3300A, the Neumann TLM103 and the Rode NT2000.



CharterOak Acoustics E700 Multi Pattern Condenser Microphone
By Roy Stein, Tony Gross | November 2006

This past decade has witnessed an invasion of mics that have been tough on tradition. Chinese-manufactured, large-diaphragm studio condenser mics that copy both the circuitry and the external housing of their Western counterparts have found their way into many recording studios, as they're cheap in comparison to their erudite ancestors. However, in many cases the similarities end at sharp looks, and with so many different brands flooding the market, one wonders which of these mics is wise to buy . . . if any.

Perhaps we should take some advice from Aristotle and Lao-Tzu, and embrace the middle ground which is where the CharterOak E700 lies. This robust, dual-diaphragm FET condenser mic shares some characteristics with the import competition to keep costs reasonable. Sure, some of its basic components, including circuit cards, metal work, and the flight case, are manufactured at facilities that work with other rebranders of microphones, but that's where the cloning around stops and individual design and quality control steps in.

Starting with a piece shipped in from China in rough assembled form, the mic is then biopsied and reassembled by hand with Xicon, Mial, and WEMA polystyrene and polypropylene capacitors to optimize the audio path. Before shipping, each mic goes through a final testing phase before it is stamped with its coup de grâce: a lifetime warranty.

We were informed that if we took the mic apart we wouldn't find any cheap hookup wire, and the wiring would be neatly in its place. Way too late for that; within hours of its arrival we had that sucker pithed like kids on a frog in Biology 101. The split circuit board design was nesting on a rugged but cleanly machined platform, and only Teflon-coated wire is used to make the connections between the capsule and head amplifier to ensure maximum noise rejection and to faithfully reproduce detailed highs.

When it comes to design and quality control, CharterOak appears to be demanding. For example, originally the E700 employed a Chinese output transformer. However, only 11 out of 40 of those transformers passed the company's quality control standards. Starting at s/n 0012, it was replaced with an American component. Also, beginning with s/n 0040 CharterOak has replaced the 3-position pad and 3-position pickup pattern switch with a heavy-duty 3-position toggle, rather than the earlier model's slide switch. Alright, it's all sounding sweet . . . in theory.

An organic-sounding rock band was recording in Studio A doing the standby drill: vocals, drums, bass, guitar. The clock's tickin' off billable hours, so it's a trial by fire for the E700. Typically on a kick drum we remove the front head and use either an EV RE-20 or an AKG D112 on the inside of the shell placed slightly off axis about 8" from the beater, as well as a Soundelux E47 about 8-10" outside the shell (all through API 3124 preamps), as this usually captures spectacular results. So we decided to throw the E700 solo about 4" outside the front of the kick, through the API 3124 - it was so good, we left well enough alone. Recording the kick became a single mic/mic pre chain, which freed some prime gear for other sonic territory.

Up next, acoustic guitar: a Gibson Hummingbird, known for its full-bodied, warm, velvety tone. But in a rock band competing for prime sonic real estate, it can easily get lost in the mix or, at higher levels, muddy up the track. We set up the Soundelux E47 on the low end of the guitar, off axis, along with a Røde K2 on the top end to capture the 12th fret nuances, which sounded great. Then we replaced the K2 with the E700, and had the band members take a blind test. They all chose the E700.

To cut vocals, we set up a Soundelux Elux 251 and the CharterOak E700. We ended up going with the Elux for the main track, but were not at all disappointed by how the E700 held up (a good thing, given the price difference between the two). The E700 was characterized by detailed highs, without being brittle, and an open bottom end. And by adding just a touch of compression on playback, the vocals sat nicely in the mix.

East is East and West is West. Not in 2006. By combining U.S. quality control and the selective integration of high-end components with low cost manufacturing available in China, CharterOak offers an excellent buy for the buck. The E700 would be a welcome addition to any rocking mic cabinet, or a smart choice as a first upper-level mic.

Product type: Dual-diaphragm FET condenser mic.
Target market: Higher-end studio and mid-level applications with cost restrictions in mind.
Strengths: Detailed highs along with clean, open low end. Excellent shock mount and flight case. Lifetime warranty.
Limitations: Hefty, so be careful with mic stands.



While microphone technology may not have moved on that much in the last ten years the available choice to users has been transformed by a much wider selection of brands. JON THORNTON looks at an imposing mic that seems to have defined a new position in the landscape.

