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Topping Pre90 Review (preamplifier)

amirm

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This is a review and detailed measurements of the Topping Pre90 balanced and unbalanced preamplifier. It was kindly sent to me by the company. The base preamplifier with ability to switch between RCA and XLR inputs costs US $599. There is an extension that gives you four (4) more inputs (three balanced and one unbalanced) for another $250.

Splitting the functionality into two boxes is rather unique:

Topping Pre90 Review balanced preamplifier.jpg


Unfortunately there is no immediately switch to select an input. You have to cycle through them using the "SEL" button on the left.

Remote control is provided for volume which in turn mandated relay based stepped attenuator which is quite a "high-end" feature. For any kind of home system use remote is mandatory in my book so it is great to see it implemented here. There are other cool features like setting a pre-input gain or maximum safe playback level.

The back panel shows the unusual configuration with the umbilical cord connecting the two:

Topping Pre90 Review Back Panel XLR balanced preamplifier.jpg


As you see mains power supply is built-into it as it should in this price category.

Overall fit and finish is very good.

For my testing I exclusively focused on XLR input and output.

Topping Pre90 Measurements
As usual I setup preamplifiers for "unity gain" meaning what voltage I put in, is what comes out. On Pre90 that meant setting the volume to -6 dB instead of zero. That gives us this eye popping output:

Topping Pre90 Measurements Preamplifier Balanced.png


Distortion is whopping -25 dB lower than best case threshold of hearing. Combined noise+distortion as represented by SINAD is 5 dB better than said threshold. And this includes the noise from my analyzer. Likely the actual performance is fair bit better.

Suspecting some of the good noise figure comes at the expense of lower than normal input impedance, I jacked up the default 40 ohm output impedance of my Audio Precision analyzer to 200 ohm. The result was that the output from the Pre90 dropped down to 3.6 volts (instead of 4). One click on the volume control compensated for that nicely and give me the same good performance just as well:

Topping Pre90 Measurements Preamplifier Balanced source impedance 200 ohm.png


So there is really no penalty to the lower input impedance.

I wanted to test the effect of the external box so I selected one of its inputs and ran the dashboard again (with 40 ohm impedance);

Topping Pre90 Measurements Preamplifier Balanced External Input.png


As you see the external input works just as excellently as the internal input.

EDIT: here is the RCA performance:
Topping Pre90 Measurements Preamplifier RCA.png


Signal to noise ratio (combined with my analyzer input) is 21 bits and rises to almost 22 bits with full volume:
Topping Pre90 Measurements Preamplifier SNR Balanced.png


Note that Topping advertises much higher numbers. They do that by using a noise amplifier, measuring the results with AP, and then dividing the output by the gain of the noise amplifier. By doing so the remove the effect of Audio Precision analyzer's self noise and get much higher SNR. That is customary in chip industry. For us to keep things consistent we will continue to test as we have as any performance above what I am showing is academic anyway.

Note that the Pre90 can go up to +10 dB gain. Doing so though has a penalty in overall noise. To show the effect of output level/gain, here is a sweep:

Topping Pre90 Measurements Preamplifier Balanced THD+N vs Level.png


As you see you can get to 8 volts while maintaining the full performance of the preamp. There is more gain left if you want to drive an amplifier like Benchmark AHB2 in low gain or Purifi without its input buffer.

Frequency response is almost flat to 80 kHz:
Topping Pre90 Measurements Preamplifier Balanced Frequency Response.png


There is a bit more droop in my measurements vs Topping. Not sure why but it is immaterial.

