AIYIMA T20 Tube Pre-amplifier Review

[SMen]

Easily explained. From Amir's measurements, harmonics marked by me:

View attachment 497607

3rd harmonic (odd) is louder than the 2nd (even). Ideally for "tube sound", that is "pleasant" distortion, you'd want the 2nd be louder and the 3rd be lower. And then an evenly decaying spectrum above that. This here doesn't do that. Even the remaining spikes are 5th, 7th, and 9th harmonics. All odd. Meh. Why have tubes when the whole thing doesn't even show typical tube distortion?

Then, actual audibility: even the highest spike, the 3rd harmonic, is so low in level (-80dB), it will be inaudible in all but very high playback levels, and then it gets easily masked by everything else: speakers, room, ears.

So, you get exactly nothing from this device that resembles "tube sound". Neither is the distortion spectrum the "right" type, nor is it high enough to be relevant for listening. It's a nothingburger.

Compare to "proper" tube distortion View attachment 497609
From this thread https://www.audiosciencereview.com/...-world-tube-preamplifier-about-2-7-thd.18392/

That's what you'll want for "real tube sound". The difference should be easy to see. A nicely decaying spectrum with 2nd dominating, high enough to be barely audible. Overdrive it a little bit, and it becomes obvious.

Excellent thank you!

And also an excellent thread you link to .... I can delve into this further.

I'm not really seeking a 'real tube sound', and in use the T20 simply works well - surprised me.

If I take the second harmonic, there is a big jump from -98 approx (2) in the first, to the -44 approx. on your second graphic ...



So in the context of the T20 I've been wondering what all the fuss has been about when I looked back to Amir's review.

Hi.

Bravo and thank you Ropeburn: You have been able to summarize my remarks in a concise way that is much more understandable to all

All I want to say is that this device does meet expectations regarding a certain aesthetic, but absolutely not the expectations that is required of a device that would correctly reproduce the 'sound' of a tube device worthy of the name with a circuit designed in 'the rules of the art' and the 'technical constraints' from which it stems.

That said, at the price at which it is offered, only a well-designed software (provided that it is well understood and used) will be able to give a user the correct and expected results to simulate listening to a lamp device, but of course you will not have made any visual and aesthetic changes to your installation

Finally, the important thing is that this device pleases its user, that it has very correct measurements despite the use of tubes as Amirm has pointed out so well, although it does not technically bring the characteristics that this device should offer to the listener, i.e. a 'typical tube sound'

Yes - I think the goal of the product itself needs to be taken into account when judging the product. You have pointed to different circuits.

Would certain valve choices tend to favor higher second harmonic vs 3rd ... or is this completely constrained by the circuit used in the T20? Just to get some perspective.


Still, plugging the T20 peak levels in I get:
Relative harmonic levels

• H2 (2 kHz at −98 dBc): ≈ 0.0013% distortion
• H3 (3 kHz at −82 dBc): ≈ 0.0079% distortion
• H5 (5 kHz at −110 dBc): ≈ 0.00032% distortion
• H6 (6 kHz at −102 dBc): ≈ 0.00079% distortion
• Total THD: ≈ 0.0086% (dominated by H3)

And I understand harmonic distortion below ~0.1% is generally inaudible in music playback ... so even if a valve swap changed to THD dominated by H2 theoretically) ... none of this would be audible anyway at these levels.
I don't think I would try and convince the tube rollers of this! Fun

 

[ICIETDIYEUR]

Well.

If we take your reasoning, which is correct, then what I said during my first speech is just as well founded:
it's totally useless to have included 'valves' in the circuits of a device that probably works very well, knowing that they do not bring the expected results (production of audible even-numbered harmonics) but on the contrary necessarily degrade the measurements (technical characteristics of 'valves' VS OP AMPS) and that it would therefore have been better to delete them

This does not prevent my remarks about the valves as well as their qualities (or not) respectively from not being relevant, for example of the tubes dedicated to audio as well as those that are not and the sound reproduction characteristics of the latter.

A concrete and very simple example is that valves that do not have an anti-microphonic device will necessarily induce more distortion than those designed to combat this phenomenon

As for the 'sound colouring' of certain valves compared to others, it is not a question of 'magic' but of science thanks to the use of well-chosen shapes, materials, characteristics (and others) to obtain this desired 'famous colouring', just like a cook who will embellish a dish with different ingredients...

