StradiTube.. review incoming (any requests?)

[Treehaus Audiolab]

Hi Everyone,

I was having a deep late night dive into rare Telefunkens a few months back and came across Stradi Tube from Korea. I was super curious about what they offered, given they make modern replicas of a lot of classic German DHT tubes which no-one else does. They also have some rather unique DHTs that are specifically re-engineered for very low noise and thus can be considered for preamplifier/ phono stage duties. (DHTs are inherently noisy so at low signal levels they can be more challenging to implement). I spoke to John there, and now I am in possession of three of their tube varieties. One is a Telefunken variant that I want to possibly develop some future things around and the other two are 300B variants:

300B - Basically a WE300B clone with its intent to possess that classic 300B sound.
S300B - This one is more unique. It has a different shaped bottle, and it basically a Siemens tube developed to run at 300B specs to be drop-in on 300B amps.

I am still getting hours on them before I deep dive on all their nuances and how they compare to new production WE300Bs. That said, the initial sound is VERY nice. They are definitely top-tier 300Bs and its probably one of those things that will be a matter of listening preference and system setup. In particular, the S300B sounds VERY much like a VT-52; cleaner and more exacting than the usual 300B sound, but still possessing the liquidity I find 801A lacking when used as a power tube.

I know there has been some talk around these tubes, so if anyone has something in particular you want me to listen when I get a bit deeper into to the listening, please let me know.

COMMERCIAL DISCLAIMER: Stradi provided the telefunken 242 clones as a sample for product development. I purchased the 2 pairs of 300Bs. Considering there is so little info out there on these tubes, I figure its for the "greater good" of the audiophile community to post up my listening impressions.

 

[the sound of Tao]

Thanks Rich… very much looking forward to what you discover with these as they settle in and also importantly how reliable they proved to be in the long run.

It’s great to have some new options aiming at the top end of DHT especially with the S 300B in what sounds potentially a slightly more neutral variant of 300b… is the tonal balance on that still somewhere in the ballpark of the current production WE 300B… also keen to hear more about the Telefunken 242 variant.

Just checked out their site… wow fantastic options there. Thanks for the share on these.

Stradi Tubes

 

[Golum]

Fantastic topic! So far, there was only short feedback from Lukasz (LampizatOr) who loved their tubes but not going into any specific details SQ wise.

Thanks for the effort!

 

[Treehaus Audiolab]

Thanks Rich… very much looking forward to what you discover with these as they settle in and also importantly how reliable they proved to be in the long run.

It’s great to have some new options aiming at the top end of DHT especially with the S 300B in what sounds potentially a slightly more neutral variant of 300b… is the tonal balance on that still somewhere in the ballpark of the current production WE 300B… also keen to hear more about the Telefunken 242 variant.

Just checked out their site… wow fantastic options there. Thanks for the share on these.

Stradi Tubes

It won't be until sometime next year where I can get deeper on the 242 as I dont have a piece of equipment that runs them yet. The 300Bs, of course, are pretty easy.

Long term reliability I will keep an eye on; they do seem generally well made. Thick glass, nice base, etc.

 

[Synaxis]

Hi Everyone,

I was having a deep late night dive into rare Telefunkens a few months back and came across Stradi Tube from Korea. I was super curious about what they offered, given they make modern replicas of a lot of classic German DHT tubes which no-one else does. They also have some rather unique DHTs that are specifically re-engineered for very low noise and thus can be considered for preamplifier/ phono stage duties. (DHTs are inherently noisy so at low signal levels they can be more challenging to implement). I spoke to John there, and now I am in possession of three of their tube varieties. One is a Telefunken variant that I want to possibly develop some future things around and the other two are 300B variants:

300B - Basically a WE300B clone with its intent to possess that classic 300B sound.
S300B - This one is more unique. It has a different shaped bottle, and it basically a Siemens tube developed to run at 300B specs to be drop-in on 300B amps.

I am still getting hours on them before I deep dive on all their nuances and how they compare to new production WE300Bs. That said, the initial sound is VERY nice. They are definitely top-tier 300Bs and its probably one of those things that will be a matter of listening preference and system setup. In particular, the S300B sounds VERY much like a VT-52; cleaner and more exacting than the usual 300B sound, but still possessing the liquidity I find 801A lacking when used as a power tube.

I know there has been some talk around these tubes, so if anyone has something in particular you want me to listen when I get a bit deeper into to the listening, please let me know.

COMMERCIAL DISCLAIMER: Stradi provided the telefunken 242 clones as a sample for product development. I purchased the 2 pairs of 300Bs. Considering there is so little info out there on these tubes, I figure its for the "greater good" of the audiophile community to post up my listening impressions.

Awesome! Thanks for doing this and I can't wait to hear what you think about them.

 

[Golum]

You're not testing their 5u4g by any chance?

 

[Treehaus Audiolab]

You're not testing their 5u4g by any chance?

