Preview of c421 Enclosure

While we eagerly await the release of c421, here are a few rough, rendered previews. The enclosure will be composed of black anodized aluminum with black or natural brushed aluminum end panels, unless we’re persuaded differently!

Screws, light pipes, and the battery are not shown…

Rear view of c421, showing countersink screw holes. Color of end panels not final!


Obligatory size comparison to a popular portable source
Size comparison at another angle

We expected to have real samples in hand by now. So what happened?

A reputable aluminum extrusion shop promised us 6-8 week lead time and a a competitive price, so we faxed over the deal on July 1. Three weeks passed and I recieved a phone call from their company president, Bob. He said, “Hi, John. I have some bad news . . . We dropped the ball on this one.”

Bob’s company  had severely underestimated their bid and refused to fabricate C421’s enclosures unless we forked over another $10,000. Wasn’t gonna happen, Bob! $10k would have ruined our project goals.

Although this delayed c421 by three weeks, everything has worked out for the best. We’ve used the extra time for additional circuit tweaking. And, we signed a better enclosure deal with an amazing extrusion shop whose manufacturing plant is only four hours south of our office! Their staff has kindly invited JDS Labs to witness on-site sample inspection.

Samples are due approximately 4 weeks from today. I will personally inspect the enclosures and post pictures if possible. Final device specifications and pricing will follow soon afterwards.

One final note: We’ve received countless offers from past customers and new faces seeking to review c421. Thank you! The first production batch will be a small run of only 100 units. Just two amps will go out for initial review (more later). A pre-order page will be posted around the time reviews go live, no more than 4 weeks before we can ship.

Like the design? Hate it? Let us know!

Headphone jack at front of C421 (rendering with transparency)

59 thoughts to “Preview of c421 Enclosure”

  1. love your product….i use it everyday. would love a case that is not an altoids tin, but love the layout of the tin…the volume knob is first class and a good volume knob is most important. would love to see a clean design with a volume knob front and center. just my 2cents. in fact, many times i’ve thought just spraying the altoids case silver would do the trick for me. would you consider having that as an option to sell or as a one off custom job? thanks!

    1. Thanks for looking, Robb. The knob was “front and center” on the cMoyBB v2.00 and v2.01 back in 2007 and 2008. This seemed like a good idea at the time, but the positioning interfered with larger input cables and headphone cords so it was difficult to turn the knob. This would have been fine in a larger enclosure, just not in the Altoids tin. Unfortunately, painting Altoids tins wouldn’t be feasible from a cost perspective for us.

  2. Hi John,

    Firs things first: I am a proud owner of the cMoyBB v2.03, I literally almost use it every day. With the exception of when I’m not in the office, not reading, not playing the 360 or when the girl isn’t plain old hogging the T.V!

    The initial announcement of the C421 really made my ears perk up. Considering I use the cMoyBB every day, the literal big brother can really only be a big improvement.

    But John, there’s one problem with improvement, I can’t fault the BB, it sounds as good as a separate hifi. Where could this amp take my audio experience? The next level? If there is one!

    The BB 2.03 really is a remarkable bit of kit, and I’d say it’s less of a cmoy amp and has actually moved on to become highly refined. It’s able to power up to 600 Ohm cans when the gain is correctly set (or plugged into the mains) which is impressive by any standards.

    In my eyes, the cMoy palms off amps like the Graham Slee Voyager and FiiO E7 with ease, especially considering their functionality and price point v.s the audio quality of the cMoyBB.

    One surprise for me was that the E7 has an audible hiss, a problem which I’ve not noticed on your amp, at any volume.

    So, with all that said, I can’t wait to hear this new amp 🙂

    Moving on from singing your praises:

    What features could this new (untamed) beast possibly boast over the BB, other than (first guessing) better interference reduction, li-ion battery, buffer(s) and an on-board charging circuit?

    The sound of the BB is spot on, it’s transparent with no distortion, even when the bass-boost is on. Improving on that is gonna be a tough one.

    You’ve also said that this amplifier contains 3 op-amps, which, to me almost sounds like an instrumentation amplifier… Only time will tell what you have in store for us.

    The design itself looks sweet, with a black anodized smooth finish and it’s very slim. It looks like it could be melded with the iPhone itself to create the iC421!

    The bass and gain switches look short dumpy, but that’s a good thing. It means they won’t catch on anything. There’s nothing worse than a 4 inch switch for gain, because flicking that thing by accident mid-track could mean certain death for your headphones and hearing.

    The only worry I have is the On/Off switch. It’s either got to be tough to move to prevent accidents, or very easy to ‘flick’, meaning that an accidental knock could switch it on. Especially if it’s being stored in a headphone carry-case and is being jolted around. You may want to have it switch on when headphone jack completes the circuit, rather than a switch. Just an idea.

