Topping Pre90 line preamplifier Measurements

Sidebar 3: Measurements

I measured the Topping Pre90's performance with my Audio Precision SYS2722 system (see the January 2008 As We See It), repeating some tests with the magazine's higher-performance APx555 system.

The Pre90's volume control operated in accurate 0.5dB steps. The maximum gain at the unbalanced outputs was the specified 10dB for both the balanced and unbalanced inputs; the maximum gain at the balanced outputs was the specified 16dB for both types of inputs. The preamplifier preserved absolute polarity (ie, was noninverting) with both balanced and unbalanced inputs and outputs. (Its XLR jacks are wired with pin 2 hot, the AES convention.)

The Pre90's unbalanced input impedance was 9.9k ohms at 20Hz and 1kHz and 9.6k ohms at 20kHz. The balanced input impedance was low, at 2k ohms from 20Hz to 20kHz, which might give a bass-light balance with source components that have a tubed output stage. The balanced output impedance was the specified 40 ohms at all audio frequencies, which is usefully low. The unbalanced output impedance was 21.5 ohms, again from 20Hz to 20kHz.

The preamplifier's audioband frequency response was flat in balanced mode (fig.1, blue and red traces), with the ultrasonic rolloff reaching –0.5dB at 100kHz. Fig.1 was taken with the Pre90's volume control at its maximum setting of "16." Both the frequency response and the superb channel matching were preserved in unbalanced mode, at lower settings of the control, and into low impedances (fig.1, cyan and magenta traces).


Fig.1 Topping Pre90, balanced frequency response with volume control set to "+16.0" at 2V into 100k ohms (left channel blue, right red), 600 ohms (left cyan, right magenta) (0.5dB/vertical div.).

The Topping preamp's channel separation was superb, at 110dB in both directions below 2kHz, and decreased only slightly, to 90dB at the top of the audioband (not shown). The Pre90 offered extremely low noise in both balanced and unbalanced modes, with no power-supply–related spuriae in its output even with the volume control set to its maximum (fig.2). The wideband, unweighted signal/noise ratio, measured at the balanced outputs with the unbalanced inputs shorted to ground and the volume control set to "+16," was 66.5dB in the left channel, 73.8dB in the right, both ratios ref. 2V output. Restricting the measurement bandwidth to the audioband increased the S/N ratio to a superb 118.8dB in both channels, while switching an A-weighting filter into circuit further improved this ratio, to 121.5dB. The Pre90 is one of the quietest preamplifiers I have encountered.


Fig.2 Topping Pre90, balanced spectrum of 1kHz sinewave, DC–1kHz, at 2V into 100k ohms (left channel blue, right red) and at 0V (left cyan, right magenta) (linear frequency scale).

Fig.3 plots the percentage of THD+noise in the Pre90's balanced output against the output voltage into 100k ohms. We usually specify clipping voltage as when the THD+N reaches 1%. However, as you can see from this graph, the output voltage actually decreases as the input voltage increases after the abrupt rise in distortion at 17V. The same behavior was apparent with the Pre90's balanced output driving 600 ohms (fig.4) and with the unbalanced output (fig.5). According to Topping, this behavior is due to the Pre90's protection circuit operating when the volume exceeds a preset limit.


Fig.3 Topping Pre90, balanced distortion (%) vs 1kHz output voltage into 100k ohms.


Fig.4 Topping Pre90, balanced distortion (%) vs 1kHz output voltage into 600 ohms.


Fig.5 Topping Pre90, unbalanced distortion (%) vs 1kHz output voltage into 100k ohms.

The THD+N was extraordinarily low at normal output levels of a few volts, so I measured how the Pre90's distortion changed with frequency at 11V. Despite the very high voltage level, the THD+N percentage was extremely low into both 100k ohms and 600 ohms, at 0.0004% (fig.6), with a slight increase in the top audio octaves. With a 50Hz tone at 2V into 100k ohms (fig.7), the harmonics at 100Hz, 150Hz, and 250Hz were close to the residual levels in the Audio Precision SYS2722's signal generator. I therefore repeated the spectral analysis at 10V into 600 ohms (fig.8). Despite the stressful conditions, the second and third harmonics each lie close to –120dB (0.0001%). At higher frequencies (fig.9), the third harmonic was slightly higher than the second, but both are still vanishingly low in level.


