EMT 128 phono preamplifier Measurements

Sidebar 3: Measurements

I measured the EMT 128 phono preamplifier (serial number U-102) with my Audio Precision SYS2722, repeating some of the testing with the magazine's higher-performance Audio Precision APx500. The results were consistent with both systems.

The output impedance, specified as <500 ohms, was a relatively low 320 ohms at 20Hz, 312 ohms at 1kHz, and 246 ohms at 20kHz. The 128 inverted absolute polarity; either the XLR output jacks are connected with pin 3 "hot" or there is an odd number of anode-coupled amplification stages. (Each channel uses three subminiature tubes.) The gain at 1kHz was 62.5dB with the internal jumpers set to "–6," which I understand was how MF auditioned the preamplifier. With the jumpers set to "0," the gain at 1kHz was 68.9dB. Though these figures are slightly below the specified gains of 64dB and 70dB, my measurements will be reduced by the voltage-divider action of the SYS2722's output impedance of 20 ohms and the EMT's input impedance at 1kHz, which was 191 ohms. The input impedance at 20Hz was slightly lower, at 169 ohms, but the impedance was much lower at the top of the audioband, at 29 ohms.

The EMT 128's RIAA correction was superbly flat from 30Hz to 10kHz, though the right channel (fig.1, red trace) was 0.3dB higher than the left (blue trace) in the midrange and treble. The response was down by 1dB at 10Hz and 20kHz, with a slight peak at 25kHz, perhaps due to the output transformer, disturbing the ultrasonic rolloff. The response with the equalization set to "DIN 78" (fig.1, green and gray traces) peaked by 3dB at 10kHz compared with RIAA, but the low frequencies were not attenuated by the expected 3dB at 50Hz (footnote 1).


Fig.1 EMT 128, response with RIAA correction into 100k ohms (left channel blue, right red) and with DIN 78 correction (left green, right gray) (1dB/vertical div.).

Channel separation was very good, at 80dB in both directions at 1kHz and below, but it dropped to 40dB at the top of the audioband. Spectral analysis of the EMT's low-frequency noisefloor (fig.2) indicated that random noise components were low in level, though with power supply–related spuriae a little higher in level in the right channel (red trace) than the left (blue). The EMT's unweighted, wideband S/N ratio, referred to an input signal of 1kHz at 500µV, was a good 61.3dB in the left channel, 63.4dB in the right. Restricting the measurement bandwidth to 22Hz–22kHz increased the ratios to 65.5dB, left, and 64.0dB, right, while switching an A-weighting filter into circuit increased both ratios to 76.3dB. These figures were assessed with the gain set to "–6." Setting the gain to "0" decreased the ratios by the expected 6dB.


Fig.2 EMT 128, gain set to "–6," spectrum of 1kHz sinewave, DC–1kHz, for 500µV input (linear frequency scale).

Even at the lower gain setting, the EMT 128's overload margins were on the low side, at 9dB at 20Hz, 8.3dB at 1kHz, and 3.5dB at 20kHz, all ref. the nominal MC level of 1kHz at 500µV. These margins were all reduced by 6dB at the higher gain setting.

I note that MF did some of his auditioning with the Miyajima Madake Snakewood (250µV nominal output at 1kHz), which would not have resulted in problems with the EMT's overload margins. The Ortofon Verismo (200µV nominal output) would also have been a good match. But with EMT's Novel Titan phono cartridge, which has what MF told me was "a healthy 1mV output at 5cm/s," the 128's overload margins will be marginal.

With a 1kHz signal at 500µV, the second harmonic was the only significant distortion product present, at a relatively high –50dB (0.3%, fig.3). At 250µV input, the second harmonic dropped by 5dB, but it rose to –43dB (0.7%) at 1mV, with the third harmonic making an appearance at –80dB (0.01%). As long as it is not accompanied by higher-order harmonics or intermodulation products, the second harmonic is difficult to hear, even with pure tones, as it is musically consonant (footnote 2). However, I suspect that this behavior would endow the EMT preamplifier with a rather full, even lush sound character. These distortion measurements were taken with 100k ohms load impedance. Reducing the load impedance to the current-demanding 600 ohms increased the level of the second harmonic by 10dB. The EMT 128 will work best with a line preamplifier that has an input impedance of 10k ohms or higher.