IT’S BEEN SAID BEFORE, not least by me, but the world of microphone manufacturing is a long way from where it was even ten years ago. For sure, the big players are still there updating their product ranges, or in some cases still busily producing designs that have been around for several decades. But added to this have been an everincreasing number of new entrants. Broadly speaking, they can be split into two categories — those who go down the ‘boutique’ route with highly specified, hand-crafted and usually very expensive offerings, and those who seem largely intent on maximising the lower reaches of the price/performance curve. It’s probably also fair to say that the latter rely heavily on manufacture and assembly in China.

In this context then, it’s not surprising that I hadn’t heard of USA-based CharterOak Acoustics or its microphone range before the E700 turned up for review. Founded in 2002 by engineer Michael Deming, CharterOak has quietly developed a line of microphones that have attracted a significant following. To begin with, the product range was exclusively comprised of large diaphragm capacitor designs with valve-based electronics, but the E700 marks the first FETbased offering.

Featuring a dual 1.22-inch centre terminated diaphragm, the E700 features a switchable polar response (cardioid, omni and fig-8) and a twoposition pad (-10 and — 20dB). It’s a fairly squat looking microphone, with considerable girth and heft to it, and comes supplied in a hard case together with a basic shockmount. Finished in silver and black, it looks the part certainly, but I couldn’t help but get a sense of deja-vu — the smell of the packaging, the
construction of the microphone, even the supplied case seemed familiar and these things reminded me of brands of Chinese origin. A quick call to Michael Deming confirmed this — the majority of the components, including the diaphragms are indeed manufactured in China. The units are then pulled apart, checked, reassembled and tested in CharterOak’s facility in Enfield, Connecticut.

Michael was keen to point out to me that a great deal of time had been spent with their Chinese manufacturing subcontractors fine-tuning the construction of the diaphragms and selecting quality components for the electronic stage and transformers, which was encouraging — nevertheless the E700 is pitched at a price point that gives it some stiff competition from some pretty established brands (US street price $999). A quick poke around the internals reveals a tidy looking PCB with all discrete circuitry, and a hefty output transformer whose casing forms part of the structure of the microphone.

In use, the E700 sets up quickly, and despite its weight, the supplied shockmount holds it very securely. It sounds pretty quiet — equivalent noise is quoted at 17dBA — and it delivers a nice healthy output level. On a variety of close miked sources, the E700 sounded very impressive — in comparison to a 414-BULS used as a reference it more than held its own, and actually sounded remarkably similar on the cardioid setting. There’s plenty of detail, lots of low frequency extension, and it's ever so slightly ‘hard’ at the top end.

Moving on to drums, and positioned as an overhead above the kit on an omni setting, and the E700 again sounded similar. Good transient response meant that there was plenty of punch to the sound, and the slight lift in the microphone’s frequency response around 10kHz kept things sounding detailed as distances increased. Low frequency extension was good, but in comparison with the 414 sounded a little more rounded in this respect — not a bad thing as it helped curb some less than pleasant hard resonances. This trait was even more pronounced when the E700 was set up as a distant room microphone — preferable in
some ways to the 414.

The acid test with any microphone of this type, though, is vocals. Male vocals were the order of the day on the test session, and it’s clear that the E700 has been tuned pretty well to this task. As the 414 isn’t my favourite in this application, the E700 was compared to an Audio Technica 4050, which can deliver stonking results on most voices straight out
of the box.

The E700 sounded a little less mellow than the 4050, certainly bringing out a little more ‘spit’ in the voice, but used close up has terrific presence and depth — a definitely larger than life vocal sound that would suit broadcast and voice-over applications as well as music tracks. Although it never sounds overexaggerated, the E700’s performance didn’t seem to take EQ quite as well as the 4050 though — trying to dip the low-mids slightly and dial in some HF lift started to deliver results that sounded unnatural quite quickly.

This might just be a function of familiarity with the microphone though, and more time playing around with EQ bands might help. Interestingly, for its other (valve-based) models, CharterOak offers a customisation service, where by changing valve types and altering component values in the electronics the response of the microphones can be tweaked to the customer’s preference. Sadly, this isn’t on offer with the E700; as Michael Deming explained, there just isn’t enough scope in the FET-based amplifier design to accommodate the tweaks.

All of which leaves me trying to decide where the E700 belongs in the scenario I outlined at the start. Calling it a boutique microphone wouldn’t be strictly accurate. And putting it in the category of exploring those lower reaches of price and performance would be distinctly unfair — this is a quality piece of kit, backed up by a lifetime warranty for parts and labour. And it sounds good. It’s not as much of a ‘one-trick-pony’ as perhaps the AT4050 is, but it does have a definite sound to it. And if you like that sound, then it works beautifully. I think that CharterOak has actually defined a new position in the microphone landscape — quality design and Chinese manufacture, together with the attention to detail and the ear of an experienced engineer means that everybody stands to gain.

