Nitsch ECP Audio DSHA-3FN technical measurements

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  1. atomicbob

    atomicbob dScope Yoda

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    Nitsch ECP Audio DSHA-3FN technical measurements

    Standard Prologue
    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 technical measurements posts.

    The data presented were collected as follows:
    1. PrismSound dScope III, picoscope 5243B, Keysight 34465A, Tektronix ADA400A balanced probe
    2. Balanced XLR cables Belden 1800F with Neutrik 110R AES connectors (if used)
    3. Single Ended cables Audioblast HQ-1 3 ft with Rean RCA connectors
    4. 32 and 300 ohm loads used for measurements
    5. dScope analyzer sample rate 48 KHz unless otherwise noted
    6. 0dBu level used for testing unless otherwise noted
    7. Amplifier input to output gain set for 0 dB unless otherwise noted
    8. Audioquest Forest and Schiit Pyst USB cables used with measurement equipment
    9. Vaunix Lab Brick USB hub
    10. Shielded 14AWG and 16AWG power cables
    11. ESD, EMI/RFI controlled lab bench and workspace

    Measurements are made in accordance with AES17:2015

    Sensitivity data for two headphones to keep in mind while viewing these measurements:
    HD 650 impedance 300R, sensitivity 98 dB/mW
    HE-500 impedance 38R, sensitivity 89 dB/mW

    SPL levels for above headphones for reference:
    0 dBu 300R 2.00 mW - 101 dBSPL @ 98dB/mW
    0 dBu 30R 20.00 mW - 102 dBSPL @ 89dB/mW

    All testing performed at 0 dBu unless otherwise noted.
    This level is consistent with listening to headphones (referenced above) at 90 dBSPL average with peaks to 100 dBSPL, if the music has 10 dB Peak to Avg ratio. That is LOUD for long listening sessions.

    DSHA-3FN
    Measurements commenced after 1 hour of warmup each session.
    Measurements were performed over a period of several months.

    Index
    Post 1 – Measurement setup description, highlights
    Post 2 – Bal input 300 ohm load
    Post 3 – Bal input 32 ohm load
    Post 4 – SE input 300 ohm load
    Post 5 – SE input 32 ohm load
    Post 6 – Square wave response
    Post 7 – 19+20 KHz IMD
    Post 8 – reserved for corrections and / or additional data

    Measurement setup picture:
    01 DSC_1041_small.jpg
    Standard setup with DSHA-3FN for 300R and 32R loads
    Tektronix ADA400A differential probe to the right of the DSHA-3FN

    Listening evaluation picture:
    02 DSC_0994_small.jpg
    DSHA-3FN inputs switched between Holo KTE Spring 2 and Spring 3 Bal & SE outputs. Listening evaluation amp volume set for 0 dB gain with Goldpoint SA2X and SA2 external stepped attenuators employed to set level.
    There are plenty of impressions threads on the forum where more detailed and nuanced thoughts about the various components are discussed. For my preferences, either I like how a system renders music or I don’t. I enjoy this amp in this system, a lot.

    WARNING: DSHA-3FN has balanced differential outputs. Only fully balanced connections between headphones, IEMs are to be used. 4 wire to 3 wire adapters WILL DESTROY the amplifier output. Don’t do this.

    Notable highlights:
    First, well done Doug and CeeTee! This is an incredible headphone amplifier.
    Nearly perfect gain linearity spanning over 110 dB range in balanced input operation
    ± 1 dB gain linearity over 120 dB range in balanced input operation
    SNR greater than 123 dB in balanced input operation
    Excellent square wave response
    Bandwidth: DC to greater than 168 KHz
    Clarity and tube magic yet no tubes

    Due to some very interesting attributes of this amp I will provide additional commentary and interpretation from which I would normally refrain.

    Let's get this out of the way.
    Generator level set to 0 dBu, Amp set for 0 dB gain with 300R load
    Balanced input:

    THD+N: 0.01297% Left channel (SINAD 77.7 dB)
    THD+N: 0.01179% Right channel (SINAD 78.6 dB)


    Those who worship THD+N / SINAD should stop at this point and dismiss this amp. The remainder will be a waste of time. However if you consider there is more to an amp than SINAD / THD+N please continue. This special sounding amp offers another opportunity to demonstrate how chasing low distortion numbers out of context is the very definition of foolishness.