Fig.3 EMT 128, gain set to "–6," spectrum of 1kHz sinewave, DC–10kHz, into 100k ohms for 500µV input (linear frequency scale).

High-order intermodulation distortion with an equal mix of 19kHz and 20kHz tones at a peak input level equivalent to 1kHz at 250µV was extremely low in level (fig.4). Though the second-order difference product at 1kHz lay at –54dB (0.2%), this will be sufficiently low in level not to have audible consequences.


Fig.4 EMT 128, gain set to "–6," HF intermodulation spectrum, DC–30kHz, 19+20kHz into 100k ohms for 2.5mV peak input (linear frequency scale).

Its performance on the test bench indicates that EMT's 128 phono preamplifier will work best set to its lower gain and with low-output moving coil phono cartridges, like Ortofon's Verismo. I am puzzled, therefore, why its overload margins are low when used with EMT's own Novel Titan.—John Atkinson

Footnote 1: This assumes that DIN 78 is indeed the same as IEC N78, as EMT's Micha Huber told Jim Austin in an email.

Footnote 2: I created tracks on Stereophile's Test CD 2 so listeners could hear at what percentage of second, third, or seventh harmonic they become aware of the distortion.

HiFiction AG/EMT Tontechnik
US distributor: Wynn Audio
20 Wertheim Ct. unit 31
Richmond Hill, ON L4B 3A8, Canada

Glotz's picture

I've worn them... VERY tight! Lol..

Kursun's picture

Another $12.000+ phono preamplifier with only 3.5 db overload headroom!

According to a Shure research, maximum recorded velocities on records reach 50 cm/sec.

So a cartridge output with 5 mV@ 5 cm/sec will reach 50 mV/sec on peaks.
This means that absolute minimum of 20 db overload headroom is required. (MM or MC)

Jack L's picture


Per J.A. bench test report, 3.5dB@20KHz was test signal, not actual music signal picked up from the LP grooves. So you think a LP can deliver 20KHz music signals strong enough to overload the premp???? I doubt it very much.

Above said, the latest HD Vinyl is just around the coner. So 20KHz LPs is no longer some fancination.

Back in 2018, an Austrian startup invented a digtial mapping technology which digitally map the music signals into a 3D map which is then inscribed onto the vinyl stamper via lasers.

Yes, I think the HD Vinyl could theorettically be extended up to 20KHz. But would it sound as musical like its pure analogue format ?????? Or just another CD sound alike ?? Too early to tell now.

Unlike CD which adjust automatically its rotation speed to keep the laser linear veloicity constant, the tangential stylus speed (1.466666ft/sec) is not constant but varies as per the styuls location on the groove. Faster velocity near the edge of the LP.

From the design viewpoint, the low overload headroom of this preamp could be caused by too much gain caused by using 3 twin-pentodes in the signal path per channel, IMO. More gain would cause more 'pain' musically.

I would not use so many active devices for a phonostage considering SUT is already intalled for MC cartridge input.

Listening is believing

Jack L

Kursun's picture

Do you sincerely doubt an LP can deliver 20 kHz signal?
I am an engineer and I don’t doubt an LP can deliver 20 kHz.
Well, anyway,
Science does not rely on doubts, but facts.
“The high-frequency response of vinyl depends on the cartridge. CD4 records contained frequencies up to 50 kHz. Frequencies of up to 122 kHz have been experimentally cut on LP records.” (wikipedia)

BTW, don’t forget RIAA recording curves boost high frequencies by up to 20 db (@20 kHz) as pre-emphasis. There are high amounts of high frequencies on records. During playback, RIAA de-emphasis by the phono preamplifier attenuates them. If it is not overloaded that is…. Groove surface noise is also attenuated accordingly in the process.