Fig.6 Topping Pre90, balanced distortion (%) vs frequency at 11V into 100k ohms (left channel blue, right red), 600 ohms (left cyan, right magenta).


Fig.7 Topping Pre90, balanced spectrum of 50Hz sinewave, DC–1kHz, at 2V into 100k ohms (left channel blue, right red; linear frequency scale).


Fig.8 Topping Pre90, balanced spectrum of 50Hz sinewave, DC–1kHz, at 10V into 600 ohms (left channel blue, right red; linear frequency scale).


Fig.9 Topping Pre90, balanced spectrum of 1kHz sinewave, DC–1kHz, at 3V into 200k ohms (left channel blue, right red; linear frequency scale).

Tested for intermodulation distortion with an equal mix of 19 and 20kHz tones at a peak level of 10V into 100k ohms, the second-order difference product at 1kHz lay at –130dB (0.00003%), and the higher-order products were all below –115dB (fig.10).


Fig.10 Topping Pre90, balanced HF intermodulation spectrum, DC–30kHz, 19+20kHz at 10V into 100k ohms (left channel blue, right red; linear frequency scale).

The Pre90 preamplifier's measured performance is simply superb. The fact that that performance can be achieved in such a small chassis and for such a low price suggests that Topping has some serious audio engineering talent in-house.—John Atkinson

Guangzhou TOPPING Electronics & Technology Co., Ltd.
Authorized US retailer Apos Inc.
1400 Coleman Ave., #E23
Santa Clara, CA 95050
(510) 858-6585

Bob Loblaw's picture

Topping has been building excellent equipment for a few years now. The technical performance absolutely embarrasses many more expensive manufacturers. If accuracy is the goal then it begs the question why anyone would need to spend more than $599 on their pre-amp.

MatthewT's picture

The cost-complainers a bit, at least for this review. OTH, "Made in China" is ringing the Pavlov bell. Great review as well, thanks.

tonykaz's picture

Amazing, Mr.KR, it's like comparing a Kia Soul to a Mercedes S Class.

I trust your assessments in these matters.

The headphone people have also been praising Topping lately, they have superb transducers, support gear and high standards.

Still, it's a bit surprising to see the famous multi-channel authority reaching out to dabble in modest gear like this.

If you're impressed with this piece you must also own outstanding everything .

Tony in Florida

Kal Rubinson's picture

Amazing, Mr.KR, it's like comparing a Kia Soul to a Mercedes S Class.

Why would I turn it down? It does represent a full frontal attack on one's perceived biases.


Still, it's a bit surprising to see the famous multi-channel authority reaching out to dabble in modest gear like this.

Yes, so I had to buy 3 of them.


If you're impressed with this piece you must also own outstanding everything.

It is hard to know if this is tongue-in-cheek but, fwiw, the associated equipment is always listed.

tonykaz's picture

and I read every word you write ! You are one of the greats ( like Mr.JA ) and one of pillars that make Stereophile the impressive institution that it is.

Tony in Florida

CG's picture

TI and ADI have both made incredible progress in their opamps suitable for audio. Great example right here.

georgehifi's picture

Incredible measurements, backed by Audio Science Review (ASR)also

Looks to be as good as going direct from dac (with volume) to poweramp/s.
Yet this has adjustable gain settings and anything you could want.

I doffs me hat to this one. And say goodby to highend preamp prices

Cheers George

Glotz's picture


James Romeyn's picture

I enjoyed this review. Kal writes where the rubber meets the road.

I interpret this bold review, comparing ca. $1k to ca. $18k preamps to mean that Stereophile has the guts to risk stepping on the toes of the most highly respected OEMs, even those who pay Stereophile's bills. If I'm correct, then let me make this bold claim in an area where I, a vendor, have absolutely no financial interest.

My friend Luis is a degreed full-time Linux/network system engineer. Luis built my large custom server/streamer computer running the most advanced and refined versions of HQ Player. The main computer parts cost with the best discounts came to ca. $1500; HQ Player costs ca. $165. I don't know Linux from Linus of Peanuts fame; Luis sets up everything remotely. But Luis claims someone versed in Linux could replicate his work.

