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The worlds smallest SET amp, also I believe the only battery powered SET amp commercially available.

A Review On: Analog Squared Paper TU-05b

Analog Squared Paper TU-05b

Rated # 25 in Portable Amps
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Review Details:
Audio Quality
Purchased on:
Price paid: $1,070.00
Posted · 5682 Views · 3 Comments

Pros: Clarity, speed, detail retrieval, musicality

Cons: Not an amp for Bass heads!

Review of the Analog Squared Paper TU-05 transportable Tube amp..

I thought is was time to do a more comprehensive review of this amp as I have now 7 weeks and around 250 hours use of the amp under my belt.

This review will be based upon using non standard tubes. There is nothing wrong with the sound of the stock tubes it comes with. If I had not heard another tube I would have been happy with the sound of the Tung Sol/ Sylvania combination that Shikata San provides with the amp. However they are I have found somewhat microphonic and even with many hours use that never really subsided.

One of the many great things about this amp is the tubes it uses! They were designed for old radio sets both domestic and military and so were made in very large numbers and thus are relatively cheap to buy so you can afford to tube roll to your hearts content (I know I did!) To give you an idea and set of four Mullards tested NOS came to less than $40 including shipping.

More on tube rolling in a little while but first initial impressions of the amp.

Shikata San builds these one at a time and to your individual requirements if necessary but to call this amp a product of a DIY builder earning a few bucks on the side would do a great injustice to both Shikata San and his amps.

I prefer to think of the maker and company as a bespoke audio company crafting beautifully made amps for people who's main motivation is to extract the most from a musical performance.

This is definitely a niche product and will not appeal to many. It is not a bass lovers amp. If you like thumping bass look elsewhere. It is most certainly hand made and all that comes with a hand made product so if your looking for paper thin joints in the case work look elsewhere. Having said that the case is beautifully hand crafted, solid and looks wonderful to my eyes. One thing more about the case. It is something that requires some sort of stabilization so as to prevent it toppling over. I cobbled together with wood a frame to hold it in and to isolate it. (Isolation has become less important with different tubes but if you use the stock ones you will need something like cork or sorbothane under the amp to help with microphonics).

Inside though is where it is at! Everything is beautifully laid out and hard wired. Top quality components are used with note especially to the stepped attenuator which is the best volume pot I have used. Even with sensitive IEM's there is no channel imbalance at low volumes.

Oh yes, this amp does something that I have not seen in any other class A all tube amp and that is drive low impedance headphones, right down to 8 Ohms!

You have to treat this amp somewhat like you would a low powered SET amp in that the headphones you use need to be carefully matched to the amp. This is not a huge issue unless your headphones are rated over 200 Ohms as this amp does not drive headphones with greater than that.

I really encourage you when ordering to tell Shikata San what headphones you use. I did and he ended up giving me an amp with two gain settings, Low (8~32 Ohm) and mid (16~120 Ohm) You can also have the option to replace one of those settings with a High setting (64~200 Ohm).

One of the great reviewers here on Headfi, AnakChan tried a demo amp recently at a HiFi show in Japan but experienced a mis-match with headphones and amp that produced distorted bass. I am looking forward to hearing his thoughts on the amp when he gets a proper review sample and is matched with appropriate headphones

I promise that I will come to what this amp sounds like soon but first I want to talk tubes!

I truly feel that to do this amp full justice one needs to hunt out some higher quality NOS vintage tubes. Over the past few weeks I have gone on a binge of tube buying so as to not only get the desired sound for me but also hopefully to help anyone else lucky enough to purchase this amp get the very best out of it.

Now, if the stock tubes were not microphonic I would find them very enjoyable (BTW it has not only been my amp that had microphonic tubes, another member here experienced the same with his) however there are gains to be had in experimenting.

I dont want to say one tube is better than the other but rather say that differing brands bring slight sonic differences to the table. Want a warmer signature? Then go for Mullards, Want more air and treble? Go for German tubes such as Telefunken or the ultra rare Lorenz Stuttgart made tubes ( I managed to score two of these rare beauties for the Voltage gain/ 1U4 stage and am really glad I did!)

Want something a little sweeter combining the best of those two brands then La Radiotechnique from France might be the answer.

Good all-round worka-day tubes that sound great can be found in RCA's or GE's from the US.

I have found two combinations for me that rise above the rest. An all Mullard set up or, my favourite after much switching, Mullards in the power section (3S4) and the Lorenz's in the voltage gain section (1U4).

The Mullards underpin the music with a firm foundation and a deeper tighter bass while the Lorenz's bring speed, detail and air to the mids and treble. This combination is very far removed from what one thinks of traditional tube euphonic sound which brings me to what it sounds like!

Well, in a word, nothing!
I feel this amp is almost transparent, sure it brings traits to music but none that are not already on the recording in the first place. I feel it conveys music authentically. A guitar sounds like a guitar, a piano sounds like a piano, drums.. Well, you get what I mean! Even electronics such as in Kraftwerk's music sounds like electronics.