Even at 1 kHz, signal velocity can reach 30 cm/sec.
That will be 30 mVs for a cartridge with 5 mV@ 5 cm/sec output.
It means absolute minimum of 15.6 db overload headroom is required at 1 kHz.
At 1 kHz this phono preamplifier provides only 8.3 db overload headroom.

Now what? Would you claim you doubt an LP can deliver 1 kHz?

A fancy casework and price does not make a good phono preamp.
Good engineering does.

20 kHz on LP records was never a fascination. It is/was always there.
Forget about what you call HD LP. Such claims are probably already extinct as a dodo.
An LP is as good as it gets.

Jack L's picture


CD4 LP invented by JVC in 1970 but died in 1979 for good ! Yes, its carrier frequency is 45KHz for the L-R channels FM multiplex signals (30KHz centre). But not its audio frequenc spectrum which I asked you about any LPs.

FYI, the audio frquency response for the CD4 LP L+R channels: 30-15KHz & same for its L-R channel: 30-10KHz with poor channel separation. No wonder CD4 lasted only a few years before it folded up.

Music comes from musical instrument which produce music. Let's take them from classical music"
Soprano 250Hz-1KHz (high enough to break a glass), Baritone 110-425Hz,
Top piccolo 630 - 5KHz. Clarinet B flat/A 125Hz-2KHz.
So tell me what musical instrument can generate 20KHz strong enough to
overload any preamp ???

BTW, HD Vinyl is a new startup invention to replace conventional cutter with laser to cut the stamper. It is the lastest revoluatinary vinyl invention, pal.

More to tell you, Mr. Engineer later as it's late now. I got to go now.

Jack L

PS: FYI, I'm an electrical engineer with dacades involvement in electrical power industries. My hobbyis DIY audio electronics.

Kursun's picture

Do you claim 20-5000 Hz frequency response is all there is and all it takes for hi-fi music reproduction?
Name of the game is harmonics. Cymbals for example, go way beyond 20 kHz.

If that is not enough,
“******** recording ******* RIAA curve” boosts high frequencies before cutting the record by 20 db!!!! (10 times)!!!! at 20 kHz! ************

************ Shure Company data state there are incredible amounts of signal peaks at 20 kHz on records. **************

This preamp can’t meet the absolute minimum overload headroom specs at any frequency either.

************ I have written all these facts before… Don’t you read or can’t you process what you read? *************

I mentioned CD4 only because you claimed LP records can’t reach 20 kHz. They do, and much beyond to ultrasonic frequencies! And you said 20 kHz is a “fascination” :) that what you call “HD records” will provide. Remember?
Don’t you understand what you read?

Jack L's picture


Slow down & take a breath! Mr. Engineer ! Don't get heart attack ! Mr. Engineer.

I said before I closed my last post to you last nite:
"More to tell you, Mr. Engineer later as it's late now. I got to go now." Obviously you did not read it, right?

Please don't put yr words in my mouth: I never claimed 20-5KHz is "all it takes for hifi music reproduction" !! You've jumped the gun before I can carry on with my explanation here now !

Yes, you are correct about the higher orders of harmonics above the fundamental frequencies of a vocal & a music instrument.

According to Neumann, Berlin, "the origin of all studio microphones", Taking reference of human voice: 200-8KHz, any frequencies above 6kHz - 20KHz are high orders of harmonics, in form of brilliance & air. What we hear sibilances & harshness lie between 6-8KHz.

20KHz is the high frequency audio standard for audio equipment. Not the frequency response of vocals & musical instruments that produce the music. Please differentiate the difference. We listen to music live/reproduced not sinewaves used in any bench tests. Don't mix up as they are totally different: apple vs orange.

My question to YOU in my first post to you was: "So you think a LP can deliver 20KHz music signals strong enough to overload the premp???? I doubt it very much." I stated very clearly to you: "music signals", not sineweave/squarwave test signals used in bench tests.

