Massdrop Cavalli Tube Hybrid amp technical measurements

Discussion in 'Headphone Amplifier Measurements' started by atomicbob, Mar 8, 2018.

  1. atomicbob

    atomicbob dScope Yoda

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    Massdrop Cavalli Tube Hybrid (MCTH) technical measurements

    If you are unfamiliar with audio measurements please use a search engine with the query:
    "audio measurements" or "audio measurement handbook"
    Look for publications by Richard C. Cabot and also by Bob Metzler, both from Audio Precision. There are other useful publications as well. These will provide basic knowledge.
    Interpretation of the following measurements is beyond the scope of this post.

    The data presented were collected as follows:

    1. PrismSound dScope III, picoscope 5243B, Keysight 34461A DMM
    2. 300 and 30 ohm loads used for measurements
    3. Unbalanced cables Worlds Best Cable Gotham GAC-2 RCA
    4. Vaunix Lab Brick USB hub for measurement equipment
    5. Audioquest Forest and Schiit Pyst USB cables used for measurement equipment
    6. Amplifier gain adjusted to 0 dB gain @ 0.775 Vrms 0 dBu
    7. MCTH gain knob at approximately 1:30 to achieve 0 dB gain
    8. Electro Harmonix 6922 driver tube (stock)
    9. 14 and 16 AWG sheilded power cables used

    Reference levels :
    +9 dBu 300R 16.00 mW - 110 dBSPL @ 98dB/mW
    0 dBu 300R 2.00 mW - 101 dBSPL @ 98dB/mW
    -10 dBu 300R 0.20 mW - 91 dBSPL @ 98dB/mW
    -20 dBu 300R 0.02 mW - 81 dBSPL @ 98dB/mW

    +9 dBu 30R 160.00 mW - 110 dBSPL @ 89dB/mW
    0 dBu 30R 20.00 mW - 102 dBSPL @ 89dB/mW
    -10 dBu 30R 2.00 mW - 92 dBSPL @ 89dB/mW
    -20 dBu 30R 0.20 mW - 82 dBSPL @ 89dB/mW

    Reference data on two headphones:
    HD 650 impedance 300R, sensitivity 98 dB/mW
    HE-500 impedance 38R, sensitivity 89 dB/mW

    Highlights
    Transient response is excellent with the high bandwidth available on this amp (see 30 ohm load part 2 of 3 below)
    Square wave response is nearly as perfect as Liquid Crimson.
    Great sound with stock tube and supplied SMPS which make this amp a high performance/price ratio. Noticeable improvements in noise floor, distortion and low end grunt when used with an LPS.
    Measured performance difference minimal between 30 and 300 ohm loads.
    Effortless sound with low distortion let me listen louder than my usual level. Had to keep reminding myself to reduce levels back to my normal.

    My personal preferences include listening typically at an average of 75 dB SPL. Assuming a typical Peak to Average ratio of 10 dB puts peaks at 85 dB SPL. This suggests the measurements at -20 dBu
    represent my experience with HD6x0 and HD800 headphones. Auditory experiences for someone listening 10 dB SPL average higher may diverge from my own experiences.

    editorial - I believe there is a tendency to focus excessively on numbers such as THD attempting to reduce a complex topic to a single number representing a sort of goodness rating. Graphs can present far more data conveying a better understanding of the measurement over a range of frequency, levels, etc. Please don't read too much into the numbers presented.

    Picture of the Audio Lab setup for MCTH measurements
    measurement setup mcth small.jpg
    Linear Power Supply shown but SMPS used for 30R and 300R measurements in first six posts.
    LPS used for 30R measurements in posts 7 and 8. 300R was not repeated with LPS as they were so similar in SMPS measurements.

    300 ohm load part 1 of 3

    MCTH THD+N THD nth harmonic distortion (A04) FFT 0dBu 300R load

    20180307 mcth A04 THD+N  THD  nth-HD FFT 300R 4XF.png

    MCTH THD THD+N vs Freq 0dBu 300R
    20180307 mcth THD THD+N vs Freq 300R 4XF.png

    MCTH 1 KHz spectrum Left and Right 0dBu 300R load
    20180307 mcth 1 KHz THD+N THD FFT 0dBu 300R 4XF.png

    MCTH 50 Hz + 7000 Hz spectrum Left and Right 0dBu 300R load
    20180307 mcth 50+7000Hz 0dBu 300R 4XF.png