    Numerical distortion specification for DSHA-3FN:
    THD+N < 0.015% at 1 KHz, 0 dBu, 300R load

    This specification represents an extremely small bit of information with respect to the amplifier performance. Published THD+N has been around since the beginning of audio measurements. So it continues to be published out of tradition.

    ECP Audio DSHA-3FN Distortion at 1 KHz, 0 dBu, 300R load
    03 20230627 DSHA-3FN A04 Distortion 300R 0dBu.png
    In this measurement suite the THD+N measures as expected verifying the specification. However more metrics have been added along with the L and R channel FFTs. Observe that 3rd harmonic is the major contributor to THD+N at 0 dBu. Also note how 60 Hz AC Hum is observed to be -127 dBu in the L ch and -124 in the R ch, and aggregate noise is approximately -108 dBu in both channels yielding a very low noise background, essentially black.

    ECP Audio DSHA-3FN Distortion at 1 KHz, 0 dBu, 300R load L ch
    04 20230804 DSHA-3FN Distortion 0_16pct single point graph edited.png
    In this graphic observe how the numerical specification denotes a singular operating point performance. Very limited information.

    Consider expansion of the performance profile by sweeping over a range of levels and decomposing the THD+N into a few specific constituent measures.

    ECP Audio DSHA-3FN Distortion vs amplitude 1KHz 300R -40 to +10 dBu L ch
    05 20230803-1 DSHA-3FN Distortion vs amp 300R normal level - annotated.png
    This expanded measurement reveals DSHA-3FN to have a much more complex behavior which cannot possibly be inferred by the numerical specification. In the graph 3rd harmonic distortion, D3 varies over level and is the dominant contributor to THD+N above approximately -17 dBu. Below that level PS Noise becomes the dominant contributor to the THD+N metric.

    What happens above +10 dBu with a 300R load?
    ECP Audio DSHA-3FN Distortion vs amplitude 1KHz 300R above +10 dBu L ch
    06 20230803-1 DSHA-3FN Distortion vs amp 300R high level - annotated.png
    At these high levels, way too loud for anything but very short moments of listening, D3 is the dominant contributor to THD+N until +15 dBu where D2 becomes the dominant contributor up to the onset of clipping distortion. PS Noise contribution is insignificant.

    While the graph below is for a 32R load, the behavior of the PS Noise is representative for a range of loads.
    ECP Audio DSHA-3FN Distortion vs amplitude 1KHz 32R -40 to +10 dBu L ch
    07 20230803-1 DSHA-3FN Distortion vs amp 32R FFT 1 - annotated distortion.png
    Trace ID:
    Yel: THD+N
    Grn: 2nd harmonic distortion (D2)
    Brn: 3rd harmonic distortion (D3)
    Red: 4+HD+N (crap factor including AC mains noise)
    Blu: FFT 1 KHz -20 dBu 32R load

    In the graph 3rd harmonic distortion, D3 varies over level and is the dominant contributor to THD+N above approximately -16 dBu. Below that level PS Noise becomes the dominant contributor to the THD+N metric. At approximately -17 dBu D3 drops below D2 and becomes significantly lower.

    PS Noise is the greatest contributor to THD+N below approximately -16 dBu, observe the PS Noise comprises of 60, 120, 180, 420 and 660 Hz. It is not a single large spike but spread out over the fundamental and 4 harmonics. THD+N captures the aggregate of these PS Noise frequencies but doesn’t provide sufficient information as to audibility. All those noise spikes are at or below -119 dBu which will be inaudible on even the most sensitive IEMs.

    Note about threshold of AC Mains noise perception
    In my acoustic lab when listening between 65 and 75 dB SPL on headphones with sensitivity of 95 to 100 dB/mw, mains noise of -75 dBu is at the threshold of perception. At this level I perceive the blackground compromised and a certain sourness to the listening experience that would mostly disappear when listening level was increased to 75 to 85 dB SPL. Mains hum between tracks is still evident. In normal home environments ambient noise masking is likely sufficient to hide this issue if AC mains noise is at or below -75 dBu. If AC mains noise is at or below -85 dBu then I no longer perceive it with the headphones of the sensitivity mentioned in my very quiet acoustic lab. Most listeners will be undisturbed by this issue to which I am so sensitive. DSHA-3FN PS Noise spikes are at or below -119 dBu which is 44 dB lower than the threshold of audibility for most headphones.


