NITSCH x Schiit Magni Piety Technical Measurements

NITSCH x Schiit Magni Piety 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, Cal Test CT2593-2 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.

Magni Piety
Measurements commenced after 1 hour of warmup.
Measurements were performed over a period of several days.

Index
Post 1 – Measurement setup description, highlights
Post 2 – 300 ohm load, High gain setting
Post 3 – 300 ohm load, Low gain setting
Post 4 – 32 ohm load, High gain setting
Post 5 – 32 ohm load, Low gain setting
Post 6 – miscellaneous observations
Post 7 – reserved for corrections and / or additional data

Measurement setup picture:

Standard setup with schiit load for 300R and 32R loads

Listening evaluation picture:

Magni Piety inputs switched between Yggdrasil LIM and Holo Spring 2 KTE SE outputs.
ECP DSHA3-F switched balanced inputs between Yggdrasil LIM and Holo Spring 2 KTE balanced outputs.
This provided considerable flexibility during listening sessions. 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 it renders music or I don’t. Piety often felt as if it was a skillful combination of the powerful bass reminiscent of EC 300B, magic mid-range of SW51+ and high end transient response usually associated with Cavalli amps. I will be acquiring several for my lab.

Notable highlights:
Due to some 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 first.
Generator level set to 0 dBu, Amp set for 0 dB gain with 300R load, High gain selected:

THD+N: 0.00168% Left channel (SINAD 95.5 dB)
THD+N: 0.00169% Right channel (SINAD 95.4 dB)

These are respectable levels but do not rival the lowest achieved by very high Negative FeedBack (NFB) designs. 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.


The greatest components contributing to Piety’s THD+N are AC mains noise. However these residual noise components are considerably below the threshold of perception for many common headphones. For Sennheiser and other headphones with similar sensitivities that threshold is -75 dBu.


Trace ID:
Yel: THD+N
Blu: 60 Hz AC mains noise
Red: 120 Hz AC mains noise
Grn: THD (Total Harmonic Distortion excluding noise)
Below approximately +6 dBu 60 Hz mains noise dominates the THD+N measurement. Above +6 dBu THD becomes the dominant contributor to THD+N.


From the chart above note that most headphones won’t produce sufficient SPL to allow audible detection of Piety AC mains noise. Only the insanely sensitive Shure SE215 and Westone UM2 (and IEMs with similar sensitivities) might approach threshold of perception in very quiet ambient conditions.


Trace ID:
Yel: THD+N
Grn: 2nd harmonic distortion (D2)
Blu: 3rd harmonic distortion (D3)
Red: 4+HD+N (crap factor including noise)
As previously shown AC mains noise dominates THD+N measurement below approximately +6 dBu. Above +9 dBu D2 dominates THD+N until approximately +17 dBu where D3 becomes dominant.

Between this sweep measurement and the previous one above it may be observed how THD+N obscures a clear picture of the distortion profile for a given component. Think of THD+N as a lossy data compression technique. The danger with such data reduction is some distortions are of more concern than others. Distortion at some frequencies are more audible than others thanks to the non-linear behavior of the Human Auditory System as demonstrated with ISO Contours of Equal Loudness (Fletcher-Munson curves.)

magni piety gain linearity 300R Hi Gain L ch

Consider what happens when a pair of headphones produces 100 dB SPL at 0 dBu output from Piety. This implies 0 dB SPL when Piety output is -100 dBu. Over that range Piety has excellent gain linearity.

magni piety 20 Hz square wave response 2Vpp 1uS div no filter 300R Hi gain

Piety has a DC coupled output which is demonstrated by the perfect square wave response shown in the overview inset. The vertical line in the inset denotes what part of the overview has been zoomed for the main display. Zoom factor of 10,000 is necessary to observe 1.243 uS rise time 10% to 90% response when presented a fast step input from the signal generator. Using the following formula