    MCTH 600 Hz + 1700 Hz spectrum Left and Right 0dBu 300R load
    20180307 mcth 600+1700Hz 0dBu 300R 4XF.png

    MCTH IMD spectrum Left and Right -16dBu 300R load
    20180307 mcth 19+20KHz -16dBu 300R 4XF.png

    MCTH residual noise spectrum Left and Right A=0dB 300R load
    20180307 mcth residual noise A=0dB 300R 4XF.png
     
    Last edited: Mar 8, 2018
  2. atomicbob

    atomicbob dScope Yoda

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    300 ohm load part 2 of 3

    MCTH square wave 20 Hz 2 Vpp 10 mS / div 300R load 100 KHz BW
    20180307 SigGen mcth 20 Hz square 2000mVpp 10mS div 100KHz filter 300R.png
    Square wave very close to Liquid Crimson - Well done Cavalli, especially at this price point.

    MCTH square wave 20 Hz 2 Vpp 10 mS / div 300R load 5 MHz BW
    20180307 SigGen mcth 20 Hz square 2000mVpp 10mS div 5MHz filter 300R.png

    MCTH square wave 20 Hz 2 Vpp 10 uS / div 300R load 100 KHz BW
    20180307 SigGen mcth 20 Hz square 2000mVpp 10uS div 100KHz filter 300R.png

    MCTH square wave 20 Hz 2 Vpp 1 uS / div 300R load 10 MHz BW
    20180307 SigGen mcth 20 Hz square 2000mVpp 1uS div 10MHz filter 300R.png

    MCTH amplitude - phase - gain (A01) 300R load 10 MHz BW
    20180307 mcth A01 amplitude - phase - gain 300R.png

    MCTH signal to noise (A07) 300R load
    20180307 mcth A07 SNR 300R.png

    MCTH THD+N THD nth harmonic distortion (A04) 300R load
    20180307 mcth A04 THD+N  THD  nth-HD 300R.png

    MCTH Crosstalk (A08 A09) 300R load
    20180307 mcth A08 A09 Crosstalk 300R.png
     
    Last edited: Mar 8, 2018
  3. atomicbob

    atomicbob dScope Yoda

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    300 ohm load part 3 of 3

    MCTH Frequency Response and Interchannel Phase pg 1/2 300R load
    G2_L1T2_1_A.png

    MCTH Frequency Response and Interchannel Phase pg 2/2 300R load
    G2_L1T2_1_B.png

    MCTH Gain vs Amplitude Left 300R load
    G2_L1T3_1_A.png

    MCTH Gain vs Amplitude Right 300R load
    G2_L1T3_1_B.png

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

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

    MCTH THD+N vs Amplitude Left 300R load
    G2_L1T5_1_B.png

    MCTH THD+N vs Amplitude Right 300R load
    G2_L1T6_1_B.png

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

    MCTH Crosstalk Right to Left vs Frequency 300R load
    G0_L1T11_1.png

     

    Attached Files:

    Last edited: Mar 8, 2018
  4. atomicbob

    atomicbob dScope Yoda

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    30 ohm load part 1 of 3

    MCTH THD+N THD nth harmonic distortion (A04) FFT 0dBu 30R load
    20180307 mcth A04 THD+N  THD  nth-HD FFT 30R 4XF.png

    MCTH THD THD+N vs Freq 0dBu 30R
    20180307 mcth THD THD+N vs Freq 30R 4XF.png

    MCTH 1 KHz spectrum Left and Right 0dBu 30R load
    20180307 mcth 1 KHz THD+N THD FFT 0dBu 30R 4XF.png

    MCTH 50 Hz + 7000 Hz spectrum Left and Right 0dBu 30R load
    20180307 mcth 50+7000Hz 0dBu 30R 4XF.png

    MCTH 600 Hz + 1700 Hz spectrum Left and Right 0dBu 30R load
    20180307 mcth 600+1700Hz 0dBu 30R 4XF.png

    MCTH IMD spectrum Left and Right -16dBu 30R load
    20180307 mcth 19+20KHz -16dBu 30R 4XF.png