    ECP Audio DSHA-3FN Distortion vs Frequency Bal input 0 dBu level 300R load
    08 20230627 DSHA-3FN A05 THD+N 2nd 3rd 4+HD+N vs frequency 300R.png
    Trace ID:
    Yel: THD+N
    Grn: 2nd harmonic distortion (D2)
    Blu: 3rd harmonic distortion (D3)
    Red: 4+HD+N (crap factor including AC mains noise)
    Distortion vs frequency also demonstrates a far more complex behavior for this amp than possible from numerical THD+N spec.

    ECP Audio DSHA-3FN Dynamic Range Bal input 300R load
    09 20230630 DSHA-3FN Bal in 300R load dynamic range.png
    Impressive performance! When a system is gain staged correctly this covers threshold of hearing to threshold of discomfort, rock concert levels.

    DSHA-3FN Output Impedance
    10 20230630 DSHA-3FN output impedance.png
    Output impedance is 4.9 Ω
     
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  2. atomicbob

    atomicbob dScope Yoda

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    Bal input 300 ohm load

    DSHA-3FN Distortion FFT 300 ohm load Bal input
    01 20230627 DSHA-3FN A04 Distortion 300R 0dBu.png

    DSHA-3FN Distortion vs Amplitude 300 ohm load Bal input

    02 20230627 DSHA-3FN A00 THD+N 2nd 3rd 4+HD+N vs Amp 300R +10dBu start.png

    DSHA-3FN Distortion vs Frequency 300 ohm load Bal input

    03 20230627 DSHA-3FN A05 THD+N 2nd 3rd 4+HD+N vs frequency 300R.png

    DSHA-3FN 50 + 7000 Hz 300 ohm load Bal input - Left Channel

    04 FFT_2_L1T13_1_A.png

    DSHA-3FN Gain Linearity 300 ohm load Bal input - Left Channel

    05 G2_L1T3_1_A.png

    DSHA-3FN THD+N vs Frequency 300 ohm load Bal input - Left Channel

    06 G2_L1T5_1_A.png

    DSHA-3FN Residual Noise 300 ohm load Bal input - Left Channel

    07 FFT_2_L1T16_1_A.png

    DSHA-3FN Multitone 300R 0 dBu Bal input - Left Channel

    08 20230627 DSHA-3FN Multitone 300R 0 dBu total level.png

    DSHA-3FN Multitone 300R -10 dBu Bal input - Left Channel

    09 20230627 DSHA-3FN Multitone 300R -10 dBu total level.png
    When measuring at a level consistent with approximately 90 dB SPL for many popular headphones observe the significant drop in distortion spikes between the source tones. Very clean performance.

    Complete Bal input 300 ohm load measurement report pdf attached
     

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  3. atomicbob

    atomicbob dScope Yoda

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    Bal input 32 ohm load

    DSHA-3FN Distortion FFT 32 ohm load Bal input
    01 20230627 DSHA-3FN A04 Distortion 32R 0dBu.png

    DSHA-3FN Distortion vs Amplitude 32 ohm load Bal input

    02 20230627 DSHA-3FN A00 THD+N 2nd 3rd 4+HD+N vs Amp 32R +10dBu start.png

    DSHA-3FN Distortion vs Frequency 32 ohm load Bal input

    03 20230627 DSHA-3FN A05 THD+N 2nd 3rd 4+HD+N vs frequency 32R.png

    DSHA-3FN 50 + 7000 Hz 32 ohm load Bal input - Left Channel

    04 FFT_2_L1T13_1_A.png

    DSHA-3FN Gain Linearity 32 ohm load Bal input - Left Channel

    05 G2_L1T3_1_A.png

    DSHA-3FN THD+N vs Frequency 32 ohm load Bal input - Left Channel

    06 G2_L1T5_1_A.png

    DSHA-3FN Residual Noise 32 ohm load Bal input - Left Channel

    07 FFT_2_L1T16_1_A.png

    DSHA-3FN Multitone 32R 0 dBu Bal input - Left Channel

    08 20230627 DSHA-3FN Multitone 32R 0 dBu total level.png

    DSHA-3FN Multitone 32R -10 dBu Bal input - Left Channel

    09 20230627 DSHA-3FN Multitone 32R -10 dBu total level.png
    When measuring at a level consistent with approximately 90 dB SPL for many popular headphones observe the significant drop in distortion spikes between the source tones.