    There have been a few times, when I’ve taken off my headphones, stopped the music but left the amplifier on and the cMoyBB has whittled away at my battery. So now I usually just unplug the headphones anyway, or turn it off, if I remember.

    Again, on any piece of equipment, if anything sticks out and is thin, it looks to me like it could be prone to catching and possibly breaking; and it’s usually the case. My Shure SRH840s have two thin cables going from the headband into the ear cups. I’ve always got to be careful when handling the headphones, just in-case I catch a finger on the cable and tug it out.

    The simple on/off potentiometer is a great feature of the cMoyBB. Alas, I know this isn’t a simple cmoy amplifier any more, and it’s moving up the ranks, so design changes are expected.

    If all fails, re-instate the potentiometer, it’s always a winner, as people may get a nasty surprise when they plug in their headphones, flick the amp to ‘On’ and Pendulum blasts their headphones in half as their volume crept up to 80% on the dial without them noticing.

    Or would it be possible for the volume to be reset every time it’s turned off? That could be a good safety feature, but from an engineering standpoint I have no idea how you’d implement that one.

    Some questions:
    In regards to the above on/off worries, will it still feature the auto on/off feature the cMoyBB has? (headphones removed = off) Which has saved me many recharges.

    Will the battery be replaceable? Not that it will die off that quickly, but I’ve had my iPhone 4 for a year now, and the battery life has degraded ever so slightly.

    If you were to give this new amp an industry standard quality rating, what would you say the C421 would be competing with?

    iBasso T3D (£120), Meier-Audio Corda Move (£150), Headbox Headamp II (£100), Headbox SEII (£180), Graham Slee Voyager (£188), or would you go higher, such as, iBasso DB2 (£320)/iBasso PB2 (£349), Graham Slee Solo/Linear (£500~600).

    I would throw the Lehmann Black Cube into that list, but then again, you can pick up an Matrix M-Stage BCL clone for about £160. I’ve negated any DAC amps from the list.

    When will you be releasing the ‘geek sheet’ on this amp? So we can all oogle at the THD, gain, output impedance and SNR?

    Other thoughts:

    The only other place you could take the C421 in the future is to include a DAC. It has the mini-USB port there already. Constructing a PCB with a couple of Wolfson WM8740s in mind would really take you into the big-big-boy leagues; your cmoy BB really holds its own against other more expensive amps and I really hope to see that kind of functionality creeping out in the future; as not only would I buy it immediately, it would add major retail value! It would put the C421 on par with brands such as iBasso, NuForce et al.

    The FiiO E7 has the 8740 and the DAC is superb, it’s just a shame the amp itself isn’t great, hence why I avoid using it. I’ve been wanting to get hold of the E9, so I could have the high(er) quality desktop amp coupled with the superb Wolfson DAC in the E7.

    Keep up the good work John, I’ll provide more feedback as you give us more details.

    Kind regards,
    Jamie McAllister.

    1. “In regards to the above on/off worries, will it still feature the auto on/off feature the cMoyBB has?”

      We put much consideration into the on/off switch. Yes, it’s a tough, satisfying toggle that will not be accidentally switched. It protrudes slightly more in these renderings than it will in the final product. If you manage to accidentally toggle the switch–and I don’t think you will–the flat/countersunk screws can be swapped for 3mm socket cap screws to serve as an extra barrier. I know, a picture would be helpful. I’ll post one when production samples are complete.

      Auto on/off had to go in order to improve amplifier performance and minimize enclosure size. Those mechanical “auto” power switches in the cMoyBB hindered a strong 4-layer PCB layout, so we eliminated them. The feature could be regained by non-mechanical means, but that would have added significantly to cost. We wanted to keep C421 as simple as possible for a smart Li-Ion, USB charging amp. Fewer features equate to greater focus on SQ.

      “Will the battery be replaceable?”

      Yes, the Li-Ion battery is easy to obtain and replace. Unscrew the front or rear panel and the board slides out. The battery connects via common 3-pin Molex connector.

      “If you were to give this new amp an industry standard quality rating, what would you say the C421 would be competing with?”

      As always, I’ll leave that up to you guys! We use a design process unlike others; every new circuit eliminates a shortcoming of an earlier design. C421 consists of many unreleased circuit ideas, so it’s a substantial step up. Basically, we don’t try to fit amps into a certain market segment, or attempt to compete with X competitors’ offerings. We’re competing with ourself. The cMoyBB has always surprised folks by its value, and I expect that trend will continue with our upcoming and future offerings.

      “When will you be releasing the ‘geek sheet’ on this amp? So we can all oogle at the THD, gain, output impedance and SNR?”

      You’ll have to wait for the pre-order page. 🙂 Excluding losses and output characteristics of the opamp, we added no more than 0.1 ohm to output-Z.

