AIYIMA T20 Tube Pre-amplifier Review

[ICIETDIYEUR]

Hello.

The type of setup you describe is an RC coupled circuit: the circuit is indeed very simple with only one triode per tube BUT you get a high output impedance, a medium distortion rate and a passable bandwidth.

I doubt that this is the goal sought in a so-called 'Hi-Fi' installation...

On the other hand, if it is an SRPP setup: you are indeed using two triodes per tube BUT the output level is high and without saturation, the output impedance is low, the frequency response is 'very good' with perfect linearity (you can get from 9Hz to 500 KHz) and the input impedance is high.

It seems to me that this second case is much more clearly in line with the objective sought for a 'Hi-Fi' installation

Illustration SRPP diagram ->

All that remains is to feed the tube properly but that's another matter...

Otherwise you will only have obtained nice lighting effects but there are dedicated devices for this

When I look at the size, the vents of the case as well as the power transformer, it seems to me that Fiio used at least the 'right ingredients' to achieve this, however I don't know the diagram, or even the device in real life ->

 

[SMen]

Hello.

The type of setup you describe is an RC coupled circuit: the circuit is indeed very simple with only one triode per tube BUT you get a high output impedance, a medium distortion rate and a passable bandwidth.

I doubt that this is the goal sought in a so-called 'Hi-Fi' installation...

On the other hand, if it is an SRPP setup: you are indeed using two triodes per tube BUT the output level is high and without saturation, the output impedance is low, the frequency response is 'very good' with perfect linearity (you can get from 9Hz to 500 KHz) and the input impedance is high.

It seems to me that this second case is much more clearly in line with the objective sought for a 'Hi-Fi' installation

Illustration SRPP diagram ->

View attachment 495449

All that remains is to feed the tube properly but that's another matter...

Otherwise you will only have obtained nice lighting effects but there are dedicated devices for this

When I look at the size, the vents of the case as well as the power transformer, it seems to me that Fiio used at least the 'right ingredients' to achieve this, however I don't know the diagram, or even the device in real life ->

View attachment 495450


View attachment 495451

It all seems very speculative!
But I think it is important to note that the T20 is balanced in operation ... and measures pretty well.

I was surprised by this review of the T20. Somehow I doubt the FiiO Warmer will review so well if it shows up here on ASR!

Still, FiiO's founder seems to be an enthusiast, so we can expect some more interesting products from this company ... in fact all these companies seem to be competing in interesting directions for enthusiasts of all persuasions.

 

[Jon L]

I was surprised by this review of the T20. Somehow I doubt the FiiO Warmer will review so well if it shows up here on ASR!

I'd be interested in seeing Fiio Warmer R2R DAC measurements, especially if measurements correlate with user comments regarding treble not being quite all there..

 

[KL....]

whether the assembly is SRPP or SEPP does not matter

Thank you, @ICIETDIYEUR, you seem very confident that the T20 is SEPP and not Cathode Follower? If ok, please (further) clarify your confidence?

Perhaps it is the SEPP/SRPP Gain, Current followers, Canceling even-order Harmonics/reducing Distortion, and is a Line/Driver stage, although a Cathode Follower has very low Output Impedance and SRPP/SEPP are considered as sophisticated variations of the Cathode Follower principle, reasonable, but please (further) clarify your confidence?

 

[ICIETDIYEUR]

People hi

For those who don't know, haven't understood (or are 'pretending' not to understand), I want to show you a 'schematic diagram' that allows you to better see what I define as a DAC with a fully balanced output audio circuit.

In the small synoptic that follows, it includes a pre-amplification section (the most accurate would actually be to say that it is an attenuator) ->

▶︎ At point '1' (DAC chip) the symmetrical signals obtained for each channel are:
- for the right, by the pin 'DAC1' for the +, the pin 'DAC1B' for the - and the pin 'AGND_DAC1' for the audio ground.
-for the left, by the pin 'DAC2' for the +, the pin 'DAC2B' for the - and the pin 'AGND_DAC2' for the audio ground.
At this level, the symmetric signals obtained are current (intensity) signals.

▶︎ At point '2' (with OP AMPS for this example): a 'transimpedance' (I/V) circuit mounting converts balanced signals into voltage, while adjusting the latter for the 'needs' of the circuit.
At this level the circuit is still 'full balanced'.