    Complete Bal input 32 ohm load measurement report pdf attached
     

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    Last edited: Aug 7, 2023
  4. atomicbob

    atomicbob dScope Yoda

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    SE input 300 ohm load

    Single ended input will lose the advantages a Balanced input topology provides. Noise floor will be higher, gain linearity range reduced, dynamic range reduced, etc. However, transient response, frequency response, multitone performance will remain relatively the same. Given the exceptionally high performance experienced using Balanced input, the convenience of SE input should result in hardly any audible difference.

    DSHA-3FN Distortion FFT 300 ohm load SE input
    01 20230630 DSHA-3FN A04 Distortion 300R 0dBu.png

    DSHA-3FN Distortion vs Amplitude 300 ohm load SE input

    02 20230630 DSHA-3FN A00 THD+N 2nd 3rd 4+HD+N vs Amp 300R +10dBu start.png

    DSHA-3FN Distortion vs Frequency 300 ohm load SE input

    03 20230630 DSHA-3FN A05 THD+N 2nd 3rd 4+HD+N vs frequency 300R.png

    DSHA-3FN 50 + 7000 Hz 300 ohm load SE input - Left Channel

    04 FFT_2_L1T13_1_A.png

    DSHA-3FN Gain Linearity 300 ohm load SE input - Left Channel

    05 G2_L1T3_1_A.png

    DSHA-3FN THD+N vs Frequency 300 ohm load SE input - Left Channel

    06 G2_L1T5_1_A.png

    DSHA-3FN Residual Noise 300 ohm load SE input - Left Channel

    07 FFT_2_L1T16_1_A.png

    DSHA-3FN Multitone 300R 0 dBu SE input - Left Channel

    08 20230630 DSHA-3FN Multitone 300R 0 dBu total level.png

    DSHA-3FN Multitone 300R -10 dBu SE input - Left Channel

    09 20230630 DSHA-3FN Multitone 300R -10 dBu total level.png
    When measuring at a level consistent with approximately 90 dB SPL for many popular headphones observe the significant drop in distortion spikes between the source tones.

    Complete SE input 300 ohm load measurement report pdf attached
     

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  5. atomicbob

    atomicbob dScope Yoda

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    SE input 32 ohm load

    DSHA-3FN Distortion FFT 32 ohm load SE input
    01 20230630 DSHA-3FN A04 Distortion 32R 0dBu.png

    DSHA-3FN Distortion vs Amplitude 32 ohm load SE input

    02 20230630 DSHA-3FN A00 THD+N 2nd 3rd 4+HD+N vs Amp 32R +10dBu start.png

    DSHA-3FN Distortion vs Frequency 32 ohm load SE input

    03 20230630 DSHA-3FN A05 THD+N 2nd 3rd 4+HD+N vs frequency 32R.png

    DSHA-3FN 50 + 7000 Hz 32 ohm load SE input - Left Channel

    04 FFT_2_L1T13_1_A.png

    DSHA-3FN Gain Linearity 32 ohm load SE input - Left Channel

    05 G2_L1T3_1_A.png

    DSHA-3FN THD+N vs Frequency 32 ohm load SE input - Left Channel

    06 G2_L1T5_1_A.png

    DSHA-3FN Residual Noise 32 ohm load SE input - Left Channel

    07 FFT_2_L1T16_1_A.png

    DSHA-3FN Multitone 32R 0 dBu SE input - Left Channel

    08 20230630 DSHA-3FN Multitone 32R 0 dBu total level.png

    DSHA-3FN Multitone 32R -10 dBu SE input - Left Channel

    09 20230630 DSHA-3FN Multitone 32R -10 dBu total level.png
    When measuring at a level consistent with approximately 90 dB SPL for many popular headphones observe the significant drop in distortion spikes between the source tones.