In the end, the result obtained with the dish will be comparable to what you will get from a sound reproduction device: it is a matter of taste, very personal and subjective

 

[gwing]

Would certain valve choices tend to favor higher second harmonic vs 3rd ... or is this completely constrained by the circuit used in the T20? Just to get some perspective.

This is essentially going to be controlled by the amplifier design not the particular valve used. A well designed valve amp is likely to be operating its valves in their linear region so as to minimize distortion so if you swap to an unsuitable alternative valve with different characteristics you may take it out of its linear response zone resulting in substantially increased and unpredictable distortions but from your posts I don't think this is what you are looking for. I'd stay with the standard valves unless you can find compatible but prettier ones.

The specific balance between second and third harmonics is mainly going to be determined by the circuit and transformer design choices which can result in third harmonic distortion being completely/largely cancelled out in the transformer thus creating a large/infinite change in the ratios of 2nd and 3rd harmonic distortion.

I haven't seen the circuit design for the T20 but I suspect it doesn't even have an output transformer, and given that it is such a low distortion device in the first place any change you might make to the balance between 2nd/3rd harmonics isn't likely to be audible anyway. I did note that the pre-amp listening test mentioned in the posts above was for an amp with 2% distortion, given that I once owned Leak amplifiers that were built in the 1940s and achieved 0.1% distortion even back then, 2% is a very low bar.

 

[SMen]

This is essentially going to be controlled by the amplifier design not the particular valve used. A well designed valve amp is likely to be operating its valves in their linear region so as to minimize distortion so if you swap to an unsuitable alternative valve with different characteristics you may take it out of its linear response zone resulting in substantially increased and unpredictable distortions but from your posts I don't think this is what you are looking for. I'd stay with the standard valves unless you can find compatible but prettier ones.

The specific balance between second and third harmonics is mainly going to be determined by the circuit and transformer design choices which can result in third harmonic distortion being completely/largely cancelled out in the transformer thus creating a large/infinite change in the ratios of 2nd and 3rd harmonic distortion.

I haven't seen the circuit design for the T20 but I suspect it doesn't even have an output transformer, and given that it is such a low distortion device in the first place any change you might make to the balance between 2nd/3rd harmonics isn't likely to be audible anyway. I did note that the pre-amp listening test mentioned in the posts above was for an amp with 2% distortion, given that I once owned Leak amplifiers that were built in the 1940s and achieved 0.1% distortion even back then, 2% is a very low bar.

Very interesting about the Leak amplifiers achieving 0.1% distortion. I'm using the directly compatible 12AX7 Tung-sols in the T20 and they are working fine - the T20 is a hybrid - well out of my comfort zone pre-purchase ... hence my surprise on actually using it!

There were a number of posts that I think were suggesting that the higher distortion might be an objective for valve pre-amps - to have the 2nd harmonic, but this is something I do not understand ... your Leak amplifier comparison rather nails it. I remember reading about Leaks often when growing up though I never owned one.

Regardless of audibility thresholds, and this may simply be due to other circuit design factors, this little T20 gives excellent and solid left, right, and center images - and at all volumes. Very impressed for < 120 GBP delivered!

 

[morejazzplease]

Anyone compare #Aiyima T20 pre amp to #Fosi Zp3 only in sound quality ?

I actually did this last night! Of course, full acknowledgement that these are my personal subjective impressions in my room on my system! That said, I do find value (if not just for entertainment) in reading other people's thoughts on sound, so I am happy to share!

My system:

• (Vinyl): Technics SL-1800 Mk1 W/ AT VM740xML cartridge > Hegel V10 Phono Stage > [PREAMP] > Schiit Wotan Power Amp > Wharfedale Linton 85th
• (Digital): CD/TV/Steaming into WiiM Ultra > Fosi ZD3 DAC > [PREAMP] > Schiit Wotan Power Amp > Wharfedale Linton 85th

Before getting the Aiyima T20 for $135, I was using a Fosi ZP3 as the Preamp in my system. I had many issues with the ZP3 to be honest! I returned two of them because the tone control circuit caused audible-from-the-listening-position tweeter hiss when enabled. Unfortunately, when bypassed, it also disabled the ZP3's HPF function too which is one of the main reasons I bought it in the first place! I eventually accepted this fault and just kept the tone control bypassed. It is pretty much silent in my system when bypassed.