▶︎ At point '3': an LPF (Low Pass Frequency) circuit limits the high-frequency bandwidth, often to the 'aliasing frequency' determined by the Nyquist frequency, which is equivalent to half the sampling frequency.
This prevents the OP AMPS from being 'worked' for nothing, but above all it prevents unwanted signals from sampling from remaining in the audible band.
At this level the circuit is still 'full balanced'.

▶︎ At point '4': A four-channel 'volume chip' (stereo balanced signals) NJW1195A is inserted into the circuit as an attenuator for volume control.
For a maximum volume (the highest level of your settings), its resistance is almost zero and it is increased to its maximum to decrease the volume (the lowest level of your settings).
At this level the circuit is still 'full balanced'.

▶︎ At point '5': one buffer per OP AMPS output is added to refine the linearity (make 'transparent') of the signals.
This buffer is not always used (or sometimes necessary) and is most often found on devices where the audio circuit has been more careful in its design, such as in 'higher range' devices.
At this level the circuit is still 'full balanced'.

▶︎ At point '6': micro relays or 'chips' with the same functionality are inserted just before the output connectors in order to prevent different 'POP' noises during the various circuit switches for the needs of the device and its use. They will protect your ears from unpleasant and unwanted noises but will also protect the devices connected to its output as well as itself.
At this level the circuit is still 'full balanced'.

So as you can see, from the DAC chip to the output via the connectors, the signals remained fully balanced and did not undergo a 'transformation' to 'simulate' a balanced signal from a single end SE signal as is often the case with many devices.

What is the point of using DAC chips with excellent characteristics if this is not the case for the audio circuit?...

-----------

NB: Seriously KL... no matter the type of assembly of the tubes of this device: can we talk about a 'serious' tube circuit when the device and all its circuits are powered from a single 12V/2A mini transformer...

By the way, I would be curious to know the temperature of this transformer after 2 hours of listening!
A single 2AX7 with its heaters in series (requires 12.6V) consumes 0.15A. In parallel (requires 6.3V) consumes 0.3A. I'm not talking about the rest of the circuit but it seems that the proposed transformer is 'sized' too little or not enough...

Moreover, if the tubes do not have their 'heaters' carefully powered (see Francis IBRE's book 'bien entendu' for perfect understanding): I don't give much as to their lifespan, it will make the dealers happy

 

[ICIETDIYEUR]

People hi

Some videos on the Fiio WARMER R2R DAC ->

NB: It will have been noted that the temperature measured above the closed case (although 'ventilated' naturally) is 52°C.
What about tubes without any protection that can be accessed directly (by a child for example) with the T20?

 

[SMen]

People hi

Some videos on the Fiio WARMER R2R DAC ->

Just saying this is the wrong thread!

 

[ICIETDIYEUR]

Measuring the temperature of the tubes without any protection of the AIYIMA T20 is not the right topic?

 

[morejazzplease]

Measuring the temperature of the tubes without any protection of the AIYIMA T20 is not the right topic?

You are filling this thread with posts, diagrams and now links related to an entirely different product in an entirely different category! Personally, I don't see how your opinion on DAC circuits that are fully balanced has anything to do with the preamp that this thread is based upon. You keep speculating things about different products you don't seem to actually own and then posting rambling follow up posts that relate to your speculations. It is not on topic and contributes nothing to the conversation regarding the Aiyima T20.

You are clearly intelligent, but read the room.

 

[mhardy6647]

People hi

Some videos on the Fiio WARMER R2R DAC ->

NB: It will have been noted that the temperature measured above the closed case (although 'ventilated' naturally) is 52°C.
What about tubes without any protection that can be accessed directly (by a child for example) with the T20?

Why do they have a couple of 6SN7 twin triodes in this image with a box that uses (four) 12AX7 twin triodes? They're quite similar in performance, but not exactly interchangeable.

 

[Ropeburn]

View attachment 496245
Why do they have a couple of 6SN7 twin triodes in this image with a box that uses (four) 12AX7 twin triodes? They're quite similar in performance, but not exactly interchangeable.

Serving suggestion

 

[ICIETDIYEUR]

People hi

The Fioo WARMER originally uses JJ brand E88CCs.

However, these are not initially intended for audio at all because they have too much "dispersion"

Their equally bad replacements carry the references 6DJ8, ECC88, 6922, whatever the brand (even 'GOLD LION ).

The only completely compatible tubes are professional models which have anti-microphonic construction and are therefore the best for audio reproduction

However, the references used (E188CC, 7308) are no longer manufactured or are only available in the 'NOS' version and available at very high prices (often more expensive than the device and there are 4 of them !)

