Award-winning microphone engineering from Michael Joly

- The Apex 460 Mod - MJE-K47 capsule & mod suite for your mic

~~$499.00~~ $449.00

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OktavaMod-Improved Low Cost Mic Beats U 47 and M 49

Grammy award-winning enginner William "Dr. Bill" Pearson of Mindseye Productions recently helped a client choose a new mic for an upcoming album project. Bill assembled nine different mics (FET and tube types), composed a special tune to stresssss-out the mics and recorded all mics of each type simultaneously. On playback, he didn't tell the client what he was listening to. The client chose an OktavaMod Apex 460 and MK-319 DPE to purchase.

After the in-studio shootout Bill posted the audio of his sessions to GearSlutz.com and invited members to choose their favorite FET and Tube mics. Here are the results from the tube category....

Voting Results - GearSlutz.com Poll
Here's some audio from the sessions -

SOUND FILE: Neumann U 47
SOUND FILE: Neumann M 49
SOUND FILE: OktavaMod Apex 460

There are 18 soundfiles total (9 mics, FET & tube, solo'd voice & in-mix) and lots of discussion at the GearSlutz link above.

The Story Behind The Win -

The low cost Apex 460 is a hugely popular multi-pattern, tube condenser mic manufactured in China and offered for sale under a number of brand names (ACM-1200, Nady TCM-1150 etc). Unfortunately the stock mic has less-than-rigorous design and execution that limit its potential.

But it is a great platform to upgrade and is capable of boutique mic performance when re-engineered. The modifications described here focus on a number of areas that have not been addressed and offer a substantial sonic return on the investment.

MJE-K47 Modified Apex 460 with new longer headbasket and more...
Good News Dept: Transformer Performance -

The stock transformer is a very acceptable performer if the stock cathode-follower topology is maintained and modifications implemented (capsule and tube swap) to avoid transformer saturation at high frequencies. I confirmed the 460's published SPL spec of 1% THD @ 125 dB @ 1kHz , then injected a test signal to produce the same level at the output of the mic. Sweeping the oscillator from 20Hz to 20kHz the THD remained 1% +/- 0.5%. Even raising the oscillator level to produce 5% distortion at 1kHz the transformer still passed 20Hz and 20kHz without an increase in THD.

This is Michael Joly writing, founder of OktavaMod. Click "buy now" to purchase a full suite of modifications developed for your Apex 460 or similar mic. Or read on then click "contact me" below and send me your questions.

The stock transformer's phase shift is +18 degrees at 20Hz and - 22 degrees at 20kHz - a fairly subtle flaw that pales in comparison to the gross mismatch between the stock K67-type capsule and flat frequency response circuit found in the Apex 460 (more on this later).

Upgrading to the flatter-response MJE-K47 capsule and lower gain 6072 tube provides 12-14 dB greater headroom in the transformer at 8kHz compared to stock mic - and the stock transformer no longer contributes to HF harshness. In my opinion, the expense of replacing the stock transformer is not entirely justified and this modification leaves it intact.

Headbasket Issues-

The stock Apex 460 headbasket top ring partially obscures the capule diaphragms. This physical arrangement creates sound reflections between the ring, diaphragms and multi-layer grille. In addition, the headbasket side bars create additional reflection surfaces - especially for sounds entering off-axis when the mic is used in the omni mode. The flat base plate below the capsule offers yet another source of internal headbasket reflection and standing wave coloration.

Apex 460 with new longer headbasket and MJE-K47 capsule
I've created a solution to these issues by modifying the headbasket, capsule mount and capsule base plate. In the picture above you can see a new 10mm taller "Floating Top" headbasket that has no side bars - a signature technique I use to reduce headbasket reflection coloration. An MJE-K47 capsule wired with Evidence Audio LYRIC solid core sits in a new saddle 6mm lower than stock. As a result of these two mods the headbasket top ring has been moved 16mm away from the capsule to significantly reduce reflection coloration. Not visible is a conical diffuser installed below the capsule used to eliminate standing waves created by the reflective base plate.

