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MM Expander | RIAA Converter

AFE-10 | AFE-11

Manufacturer: AURORA SOUND Inc.
Price (when reviewed):
AFE-10 – 2099 PLN | AFE-11 – 2490 PLN

Contact: AURORA SOUND Co., Ltd.
Rojuman III 102, Rojuman III 102
76-4 Tsukaoka-cho, Asahi-ku, Yokohama
241-0805 JAPAN


Provided for test by AUDIO ATELIER


Images: Wojciech Pacuła | Aurorasound

No 207

August 1, 2021

AURORASOUND is a Japanese company founded in 2010 by Mr. SHINOBU KARAKI. Its offer includes line and phono preamplifiers as well as amplifiers, including a tube power amplifier. This time we are testing the first two devices from a series of accessories intended to improve listening experience in existing systems.

HAT OR WHO IS AN AUDIOPHILE? The short answer is that it is a man for whom the sound quality of the music played by his/her system is a part of its artistic side, therefore it is important to him, often on a par with the music itself.

A long answer would be very long, so for the purposes of this test let me cut it short a bit: an audiophile is a man who tries to achieve the best possible sound quality of the music reproduced by his system, because the sound, i.e. the physical representation of music, is part of its artistic expression. For this purpose, he uses various techniques, from the selection of appropriate sound sources, through amplifiers and loudspeakers, to connecting and power cables and ending with anti-vibration products. He selects individual elements of this audio signal’s path in a series of listening sessions, that is by conducting an experiment based on a test by inspection.

I think that the shortened version and the first part of the extended version have recently become more and more accepted outside the audiophile circle. Academic science currently recognizes a dependence between music and the way it is presented - primarily at the recording level, but the other side also benefits from it, that is its playback.

However, there are aspects of our industry that for people from outside of it defy common sense and their knowledge. I think that some of the accessories, and even audio products from the main groups, are really crazy. However, it is precisely such madmen that make us question the rules, seemingly impossible to break. Once strained, they often turn out to be just convenient lockpicks, not something real, and breaking their foundations is a simple way to improve the sound, which is what audiophiles care about the most.


I DON'T KNOW IF YOU REMEMBER, but during the test of the PREDA-III line preamplifier from the Japanese company Aurorasound, its founder and chief designer, Mr. SHINOBU KARAKI-san mentioned that he is currently working on a completely new series of products to be named Analog Frond End (HF № 205 ⸜ May 1, 2021 | see HERE; accessed: 31.05. 2021). In the specialized Anglo-American (and also Japanese) press, "front end" is synonymous with a sound source, be it a digital player, tape recorder or turntable. The name 'Analog Front End' speaks of products related to analog sound sources, which - as the head of Aurorasound said - "improve the quality of analog audio listening".

Two products were already introduced the first ones in the new series: the AFE-10 and AFE-11, and soon the AFE-12 will be added (we are testing AFE-10 and AFE-11). The first is an expander for MM cartridges, allowing for a more precise adjustment of their load, and the second is a device that allows you to send the signal from a CD player to a phono stage, using the inverted RIAA curve; The AFE-12 is supposed to be an equalizer with many correction curves, intended for 78 rpm and monophonic records.

While AFE-10 is a technically an understandable and even classic product, the AFE-11 is a real "freak" - it is devices of this type that stun people "outside of the audiophile world", and make us look like the „crazy ones”. As it is about to turn out - wrongly.


The AFE-10 HAS A CORPORATE NAME: AN MM EXPANDER, which reflects its place in the audio signal’s path well, but does not fully describe its purpose. It is a small, black box measuring 111 x 120 x 35 mm (width x depth x height) and weighting only 400 g, which is a passive impedance and load capacity corrector for a MM cartridge. One connects it between a cartridge and a MM phono preamplifier with an input impedance of 47 kΩ; The manufacturer's website also says that it works equally well between a step-up transformer and a MM preamplifier.