Two NUCs, both tiny compared to the server/streamer, perform discrete functions: a larger NUC (ca. $250) solely performs Roon library functions (IOW no or as little as possible Roon DSP); the smaller NUC (ca. $150) solely renders with USB output > DAC. Lifetime Roon cost is $500 last I checked.

HQ Player performs extreme filter, up-sampling and demodulator functions in either DSD or PCM. Setup options go on almost to infinity and the author Jussi in Norway constantly upgrades for FREE! The DAC is a Holo Audio Spring 3 KTE, set permanently for true NOS/non-oversampling ("true" means some DACs with "NOS" perform some OS functions.)

Multiple online reports of HQ Player users employing it as described above, including myself, my wife with much better ears than my own, and several friends, prefer this setup over anything else they have heard even cost-no-object. I suspect my server/streamer rig competes with cost no object including dCS rigs in the range of $50k and up.

I suspect, because Herb Reichert is apparently unfamiliar with HQ Player as described (HQ Player on a lesser computer provides commensurately less audio performance) that it would give him a completely new and fresh perspective on the true potential of his Holo Audio May KTE DAC (in NOS mode.)

Compared to the best streaming applications, I suspect spinning silver discs and streaming on consumer laptops/desktops are grossly lacking as professional reviewer tools.

Anton's picture

If I needed a preamp, I would simply jump into this and save loads of cash.

I've read good things about their amplifier, as well.

Nice to see this sort of product get such a focused review, many thanks.

Glotz's picture

Loved this review and your ongoing integrity and honesty in reviewing!

I will NOT China-bash, but please keep in mind this preamp would be much more expensive if made in the U.S.

tonykaz's picture

Schiit builds comparable at comparable prices.

Tony in Florida

georgehifi's picture

Something says to me, they wouldn't measure up like this thing does.

Cheers George

Kal Rubinson's picture

Hold that thought. :-)

tonykaz's picture

What is that something ???

Not just Schiit but all of these Audio Designers have the tools and incentives to build outstanding.

Especially considering that they can sell direct and have direct feedback from their Customer Base.

In the old days of the 1980s, William Z Johnson built to satisfy his Dealer Network .

Now-a-days I can write a note to Paul at PS Audio, Jason at Schiit, Devore, and even Call Manufacturers Direct and get answered by a real person ( maybe even the designer himself )

2020 heading into 2030 seems like a whole new world for us DIY folks, we have much better tools and we don't have to be worshipful to the guys promoting $250,000 record players.

Tony in Florida

Robin Landseadel's picture

If you have been following Amir's reviews at ASR you would be aware that Topping gear always measures great and Schitt gear sometimes measures great and sometimes doesn't.

tonykaz's picture

Measurements vary, I think.

I invest based on listening over a period of time and based on the performance compared to my established standards.

I value Mr.JA's lab bench evaluations and insights.
I also evaluate gear on the Bench and generally agree with Mr.JA's reveals. I'm measuring to confirm proper operation not Sound Quality performance ( which generally bears no relevance to measurements.)

Schiit gear are the best Value for Money products in Home Audio's long History. ( as far as I can tell )

Tony in Florida

Robin Landseadel's picture

Schitt's measurements do vary, depending often on the basic circuit design. And they do offer some of the more unique [and technically dubious] products at unusually low prices, credit where credit is due. Some products, as far as I can tell, are outstanding. Some are underperforming. I have yet to see any measurements of Topping gear at ASR that are not outstanding.

Glotz's picture

The measurements on ASR. The Schiit Modius DAC is a good example. For $200, they compete quite nicely with Topping DACs.

I own it. It is a great placeholder DAC until I can afford something more auspicious.

bhkat's picture

Topping isn't an American or European company that has off-shored manufacturing to China while trying to obscure this fact. It is a Chinese company and therefore is standing on their own. They make great components.

Long-time listener's picture

After listening to the NAD M51 DAC for a number of years, I saw the measurements of the Topping D90SE -- their top of the line -- and decided to buy it. At less than half the price, it was a definite upgrade, with an audible difference. I'm extremely happy with it.

