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The all new Continental Dual Mono

Discussion in 'Portable Headphone Amps' started by kb, Mar 26, 2015.
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  1. seedubchris
    Thats not surprising. In the pro audio world the nos jan (Joint Army Navy) tubes from the old days are the ones to have clearly. I got the impression that the only use for these type of miniaturized tubes was for military applications . Bigger tubes are much easier to manufacture and therefore cheaper . One reason why I'm surprised the Telefunken's are not better performers is tele was a military industrial contractor for Germany. Their larger tubes are highly sought after and huge money for the right low noise variants. I'm just getting to know the cdm so its nice to have some feedback on the tube rolling . User Haiku speaks of some oldie nos sonnotone tubes that are different from the standard ones sold through alo. These are the kind of old milspec tubes I would hope to eventually be able to find for the reasons you stated regarding manufacturing specs. Good luck with the Ray 6021. Hope its all the sound with half the heat/power consumption.
  2. vlach
    Has anyone here compared the CDM to desktop tube amps purely from a SQ stand point? I'm so impressed by what the CDM provides from a transportable form factor that i wonder if i would get even better sound (aside from more power reserve) from something like the WA6 or something equivalent in the sub $1000 range.
    Last edited: Jan 26, 2018
  3. thecrow
    As highlighted in this review http://headphone.guru/the-alo-continental-dual-mono/ the alo cdm is a handy amp with the hd800.

    But the woo wa2 (over $1000) has a defnite better sound. Better spacing. Better detail. Silkier, rounder sound. But the wa2 otl is a great option for the hd800

    For the elear and lcd2 i found the burson conductor a little bit better than the alo cdm. That little bit of extra power is what makes most of that small improvement, but i was not listening to the headphones through balanced wth the cdm that gives more power
  4. vlach
    Thank you thecrow, your thoughts are similar to mine in that a full size tube amp would most likely yield even better sound. It turns out i prefer the HE-500 with the CDM compared to the HD800, for the simple reason that mids are thicker, more organic and sound more natural. From that perspective, i believe something like the WA6/WA6SE would be a better match (lower impedance output) than the WA2 which is OTL and optimized for higher impedance headphones.

    I'm enjoying the CDM so much that my BHA-1 is getting lonely even though it does a few things better like scale, resolution, precision, tighter bass, etc. but it simply can't match the luscious mids of the CDM. Any improvement over the CDM would make me ascend straight into heaven :)
    Last edited: Jan 27, 2018
  5. bflat
    What the hell is this?


    The future!

    So here is what I did. First I got the new Fiio Q5


    Instead of the line out (on top of the Q5) I decided to use the balanced headphone out and imho it sounds better than line out. I had a custom made TRRS cable from Headphonelounge (Ted Allen). I made a DIY ground only cable (copper). So now I got balanced in and out. You might say this is double amping and technically it is, but also pretty much the same thing that AK calls line out. But given the high input impedance of the CDM, the Q5 outputs at essentially no load so at the best measurements.

    Now why go through all the trouble if I have a SP1000 I could use? With Q5 I get:
    • Coax input (using in desktop mode with coax from my SU-1)
    • Optical input
    • Apt-X (yes! Q5 is a BT RECEIVER and connects to your source via Apt-X and AAC for iOS)
    Can't do any of the above with the SP1000 and quite frankly, I'm really too lazy having to connect/un-connect my SP1000 to the CDM all the time. I also found the USB DAC feature of SP1000 mediocre. It was much better just as a DAP. Q5 is no different - USB is so so, but coax is so much better if you have top notch DDC like an SU-1.

    But my biggest surprise is how good the Aptx and AAC bluetooth connection sounds! I tried my iPhone and Aptx from my Android tablet. Fiio's Q5 has the decoded BT stream bypassing the BT codec and going straight to the 2 x AKM4490 DACs.

    The overall sound to me is analog/organic with better extension high and low compared to built in DAC. Reminds me a lot of my AK380Cu. Q5 has a touch more mid bass than I like so I changed the CDM tubes back to Telefunken 5719 and that pairs great.

    Couple more notes:
    • The charging port is on the left side of the Q5 so it does not get in the way of the top and bottom ports. You can still use the usb port on the bottom for both charging and data. It is covered up with my cables in the photo. I don't intend to use the usb for data.
    • At the moment, coax and optical do not support DoP. Not sure if that's a hardware limitation. USB works fine for DoP.
    • No EMI issues from bluetooth in an hour of testing.
    • Q5 has an iOS app that lets you select different filters for the AKM4490 DACs. Wish AK would implement that!
    • You could also take the line out of the CDM to the line in of the Q5 and have a solid state balanced amp! Or just use the Q5 stand alone for that LOL.
    • Q5 does not have wifi so no DLNA.
    • Q5 has a bass boost option.
    I ordered a Q5 promotional package directly from Fiio but I think the US resellers should have them by mid Feb and MSRP is $359. I consider that a pretty good price to upgrade the CDM DAC to a modern design with a lot of ways to connect it.

    Pretty happy with this combo and has given new life to my CDM!