My Aiyima T20 has new production Tung-Sol 12AX7 tubes in it. They have been breaking in for the last few weeks and seem to have settled down. They did have a noticeable impact to the sound signature of the preamp over the stock PSVANE tubes. That difference is perceived as being better or more pleasing to my ears!

Comparison between Aiyima T20 and Fosi Audio ZP3:

Last night I did some A/B swapping between the two preamps in my system. Before I get attacked, I make no claim that this was scientific, perfectly level matched, double blind experimentation! I had to swap the input cables and the output cables between the two, so take that as you will. My wife and I were shocked how much of a difference there was between the two. Because we have been listening to the T20 for weeks, this was our "control" preamp. Swapping to the ZP3 made the digital side of our system sound rather two dimensional with far less bottom end impact but also sounded a bit more detailed to us. My wife described the ZP3 as sounding more detailed but like a "wall of sound" rather than "being in the sound" like the T20 feels to her. I mainly noticed the difference in the highs and lows. The highs felt sharper and extended more than the T20, but also sounded sibilant to me at times when the volume was higher. The low end felt really anemic to be honest! It was probably the most impactful / obvious impression to me as soon as we switched to the ZP3. Call the T20 an "effects box" if you want, but it certainly makes digital audio sound more pleasing to us on our system compared to the ZP3.

Listening to our vinyl system through each preamp was interesting! I actually felt like there was less of an obvious difference between the two compared to the perceived differences on the digital side of things. We both still felt like the low end was significantly stronger and more pleasing on the T20! The highs were not as much of a difference between the two preamps listening to vinyl that they were on digital. I will say that the sound of vocals on the T20 are stunning! They sound clearer to me in the mixes, felt more forward in the sound stage and have a textured tone that just sounds so good to me! Wood instruments have more of a full bodied "woody" texture to them too. Brushes on a snare drum sound life-like. Again, we both preferred what the T20 brought to our system when listening to our vinyl signal chain.

If I had to focus down my impressions, I would say the ZP3 is fine, probably more analytical and likely more "true-to-source". However, the T20 just sounds more full-bodied, with a pleasing soundstage, better low end, and a midrange tone that just makes the music I listen to incredibly pleasing (60s-70s Psych rock & Jazz). If those qualities of the T20 are due to distortion and technical flaws compared to the ZP3, so be it! I care about measurements only up to the point of confirming devices are not deeply flawed technically. Beyond that, I only care about how I feel when I listen to my system (even if its psychoacoustic). My stereo system is for my wife and I, and I don't feel any need to justify our system choices to anyone else. I get pleasure from listening to music on our system and if a new piece of gear increases that pleasure for any reason, then I'm happy. Our listening tests last night confirmed to us that we are more happy with the T20 in the system than the ZP3!

At least the T20 does what it is designed to do without any obvious flaws that detract from listening enjoyment and usability! The fact that all three ZP3s I tried exhibited hissing when the tone control circuit was enabled (audible from the listening position) frustrates me. The fact that bypassing the tone controls also renders the HPF function unusable frustrates me as well. Those flaws render the main functionality features that differentiate the ZP3 from other products in its price range unusable. Combine all that that with the idiotic (though mostly not an issue) volume control implementation and I feel strongly that the ZP3 is a deeply flawed product which should be avoided.

My only complaints about the T20 are that the blue LED is crazy bright and I do not like the massive and bright volume numbers / screen. Thankfully, the remote has a "lights off" button (but they turn back on if you adjust the volume). A bit of dimming tape over the LED fixed that issue! Overall, I am happy with it for $135 lmao. Insanely fun and it has increased our enjoyment of our system! Your mileage may vary.

 

[SMen]

If I had to focus down my impressions, I would say the ZP3 is fine, probably more analytical and likely more "true-to-source". However, the T20 just sounds more full-bodied, with a pleasing soundstage, better low end, and a midrange tone that just makes the music I listen to incredibly pleasing (60s-70s Psych rock & Jazz). If those qualities of the T20 are due to distortion and technical flaws compared to the ZP3, so be it! I care about measurements only up to the point of confirming devices are not deeply flawed technically. Beyond that, I only care about how I feel when I listen to my system (even if its psychoacoustic). My stereo system is for my wife and I, and I don't feel any need to justify our system choices to anyone else. I get pleasure from listening to music on our system and if a new piece of gear increases that pleasure for any reason, then I'm happy. Our listening tests last night confirmed to us that we are more happy with the T20 in the system than the ZP3!