The only thing I don't like about the company -- something that actually makes no difference whatsoever -- is that their name sounds kind of goofy to me. I wonder where they got it. Anyway, I'm not complaining. I'll continue to buy their stuff when it suits my needs.

thatguy's picture

With all these references in the comments to China bashing, do people realize that it is entirely possible to think the Chinese people are great and capable of making quality products and still be shocked by the actions of their government to the point of not wanting to help support them and what that government does.

Jack L's picture

...... and still be shocked by the actions of their government." qtd thatguy.


I fully appreciate to you have spoken out the background behind the sentiment of China bashing. Not the great Chinese civilization dated back thousands years, but it is "that government" today !!!!!!!!

But let's stop here now as politics should not be discusssed here.

Jack L

michelesurdi's picture

a brave review.time to wakeup to realities.if i had the money i'd buy the pass and keep it for a lifetime,but then i'm a hi fi it is i'm buying the topping on the strength of J.A.'s work.

synapse-md's picture

I've been a Stereophile reader since 1992, but this is my first time commenting here. I appreciate the rigor and openness with which this relatively inexpensive preamp has been assessed, in similar vein to the recent reviews of Okto Research's products. Top-flight audio quality certainly has become more accessible.

Given the very limited input complement of the Pre90 (Just one set of balanced inputs!), can KR/JA comment on whether there are any subjective or measurable differences when running inputs through the Ext90 vs the Pre90 itself?

The signal paths, to the degree that some audio signals will run through the umbilical alongside power and control, must be at least a little different.

GRBH's picture

Audio Science Review tested this pre amplifier and extension box in December of 2020. One XLR input from the extension box was tested and the results indicated near identical performance to that of an XLR input to the preamplifier itself.

synapse-md's picture

I missed that! I do wish he had tested channel separation, but agree that from what these data show, there’s unlikely to be an audible difference.

Thanks for the link.

GRBH's picture

You may have missed seeing this, but Amir did an alternative measurement to separation, that of crosstalk. Not clear as to whether the measurement was that of the preamp or extension box. The following was his comment to that measurement.

"Crosstalk was more than good enough for what we need but shy of the best that can be done"

Kal Rubinson's picture

Given the very limited input complement of the Pre90 (Just one set of balanced inputs!), can KR/JA comment on whether there are any subjective or measurable differences when running inputs through the Ext90 vs the Pre90 itself?

As far as I can recall, I did not send the Ext90 on to John for testing and I tried the inputs on it only to confirm that they functioned properly.

However, since you asked, I will do a quick test later today and append the results to this message. I do not expect any difference.

synapse-md's picture

Thanks. Appreciate you taking the time to do that.

Kal Rubinson's picture

This was only a brief test. I connected an XLR Y-splitter to the DAC output and its outputs to the main Pre90 XLR input and the #1 XLR input on the Ext90. With a 4-5 musical selections, I did a non-blind A/B comparison between the two inputs, toggling between them, and could not hear any difference in level, tonality or noise. All that was added was the click of the relay at the transition. FWIW.

MatthewT's picture

Very much!

synapse-md's picture

Great to hear. Thanks again for taking the time to do this comparison.

nidaje's picture

Quote: It fits my needs, and it fits my ears, so for me it's a great bargain.
Great review KR.
Although I consider myself to be both experienced and insightful in assessing hi-fi audio equipment, I too have found it hard to believe that equipment in this price range can represent a real and interesting option in the "high end" segment. Thank you for challenging my prejudice on the "right stuff".

georgehifi's picture

"I too have found it hard to believe that equipment in this price range can represent a real and interesting option in the "high end" segment."

The it's just usually the case work that probably tickles your fancy, what's under the skirt "can" be almost the same in monitory/technology/and sound value.

Cheers George

nidaje's picture

I know George and "almost" agree. I am impressed. Given years of trade sanctions the Chinese have no problems producing high performance devices in that pricerange filled with the best components often from the best American/European/Japanese manufacturers. And it seems they are so capable that they can beat the best western electronic designers. No wonder they placed a Rover on Mars too. I am in the market for a new preamp and two of these will probably serve my needs for inputs too.