The goal of AFE-10 is to precisely match the load to a specific MM cartridge. This problem has been known for years, but few manufacturers are doing anything to solve it. The fact is that the industry standard is a 47kΩ load for this type of cartridge, no matter how it really should be loaded. While such adjustment is a standard in the case of MC cartridges, it applies to MM, IM or MC HO models extremely rarely. And the mismatch of impedance and capacitance results in the modification of the frequency response - as in the figure below:

One finds two knobs, two toggle switches and one large button on the top of the device. Use the upper knob to change the load impedance in six steps: 47, 23, 15, 6.8, 3.6 kΩ and 900 Ω. The lower is used to adjust capacitance, also in six steps: +470, +330, +220, +100, + 47 and +0 pF. Remember that while the impedance introduced by the tested device is in no clear way related to the impedance of the connecting cable, the capacity absolutely is. The advantage of the capacitance values is that it will increase the capacity of the interconnect connecting the cartridge and the AFE-10 by that much.

The two small switches I mentioned help in listening to mono records and mono cartridges. With the first one, "Stereo / Mono", we can eliminate the noise coming from the vertical movement of the stereo cartridge that plays a MONOPHONE RECORD. On the other hand, the second, "GND Lift", will eliminate the hum that occurs after connecting some MONOPHONIC CARTRIDGES. And there is also a large, orange "MUTE / Degauss" button, with which we will mute the signal and by the way - if we have a step-up matching transformer connected earlier - we will remove the residual magnetization of the transformer and MC cartridge.


The AFE-11 IS A COMPLETELY DIFFERENT "ANIMAL" even though also this device requires the use of a phono stage. The brand name for this product is RIAA CONVERTER, which - again - reflects its function well, but says nothing about its purpose.

If we go back to what I mentioned at the beginning, that is, the label of "unbalanced madmen" that some non-audiophiles try to pin on us, then the AFE-11 would be one of the most dangerous weapons in their arsenal. It is a device that, from a logical point of view, seems to be an offense to common sense.

The RIAA Converter is used to modify the line signal from an analog output of a CD, SACD or music files player. It converts the 2V linear signal (this is a standard for the CD format), reducing its voltage to 5 mV, characteristic for MM cartridges, and corrects the frequency response by applying an inverted RIAA curve. The signal from its output is sent to the MM phono preamplifier, where it is treated as if it came from a MM phono cartridge.

The "madness" of this solution is that the high voltage signal is reduced to a very low level one, so we increase the noise, and additionally we are dependent on the precision of the RIAA curve correction circuits - twice! What's all this for? - The manufacturer's website says:

The AFE-11 deletes digital noise and unnecessary high frequency noise of CD or DA converter signal. And external phono stage amplifier will decide the ultimate sound character, which converts digital sound to an analog one.

⸜ source: AFE-11 RIAA Converter,; accessed: 1.06.2021.

So - the point is to make the "digital sound" more "analog". Crazy? - A bit, but such ideas throw us out of our comfort zone, making us think.

Interestingly, this is not Mr. KARAKA's idea, but a concept presented for the first time in 1998 by BOBA CARVER in his Sunfire Classic Vacuum Tube Control Center preamplifier. In addition to the line and phono inputs, it also had a module with an inverted RIAA curve, which could be connected to the MM input using a short interconnect. This solution was called PRECISION INVERSE RIAA NETWORK and it aroused great controversy in the audio industry.

The portal wrote about this solution:

Yeah, I know, what in the hell is this new creation by Bob Carver? Very simple. A CD player's analog output is fed into the input of the Inverse RIAA phono jacks. The output of the Inverse RIAA circuit is fed-via short interconnect cables-to the Moving Magnet (MM) input of the phono stage. And voila, LP sound from a CD!

The CD player's analog output is being treated as a signal coming directly from the recording microphones. The Inverse RIAA circuit applies the standard RIAA recording curve processing to this signal, attenuating the signal level of the lows and increasing the signal level of the highs; in the real analog LP world this "signal processing" is a necessary requirement for reasons that I will not go into here. This "processed" signal could then be fed directly to the cutting head which would "cut" the appropriate information into the surface of a lacquer-coated recording disc.

Sunfire Classic Vacuum Tube Control Center (AKA a tube preamp)„Sound Off” Volume VII, Number 2, December 1998, source:; accessed: 1.06.2021.

The author of this test compares the principle of the inverted RIAA curve to the record cutting process, in which the linear signal is subjected to exactly the same correction. The AFE-11 is therefore a device which aims to bring the sound of digital sources closer to that of an analog disc. For this purpose, it introduces correction to the audio signal (it is a filter) and requires the use of a MM phono preamplifier, which, as the manufacturer declares, gives the whole a proper character.