    Complete SE input 32 ohm load measurement report pdf attached
     

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  6. atomicbob

    atomicbob dScope Yoda

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    Square wave response

    Amplifier is adjusted to produce 0 dB gain with a 1 KHz sine wave for 300 ohm load measurements. This calibration is performed again for 32 ohm load measurements. Measurements are made with at 20 Hz square wave. SG = Signal Generator

    Bandwidth Estimation formula:
    BW (MHz) = 0.35 / RT (mS)
    Where RT = 10 to 90% Rise Time

    DSHA-3FN SG 20Hz sqr 2Vpp 500nS div 5MHz fltr 300R Bal
    01 20230630 SigGen DSHA-3FN 20 Hz square 2Vpp 500nS div 5MHz filter 300R - BW calc Bal.png
    0.35 / 2.079 uS = 168.4 KHz

    Transient response is exceptional. Percussive sounds benefit from this behavior.

    02 20230630 SigGen DSHA-3FN 20 Hz square 2Vpp 50uS div 5MHz filter 300R - overshoot calc Bal.png
    There is a large overshoot with an exceptionally short ring time which will be damped by headphones due to limited ability to respond above 40 KHz.

    The following square wave measurements demonstrate essentially the same performance as for Balanced input 300R load shown above.

    DSHA-3FN SG 20Hz sqr 2Vpp 500nS div 5MHz fltr 32R Bal
    03 20230630 SigGen DSHA-3FN 20 Hz square 2Vpp 500nS div 5MHz filter 32R - BW calc Bal.png
    0.35 / 2.127 uS = 164.6 KHz

    04 20230630 SigGen DSHA-3FN 20 Hz square 2Vpp 50uS div 5MHz filter 32R - overshoot calc Bal.png

    DSHA-3FN SG 20Hz sqr 2Vpp 500nS div 5MHz fltr 300R SE
    05 20230630 SigGen DSHA-3FN 20 Hz square 2Vpp 500nS div 5MHz filter 300R - BW calc SE.png
    0.35 / 2.053 uS = 170.5 KHz

    06 20230630 SigGen DSHA-3FN 20 Hz square 2Vpp 50uS div 5MHz filter 300R - overshoot calc SE.png

    DSHA-3FN SG 20Hz sqr 2Vpp 500nS div 5MHz fltr 32R SE
    07 20230630 SigGen DSHA-3FN 20 Hz square 2000mVpp 500nS div 5MHz filter 32R - BW calc SE.png
    0.35 / 2.085 uS = 167.9 KHz

    08 20230630 SigGen DSHA-3FN 20 Hz square 2000mVpp 50uS div 5MHz filter 32R - overshoot calc SE.png
     
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  7. atomicbob

    atomicbob dScope Yoda

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    19 + 20 KHz IMD CCIF

    DSHA-3FN 19+20KHz IMD CCIF 300R Bal input
    01 20230630 DSHA-3FN Bal in 300R load 19+20K IMD.png
    IMD is exceptionally low. Insignificant distortion.

    DSHA-3FN 19+20KHz IMD CCIF 300R Bal input
    02 FFT_2_L1T15_1_A Bal 300R.png
    03 FFT_2_L1T15_1_B Bal 300R.png

    DSHA-3FN 19+20KHz IMD CCIF 32R Bal input

    04 FFT_2_L1T15_1_A Bal 32R.png
    05 FFT_2_L1T15_1_B Bal 32R.png

    DSHA-3FN 19+20KHz IMD CCIF 300R SE input

    06 FFT_2_L1T15_1_A SE 300R.png
    07 FFT_2_L1T15_1_B SE 300R.png

    DSHA-3FN 19+20KHz IMD CCIF 32R SE input

    08 FFT_2_L1T15_1_A SE 32R.png
    09 FFT_2_L1T15_1_B SE 32R.png
     
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  8. atomicbob

    atomicbob dScope Yoda

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    Clarification about DSHA-3FN Balanced vs unBalanced (SE) input

    It isn't the Amp (nor source) but the connection method that has different CMRR immunity. Bal inherently can achieve 120 dB while unBal often only makes 100 dB, 20 dB less. Loss of measurement performance is due to the connection method, not the Amp or source. Residual noise levels being discussed are approximately 775 nV for Bal vs 7.75 uV for SE. The measurements are in dBu which is an absolute level. Most headphones will only produce between 1 and 10 dB SPL at 7.75 uV and only a few IEMs might produce around 30 to 40 dB SPL at such levels. Also given the noise is mostly 660 Hz and below, it is doubtful even listeners with the highest sensitivity IEMs would detect any PS Noise thanks to basilar membrane performance as depicted on ISO Contours of equal loudness.

