Cavalli Liquid Carbon technical measurements

Discussion in 'Headphone Amplifier Measurements' started by atomicbob, Dec 16, 2015.

  1. atomicbob

    atomicbob dScope Yoda

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    Liquid Carbon Technical Measurements Balanced inputs and outputs

    The data presented were collected as follows:

    1. PrismSound dScope III, picoscope 5243B
    2. 300 and 30 ohm loads used for measurements
    3. Balanced cables Canare L-4E6S starquad with Neutrik XLR connectors
    4. Unbalanced cables DH Labs Silver Sonic Air Matrix RCA (for picoscope)
    5. Vaunix Lab Brick USB hub
    6. 0 dB gain @ 0.775 Vrms 0 dBu except as noted for square wave measurements
    7. Liquid Carbon gain switch set to High

    0.775 Vrms @ 30 ohms is 20 mW producing 102 dB SPL in HE-500 with sensitivity of 89 dB/mW
    0.775 Vrms @ 300 ohms is 2 mW producing 105 dB SPL in HD650 with sensitivity of 102 dB/mW

    Picture of the Audio Lab setup for Liquid Carbon
    20151214 Liquid Carbon dScope picoscope setup.jpg

    Liquid Carbon square wave 20 Hz 2 Vpp 10 mS / div 300R load
    20151120 SigGen LiqCarb 20 Hz square 2000mVpp 10mS div 100KHz filter.PNG

    Liquid Carbon square wave 20 Hz 2 Vpp 10 uS / div 300R load
    20151120 SigGen LiqCarb 20 Hz square 2000mVpp 10uS div 5MHz filter.PNG

    Liquid Carbon amplitude - phase - gain (A01) 300R load
    Liquid Carbon A01 amplitude - phase - gain 300 ohm load.png

    Liquid Carbon signal to noise (A07) 300R load
    Liquid Carbon A07 SNR 300 ohm load.png

    Liquid Carbon THD+N THD nth harmonic distortion (A04) 300R load
    Liquid Carbon A04 THD+N  THD  nth-HD 300 ohm load.png

    Liquid Carbon Crosstalk (A08 A09) 300 ohm load
    Liquid Carbon A08 A09 Crosstalk 300 ohm load.png
     
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    Last edited: Dec 16, 2015
  2. atomicbob

    atomicbob dScope Yoda

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    Part B of measurements - 300 ohm measurements part 2

    editorial - I believe there is a tendency to focus too much on numbers such as THD rather than look at distortion spectrum and type such as even vs odd in an attempt to reduce a complex topic to a single number representing a sort of goodness rating.

    Here are graphs for the various measurements

    Liquid Carbon Frequency Response and Interchannel Phase 1/2 300R load
    G2_L1T2_1_A.png

    Liquid Carbon Frequency Response and Interchannel Phase 2/2 300R load
    G2_L1T2_1_B.png

    Liquid Carbon Gain vs Amplitude Left 300R load
    G2_L1T3_1_A.png

    Liquid Carbon Gain vs Amplitude Right 300R load
    G2_L1T3_1_B.png

    Liquid Carbon THD+N vs Frequency Left 300R load
    G2_L1T5_1_A.png

    Liquid Carbon THD+N vs Frequency Right 300R load
    G2_L1T5_1_B.png

    Liquid Carbon THD+N vs Amplitude Left 300R load
    G2_L1T6_1_A.png

    Liquid Carbon THD+N vs Amplitude Right 300R load
    G2_L1T6_1_B.png
     
    Last edited: Dec 16, 2015
  3. atomicbob

    atomicbob dScope Yoda

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    Part C of measurements - 300 ohm load measurements part 3

    Liquid Carbon Crosstalk Left to Right vs Frequency 300R load
    G1_L1T10_1.png

    Liquid Carbon Crosstalk Right to Left vs Frequency 300R load
    G0_L1T11_1.png
    Liquid Carbon 50 Hz + 7000 Hz spectrum Left and Right 300R load
    20151214 LiqCarb 50+7000Hz dual tone 0dBu 300R.png

    Liquid Carbon 600 Hz + 1700 Hz spectrum Left and Right 300R load
    20151214 LiqCarb 600+1700Hz dual tone 0dBu 300R.png
     
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    Last edited: Dec 16, 2015
  4. atomicbob

    atomicbob dScope Yoda

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    Part D of measurements - 30 ohm load measurements part 1

    Liquid Carbon Frequency Response and Interchannel Phase 1/2 30R load
    G2_L1T2_1_A.png

    Liquid Carbon Frequency Response and Interchannel Phase 2/2 30R load
    G2_L1T2_1_B.png

    Liquid Carbon Gain vs Amplitude Left 30R load
    G2_L1T3_1_A.png

    Liquid Carbon Gain vs Amplitude Right 30R load
    G2_L1T3_1_B.png

    Liquid Carbon THD+N vs Frequency Left 30R load
    G2_L1T5_1_A.png

    Liquid Carbon THD+N vs Frequency Right 30R load
    G2_L1T5_1_B.png

    Liquid Carbon THD+N vs Amplitude Left 30R load
    G2_L1T6_1_A.png

    Liquid Carbon THD+N vs Amplitude Right 30R load
    G2_L1T6_1_B.png
     
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    Last edited: Dec 16, 2015
  5. atomicbob

    atomicbob dScope Yoda

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    Part E of measurements - 30 ohm load measurements part 2