MJE-K47 - The right capsule for flat frequency response circuit mics
Capsule / Circuit Mismatch -

The Neumann K67 capsule was designed with a built in high frequency response peak. This was then followed in the U 67 and U 87 microphones with complimentary HF de-emphasis achieved through negative feedback. This topology created an acoustic pre-emphasis / electronic de-emphasis system that offered the benefits of increased headroom, sibilance reduction and timbre control.

But the Apex 460 uses a flat frequency response circuit - the 8kHz peak created by the stock K67-type capsule flies right through the two-stage circuit, whacks the transformer hard then delivers a load of harsh HF to your ears - the stock capsule and circuit topology actually exacerbates sibilance instead of reducing it. I've found the flatter, more midrange-focused K47-type capsule is a better choice for the flat response Apex 460 circuit and actually produces a more "Neumann-esque" timbre balance as a result.

Introducing the MJE-K47S Large Diaphragm Capsule

The K67-style capsule is simply too bright to be used in a flat response circuit. The MJE-K47 (Michael Joly Editions K47-style) capsule is the result of my painstaking search to find a capsule producer who could manufacture a K47-style capsule to my quality control standards - and do so at an affordable price.

Each MJE-K47 capsule is individually tested in an anechoic chamber and tracks an actual K47 capsule response within +/- 1.5 dB across the audio spectrum. Your mic will be returned to you with a modification Certificate of Authenticity and your individual capsule's anechoic chamber response.

The MJE-K47 capsule will re-voice the Apex 460 - it removes a searing top end peak and shifts the timbre balance to a subtle midrange emphasis. In addition, the MJE-K47 capsule has all the wonderful low end proximity effect we've come to love from classic K47-equipped mics. The modified headbasket and MJE-K47 capsule work together as a system to provide a more balanced and natural frequency response without excessive HF rise or sibilance.

Actual Unsmoothed MJE-K47 Capsule Frequency Response
Note Classic "47" Timbre-Balance and near-identical front / back curves
(Top curves: front & back on-axis plots, bottom curve: -180 degree response)

Tube Upgrade -

I've been using low noise, 6072a tubes as an upgrade from the stock tube. Not only are these tubes sweeter sounding with lower noise than the stock tube but the lower gain of the 6072a gives the transformer more headroom. By removing the K67-type capsule with its peaked HF and using a tube with lower gain the stock transformer performs quite well and only has to be replaced if you're both obsessive and have some extra cash burning a hole in your pocket.

Signal Path Capacitor and Wiring Upgrades -

All signal path capacitors are upgraded from stock to non-polarized types that have been field proven in my other Premium Electronics mods. Evidence Audio LYRIC HG solid core copper wire will be used to preserve maximum fidelity in the low level / high impedance capsule-to-tube circuit.

Great Results, Easy to Order -

The end result - your Apex 460 or similar mic will be transformed into a boutique mic featuring the MJE-K47 capsule that oozes good old classic tube mic voicing without excessive high end boost. Your digital recordings will be better as a result.

Click "Add to Cart" to purchase the Apex 460 MJE-K47 modification suite. The introductory price is only $449. Remember, this price includes: installation of a new MJE-K47 capsule, 6072a tube, complete headbasket rebuild and all non-electrolytic signal path capacitors. Once you order you'll get an immediate confirmation email. By the close of the next business day you'll receive a personal email with your scheduled modification and return ship dates. Questions? Just click "Contact Me" - best, Michael

Ps - To save shipping on costs just send the mic alone to me - enclose the mic in several inches of packing material - rolled up in a couple of inches of bubble wrap then placed in a carton is quite safe. You don't need to send the power supply or cables - I have those in my shop.

New MJE-K47H Large Diaphragm capsule head for SDC bodies

Award-winning Microphone Design by
Michael Joly

Current Reviews: 7

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