I am using the same valves as you, and I have the same impressions ... great to read yours. Bit of a relief really. I'm not far off your tastes in sources either!

I think by default measurements are at full volume, and with tone controls out of circuit - these would need to be measured separately if in circuit.

As I've said in previous posts I hear more full bodied vocals, strings etc. and well defined sound stage It works wonders with poor'ish broadcasts, as well as good quality sources. Nice system!


Post edit: I'm all for listening bias being attributed to all kinds of products such as cables, or dacs, power sockets etc. but when I swap the T20 for my direct dac or high quality passive attenuator I most certainly hear fuller body. However swapping my DAC with volume control to my passive ladder and I had might as well be swapping cables (or dacs, or power sockets etc)

 

[ICIETDIYEUR]

Hi.

Some more informations about this device ->

It will be noticed that the tubes are used as a 'buffer' (without gain) just with the digital volume control chip and that the output signal goes through simple OP AMPS with link capacitors and then 'mechanical' relays: replacing the tubes will have almost NO impact on the sound reproduction with the circuit used for this device (I had said that without the tubes the device would be more efficient and I was therefore right: measurements would come without any problem to confirm what I am saying here, it's just a question of logic related to the technology used).

To conclude, a DAC at ~200 euros (TOPPING D50 III, SMSL DO100 PRO, FOZI ZD3) already does just that... only better

And, for about the same price with an O-NOORUS D4 pro or D3 pro you will even get the extra amp, again with the D4 for only half the price !!!

Personal opinion: if I found the aesthetics of this device to my liking, it would be powered and powered on to 'look pretty' next to the elements of my system BUT it would not be connected to them

Have a nice day

 

[Tontom]

"Im Aiyima T20 (Modell 2025) fungieren die beiden 12AX7 (ECC83)-Röhren als zentrale Spannungsverstärkungsstufen innerhalb der Vorverstärkerschaltung.
Im Gegensatz zu billigeren „Hybrid“-Geräten, bei denen Röhren oft nur als dekorativer Puffer ohne nennenswerte Spannung fungieren, übernimmt die Röhre im T20 eine aktive Rolle:
Echte Anodenverstärkung: Die Schaltung verwendet ein internes Netzteil, das die Spannung für die Röhren auf 180 V erhöht. Dadurch kann die 12AX7 in ihrem idealen Kennbereich arbeiten und das Signal tatsächlich verstärken.
Klanggestaltung: Die Röhren fügen dem Signal die typischen harmonischen Verzerrungen (Obertöne) hinzu, was für einen wärmeren, räumlicheren und „analogen“ Klang sorgt.
Vollständig symmetrisches Design: Jede der beiden Röhren (Doppeltrioden) verarbeitet einen Kanal der vollständig symmetrischen Signalkette im T20.
Interaktion mit Operationsverstärkern: Die Röhren arbeiten mit Operationsverstärkern (wie dem OPA1612 oder LME49720) zusammen. Während die Röhren für den Klangcharakter und die Primärspannungsverstärkung verantwortlich sind, gewährleisten die Operationsverstärker eine stabile Impedanzwandlung und geringes Rauschen am Ausgang. "
(Google KI)

Einen schönen Tag noch

 

[Ropeburn]

"Im Aiyima T20 (Modell 2025) fungieren die beiden 12AX7 (ECC83)-Röhren als zentrale Spannungsverstärkungsstufen innerhalb der Vorverstärkerschaltung.
Im Gegensatz zu billigeren „Hybrid“-Geräten, bei denen Röhren oft nur als dekorativer Puffer ohne nennenswerte Spannung fungieren, übernimmt die Röhre im T20 eine aktive Rolle:
Echte Anodenverstärkung: Die Schaltung verwendet ein internes Netzteil, das die Spannung für die Röhren auf 180 V erhöht. Dadurch kann die 12AX7 in ihrem idealen Kennbereich arbeiten und das Signal tatsächlich verstärken.
Klanggestaltung: Die Röhren fügen dem Signal die typischen harmonischen Verzerrungen (Obertöne) hinzu, was für einen wärmeren, räumlicheren und „analogen“ Klang sorgt.
Vollständig symmetrisches Design: Jede der beiden Röhren (Doppeltrioden) verarbeitet einen Kanal der vollständig symmetrischen Signalkette im T20.
Interaktion mit Operationsverstärkern: Die Röhren arbeiten mit Operationsverstärkern (wie dem OPA1612 oder LME49720) zusammen. Während die Röhren für den Klangcharakter und die Primärspannungsverstärkung verantwortlich sind, gewährleisten die Operationsverstärker eine stabile Impedanzwandlung und geringes Rauschen am Ausgang. "
(Google KI)