    Liquid Carbon Crosstalk Left to Right vs Frequency 30R load
    G1_L1T10_1.png

    Liquid Carbon Crosstalk Right to Left vs Frequency 30R load
    G0_L1T11_1.png

    Liquid Carbon 50 Hz + 7000 Hz spectrum Left and Right 30R load
    20151214 LiqCarb 50+7000Hz dual tone 0dBu 30R.png

    Liquid Carbon 600 Hz + 1700 Hz spectrum Left and Right 30R load
    20151214 LiqCarb 600+1700Hz dual tone 0dBu 30R.png
     
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    Last edited: Dec 16, 2015
  6. atomicbob

    atomicbob dScope Yoda

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    Last edited: Dec 16, 2015
  7. atomicbob

    atomicbob dScope Yoda

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    reserved.
     
  8. jowls

    jowls Never shitposts (please) - Friend

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    Thanks for this. I am a total novice at interpreting the results but there seems to be a disparity between channels. Significant?
     
  9. atomicbob

    atomicbob dScope Yoda

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    The left channel is approximately 0.3 dB higher in level than the right channel. I don't think many would notice a balance pan of 0.3 dB. The right channel is slightly quieter and lower in distortion. Channel imbalances exist in nearly every amplifier and one reason for the L-R balance control on preamps. When listening to the amp, if someone were asked to describe any differences observed between the left and right channels, I am confident they would be hard pressed to hear any.
     
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  10. SSL

    SSL Friend

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    Any other commentary? Need someone to tell me how to think.
     
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  11. Za Warudo

    Za Warudo Acquaintance

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    Mine has a weird issue where sometimes the left channel is louder, even when the volume is at minimum on low gain. Usually it goes away when I turn up the volume.
     
  12. Clemmaster

    Clemmaster Friend

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    Channel imbalance is worse at lower volume. That's typical with potentiometers.
     
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  13. Psalmanazar

    Psalmanazar Most improved member; A+

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    All small potentiometers have channel imbalance. That's the main problem with small form factor amps.
     
  14. Asgeir101

    Asgeir101 Rando

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    These are interesting measurements. It would be cool to see if you (@atomicbob) could run similar measurements of the liquid Crimson so we can contrast Alex's smaller and larger designs
     
  15. mtoc

    mtoc SBAF's Resident Shit-Stirrer

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    What're the black and red things on the cables?
     
    Last edited: Dec 27, 2015
  16. Armaegis

    Armaegis Friend

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  17. Xen

    Xen Friend

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    Man, do I love this forum. @atomicbob another highly informative and educational post. I now understand something that has bugged me (a tiny tiny bit) for 30+ years and that is what does the "loudness" button actually do? I now know why hitting the 3x gain (aka "Loudness") button on the Carbon produces a "V"-shaped FR in my head. While all frequencies may get an equal gain boost, psychoacoustically, the mids are not perceived to be boosted as much as high frequencies and low frequencies.

    On the spectrum plots, is that little mound of noise out there at 47KHz an artifact or a misbehaving (variability in?) component on the left channel? Obviously not audible as it is below -105 dB.

    I also noticed that I had sound bleeding through my right channel at minimal volume and 1x gain. Knowing that this is a well-known issue with any small potentiometers is a relief. Thanks @Clemmaster and @Psalmanazar ! I took out my digital multimeter and collected the output voltages at different volume positions. From my unsanctioned measurements, my Liquid Carbon has slightly worse channel imbalance than atomicbob's with 0.9 db at 9 oclock and 0.5 db at 12 oclock and 3 oclock positions. I measure both of my balanced cables and the maximum difference in Vrms was about 0.1 mV, which is insignificant in terms of calculated sound levels.

    Below is a pciture of my unsanctioned measurements. Please feel free to remove them if this is the wrong place.
    Cavalli Liquid Carbon Output Voltage Formatted.gif
    EDIT: Forgot to add the headphone specifications, which were 50R impedance and 90 dB/mW sensitivity.
     
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    Last edited: Dec 27, 2015
  18. atomicbob

    atomicbob dScope Yoda

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    It's on my list of things to do. Had hoped to look at measuring today when headphone sensitivity measurements took front stage.
     
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  19. Colgin

    Colgin Friend

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    Ugh! I finally received my LC yesterday. I only had a little time to listen to it but all was well. I was only using the SE output while I wait for balanced cables to arrive. I let the amp burn in over night following the manual instructions precisely. Today, the right channel was pretty much dead. [​IMG] I checked all my connections to make sure everything was OK and tried a few different headphones. I finally realized that the right channel would come back if you basically turn the volume knob all the way to the right. This was not an issue yesterday. Channel imbalance is one thing, but this is ridiculous. I should not have to be at max volume to hear the right channel. I have to contact Cavalli, but may ask for a refund rather than repair. Given my and other similar issues I have read about I don't have that much long-term confidence in this build although I am sure it sounds lovely (honestly, my listening was very brief).
     
  20. Xen

    Xen Friend

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    Seems there might be some major QA/QC issues with the pots. Mine was diagnosed as "damaged" and Dr. Cavalli is replacing the board.

    If I remember correctly, one of the delays was because of a volume pot issue. This could be further fallout from that delay. Did the potentiometer manufacturer rush through orders? Did Cavalli find a new source of pots that were not what he wanted? So many questions...
     

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