Good build quality; very nice ‘big’ vocal sound; nice rounded sound to LF; good detail and transient response.

Might be a little overstated for some applications and be a little hard to pull into shape with EQ.

As Jon points out in the review, there are other mics in the CharterOak stable. There’s the SA538 side-address dual-diaphragm valve condenser, which employs a centre-terminated S-1 capsule, the SA538B side-address dual-diaphragm valve condenser, which employs a side-terminated S-2 capsule, and the S-3 capsule S600 front-address valve condenser, which is sold in sequentially numbered pairs.

Reviews. CharterOak SA538, SA538B, E700 & S600

“CharterOak microphones reviews in PROSOUND April ’07 Edition”

CharterOak condenser microphones are manufactured in the factory located in
Connecticut, U.S.A. Only the parts with well selected and passing the very severe
quality criteria are assembled in the rigid body which is being machining from the brass. And, furthermore, after 7 days aging for the tubes and testing in the studio
environment for more than 30 minutes, the microphones will be delivered to the
customers. In addition to this, such accessories as the flight case, the power supply, theshock mount, the cables, etc. will be checked severely. By taking care of this
fundamental points in order to manufacture the products, the credibility will be
increased and the products will attract customers’ attention and the firm position of the products will be established, which is a short cut to be successful for the products.

The products which I would now like to introduce you this time are 4 types of the
condenser microphones manufactured by CHARTEROAK ACOUSTIC DEVICES in
U.S.A. They are SA538, SA538B, S600 and E700.

First of all, from the external appearance of the microphones, the black shiny finish is afeeling like having its very expensive products and the microphones have a feeling of having its enough weight. Furthermore, except E700 which is solid state type, the exclusive power supply will come with the microphones. About SA538 and SA538B, as they equip the switch with 9 steps of which the directivity can be selected from non-directivity to cardioid.

Let’s try to test them!

First, let’s start from SA538. This is a dual diaphragm tube type condenser
microphone(SA538B is the same.).

Checking it with vocal, it sounds like thinking of a vintage microphone and the
bandwidth ranging from mid-low sound to low sound is solid. Nevertheless, it is not
like a dull sound, but, it has apparently a feeling of existence against the sound source in the back. Listening to only the vocal track carefully, it is understood well that the room noise was not almost felt. Then, after recording while selecting the directivity newly, with transferring gradually from non-directivity to cardioid(middle value), the noise is becoming decreased and it is a feeling that I went to the country side where has clean air, being away from the city. In doing like that, the high technique is necessary in order to decrease only the noise, without spoiling a feeling of air. I feel that CHARTEROAK ACOUSTIC DEVICES has very high technology research level. SA538B is being the same, but, as this is a side termination type, the high frequency sound is much extending with a feeling of hybrid.

Depending upon the vocalist is if it is a male or a female, it is fat or thin, utterance is strong or not, what is the performance style of the back, etc., the choice will be changed. In the studio, I would like to have both. In either way, the microphones can realize sound image very well for which the vocalist is in the very front position of the stage and they are superb microphones, and they are also easy for mixing.

E700 is the low cost version for the above 2 microphones. This is a gold depositioned myler diaphragm and pure class A solid state type microphone. The microphone equips the switch which can be selected from 3 types of the directivity(cardioid/omni/figure 8) and the attenuator of -10dB/-20dB(sensitivity switch).Though this microphone is in the low priced range, the sound is fairly good and a feeling of clear air with less noise can be realized well.

S600 is a front address type and the tube type, but, this microphone is different in appearance from the above microphones. The top portion of the microphone is aimed at the recording object and I think it is for the purpose of recording the musical instruments. I recorded the Conga which is my favorite musical instrument. Although it is a same feeling as sounding with a feeling of existence, this microphone is likely flat in its frequency response. In its good aspect, it has a sound with non-peculiarity and wide dynamic range.

For myself, in case of recording in stereo against the recording object(2 microphones), especially to drams and percussion(also piano), not standing the microphone inside from outside, reversely, I always request to stand it outside from inside. This means that I consider it phase, but, with using this microphone, when I tried to make both settings and to compare them, I realized that there are big difference in a feeling of existence and a clearness of sound. In some sense, I am impressed with this microphone that it is honest.


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