    Note - the large black volume knob is an upgrade I made because I find the original too small and gets too hot, and volume level marker is upside down if you have the tube window facing up (and who wouldn't position that way?).
    Last edited: Jan 29, 2018
    kukkurovaca likes this.
  6. vlach
    Too funny...i changed the knob too!
    bflat likes this.
  7. seedubchris
    How does the ground cable fit into the picture. Funny the headphone out sounds better than the line out. If someone would build a kick ass dedicated line out with dap and bluetooth functionalities the might sell a few. It seems none of the dap makers have any interest in creating an alternative to the headphone out to act as source for these amps. I would love to find a true component style 4V line out for the cdm. Does anyone know what the max voltage at the balanced input of the cdm is?
    Nice creative solution to the rigging of the cdm. I'm sure it is more user friendly but does it really keep up with the ak1000 as source hardwired. I just cant imagine blue tooth keeping up unless it was apt-xhd which is only used in a few strange sources like certain cell phones.
    robbi22 likes this.
  8. bflat
    For the ground cable, you need it for CDM under the following scenario - you have both your source and CDM AC powered and you hear ground hum noise when music is not playing. Adding the ground cable eliminates the hum. The AK 2.5mm TRRS has no ground so if your connected devices have different ground potentials, you will get hum. The ground cable ensures both devices are at the same ground potential. If you listen only on batteries than the ground cable does nothing.

    If you believe AAC/MP3 sound substantially different than ALAC/FLAC lossless tracks, then no bluetooth will never achieve the same sound, even with AptX HD. If you listen to AAC/MP3 and happy with the quality, then there is practically no difference with AptX and USB as both have more than sufficient bandwidth the transmit the data unaltered. Again in the case with Q5, it bypasses the bluetooth chip DAC and goes directly to the system DAC which are AKM4490. I've always experienced that a well mastered AAC track sounds better than a mediocre mastered lossless track. Apple does a really good job of high quality masters in AAC format. I like to use Apple Music to discover new music and the interface suites my preferences.

    IMHO, I find little difference between AptX and USB input, but coax is a whole different story. More dynamic and spacious sound from coax. A lot of that has to do with the great pains I went through in my digital chain of low noise power sources, high end digital cables, iFi iGalvanic, and heavily modded SU-1. On the go, AptX is hard to beat. If a future iteration of Q5 adds wifi and DLNA support, then we can go completely wireless with no loss of data. Only problem with wifi is that it's really bad for battery life. Anyway, that is what the future holds imho and Chord is already there with Poly and upcoming Hugo 2 wifi module.

    As for using the headphone out, let me put it this way.

    Here are the measured performance of my balanced output from my Holo Level 3 DAC:

    THD - .0003%, SNR - 126 dB, 4V output

    The Q5 balanced headphone output is:

    THD - .001%, SNR - 115 dB, 3.8V output

    Both my Holo DAC and Q5 use op amps for their respective output stages (different topology and quality of course). It just so happens Q5 is a variable output.

    CDM headphone output

    THD - 0.5%, SNR - 92.6

    Neither my Holo DAC or the Q5 is holding back on what the CDM is capable of doing. The only issue with the Q5 is tonality that will only get amplified by CDM. This is where I carefully listened and determined the Q5 is a neutral tone with just a slight bump in mid to upper bass and that is more to do with my personal sensitivity to those frequencies. Overall though, the soundstage and presentation of the balanced headphone out greatly outweighs the "pure" sound of line out for me. Others may disagree but the great thing is you can use the Q5 line out and then you have both a CDM and solid state balanced output depending on the mood and headphone! I may just do that at some point.

    Lastly, I put this together so I can enjoy high quality music playback in numerous situations so definitely not for analytical listening. I have my desktop system for that.
  9. bflat
  10. tracyca
    Just received my Mullard 6021, Raytheon 6021, and Raytheon 6111wa looking forward to some tube rolling fun!
  11. phammed
    How do these pair with the campfire vegas? thanks guys!
  12. tracyca
    OMG! The Mullard 6021 sound so Amazing, I can't believe how they transformed my CDM. I don't understand how more people ant giving this amp a chance.
  13. tracyca
    20180210_172221.jpg tube rolling is fun!
  14. fordski
    Thanks everyone for the tube rolling updates! The comments regenerated my interest in this lovely DAC/Amp.

    I have a question regarding the recommended input voltage for the CDM. I've searched high and low but can't find the specs. I know 2 volts is a standard but I remember seeing a reference to the CDM accepting up to 4 volts. I'm asking as I typically use my Chord Mojo coupled with a Poly as the DAC for my CDM. It defaults to 3 volts for line out mode and can be reduced (or increased) by counting the number of clicks down (or up). (4 clicks =1.9 volts)
  15. bflat
    What you are asking is in the analog domain so you don't lose any details by lowering the voltage. Having said that, Chord has decided to set their optimal audio line out to 3V, that is what I used when I have a Mojo. The side benefit is that the SE input at 3V is nearly as loud as the balanced input at 4V. If you want to know the max input voltage before you start getting distortion on the CDM, just ask ALO. I'm guessing it would around 6V, but if you want to know if 3V is ok, the answer is yes.
    kukkurovaca likes this.
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