      “As stated above a DAC from you would be superb, also not having to deal with China when I have an issue would be nice. The language barrier can be a killer at times.”

      Hehe, I’ll see what can be done.

      “will this amp feature a crossfeed?”

      No crossfeed. It adds many passive components and negates the goal of signal transparency. Crossfeed has its purpose, but it’s rarely requested, so I didn’t feel it was worth the effort or cost to implement on C421.

      You guys are awesome!

      1. “You guys are awesome!”

        No, you’re awesome!

        Seriously though, keep up the good work John. If you keep this up you’ll be getting offers from big blue-chips to buy you off the market. You’re putting these people to shame!

        And on that note, when are you taking the market by storm? 🙂

        If you’re saying this is a ‘mid-range’ amp, and it’s going to cost about $180, in plain old Scottish, that’s £110 to me. Which is a bargain! And I bet most of your UK clients feel the exact same.

        An industry mid-range (or mid-high) amp built in the UK, I’d say, is something along the lines of a Just Audio uHA-120 – £220. And for an imported across the seas amp, sold by a licensed retailer, I’d use these two as an example: iBasso D10/D12 – £260/310 ($460/510! :o)

        I refuse to buy any of the iBasso range from UK retailers considering the US prices sit around $285 for the iBasso D12.

        So as you can see, over in the UK, the prices = ouchies. Especially when compared to US prices. We get charged almost 2x as much as you 😉 Oh the joys of importing and taxes!

        So sir, you’ve instantly halved the price (and saved my wallet from shedding more unnecessary tears). And as I’ve already heard from the cMoyBB, you’re giving me the same quality from your amp and home-made PCB design as would be expected from an industry recognised brand, albeit at a much cheaper price.

        Bring on the Pre-Order page!


  3. I can’t wait to use it, I’m going to use my iBasso D6’s aux out as a DAC when on my PC.

    As stated above a DAC from you would be superb, also not having to deal with China when I have an issue would be nice. The language barrier can be a killer at times.

    …But from using my cMoyBB 2.03, I don’t think I’ll even need customer service; as your design is flawless.

  4. Hi John,
    I think the design is very good, except that the protruding power switch creates an unwanted bump in an otherwise smooth design.

    The mini-USB port is for charging only right?

    1. Yes, the USB port is exclusively for charging. Also see the switch discussion above (it will be slightly more recessed than shown here).

  5. It looks perfect but would be better if the edges are little bit rounderin the four sides,& one question whats the story behind the name C421?would love to hear.

    1. I’d liked to have rounded the edges more (they were in our first sketches!), but doing so would have interfered with some components. The overall width would have to grow to pull off a curvier outline.

      April 21 (2010) was the date of an early schematic; the letter “C” represents “concept”. We had several earlier prototypes, but the 4-21 schematic ultimately progressed to a solid design. A final name hadn’t been selected when we made the announcement in May 2011, so the codename stuck.

  6. Right when I was about to order a CMoyBB v2.03, I read about this. This looks promising and I hope it will surpass my expectations. Now the only bad thing I see about this so far is the wait!

  7. Just have to say that John has to be the best guy around when it comes to customer service. Had a problem with the amp I purchased from him almost 2 years ago, sent him an e-mail with the problem , that day I received a response from him. Sent the amp back , the day he received the amp he found the problem didn’t charge me for fixing it , what can I say other than Thanks and I will never buy another amp or recommend another amp besides John’s. Thank You

    1. This is a longstanding debate. Digital pots are only advantageous in high-end audio when brilliantly implemented (high-end chips with top specs and excellent control algorithms). Although imbalance is nearly perfect, digital pots bring worse issues:

      1) Colored audio signal
      2) Limited input power
      3) Worse SNR and crosstalk!
      4) “Zipping” (clicking sounds) occur as volume is changed

      All of these problems have solutions, but they increase cost too much.

      An analog volume pot avoids all of the above issues and thus maintains a truer audio signal. Balance isn’t a problem at low volumes when using a low gain, even with IEM’s. We’re using 0.1% resistors in the signal path, so pot imbalance is not multiplied. Like vacuum tubes (major downsides, but still enjoyed!), analog attenuation is a well placed classical component in a headphone amp.

  8. I’m a happy diy er of your 2.03 and I love it. It’s very clear that there’s no way this could be a diy project from a quick glance at the pcb. That’s a shame but a worthwhile tradeoff for a better product. I’m eager to see reviews and specs. My personal critique of what I’ve seen so far is the usb port. I prefer micro because every phone today uses micro rather than mini. It would be great to use my phone charger to charge this. How many hours does one charge last? I love the lithium ion battery. It fits the mobile audio solution perfectly. Unfortunately I haven’t found many 9v li ion solutions. I’d also love to see the addition of a high quality dac. Almost every mobile device nowadays has an unacceptably high noise floor. It doesn’t matter how nice the headphone amp is if the source is bad. Soundcards don’t have usb out but I know it’s not logistically feasible to have an additional spdif input on this. That’s fine because soundcards have more than adequate dacs. Will this product feature customization like the cmoybb? Also is it safe to assume you’ll continue selling and supporting the cmoybb?