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

Topping Pre90 Measurements Preamplifier SNR Balanced Crosstalk.png


Intermodulation distortion test is as good as the best I have tested, the Benchmark HPA4:
Topping Pre90 Measurements Preamplifier SNR Balanced IMD Distortion.png


Same is the case for SINAD vs frequency:

Topping Pre90 Measurements Preamplifier SNR Balanced THD+N vs Frequency.png


Conclusions
Seems like the revolution we have had in high performance headphone amplifiers has bled into preamplifiers. I love it because I have a Reel Reel tape deck that I like to use occasionally in my system along with my usual DAC. Sadly hardly any premplifier could keep up with said DAC so I was degrading the performance of it to have the ability to play another analog source. With the Pre90, that compromise is no more. It is an instrument grade, more transparent than transparent, preamplifier. Other than Benchmark HPA4, I don't think it has an equal no matter how much money you spend. In that regard, it is quite a value as well although obviously not "cheap" as compared to desktop products.

It is my pleasure to strongly recommend the Topping Pre90. If you needed to have another source beside your DAC to play in your system, you now have a wonderful way to accomplish that with zero impact on performance.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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pio

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YSC

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One question, you mentioned the input impedance is low and that affected the output with 200ohm output impedance from dac which is pretty normal value, but with this impedance will it roll off the frequency response in the output?
 
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amirm

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amirm

amirm

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One question, you mentioned the input impedance is low and that affected the output with 200ohm output impedance from dac which is pretty normal value, but with this impedance will it roll off the frequency response in the output?
The source impedance in DACs is usually a couple of resistors and likely won't have a frequency dependent component to matter in audio band. So all you are left with is voltage drop which is what I tested for.
 

Francis Vaughan

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Typos - bass preamplifier, ambilocal cord.

What is the connector on the umbilical?

If the satellite unit is active, it would seem they might have missed a trick by providing for a cascading umbilical connection. It would have been cool to have the entire x90 series inter-linkable by this umbilical, and free up XLR connectors, and basically clean things up. Also add more than one satellite unit to add more inputs (if anyone ever wanted or needed) or even add more outputs.
 

Hemi-Demon

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Is that a proprietary cable that is used to mate the two devices? Seems risky, if that cable ever breaks, or wears out. Also why have a multi output device, but require the user to have to toggle through outputs with a single button?

Great review. Too expensive imo though. Also if Topping is jumping into the high end market @$900, please improve the volume selector hand feel amd remote quality. Schiit gets the win for their latest volume knob imo.
 
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trl

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Also why have a multi output device, but require the user to have to toggle through outputs with a single button?
Ease of implementation perhaps? Also, adding another small PCB inside, with added buttons/switches, might add noise and lower the final SINAD a bit.
 

restorer-john

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Possibly odd question: but is there a major difference between this and a microphone preamp? For example could you plug in a ribbon or dynamic mic into to this and then into an AD converter

Gain. Lots needed for microphones. And this has a ~2K input impedance. It's only suitable for seriously capable line drivers/DACs etc. Many CD players would be ruled out, as would tuners, cassette decks and medium output impedance capacitor coupled devices. Although JohnYang has said the RCAs are 10K input R IIRC, so they should be fine. Amir's open reel should be OK due to a likely robust line driver or 600:600R transformer for the XLRs.
 
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JohnYang1997

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Possibly odd question: but is there a major difference between this and a microphone preamp? (Besides no phantom power) For example could you plug in a ribbon or dynamic mic into to this and then into an AD converter (I've plugged ribbons/dynamics straight into a lynx hilo in the past and it worked fine except with some quiet sources, the noise floor would be a bit too high when you turned it up)
The standard mic preamp should have up to +70dB gain to work with for insensitive dynamic microphones and quiet environment. This preamp only has 10dB/16dB. And usually mic preamp has 1k input impedance and operation usually is single ended. This is not that.
So basically it wouldn't work well as it's not designed to have high gain. But at some point I plan to make some microphone preamps or AD converters even.
 

da Choge

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I don't quite get it; does the remote control only allow for volume control or can it also allow you to cycle through the inputs like you can with the "SEL" button on the front panel of the primary unit? There is no photo of the remote, so I'm not quite sure what its capabilities include.
 
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