Einen schönen Tag noch

And the AI knows this how? Why does the device show typical transistor distortion?

 

[Tontom]

Ask GOOGLE

 

[Ropeburn]

Ask GOOGLE

No. You posted this mockup writing without source. You ask it.

 

[Mort]

Ask GOOGLE

I can see you won't last long.

 

[Tontom]

No. You posted this mockup writing without source. You ask it.

Source is Google Ki as I wrote !!!

 

[Ropeburn]

Source is Google Ki as I wrote !!!

That's the problem. That isn't a source, let alone a reliable one. The sooner you understand that, the better. No need to get condescending like somehow I'm the idiot here.

 

[Tontom]

I can see you won't last long.

Oh, I've already lasted 64 years, and you?

 

[KL....]

"Im Aiyima T20 (Modell 2025) fungieren die beiden 12AX7 (ECC83)-Röhren als zentrale Spannungsverstärkungsstufen innerhalb der Vorverstärkerschaltung.
Im Gegensatz zu billigeren „Hybrid“-Geräten, bei denen Röhren oft nur als dekorativer Puffer ohne nennenswerte Spannung fungieren, übernimmt die Röhre im T20 eine aktive Rolle:
Echte Anodenverstärkung: Die Schaltung verwendet ein internes Netzteil, das die Spannung für die Röhren auf 180 V erhöht. Dadurch kann die 12AX7 in ihrem idealen Kennbereich arbeiten und das Signal tatsächlich verstärken.
Klanggestaltung: Die Röhren fügen dem Signal die typischen harmonischen Verzerrungen (Obertöne) hinzu, was für einen wärmeren, räumlicheren und „analogen“ Klang sorgt.
Vollständig symmetrisches Design: Jede der beiden Röhren (Doppeltrioden) verarbeitet einen Kanal der vollständig symmetrischen Signalkette im T20.
Interaktion mit Operationsverstärkern: Die Röhren arbeiten mit Operationsverstärkern (wie dem OPA1612 oder LME49720) zusammen. Während die Röhren für den Klangcharakter und die Primärspannungsverstärkung verantwortlich sind, gewährleisten die Operationsverstärker eine stabile Impedanzwandlung und geringes Rauschen am Ausgang. "
(Google KI)

Einen schönen Tag noch

"In the Aiyima T20 (model 2025), the two 12AX7 (ECC83) tubes function as the central voltage amplification stages within the preamplifier circuit. Unlike cheaper "hybrid" devices, where tubes often only serve as a decorative buffer without any significant voltage, the tube in the T20 takes on an active role: True anode amplification: The circuit uses an internal power supply that boosts the voltage for the tubes to 180 V." This allows the 12AX7 to operate within its ideal operating range and actually amplify the signal. Sound shaping: The tubes add the typical harmonic distortion (overtones) to the signal, resulting in a warmer, more spacious, and "analog" sound. Fully symmetrical design: Each of the two tubes (dual triodes) processes one channel of the fully symmetrical signal chain in the T20. Interaction with operational amplifiers: The tubes work in conjunction with operational amplifiers (such as the OPA1612 or LME49720). While the tubes are responsible for the tonal character and primary voltage gain, the operational amplifiers ensure stable impedance matching and low noise at the output. (Google Ki) Have a nice day!

 

[Tontom]

Oh, I'm sorry, I forgot the translation. (I'm a bit older.)
Greetings from Germany

 

[SMen]

Hi.