    MCTH residual noise spectrum Left and Right A=0dB 30R load

    20180307 mcth residual noise A=0dB 30R 4XF.png
     
    Last edited: Mar 8, 2018
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  5. atomicbob

    atomicbob dScope Yoda

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    30 ohm load part 2 of 3

    MCTH square wave 20 Hz 2 Vpp 10 mS / div 30R load 100 KHz BW
    20180307 SigGen mcth 20 Hz square 2000mVpp 10mS div 100KHz filter 30R.png

    MCTH square wave 20 Hz 2 Vpp 10 mS / div 30R load 10 MHz BW
    20180307 SigGen mcth 20 Hz square 2000mVpp 10mS div 5MHz filter 30R.png

    MCTH square wave 20 Hz 2 Vpp 10 uS / div 30R load 100 KHz BW
    20180307 SigGen mcth 20 Hz square 2000mVpp 10uS div 100KHz filter 30R.png

    MCTH square wave 20 Hz 2 Vpp 1 uS / div 30R load 10 MHz BW
    20180307 SigGen mcth 20 Hz square 2000mVpp 1uS div 10MHz filter 30R.png

    MCTH square wave 20 Hz 2 Vpp 50 nS / div 30R load 20 MHz BW
    mcth left channel rise time 2Vpp 50nS div.png

    BW estimate from rise time calculation rule of thumb formula
    BW estimate from t rise 10 to 90 pct formula.png
    Using this estimate and the measured 111.5 nS rise time above BW is estimated at 3.05 MHz. Wow! Well done Cavalli !!


    MCTH amplitude - phase - gain (A01) 30R load
    20180307 mcth A01 amplitude - phase - gain 30R.png

    MCTH signal to noise (A07) 30R load
    20180307 mcth A07 SNR 30R.png

    MCTH THD+N THD nth harmonic distortion (A04) 30R load
    20180307 mcth A04 THD+N  THD  nth-HD 30R.png

    MCTH Crosstalk (A08 A09) 30R load

    20180307 mcth A08 A09 Crosstalk 30R.png
     
    Last edited: Mar 8, 2018
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  6. atomicbob

    atomicbob dScope Yoda

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    30 ohm load part 3 of 3

    MCTH Frequency Response and Interchannel Phase pg 1/2 30R load
    G2_L1T2_1_A.png

    MCTH Frequency Response and Interchannel Phase pg 2/2 30R load
    G2_L1T2_1_B.png

    MCTH Gain vs Amplitude Left 30R load
    G2_L1T3_1_A.png

    MCTH Gain vs Amplitude Right 30R load
    G2_L1T3_1_B.png

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

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

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

    MCTH THD+N vs Amplitude Right 30R load
    G2_L1T6_1_B.png

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

    MCTH Crosstalk Right to Left vs Frequency 30R load
    G0_L1T11_1.png
     
    Last edited: Mar 8, 2018
  7. atomicbob

    atomicbob dScope Yoda

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    Linear Power Supply section

    Every measurement in this section improved often by 10 dB or more.

    30 ohm load part 1 of 3 with LPS

    MCTH THD+N THD nth harmonic distortion (A04) FFT 0dBu 30R load
    20180307 mcth A04 THD+N  THD  nth-HD FFT 30R 4XF - LPS.png

    MCTH THD THD+N vs Freq 0dBu 30R
    20180307 mcth THD THD+N vs Freq 30R 4XF - LPS.png

    MCTH 1 KHz spectrum Left and Right 0dBu 30R load
    20180307 mcth 1 KHz THD+N THD FFT 0dBu 30R 4XF - LPS.png

    MCTH 50 Hz + 7000 Hz spectrum Left and Right 0dBu 30R load
    20180307 mcth 50+7000Hz 0dBu 30R 4XF - LPS.png

    MCTH 600 Hz + 1700 Hz spectrum Left and Right 0dBu 30R load
    20180307 mcth 600+1700Hz 0dBu 30R 4XF - LPS.png

    MCTH IMD spectrum Left and Right -16dBu 30R load
    20180307 mcth 19+20KHz -16dBu 30R 4XF - LPS.png

    MCTH residual noise spectrum Left and Right A=0dB 30R load
    20180307 mcth residual noise A=0dB 30R 4XF - LPS.png
     
    Last edited: Mar 8, 2018
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  8. atomicbob

    atomicbob dScope Yoda

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    30 ohm load part 2 of 3 with LPS

    MCTH square wave was not affected by LPS.