Unfortunately no as I don't have amplifiers that use it.

 

[Golum]

I bought one today so lets see...

 

[DetroitVinylRob]

I see Stradi has a 2A3 based on Siemens Eb.

 

[Treehaus Audiolab]

I see Stradi has a 2A3 based on Siemens Eb.

That could be killer.. I am liking what they are doing with these "hybrid" designs.

 

[Golum]

OK, so far so super good. I still did not receive the tube but communication with Stradi team (John Kim) is exceptionally pleasant with the info on the shipment provided in timely manner with all the details. This "human interaction" part is really important to me.
On top they've sent me some details how they've been testing this tube model which is nice to know.
"We have been stress testing the Stradi 5U4G since May 23rd - it was manufactured around Feb this year. We tested using a mechanical timer and the test device was turned ON/OFF every 15 minutes (i.e. Repeat 15 min On -> 15 min Off -> ..).
It passed 1000 hours in Sep and is still working well(Nov 19)"
Tube arrives next week and then further info will follow.

 

[Treehaus Audiolab]

OK, so far so super good. I still did not receive the tube but communication with Stradi team (John Kim) is exceptionally pleasant with the info on the shipment provided in timely manner with all the details. This "human interaction" part is really important to me.
On top they've sent me some details how they've been testing this tube model which is nice to know.
"We have been stress testing the Stradi 5U4G since May 23rd - it was manufactured around Feb this year. We tested using a mechanical timer and the test device was turned ON/OFF every 15 minutes (i.e. Repeat 15 min On -> 15 min Off -> ..).
It passed 1000 hours in Sep and is still working well(Nov 19)"
Tube arrives next week and then further info will follow. View attachment 140114View attachment 140113

Stradi (John) is very good at keeping good lines of communication going, seems like a great guy!

Ill be doing my deep dive in the next week; I forgot I had a second pair of WE tubes here, I am breaking them in a bit then Ill do a 3-way comparison (my other pair of WE300Bs have in in use a while, and this way, all the tubes will have about 20-25 hours on them for a very fair comparison)

 

[Golum]

Stradi (John) is very good at keeping good lines of communication going, seems like a great guy!

Ill be doing my deep dive in the next week; I forgot I had a second pair of WE tubes here, I am breaking them in a bit then Ill do a 3-way comparison (my other pair of WE300Bs have in in use a while, and this way, all the tubes will have about 20-25 hours on them for a very fair comparison)

Really looking FW for Your report

 

[Golum]

FedEx was kind enough yesterday to deliver the parcel from Korea hence my initial non listening feedback.
Packaging is exceptionally well done and despite not being in the wooden box as Taka, in my book, it's not worse either as they took care about all small details. Warranty card/letter in separate nice envelope and you receive also a separate/spare card box for the tube etc.
Tube physically looks and feels extremely well done - judging by the thickness of the bulb, also no diff vs Taka.
BTW why Taka - as I somehow take it as a reference current production tube beside Elrog, EML, KR whilst Stradi price wise would be in the price range of KR/EML.
I've just inserted it into the DAC for burn in for a few hours and will give it a listen tmr or during the weekend for initial feeling.
Few pics:

 

[Treehaus Audiolab]

Golum beat me too it with the packaging pictures! According to Stradi it is designed as eco packaging. The wood boxes Takatsuki and WE come in present a bit better, but the Stradi packaging is very resourceful and creatively designed. I like it just as much.

Per John at Stradi:
"The long label is "HunMinJeongEum".
It contains the meaning that "Chinese characters and Hangul (Korean Language) are different from each other so Hangul was created".

Hangul was first created in 1443 by Sejong the Great, the fourth king of the Joseon dynasty.
He wanted the common people of the lower classes to read and write, this is why he invented Hangul.
Also he was a scientist.
While previous kings were obsessed with metaphysical, conceptual knowledge and thinking, he tried to discover scientific patterns/knowledge to improve his people's lives.

All Koreans know HunMinJeongEum well.
We wanted to let people in the world know that StradiTube is 100% designed and manufactured in Korea and we try to make great tubes that live up to his reputation."

It is a great detail.

***

I also agree with Golum, the tubes themselves seem quite robustly made. Definitely at a WE/ Takatsuki level. They arent tanks like EML tubes, but appropriately made for a top-tier 300B.

Now, onto the most important thing: The sound!

I did my testing on two of my setups.

In my demo space: The "300B-2" which is a 2 enclosure design using 801A interstage driving the 300B with Coleman regulators. Treehaus 4P1L preamp, Soulnote D-2 DAC. Treehaus Phantom of Luxury speakers (rullit field coil full range driver).

At home: "300B-1" which is a smaller amp using C3M interstage driving 300B with a regulated DC filament heater. Modified Uesugi UBROS-1 preamp and Concert Fidelity DA040 DAC. I also tried my Lyngdorf on here as well for a more "digital" front end.