It will be noticed that the tubes are used as a 'buffer' (without gain) just with the digital volume control chip and that the output signal goes through simple OP AMPS with link capacitors and then 'mechanical' relays: replacing the tubes will have almost NO impact on the sound reproduction with the circuit used for this device (I had said that without the tubes the device would be more efficient and I was therefore right: measurements would come without any problem to confirm what I am saying here, it's just a question of logic related to the technology used).

I am really not sure that "it will be noticed that the tubes are used as a 'buffer' (without gain) " is enough, along with a photo.

There are compatible valve variants that when swapped in result in significantly lower output. Surely that would not happen in a buffer circuit?

Are we supposed to see from this image that this is a Cathode Follower circuit?

I've looked back and did track this down from Aiyima:
Our T20 preamplifier circuit includes a transformer design that allows the ECC83 (12AX7) tube to reach a maximum operating voltage of 180V. The tube uses anode amplification and works together with the subsequent op-amp stage to amplify the signal. Therefore, it is not just a decorative light, but an important component that actively participates in the sound amplification.


From what I have been able to glean a simple common‑cathode gain stage seems the most likely.

• This has High output impedance
• Needs an op‑amp or transistor follower afterwards - these give a low impedance output.

Generally the first question, or the first observation of units such as these by a reviewer, especially here on ASR, would be to stipulate "the valves are used as a buffer", but Aiyima have stated the exact opposite, and it certainly was reviewed as far as I can tell as a genuine balanced pre-amplifier using tubes for gain, along with op amps which provide the low impedance output.

 

[ICIETDIYEUR]

Smen, you play with words and especially the meaning of a rather simple explanation:

how do you (especially at this noise level) want to hear a difference that could be audible (even harmonics, 'H2' especially, for example) if the signal thus reproduced passes right after AMPS OPs which also have their own characteristics (including distortion, so the harmonics) then go back through link capacitors (which also have characteristics) to go through mechanical relays with 'flexible blades' and finally exit through sockets that will allow thanks to link cables (let's hope they are of quality) to finally enter an amplifier which also has, It goes without saying, its own characteristics ?

Decades ago we had bass and treble control knobs (sometimes also midrange) that obviously allowed you to modify the final sound in terms of sound reproduction.

Maybe the video in my previous post didn't convince you ?

However, she is an expert in tube amplification and a specialist in this technology, who has seen thousands of devices pass through her hands and created them as well.

I doubt VERY much that she is telling 'salads' since she is based on the science she has mastered and practiced for many years:

AIYIMA will certainly not be able to boast of having the same level of knowledge and even less the necessary hindsight to do the same, except perhaps in her advertisements for music enthusiasts who are nevertheless novices in technique, Sorry to say it, whether you like it or not.

 

[SMen]

Smen, you play with words and especially the meaning of a rather simple explanation:

how do you (especially at this noise level) want to hear a difference that could be audible (even harmonics, 'H2' especially, for example) if the signal thus reproduced passes right after AMPS OPs which also have their own characteristics (including distortion, so the harmonics) then go back through link capacitors (which also have characteristics) to go through mechanical relays with 'flexible blades' and finally exit through sockets that will allow thanks to link cables (let's hope they are of quality) to finally enter an amplifier which also has, It goes without saying, its own characteristics ?

Decades ago we had bass and treble control knobs (sometimes also midrange) that obviously allowed you to modify the final sound in terms of sound reproduction.

Maybe the video in my previous post didn't convince you ?

However, she is an expert in tube amplification and a specialist in this technology, who has seen thousands of devices pass through her hands and created them as well.

I doubt VERY much that she is telling 'salads' since she is based on the science she has mastered and practiced for many years:

AIYIMA will certainly not be able to boast of having the same level of knowledge and even less the necessary hindsight to do the same, except perhaps in her advertisements for music enthusiasts who are nevertheless novices in technique, Sorry to say it, whether you like it or not.

The video presenter says we should read Amir's review for the objective information on page 1 of this thread, and the presenter clearly states that this is her subjective review. She recommends using the T20 with Fosi V4 monos as a use case.

There is nothing here about the valves being used as buffers in the circuit. The interesting aspect of this T20 product is that it measures well and uses valves for gain in a balanced circuit.

It is not using a digital volume control: the NJW1195 is an analog volume control IC with digital control for setting it's level. Channels are extremely well balanced (see page 1).

The T20 well built, tremendous value, and fun. There's just too much nonsense .