Bandwidth estimation: BW (MHz) = 0.35 / RT (mS)
Where RT = 10 to 90% Rise Time
0.35 / 1.243 uS = 281.6 KHz

This implies Magni Piety has a bandwidth from DC to > 280 KHz. PFA!

magni piety 20 Hz sine 30Vpp 20mS div 1MHz filter 300R Lo gain

With a 300R load and gain set to Low, Magni Piety can produce over 30 Vpp!!
Trace ID:
Blu: input to Piety
Red: output from Piety
As output approaches maximum capability observe how the signal begins to soft clip like a tube amplifier.

magni piety 20 Hz sine 30Vpp 20mS div 1MHz filter 300R Lo gain

Increasing input level further the output is clearly soft clipping, just like a tube amp. Pretty amazing for a solid state amplifier without transformers.

Magni Piety Output Impedance
Hi Gain: 0.64 ohms
Lo Gain: 0.53 ohms

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.
Magni Piety AC mains noise is below -98 dBu and will not be a problem except possibly with insanely sensitive IEMs such as Shure SE215 or Westone UM2.

 

300 ohm load, High gain setting

Magni Piety A04 THD+N THD nth-HD FFT 300 ohm load, High gain


Magni Piety 50 + 7000 Hz 300 ohm load, High gain - Left Channel


Magni Piety Gain Linearity 300 ohm load, High gain - Left Channel


Magni Piety THD+N vs Frequency 300 ohm load, High gain - Left Channel


Magni Piety Residual Noise 300 ohm load, High gain - Left Channel


Magni Piety Square Wave 2Vpp 1uS/div 300 ohm load, High gain - Left Channel

Bandwidth estimation: BW (MHz) = 0.35 / RT (mS)
Where RT = 10 to 90% Rise Time
0.35 / 1.243 uS = 281.6 KHz

Magni Piety Maximum Output 300 ohm load, High gain – Left Channel


Magni Piety THD+N 2nd 3rd 4+HD+N vs frequency 300R Hi gain


Magni Piety THD+N THD 60+120Hz vs frequency 300R Hi gain


Complete 300 ohm load, High gain measurement report pdf attached

 

300 ohm load, Low gain setting

Magni Piety A04 THD+N THD nth-HD FFT 300 ohm load, Low gain


Magni Piety 50 + 7000 Hz 300 ohm load, Low gain - Left Channel


Magni Piety Gain Linearity 300 ohm load, Low gain - Left Channel


Magni Piety THD+N vs Frequency 300 ohm load, Low gain - Left Channel


Magni Piety Residual Noise 300 ohm load, Low gain - Left Channel


Magni Piety Square Wave 2Vpp 1uS/div 300 ohm load, Low gain - Left Channel

Bandwidth estimation: BW (MHz) = 0.35 / RT (mS)
Where RT = 10 to 90% Rise Time
0.35 / 1.001 uS = 349.7 KHz

Magni Piety Maximum Output 300 ohm load, Low gain – Left Channel


Magni Piety THD+N 2nd 3rd 4+HD+N vs frequency 300R Lo gain


Magni Piety THD+N THD 60+120Hz vs frequency 300R Lo gain


Complete 300 ohm load, Low gain measurement report pdf attached

 

32 ohm load, High gain setting

Magni Piety A04 THD+N THD nth-HD FFT 32 ohm load, High gain


Magni Piety 50 + 7000 Hz 32 ohm load, High gain - Left Channel


Magni Piety Gain Linearity 32 ohm load, High gain - Left Channel


Magni Piety THD+N vs Frequency 32 ohm load, High gain - Left Channel


Magni Piety Residual Noise 32 ohm load, High gain - Left Channel


Magni Piety Square Wave 2Vpp 1uS/div 32 ohm load, High gain - Left Channel

Bandwidth estimation: BW (MHz) = 0.35 / RT (mS)
Where RT = 10 to 90% Rise Time
0.35 / 1. 282 uS = 273.0 KHz