    20230807 Bal vs unBal interconnection with xfmr input.png

    In the diagram above unBalanced has an ambient E field noise impinged on the signal. DSHA-3F operating in SE mode simply connects the input transformer appropriate for a SE connection. It is the connection method that has less noise immunity, not the amp.

    Same E field noise impinging on the Balanced connection is common to both 0° and 180° signals. In full differential mode the noise effectively cancels.
     
    Last edited: Aug 7, 2023
  9. Armaegis

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    upload_2023-8-7_15-43-2.jpeg
     
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  10. atomicbob

    atomicbob dScope Yoda

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    added a clarification about DSHA-3FN Balanced vs unBalanced (SE) input to post 8 above.
     
  11. jexby

    jexby Posole Prince

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    Hey @purr1n can this web forum software label @atomicbob content as "super f-ing valuable" and only available to the highest Patreon level $ subscriber, so that SBAF in turn can transfer the $ to atomicbob directly to fund whatever the hell he wants in life?
    i mean seriously, how is this not big money-grade contribution to the community.....
     
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  12. ecline56

    ecline56 Almost "Made"

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    What is the maximum power output of this amp in ma at the 32 ohm and 300 ohm settings?
     
  13. atomicbob

    atomicbob dScope Yoda

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    DSHA-3FN power discussion.

    How much power does this amp produce at various loads?
    How much power does a given headphone need to produce a specific SPL?
    What SPL does a listener really need?

    Clipping begins typically where distortion measurements indicate a sudden, sharp rise. Specifications often follow the rise to 1% or 10% and note the power at those levels. For sake of avoiding clipping the knee in the distortion curve denotes clipping onset.

    The following two charts appear in the original post:
    01 20230803-1 DSHA-3FN Distortion vs amp 300R high level - annotated.png
    With a 300 Ω load clipping onsets at +26 dBu.

    02 20230803-1 DSHA-3FN Distortion vs amp 32R FFT 1 - annotated distortion.png
    With a 32 Ω load clipping onsets at +6 dBu.

    The following equations compute transformation of dBu to Vrms, then Vrms for a given load R into Power:
    03 equations.png
    Using the above equations Vrms is calculated to be 15.46 for a 300 Ω load. This computes to power of 797 mW
    In a like manner Vrms is calculated to be 1.55 for a 32 Ω load. This computes to power of 75 mW

    04 DSHA-3F power.png
    Using the two power levels calculated and assuming a linear correlation, the graph above was created. Remember that the DSHA-3FN performs essentially the same as a DSHA-3F and the DSHA-3F was originally intended to bring out the best performance for Focal headphones, such as Elex, Clear, Utopia.

    As an example Focal Clear have a nominal impedance of 55 Ω. From the chart it may be inferred a Pmax of 140 mW.

    05 20230808 SPL power headphones.png
    Using the chart above Focal Clear require 0.4 mW to reach 100 dB SPL at 1 KHz. The DSHA-3FN can provide a Pmax of 140 mW to the Clears. 350 times more power than necessary to cleanly deafen the listener. DSHA-3FN will produce more than enough clean power for most of the headphones and IEMs on the chart above.

    HiFiMan HE-6 needs 50 mW to achieve 100 dB SPL at 1 KHz. DSHA-FN can produce 120 mW into 50 Ω, about 2.4x necessary. Headroom is lower so for very loud listening HE-6 users may want more power. Personally I listen at 70 to 80 dB SPL which is more than adequately powered by DSHA-3FN. But some listeners like their sound VERY LOUD and this amp might be perceived to be inadequate. Keep in mind OSHA and NIOSH recommended time exposures to loud sound levels to remain in safe operating areas or risk hearing damage.
     
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  14. ecline56

    ecline56 Almost "Made"

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    Thank you for the detailed answer Atomic Bob!
     
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