I find this amp to retrieve details that are deep within the sonic like no other amp I have heard this side of home amps such as Nagra or Naim to name two I have fairly good experience with. But all that detail retrieval is not at the expense of musicality, this is after all, a tube amp!

The ability of this amp to convey the acoustic a recording is made in, the texture of instruments or vocals is very compelling and draws one into the performance so that track after track, album after album are enjoyed until one reaches the point where the battery runs out (around 7 hours)

All of this is accompanied by an inky black, deep background. With headphones in and no music playing it feels like the world has disappeared so deep and black the sonic background is.

Treble is free from any grain, one can listen to a high note increase and never does it break down (unless you push the volume to far!) mids, well, its a tube amp, 'nuff said!

Bass, ah, bass! Now, if your into car door rattling bass then walk away right now, if your into deep deep bottomless bass then sir/madam, here is the door. However, if you like tight, defined, textured bass, bass that has you moving and grooving then this amp will provide you with limitless amounts of the stuff. Bob Marley and the Wailers sounds wonderful with this amp You can hear the distorted bass lines driving the music along and the fun is in hearing so clearly the distortion of the bass not just some wooly blob thumping away!

Acoustic bass has so much texture, notes rise and decay naturally, one can hear the bass's body move as it is played.

Strings are another strong area with this amp. One can tell gut from artificial so easily. The resonances in the body of a violin are conveyed so clearly one can hear them decay within the instrument and the waxy feeling of bow hair against string is tangible.

When it comes to percussion, the sound of a drum stick on cymbal's sounds like wood hitting metal, one can feel the texture of both. Likewise brush work on the natural skin of a drum feels grainy as it brushes against the grain of the skin.

I leave though the best for last and that is vocals.

I love early music the sound of voices in a small church or room unaccompanied are something I have experienced in real life many times and this amp conveys that perfectly I feel. Texture, and I make no apologies for multiple uses of that word in this review, is the thing with a voice.

For the emotion to be conveyed authentically so that one can fully engage with the artist one needs to feel the texture of the vocal, how the voice comes out through the mouth, how the air moving then hits the listeners ears and so engages and emotional response is vital to realistic vocal reproduction I feel.

So often now software is used in mixing to take that texture out and thus we end up with X factor vocals. Thankfully early music is immune to that I have found so that one can feel the resonance of the vocal as it hits the air and your ears hear it, this amp conveys that so well!

I want to talk a little about volume. I have noticed that there are sweet spots for each album with this amp. Take the volume too far and the sonic picture starts to fall apart, take it even further and the sound becomes harsh and glassy. Find the right volume level for each album though and it is magic! Thankfully the optional (read, you have to have this one upgrade if no other!) stepped attenuator is so accurate and does what any good volume pot should do, get out of the way of the signal that achieving the right level is effortless

And so I come to the end of this review. I do want to say again, this amp is not for everyone, in spite of my glowing review there will be many who will not like this amp as it is a gentle amp, not in your face, not a piece of HiFi, it simply gets out of the way so that the music and emotion can flow. It will not command or power, it will not take a vice like grip of music, if that is how you like music conveyed ( and note, I am not saying right or wrong, we all find our musical nirvana in different ways after all) then this amp is not for you.If you like to use a wide range of different impedance headphones or ones that are power hungry this amp is not for you.

However, if you like music conveyed in a natural way, not emphasized but rather the performance allowed to build and be created before your very ears and you are prepared to go to a little effort in matching headphones and making sure your source and music is of the highest quality (think high bit rate if your using downloaded or ripped from CD music) then this amp may be for you.

If your prepared to think of this amp as transportable rather than portable and battery life and size and weight are not issues then this amp I feel might be right up your street!

Combine that with the utterly delightful experience in dealing with the affable Shikata San and the thought that your amp is designed for your needs and the sheer quality of build and sound and I feel this amp at just over $1000 is somewhat of a bargain!


Fantastic review Ian. Totally agree that the music is presented in such a natural way and vocals sounded so real thru the TU-05B. The same warm texture and musicality is only replicated from my Red Wine Audio Isabellina, which i really enjoy a lot as well. With my TH900, i can listen for hours with much less fatigue than from my other portable set-ups. Since I cannot share impressions as vividly and lyrical as you, I like to endorse the same feelings i have with the TU-05B. Cheers.
Oh thats wonderful, I am so glad your enjoying yours as well and happy that my feelings on the amp are confirmed as to be true of its sonic signature. The isabellina has a wonderful reputation so for it to be compared to that wonderful amp is praise indeed. Have you done any more experimenting with tubes?
Thanks for such a comprehensive review of what looks like a fascinating product. I hope you don't mind if I ask a few questions? There is an option on the order page to pick just one impedance range: low-to-mid, mid-to-high, low-to-high. I have a couple of headphones (Audio Technica ATH-W3000ANV and a Thunderpants modified Fostex TR50P) also doing some research on high-end universal IEMs. Any tips on what would be an appropriate option? Also, is the battery user replaceable? And finally can you still listen to the amp while it recharges the battery? Thanks again for an enjoyable read.
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