Magni Piety Maximum Output 32 ohm load, High gain – Left Channel


Magni Piety THD+N 2nd 3rd 4+HD+N vs frequency 32R Hi gain


Magni Piety THD+N THD 60+120Hz vs frequency 32R Hi gain


Complete 32 ohm load, High gain measurement report pdf attached

 

32 ohm load, Low gain setting

Magni Piety A04 THD+N THD nth-HD FFT 32 ohm load, Low gain


Magni Piety 50 + 7000 Hz 32 ohm load, Low gain - Left Channel


Magni Piety Gain Linearity 32 ohm load, Low gain - Left Channel


Magni Piety THD+N vs Frequency 32 ohm load, Low gain - Left Channel


Magni Piety Residual Noise 32 ohm load, Low gain - Left Channel


Magni Piety Square Wave 2Vpp 1uS/div 32 ohm load, Low gain - Left Channel

Bandwidth estimation: BW (MHz) = 0.35 / RT (mS)
Where RT = 10 to 90% Rise Time
0.35 / 1.007 uS = 347.6 KHz

Magni Piety Maximum Output 32 ohm load, Low gain – Left Channel


Magni Piety THD+N 2nd 3rd 4+HD+N vs frequency 32R Lo gain


Magni Piety THD+N THD 60+120Hz vs frequency 32R Lo gain


Complete 32 ohm load, Low gain measurement report pdf attached

 

Miscellaneous Observations

How much power do you need?

Here is a chart of some common headphones and the dB SPL they will produce at 1KHz 0 dBu:

The chart above provides insight into a number of common headphones behavior when operated with 1 KHz signal at 0 dBu. Many produce between 100 and 115 dB SPL which is very loud. This reason alone justifies testing components at a more sensible 0 dBu output level than at 4V rms which is +14.3 dBu, an additional 14 dB SPL louder. Measurements for my personal use usually include testing at -20 dBu, approximately 80 dB SPL, for the Sennheiser headphones I favor. None of the power levels required begin to approach maximum output magni piety can deliver.

 

reserved 7/7
reserved for additional data and / or corrections.

 

Shouldn't the color be white?

 

The board is white, see this post on Head-Fi.

 

The PCB inside is white. Lower clam shell is light grey while upper clam shell is dark gray on the unit I received.

 

These are the final colors, atomicbob has prototype metal from powder coat color testing (with NITSCH sticker):
\
The top is semi-gloss or satin very dark grey. Black silkscreened NITSCH logo.
The bottom is a subtle nickel/brass color with a rough sandpapery finish.
His board is a first article from the board house just like in the photo!

 

What is the noise floor like with sensitive stuff? Curious how it will do with some of my IEM's.

 

My Vali 2++ and her Roll of Tubes look forward to your competition for the honored spot on the Mezzanine of the Folkvangr!

 

From post 1:
https://www.superbestaudiofriends.o...s-noise-vs-headphone-sensitivities-png.33399/
From the chart above note that most headphones won’t produce sufficient SPL to allow audible detection of Piety AC mains noise. Only the insanely sensitive Shure SE215 and Westone UM2 (and IEMs with similar sensitivities) might approach threshold of perception in very quiet ambient conditions.

If your IEMs are as sensitive as Shure SE215 and Westone UM2 then you might be able to detect a faint hint of AC mains noise.

I own Westone UM2 and using those listened to Magni Piety residual noise. In Lo gain there is no noise. With Hi gain selected I could detect the faintest bit of hiss when I held my breath in my very quiet acoustic lab. The moment I resumed normal breathing my own breath noise masked the faint hiss.

 

Magni Piety Multitone 300R Hi gain 0 dBu total level


It doesn't get much cleaner than that. Only a slight hint of AC mains noise between the tones. Other than that there is nothing but residual noise grass below -125 dBu. Impressive.

 

Love the white PCB. I've always hated red ones. First world problem indeed!

 

Really a thing of beauty.