    MCTH amplitude - phase - gain (A01) 30R load
    20180307 mcth A01 amplitude - phase - gain 30R 4XF - LPS.png

    MCTH signal to noise (A07) 30R load
    20180307 mcth A07 SNR 30R 4XF - LPS.png

    MCTH THD+N THD nth harmonic distortion (A04) 30R load
    20180307 mcth A04 THD+N  THD  nth-HD 30R 4XF - LPS.png

    MCTH Crosstalk (A08 A09) 30R load

    20180307 mcth A08 A09 Crosstalk 30R 4XF - LPS.png
     
    Last edited: Mar 8, 2018
  9. atomicbob

    atomicbob dScope Yoda

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    30 ohm load part 3 of 3 with LPS

    MCTH Frequency Response and Interchannel Phase pg 1/2 30R load
    G2_L1T2_1_A.png

    MCTH Frequency Response and Interchannel Phase pg 2/2 30R load
    G2_L1T2_1_B.png

    MCTH Gain vs Amplitude Left 30R load
    G2_L1T3_1_A.png

    MCTH Gain vs Amplitude Right 30R load
    G2_L1T3_1_B.png

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

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

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

    MCTH THD+N vs Amplitude Right 30R load
    G2_L1T6_1_B.png

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

    MCTH Crosstalk Right to Left vs Frequency 30R load
    G0_L1T11_1.png
     
    Last edited: Mar 8, 2018
  10. atomicbob

    atomicbob dScope Yoda

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    reserved 10/10.
     
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  11. gixxerwimp

    gixxerwimp Professional tricycle rider

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    @atomicbob You are the true measurebator! Amazing work.

    I can only absorb this data at a very shallow level, but I noticed that Crosstalk Left to Right vs Frequency is significantly better than Right to Left. Is this common for (tube) amplifiers? Have you noticed any correlation to audible characteristics? I wonder if crosstalk one way over the other were extremely exaggerated, it would result in a noticeable channel imbalance and/or a shift in the sound stage or imaging from one side to the other.
     
  12. atomicbob

    atomicbob dScope Yoda

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    Looney Tunes would probably use one of the following labels (measurebus proliferus) (measurebus vulgaris) (measurebus extremus)

    I've seen this channel crosstalk difference many times in tube and tube hybrids. It may be caused by the tube when a single dual triode is used for both channels. It may also be caused by wiring placement or PCB layout. The bleed from openback headphones ear to ear is likely significantly larger than the bleed from Right to Left channel indicated. Liquid Crimson and Garage1217 Project Sunrise also indicate a similar crosstalk difference. I'm not worried about it.
     
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  13. Junki

    Junki Acquaintance

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    Hi @atomicbob
    CC @CEE TEE

    Been on the market for a couple of weeks now for new DAC and AMP, and have seriously been considering the MCTH. Was wondering if you are able and willing to add some context as to why the MCTH looks like it has so much noise. THD looks great, but noise is two orders of magnitude higher than THD, which I have never seen. I see that the PSU is partly to blame, and your using the LPS cut down that noise by a single order of magnitude, but still... This noise level is clearly contributing to the poor linearity of the amplifier and making the measured SNR (and DNR by inference) look downright lackluster... I mean, -77 dB is audible and might explain some of the "airiness" that's been reported in subjective impressions.

    Anyway, any insight or reassurance is welcomed. I'm fairly new to source/amp measurements, so apologies ahead of time if you think my question is stupid.

    EDIT: I just noticed that your measured specs are no where near as good MCTH's published specs, which states SNR at -97 dB at 1Vrms into 45 ohms, whereas you measured about -78 dB at 0.775 Vrms into either 300 or 30 ohms.
     
    Last edited: Mar 30, 2018
  14. atomicbob

    atomicbob dScope Yoda

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    To focus on a single attribute without context of the others will mislead you. Can you really hear 78 dB below main signal? To test yourself perform a listening experiment with the wavefile found here. You should also read the first several posts in that thread carefully. You should then seek the references provided at the beginning of the first post in this thread. Those will help add perspective.

    I am listening to this amp with an Acopian LPS, an ADI-2 Pro DAC and Focal Clear headphones. The combination is proving to be very satisfying to my ears. There is only a slight haziness added and less low end grunt when using the provided SMPS. Transient response is phenomenal, as can be verified both audibly and shown in square wave measurement in post 5 above.
     