    1. Paul,

      Yes, we’ll continue to sell and support the cMoyBB alongside C421. A single charge lasts around 10-15 hours. We made no sacrifices to improve efficiency. I’ve been enjoying the prototype and have yet to drain the battery during a single work day! 🙂

    2. Another small thing is the screws. I believe flathead is better than philips because phillips heads are known to strip. Flatheads are readily available on every house and never strip.

  9. A designer can’t give an objective take on his own creation, so it’s best to wait for an objective reviewer. Consider this an ordinary opinion:

    I spent four hours with the amp last night, driving Beyer DT-880’s, the 250 ohm edition. Rarely do I pick these cans up because they’re so hard to drive! c421 fills them effortlessly. The sound stage is as spacious, if not more so than the cMoyBB. Low end and mids are tight and natural. Highs are not too bright, not too dull. It was important to me to create a transparent, refined amp. I feel we’ve pulled that off.

    My only concern is that I selected the amp’s sound for myself. It was 9PM when I sat down to listen, and 1:30AM when I forced myself to power down and get some rest. Didn’t want to leave the glorious music!

    NEWS: We made a couple tweets earlier this week, but haven’t posted anything here yet. I met with the enclosure fab shop on Wednesday. Samples looked great, and are approved for production! About 4-6 weeks to go.

  10. Would like to know when it is ready and the price. Do you anticipate somehow doing a V2.03 internals in the new C241 form factor?

    Do you have any experience with driving ATH-M50s with either the V2.03 or C241?

    1. Daniel,

      I do not have ATH-M50’s. It’s a popular set used by many of our customers, so I imagine cMoyBB owners have posted comments somewhere.

      There’s no way to directly translate the cMoyBB to the smaller enclosure. The Alps potentiometer and 9V battery are too thick. The main opamp circuit could be maintained, but we’ll only release a slimmer cMoyBB if it can be done affordably and without compromise (not likely).

        1. Not zero. The value is dependent on the specific opamp in the output stage (close to zero, yes).

          After much evaluation, we’ve decided to offer C421 with at least two choices for the output stage opamp. Specifics will be announced soon.

  11. A question that has not been asked before, at least not this way around:
    Could this new amp snuggle into an Altoids tin? I mean I have to admit, next to the great performance that design feature was kind of a really cool thing. Maybe as a custom job, because I would love one of those in the cMoyBBs skin. It’s obviously not for everybody, but I bet some people share my feelings for the tin.

    1. Placing the amp in an Altoids tin would be possible with a custom, revised PCB. However, a single prototype PCB costs around $500 assembled.

      1. Oh, that’s quite a hefty price tag [$500 custom amp]. Any chance the price would go down if enough people showed interest?

  12. That is great news though, you should probably ask on the preorder page when it goes online to find out how big interest is. Or post a poll about this topic at some point, something like that. But don’t let me tell you how to run your business. Thanks for the answers. : )

  13. Love the design of your new amp and am anxiously awaiting pricing and a preorder page. Have you considered red or green anodized aluminum end caps? I think just about about every other company has black or silver enclosures with black or silver end caps. I think having the red or green, colors found on an Altoids tin, end caps would add a nice touch that would be unique to a unique company like yours.

    1. Good suggestion, Scott. I’ll get pricing from the panel shop for other colors. If it’s feasible, we’ll make that an option. Thanks!

  14. I use a pair of akg k701’s, will the c421 be able to drive these? currently im using the Bass Boost cMoy v2.03 and it does an amazing job. however, im one of those people who’s always looking to improve sound quality.

    1. Yes, C421 handles demanding headphones with ease. The first batch should be done in about 3 weeks. Pre-orders go live very soon!

  15. I see a clash of titans afoot!

    * C421 enclosures will be finished on the 3rd of October.

    * Apple will ‘talk iPhone’ on the 4th of October.

    * Both of the devices will have pre-orders setup within the next 7 days.

    * Their release dates will be around the 21st-24th of October (if the C421 production line is on schedule).

    You should cut a deal with Apple… Or maybe Apple should cut a deal with you!

    Apple iPhone 5: Audiophile Edition!

    Can’t wait to hear the new amp John.

    Hurry up and get that pre-order page up! 🙂

  16. Watching this with great interest. Please advise on pricing and availabilty as soon as this has been decided. Could be just what i’m looking for.

  17. same here I have been holding off on buying other amps as an upgrade to my cmoy and the temptation level is pretty high but I can wait. Will it be any were around the price stated before that was around $175?

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.