The only comparable alternative with the same qualities are the original Russian military tubes bearing the reference 6N23P-EV (I emphasize the final term 'EV' for their reference, otherwise it has nothing to do with it)...

...we can still find 'QUAD' (4 'matched' tubes) on well-known resale sites for around 100 euros for the 4 tubes

Have a nice day

 

[Noske]

You are filling this thread with posts, diagrams and now links related to an entirely different product in an entirely different category! Personally, I don't see how your opinion on DAC circuits that are fully balanced has anything to do with the preamp that this thread is based upon. You keep speculating things about different products you don't seem to actually own and then posting rambling follow up posts that relate to your speculations. It is not on topic and contributes nothing to the conversation regarding the Aiyima T20.

It won't stop.

The Aiyima T20 has tubes so let's talk about something to do with tubes.

Sloshing all manner of tube types together. Just because.

Something's fishy.

Which is a shame because I was enjoying some erudite comments about the T20.

 

[ICIETDIYEUR]

Hi

Coming back to the AIYIMA T20 and its original tubes (JJ brand ECC83), you can get better results by replacing them with 'NOS' tubes: TESLA brand E83CC , TELEFUNKEN brand ECC803S or GENERAL ELECTRIC brand 5751.

Concerning the latter two references (ECC803S and 5751) in particular, they still exist in current manufacturing tubes by the JJ brand.

-> The ECC803S features a spiral-wound filament to reduce noise as well as longer plates that improve the accuracy of the bass and low mids.

-> The 5751 has a 30% reduction in gain, ideal for mastering the distortion and shorter plates that improve harmonic richness, more accurate mids and warmer highs.

This will allow you to tailor the tubes according to their characteristics according to the components of your system and your listening preferences

I hope I have said less nonsense this time, or rather that the terms I would have used will be easier to match the device in the thread (AIYIMA T20) for people who do not have the technical knowledge to make the link with the subject, which I can understand well and take the opportunity to apologize to them while clarifying my words a little more or ' interventions'.

 

[Mort]

for people who do not have the technical knowledge to make the link with the subject,

You show amazing inability for self reflection. I didn't think the issue was our collective technical knowledge.

 

[Ropeburn]

Hi

Coming back to the AIYIMA T20 and its original tubes (JJ brand ECC83), you can get better results by replacing them with 'NOS' tubes: TESLA brand E83CC , TELEFUNKEN brand ECC803S or GENERAL ELECTRIC brand 5751.

Concerning the latter two references (ECC803S and 5751) in particular, they still exist in current manufacturing tubes by the JJ brand.

-> The ECC803S features a spiral-wound filament to reduce noise as well as longer plates that improve the accuracy of the bass and low mids.

-> The 5751 has a 30% reduction in gain, ideal for mastering the distortion and shorter plates that improve harmonic richness, more accurate mids and warmer highs.

This will allow you to tailor the tubes according to their characteristics according to the components of your system and your listening preferences

I hope I have said less nonsense this time, or rather that the terms I would have used will be easier to match the device in the thread (AIYIMA T20) for people who do not have the technical knowledge to make the link with the subject, which I can understand well and take the opportunity to apologize to them while clarifying my words a little more or ' interventions'.

I have a feeling NOS tubes are better suited for NOS DACs.

 

[ICIETDIYEUR]

Knowledge is knowledge: it all depends on what you do with it or not...
... A point of view or a 'positioning' is quite different: it is an attitude and not a fact.

I only present facts in my 'interventions'., I do not take a position: you can check it if you really want to.

 

[Ropeburn]

Knowledge is knowledge: it all depends on what you do with it or not...
... A point of view or a 'positioning' is quite different: it is an attitude and not a fact.

I only present facts in my 'interventions'., I do not take a position: you can check it if you really want to.

The way of presenting knowledge is just as important as the knowledge itself. That includes not only formatting and structuring so it's easy to follow, but also knowing when and where it's appropriate in the first place.

 

[ICIETDIYEUR]

Knowledge is immutable: there is no time or contest to present it, it is there and no one had anything about it, not you?

If the time or the way to present them did not seem appropriate for you, we will not prevent the fact that they exist, right?

 

[Mort]

Knowledge is immutable: there is no time or contest to present it, it is there and no one had anything about it, not you?

English is probably not your first language but knowledge (a justified true belief) absolutely does change. It's not immutable.