Also to note: my speakers have a solid state powered woofer. In the demo space I also did some listening with the woofer turned off so I could more accurately judge the low end response of the tubes.

The short answer here is my listening results and impressions were the same on either amplifier. I do also want to note that my Treehaus amplifier in general are a more neutral, less "syrupy" sound than traditional 300B circuits.

All tubes had about 25-30 hours on them. I made a small playlist of about 10 tracks to use for comparison, and in between tube warm ups left some low-level ambient music playing so it wouldn't cloud my judgement on the reference tracks. Aural memory in practice isn't that good for small detail differences, and when throwing in 10-15 minutes warm up between tube rolls, I did my best!

Tubes tested were WE300B, Stradi 300B, Stradi S300B.

The Stradi 300B: This is the tube closer to the WE300B. It is actually based more on the British STC 4300B. It sounded nice during break in but WOW, in comparing it head to head, I was a bit shocked at how good it was. It is extremely liquid. However, it had tremendous percussive energy and its low level detail retrieval was impressive. I was noting more voice and instrument separation compared to the WE300B. Usually you get more liquid and emotive sort of things OR you get that next level of detail, this tube was providing both at once. Throwing some "Atoms for Peace" at these tubes didn't rattle them despite being heavy electronica. They were sort of an enigma: Smooth and liquidy and also precise, detailed and hard-hitting at the same time, with great bass extension. With lots of tubes ahead of it as in my home setup (tube DAC and pre) vocals might have been a little too smooth for some peoples taste compared to WE, but I liked it, and it really was track dependent.

The Stradi S300B: This one is based on the Siemens/Valvo Ed tube. If you like 45/71A... this is the tube for you. Its character is rather different than the Stradi 300B or the WE300B. It is super clean, with less bloom, ultra-neutral. It probably has about the same level of detail retrieval as the Stradi 300B but it is a lot more noticeable here because of how clean the sound is. It didn't get astringent, or cold sounding, like a tungsten transmitter tube; it maintained some of that 300B liquidity but it was very measured. Still had tons of percussive energy in it and good control on the low end, albeit with a little less bloom than the 300B version.

Because I voiced my amps to be a bit more neutral by design, the S300B might be considered a bit less "engaging" than the 300B version on my equipment. I tended to really enjoy it. I think if you had a more traditional 300B amp, but wanted something that shifted a bit cleaner and 45ish, then Stradi has a real winner on their hands with this variant.

Both are absolutely fantastic tubes, and really would be a matter of sonic preference. I'll be honest, I didn't expect them to both be *this* good as in the world of top 300Bs the differences can be subtle and its easy to misstep and lose the soul of this tube. I might be in love.

Also, to further this endeavor.. I shipped both pairs to @TKK to borrow for a bit, and hopefully he can provide the forum more insight. In particular, he has a Lampi DAC that uses 300bs, and he has some Takatsuki 300B which will enrich the comparisons.

 

[Golum]

Now you beat me in the sound description .
Interestingly enough despite the fact I'm using rectifier tube I wanted to write totally along the lines you used.
"It is extremely liquid. However, it had tremendous percussive energy and its low level detail retrieval was impressive. I was noting more voice and instrument separation compared to the WE300B. Usually you get more liquid and emotive sort of things OR you get that next level of detail, this tube was providing both at once. Throwing some "Atoms for Peace" at these tubes didn't rattle them despite being heavy electronica. They were sort of an enigma: Smooth and liquid and also precise, detailed and hard-hitting at the same time, with great bass extension."
Within my DAC I'm getting exactly this sort of result - fast, liquid, great detail retrieval, precise and deep bass notes but to me overall emotion it conveys within this entire tube combo I have is beautiful/seductive.
Absolute keeper...
Can't wait to try their 274b when it comes out...

 

[christoph]

Within my DAC I'm getting exactly this sort of result - fast, liquid, great detail retrieval, precise and deep bass notes but to me overall emotion it conveys within this entire tube combo I have is beautiful/seductive.
Absolute keeper...

How does the Stradi 5u4g compare sonically to the usual suspects?

 

[Golum]

Chris I don't really have any other words to use vs the ones I used above for the overall presentation. I don't have the feeling that any other usual suspect gave me an overall impression as Stradi where I was not feeling a need to get into small details exploration - like amount of bass, speed, decay as it was just too good to do that.

 

[John T]

Chris I don't really have any other words to use vs the ones I used above for the overall presentation. I don't have the feeling that any other usual suspect gave me an overall impression as Stradi where I was not feeling a need to get into small details exploration - like amount of bass, speed, decay as it was just too good to do that.

Did John give you a timeline on the Stradi 274b?

 

[Treehaus Audiolab]

Golum its good to hear your impressions were similar to mine with the rectifier. These tubes are doing some special stuff!