Similarly to the AFE-10, the '11' is in the form of a small, black aluminum box, but there are no manipulators on it, except for the power switch on the front panel. On the back there is a pair of RCA sockets to which we send the signal from a digital player's output, as well as a pair of RCA sockets, from which the signal is sent to a MM phono preamplifier input (5 mV, 47 kΩ). The device is active and is powered by an external 6V DC switch mode "wall" power supply.


⸤ HOW WE LISTENED In order to use both tested products, a MM (or MC / MM) phono preamplifier is required. And although they themselves make their mark on the sound, the most important factor is the preamplifier. For this test, I used the RCM Audio Sensor Prelude IC, which I know inside out.

When testing the AFE-10 I used the Shelter Model 201 cartridge on the SME M2 tonearm, mounted in the Transrotor Alto TMD turntable. The manufacturer of the Shelter cartridge does not inform about its internal impedance, but recommends a 50 kΩ load - a very unusual choice, considering that almost all MM preamplifiers have 47 kΩ input.

In turn, the AFE-11 was connected to the RCA output of the Ayon Audio CD-35 HF Edition SACD player, and on the other hand to the input of the RCM Audio preamplifier, on which I set the input voltage to 5 mV and the load to 47 kΩ. As it turned out, in this arrangement, I heard only silence in the speakers, and more precisely the hum of the preamplifier. Only when I switched the load to 1000 Ω, everything sounded as it should be. Perhaps this is a problem with the Sensor, but it is worth checking if your AFE-11 system is working properly before buying.

Recordings used for the test | a selection

⸜ BING CROSBY, Bing Crosby’s Greatest Hits, Decca Records/MCA Records, MCA-3031, 2 x LP (1941-1945/1977)
⸜ DIRE STRAITS, Brothers in Arms, Warner Bros./Mobile Fidelity Sound Lab MFSL-2-441, „Special Limited Edition | № 3000”, 2 x 180 g, 45 RPM LP (1985/2014)
⸜ JOHN COLTRANE QUARTET, Ballads, Impulse!/Speakers Corner Records ‎AS-32, 180 g LP (1962/2003)

⸜ GARY BURTON & CHICK COREA, Crystal Silence, ECM Records/Tower Records ⸜ Universal Music LLC PROZ-1091, „ECM SA-CD Hybrid Selection”, SACD/CD (1973/2017);
⸜ JEAN-MICHEL JARRE, Magnetic Fields, Dreyfus Disques/Epic EPC 488138 2, CD (1981/1997)
⸜ TSUYOSHI YAMAMOTO TRIO, Midnight Sugar, Three Blind Mice/Impex Records IMP8308, Gold HDCD (1974/2004)



AS WE’VE ALREADY SAID, one of the iron-clad rules in the world of audio is to simplify the audio path. It is so, that "every element sounds", each terminal, solder, any component, whether passive or active, in a word - everything affects the sound. Historically, however, the development of systems for recording and reproducing sound has evolved in exactly the opposite direction, from simple to complex.

These changes were intended to remove or at least minimize distortions. It was not always successful, because in our industry development is not linear and meanders in a really unpredictable ways, but the development generally had an arrow pointing "towards the complication". It is in opposition to this tendency that many great audio brands were created, and in opposition to "progress" (the quotas do not come from me, but let it be) the renaissance of tubes, vinyl, etc. "happened". So in audio we are dealing constantly with frictions between what is "complex" and what is "simple", and often the process of getting to "simple" solutions takes more time and effort than designing "complex" ones.

And there is a third way, in my opinion the most sensible and the most successful one, to which Einstein's famous statement applies that - to paraphrase - everything should be as simple as possible, but not simpler than necessary. And that would be the case of the AFE-10. The Aurorasound box showed that by using an additional element in the audio path, the sound can be shaped in such a way that it is better suited to our system and our expectations. The change in load impedance and capacity directly affects the cartridge frequency response - its extension and evenness.

The Shelter 201 cartridge played directly with the "default" load of the MM section of the RCM Audio preamplifier, i.e. with an impedance of 47 kΩ, sounded very well. Maybe not too resolving and without an open treble, but in its own way, it is dense and smooth (the recommended load impedance above 50 kΩ could not be implemented). Nevertheless, it turned out that it sounded even better when loaded with a much lower impedance, not even 47 kΩ, but 23 kΩ, and a capacity of 330 pF.