    Last edited: Mar 30, 2018
  15. Junki

    Junki Acquaintance

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    Thanks. I don't doubt the subjective impressions I've read so far. I just wanted to confirm that the unit and its measurement is sound.

    It sounds like the perspective here is that a 10^2 discrepancy between the measured value and the advertised value over at Massdrop is par for the course and isn't something anyone should raise a fuss about...? Feels ethically/morally corrupt. I'll pass on this amp and it raises significant doubts at least in my mind about the truthfulness of the advertised specs of Massdrop's other collabs.
     
    Last edited: Mar 30, 2018
  16. atomicbob

    atomicbob dScope Yoda

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    Did it occur to you that dynamic range as well a residual noise can vary by tube and that the tube/amp combination I measured had a tube with a lower dynamic range than the one measured by Cavalli on the day the published specifications of record were taken? Tube variance is one reason I don't get too excited about variations in dynamic range in tube hybrids. Before I thought your question was on the level. Now I am not so sure. You posted above that you are new to measurements. Now you claim a manufacturer / Massdrop is corrupt based on your conclusions which are self-admitted as inexperienced. That is a very strong statement. Are you by any chance a minion of Amir?
     
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  17. Junki

    Junki Acquaintance

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    Wow.

    I've been doing a ton of research into my next dac and amp purchase, looking for units with both measurements and subjective impressions because I value both. The MCTH has a great log of subjective impressions both here and elsewhere. You have the only measurement of the MCTH I could find with my level of Google-fu. Throughout this entire process I've been reading about source and amp measurements and what they mean.

    I notice that the measured noise level of the MCTH is really, really high. I check its specs on Massdrop and notice a huge discrepancy. I bring it up. God forbid.

    In any reasonable situation I can imagine, I'd have expected a response along the lines of "Interesting. Maybe the measured unit was defective. This is worth looking into."

    Instead, I get "It doesn't matter because you can't hear it." You're right; I bet I can't hear -78 dB below the fundamental, but it's high enough to be theoretically audible to potential buyers. Even you mentioned haze when using the unit with its stock components. But it's not just about me is it? It's about what is advertised and what is actual for a commercial product! I wouldn't have brought it up if the a measurement and the advertised value was off by a reasonable amount. But by 100x? Noise is nearly 0.1% of the signal?

    So yes, the response of "It doesn't matter. You've played yourself because I bet you can't hear it" did trigger me. It implies that advertising metrics that are that far off is condoned here. That feels ethically wrong to me. That's a subjective statement, and the reasons for me feeling this are, I would think, incredibly apparent. My following statement wasn't subjective: it brings shade into the advertised specs of other collabs. I love Massdrop collabs. This isn't news I'm happy about.

    Regarding your assertion that it should've occurred to me that you used different tubes. No it didn't occur to me. It didn't occur to me that your measurement of the device using the stock EH 6922 tube is different from the tube used by Massdrop when they measured the unit. It didn't occur to me that Massdrop would measure a unit with a different tube than what they supply with the unit commercially. It didn't occur to me that Massdrop would measure the unit in any configuration other than the configuration they sell. Apologies if this is shortsighted of me.
     
    Last edited: Mar 30, 2018
  18. rtaylor76

    rtaylor76 Can't wipe his tag

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    I am actually kind of surprised the THD and the noise dropped so much lower with an LPS.

    Bob, do you do any kind of power tests? Specs only list one power spec, and that is 1W at 50 ohms.

    Have you also tried testing crosstalk while running an out of polarity signal on the other side while while you measure the side you are testing?
     
  19. atomicbob

    atomicbob dScope Yoda

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    You infer much with the difference of one measurement. You also say you are not well versed in measurements yet you switch units from decibels to linear so as to magnify the difference in a way that suits your desire to be argumentative. There is no evidence that you will read the suggested references or experiment for yourself to help understand what information this measurement provides. Instead you take the track of suggesting ethical and moral corruption and infer that all of @CEE TEE endeavors should be painted with the same brush. That is an extrapolation no reasonably technically proficient person would make.

    Could a moderator take from post 13 on and move it from
    massdrop cavalli tube hybrid amp technical measurements to how to win friends and influence people where it belongs?
     
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  20. atomicbob

    atomicbob dScope Yoda

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    I haven't typically run the power curve tests. The limited time I have for headphone related measurements are usually oriented towards those that tell me how a given device performs at levels to which I listen. These I share as I can to this forum.
     
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