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Cypher Labs Theorem 720

Discussion in 'Portable Headphone Amps' started by drsheep, Sep 3, 2013.
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  1. Poimandres
    Thanks, I actually emailed cypher labs and I was surprised to have had my email answered directly by David, I have just asked him if they offer any mods that may get rid of the hiss for high sensitivity low ohm iems. I expect not but will update here if they do. The Theorem is a great piece in time hopefully the hiss will become less noticeable.
  2. Poimandres
    No mod yet, however since most head fiers in the Westone 4 thread recommend using the 4r with a 100 ohm resistor I finaly decided to use the one that I purchased from Ebay.  And voila hiss gone..zero..nada..non existant, totally silent black background.  They say that the resistor fixe alot of issues with the 4r my question is would it cause any other unwanted issues other than possibly draining the Theorems battery faster?
  3. shigzeo Contributor
    I don't think you will drain the Theorem's battery any faster. True you will use a small bit more voltage to achieve the same volume level at the ear, but it should be insignificant. The resistor may also change the sound nature of the 4r because the impedance can affect the crossover circuit, which generally reacts at a certain impedance input. I've not tested FRs of resisted earphones vs. unresisted, but I know some people who have gone back and forth and noticed big changes (again, you may like it, you may not) in their earphones base sound signature. If it is worth it because hiss is gone, then good.
    Back in the day, a lot of amps had high Ω output. To get them to play nicely with a pair of earphones... you needed the ER4 or a resistor. That was when people found out that the resistor also changed the sound signature of the earphone.
  4. Poimandres
    Well I decided to send the Theorem back. I really wanted to keep it as it sounds phenomenal however I was unable to get past the hiss. I opted for the clas db and glacier.
  5. Cotnijoe
    ahhh that's a shame... all these hiss talk makes me so sad...
  6. Poimandres
    It's really not that bad however OCD makes it worse. You know it's there and thus you can't help but listen for it.
  7. shigzeo Contributor
    As long as you know that every single source/amp hisses, and you are prepared for that, then I hope you are happy with your decision. That used to be my primary concern. And I was never, ever, happy. Today I'm recovering- a recovering hiss hater!
  8. Poimandres
    That may be true however if there is hiss it has been in audible in my previous amps at least to me.
  9. rmilewsk
    I have tested both the RSA intruder and the ALO international with the JH 13 pros and neither one had any noticeable hiss. The 720 had very noticeable hiss. 
  10. sean76
    I just ordered the 720 from Moon Audio.  Will there be hiss with over the ear or on ear headphones?  I am going to be using it for the senn 600 and Audio Technica ES10.  I won't be using any in ear headphones.
  11. midnightwalker
    Should be not for the HD600 and probably not for the ES10. Cross your fingers on it :)
  12. sean76
    Thanks. Now you are making me nervous. Why would such a highly recommended product have such a flaw? I was under the impression that it only has issues with the in ear headphones. Guess I was wrong.
  13. midnightwalker
    Nah, I do not think it is a flaw. Even with the earphones, I still consider the hiss at acceptable level (much softer and lower than RXMk3). Do not worry much about the ES10, I am just not sure as I never listen it with the 720. The HD600 impedance is too high to produce hiss. With iems around 90ohms or higher, I hear no hiss.
  14. SoundMinded Man
    Greetings All,
         I am a head fi rookie and this is in fact my first post.  I have been paying attention to this thread since its inception and it has been fun to see it grow.  I have taken the plunge and purchased a theorem last week from TTVJ.  It is my first external DAC as I have previously only listened to music directly through a macbook pro retina/iphone 5.  Right now all I have is the Phonak Audeo PFE 232 earphones to test it.  While my computer's direct out actually sounds very good, my initial impressions are that the theorem has unlocked a warmth, depth and clarity to familiar songs making my entire library feel uncharted...very exciting.  
         For the record, there is very, very low hiss on the low amp stage; however, I have found that the sound-stage and overall clarity drastically improves when I set the source player volume at around 25% and bump the amp to Medium with volume cranked or even High with volume at about 40%.  To my ears, as I increase the power of the amp, the music gets much brighter/punchier  (which can be good or bad depending on the song/genre) but also WAY more spacious and detailed  leading to a few of those holy SH*! moments that vindicate the price of purchase.   Unfortunately the hiss does also increase significantly on the higher gain stages.  So.... couple questions:
    1  Am I just hearing things or does the source volume precut + higher amplitude usually lead to better sound stage and clarity?
    2 Are the 232's worthy of this rig or would the Fiio E17 essentially provide similar benefits relative to the sound quality ceiling of the IEMs. 
    3 (This is the main question I'd hope to spark a thread discussion)
        What Open Ear desktop cans do you think would synergize  best with the theorem?
    I am looking for something in the $400 – $600 range and listen to a wide variety of music from 70s rock to modern trance.  My current go to album is a 24/96 vinyl rip of Herbie Hancock's Man-Child... so funky and creamy. Though, n the same listening session  earlier today  I also listened to Brothers in Arms and Random Access Memories.  So I really want something that is highly versatile and universally compatible with all music and movies.. 
    right now the sennheiser HD 600 is selling on Amazon for $400… Any thoughts?
    thanks so much and sorry for the long-winded post... I'm still a newb
  15. sean76
    Thanks for your response.  I am okay with soft hiss.  Once the music plays, I am pretty sure I can't hear it.  That's perfectly acceptable.  Any good portable headphones you would recommend to go with the 720?
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