Decreasing the load impedance cuts the highs and dampens the dynamics. Only that in this case a slight withdrawal of the treble allowed to turn up the volume knob, which made the presentation bigger and more "lively" in the sense that it was more natural. The bass has also improved, not as precisely controlled as before - after all, there are additional elements in the signal’s track, you remember what I was talking about, right? - but deeper "within" and more fluid.

In this setting, the re-edition of the old BING CROSBY album The Best of Bing had more "charm". The voice was bigger and deeper, and even the reverb added artificially by the sound engineers remastering this material did not spoil the impression. The return to the system without the AFE-10 equalizer slightly simplified the presentation in terms of timbre, but was a bit more resolving. The material I am talking about comes from old shellac and transcription records, so it is quite noisy and it crackles. But - attention - I changed the loading to 6.8 kΩ and 330 pF and the problem disappeared. Even a fairly high-recorded orchestra sounded nice, didn't "scream" anymore over Crosby's shoulder. It was great!

I started the listening session of the AFE-10 expander with the re-edition of the Ballads by JOHN COLTRANE QUARTET disc in the Speaker Corner edition, and ended with the re-edition of the DIRE STRAITS Brothers in Arms album from Mobile Fidelity. These are two different worlds of music and sound, and yet in both cases the change of loading of the Shelter cartridge, despite the fact that it did not comply with the manufacturer's recommendation, allowed for a nicer, simply better sound. Although it loses a bit of the bass attack and its compactness, I had no problem with that, because the advantages significantly outweighed the disadvantages of this solution.


IT IS AMAZING how MUCH we already know about sound, and at the same time how little we understand about it. A device like the AFE-11 is an insult to any sane person - yet it works. I would compare its impact to plugging a rather warm sounding tubes into the system. I don't even mean the timbre, but the way the sound is presented.

With the Aurorasound converter it was a bit more "present" and tangible. These two features are usually associated with an LP record and it is probably no coincidence that this is the effect I achieved. After all, Mr. SHINOBU KARAKI is a fan of the analog sound and if he offered something new, it had to meet HIS expectations. And these, as you can hear, go towards generally understood musicality - and by 'musicality' I understand fluidity and sonority, i.e. "flow".

The very dynamic and resonant album Midnight Sugar by TSUYOSHI YAMAMOTO sounded phenomenally pleasantly. I say "phenomenal" because I am used to the extraordinary sound of this album, in the Gold HDCD version from Impex Records, and yet the small Aurorasound box pushed everything I appreciate about it, and most of all the naturalness of the sound a bit forward.

I have a hard time saying it, because it sounds a bit like a flat stereotype, but the AFE-11 makes the sound more - I would really prefer not to say that - analogue. Even from such an analog sounding source as the Ayon Audio CD-35 HF Edition. Only that in the case of the Aurorasound device it is about analog vinyl, not analog tape.

The thing is that AFE-11 boosts the midrange and slightly modifies its treble towards sweetness. The bass is low, deep, but not as well controlled as from the player. Both these elements - high and low tones - are simply amazing in my RCM Audio preamplifier and the last thing I could say about them is - respectively - "sweet" and "soft". And in combination with the Japanese converter, that's what it sounded like.

However, you need to remember that we have included other components in the audio signal track, and we usually try to eliminate them. Therefore, with the AFE-11 the sound is less resolving and less differentiated. It just always sounds warmer, denser and more "sweet". It is also always more tangible and closer to us. The back of the stage is flattening, it is not that deep anymore, although this particular element is not very noticeable because we are busy with a multitude of events in the foreground.


At first glance, both AFE series devices are redundant products - the audio system can do without them. It's just that they really correct the sound nicely, positively influencing many of its aspects. I would see their use in basic, and above all, mid-priced systems. There they will show the advantages I mentioned, and their weaknesses will not be exposed. In top systems we will get not necessarily better, but definitely a different sound, so maybe it is worth trying them there as well.

Their advantages include great fluidity and "musicality" - this applies to both the MM cartridge expander and the RIAA converter. Both bring calmness and density to the equation at the expense of resolution and differentiation. If you are looking for the former, and the latter ones are not at the top of your wish list, it may turn out that this is the smallest change in your systems that will bring the greatest sound improvement without the need to replace any of the components. Interesting, isn't it?


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