So YOU still ASSUME musical instruments with fundamentals up to 5KHz can overload any preamp with their high frequency harmonics up to 20KHz !!
So I hereby ask you again: which sopranos/tenors & musical instrument can deliver 20KHz high frqeuncy strong enough to overload any preamp ???
I can tell you: NONE !

Yes, you stated your fact of bench test standard not musical standard.
You obviously fail to know the differnece.

You quoted the JVC CD4 audio frequency "fact" is fake: only 30-15KHz max. Read again CD4 facts before you quote, OK ?

HD Vinyl, not "HD reccords" you wrongly assumed, is a proprietry trademark of a very new Austrian startup with million-dollars funds for this 3D musical signal mapping sofeware invention to replace convention chisel to cut record stamper with lasers. This company held a seminar in
Berlin only last year to demonstrate the sound effect of the 3D mapping software.

I talk facts with published references, not fake news on assumption.

Listening is believing

Jack L

Kursun's picture

I see that you posted a message, but deleted later.

You are thinking in terms of FLAT frequency response.
But LP records are not recorded with flat frequency response.
I see that I have to be more specific…
PRE-EMPHASIS is applied BEFORE cutting and DE-EMPHASIS is applied WHEN LISTENING.
This is done according to RIAA curves.

1. Before cutting an LP, BASS frequencies are ATTENUATED by as much as [-]20 db at 20 Hz and TREBLE frequencies are BOOSTED by as much as [+]20 db at 20 kHz. So if you listen to LP records without applying DE-EMPHASIS, you’ll hear that it is SATURATED with TREBLE frequencies, especially around 10-20 kHz, which you’ll see below at the Shure graph.
Do you understand so far? (Capisci?)

2. The Shure graph of maximum recorded velocities found on commercial music records on the market: https://2.bp.blogspot.com/-T97Unt0UZK8/WIPt3X3bfMI/AAAAAAAAAI0/KY9inlOQ3n8j6TTwbcIlWhwkSvjqCbL-QCLcB/s1600/record%2Bwrap%2Bvs%2Baudible%2Bfrequencies.jpg
As you can see, AT BASS, there are not much high level velocities.
MOST OF THE ENERGY is around 10-20 kHz.

3. BTW, this phono preamp does not meet absolute minimum overload headroom at 1 kHz either. You had replied, “but it has improved” (with respect to 20 kHz overload headroom). But your message was deleted. Overload headroom at 1 kHz was so low to begin with, not enough is not an improvement!

I don’t care what you “doubt”!
Do you understand so far? (Capisci?)
If not, I feel sorry. But I can’t do anything for you. You have to see a doctor.

Jack L's picture


Don't yr words in my mouth again! I never think the way YOU think what I think. Moot assumption again !!!!!

RIAA is not flat frequency response. This is vinyl ABC, even high school kids know it.

You keep on talking about RIAA equalization & Shure. Please tell us more informative on vinyl, Mr Engineer !

RIAA is a standard for manufacturers to design/build phono-preamps for sale, to provide a RIAA playback curve with transition points:
75uS (2,122Hz), 318Us (500Hz) & 3180Us (50Hz) = 20Hz (+20dB). 1KHz (0dB) & 20KHz (-20dB) so that the vinyl music can be theoretically played back flat from 20Hz to 20KHz.

It is a vehicle which convey the recorded vinyl music back to flat frequency response standard : 20Hz - 20KHz.

It does not mean music recorded in a vinyl record MUST get music contents with 20KHz high frequency response.

But YOU assume all music recroded in a vinyl gets 20KHz like sinewave bench test signals. This is incorrect. Human voices & musical instrument with highest orders of harmonics do not delivery 20KHz strong enough to overload any preamp, period!

"MOST OF THE ENERGY is around 10-20 kHz"

Substantiate your above statement with published data, Mr Engineer.

I understand every word you claim. I "doubt" you still undertand what I just posted here.

YOU don't have to do anything for me. You need to see an engineering doctor to improve your knowledge in audio engineering.

Jack L

directdriver's picture

I always associate EMT with pro audio so I do miss the rackmount look of JPA-66 preamp. This audio jewelry look trend is never my cup of tea.