Robin Landseadel's picture

Great that Stereophile is reviewing Topping gear. I'm a cheapskate, seeking maximum bang for the buck. Have the Topping E30 DAC and the L30 headphone amp that also has limited preamp functions. Very nice, and at less than $300 for the pair, very cheap. Hope you get around to the Topping D90SE DAC. If ASR is right, it's SOTA for $900.

JRT's picture

Again... Thank you for another interesting review of an interesting component.

Seems strange that they would conciously choose to not include some facility to control separate levels of attenuation on each channel, some means of adjusting channel balance.

Kal Rubinson's picture

I agree with you even though I have not had a need to use a balance control for some years now. There are other points in my signal chain where it can be implemented, so I like that the Pre90 is so simple in its functions: Source selection and gain control, that's all.

remlab's picture

..with excellent loudspeaker QC and proper loudspeaker/listener placement, there really isn't much of a need for balance control anymore

remlab's picture

..Stereophile reviews John Yang's latest Topping amplifier design too. Other than total power, it almost reaches EIGENTAKT levels of performance.

tonykaz's picture

It feels like you broke thru the ice as a High Level Enabler for we budget hopefuls.

I suspect that you will now have an enthusiastic range of admiring readership searching for meaningful insights into all things Audio.

I've always seen you as an exploring navigator of hard to reach Worlds.


Tony in Florida

georgehifi's picture

@John Atkinson

Seeing you had the top off this Pre90 did you see what opamps are used? or is the active stage discrete circuitry.

Thanks George

John Atkinson's picture
georgehifi wrote:
Seeing you had the top off this Pre90 did you see what opamps are used? or is the active stage discrete circuitry.

I'm afraid I didn't look inside the Pre90. The internal photo was supplied by Topping.

John Atkinson
Technical Editor, Stereophile

David Harper's picture

Not at all like comparing a Kia to a Mercedes. In that case there are real objective differences in build quality and performance. In the case of preamps, not so much

claud's picture

However pleasing this Topping preamp is to ears and budgets, isn't anyone even curious about how it would sound compared to this review of the Parasound JC-2? JA was certainly impressed when he compared it to his Levinson 380S preamp.

Of course, neither of those preamps would work for the 5.1 system I want to build. And unlike the Topping, I certainly couldn't afford to buy two them to make it happen! BUT what if Topping had offered a multichannel preamp that sounded (to both KR and JA) every bit as great as the JC-2 but at HALF the price??

stanzani's picture

Hello Kal
I would have liked to read your opinion when comparing the pass and the topping in situation w/i and w/o preamplifier further taht topping vs pass. And yes, I would have like a bind comparison (but I am asking too much ;) )
It could be embarassing to state that no divverence between the big and the small boy :)

John Atkinson's picture
stanzani wrote:
I would have like a blind comparison (but I am asking too much ;) It could be embarrassing to state that no [divergence] between the big and the small boy :)

When I studied statistics at university 50 years ago, I learned that tests cannot prove a negative. If a test produces statistically insignificant results, that does not mean that the items being compared were identical. Instead, the results mean that if a difference exists, it was not detected under the specific conditions of the test.

John Atkinson
Technical Editor, Stereophile

reynolds853's picture

To be clear, your only comment about the impact about adding the Topping was single sentence:

Without it, I noted marginally less weight and a bit less dynamic impact.

"Marginal" and "a bit" suggest that pre-amps do not impact sound much for DACs, I suppose. I can see the case to be made for low gain components, though.

TJ's picture

Kudos to their engineering team for such an impressive product. Customer satisfaction may suffer unfortunately from the frustrating remote (cost-cutting?), Topping's QA and customer support problems, and hidden expenses for warranty service (return shipping to China plus high customs entry fees). Do we know what the failure rates are for Topping products? The user anecdotes on Amazon and the forums are disconcerting. If the failure rates are high as some say, buying one may be a game of chance.

claud's picture

Speaking of which, KR mentions having this surround switcher in his system. Although, that switcher is probably a passive device, I can't help wondering if Pass Labs like sound quality, functionality, reliability-and certainly US based tech support-would be had by have the likes of Coleman Audio or build the 5.1 preamp I need for my MCH DAC. Better quality won't come cheaply but it's hardly otherwise in this game.