StradiTube.. review incoming (any requests?)

[mariovalvola]

A review published by PT Audio of both 300B variants and the 5U4G recti:

Stradi 300B, S300B and 5U4G Vacuum Tubes | REVIEW

Hi-Fi news, gear reviews, and interviews

pt.audio

It's great that we're talking about these Korean tubes that intrigue me, but, apologies for being a little unpleasant, I would like to add:
-this is not how you test new tubes.
The manufacturer STRADI claims that their grids distort less. I asked for specific information but they did not provide it.
Serious testing should be structured like Michael Boele's test on AudioXpress on the new WE300Bs.

Fresh From the Bench: Western Electric's New Production 300B

Renowned tube expert Michael Boele offers his long-term review of a pair of 2021 new production 300B directly heated power triodes. For 10 months, Boele had the opportunity to live with and extensively use a pair of these 300Bs and his impressions and extensive testing could be directly...

audioxpress.com

When conducting serious tests, you can't just do some rough tube rolling to see what effect it has. Measurements are not used to listen to music, but they help to understand whether the products being analyzed are worth the expense.
It would have been nice if, using distortion-free driver stages to avoid the effects of harmonic cancellation, an analysis of the distortion had been carried out at just 1W at 1KHz with any FFT analyzer. By doing so, the quality of the grid as built by STRADI would have been verified. By testing both the Gm when new and after a few hundred hours with a decent tube tester, we would have obtained some indication of the emitter layer used. Another interesting test: measuring the current circulating in the cutoff area. For example: if you measure Ia at 300V with -100Vg, you should get a ridiculous anode current if the grid is well constructed and mounted. Many 300Bs reach 0mA, some reach 6mA, which is not a good thing. Usually, these tubes distort even more.
-Boele had carried out serious stress tests to verify the robustness of the tube.
After the test, the new WE tubes showed better vacuum, lower harmonic distortion, better Gm, and better pervaence. After these very useful tests, he also spent a long time listening to them, but with the knowledge that the tubes were well broken in (which is not easy) and activated in the best possible way.
Of course, this is not an article that anyone could have written (Boele is a well-equipped physicist with good experience as a DIY builder), but he has written a very informative article that explains the difference between WE and many other tubes.
I think that STRADI, in order to promote its tubes, should publish serious tests to inform the more “savvy” enthusiasts. Reticence does not pay.
Worse still, I only saw a YouTube video where a female builder measured the overall distortion of an SE amplifier (with the usual Sun-Audio type 6SN7 circuit). In these cases, if you don't consider the distortion of the driver stage, you completely misinterpret every analysis.
... Peace and love

 

[theflattire]

A review published by PT Audio of both 300B variants and the 5U4G recti:

Stradi 300B, S300B and 5U4G Vacuum Tubes | REVIEW

Hi-Fi news, gear reviews, and interviews

pt.audio

Man, so tempted to try that 5U4G...

 

[mariovalvola]

Man, so tempted to try that 5U4G...

With rectifier tubes, the limitations of novice manufacturers are highlighted.
The intrinsic robustness of older models is now a distant memory.
STRADI produces a lower-performance version of the 5U4G (not GB). This choice requires the user to pay particular attention and have in-depth knowledge of the device's circuitry.
To avoid problems, I suggest simulating the power supply with the PSUD II program, which is convenient and easy to use.
Critical problems are immediately noticeable, which are not only, in abstract terms, attributable to the first capacity. It is very important to respect the r series on the anodes (net of the Rdc of the semi-secondaries). The presence of the double inductor, etc. must be evaluated.
The other aspect that leaves one a little perplexed and amused is the tolerance of +- 2.5% on the powering up voltage. Unfortunately, in Italy, contractually, the supplier's tolerance is +- 10%.
I don't know about other countries, but I doubt that a variability of 2.5% can be guaranteed. The light grid must be stabilized, or even the 3A powering up of the rectifier must be stabilized!!!

 

[John(Stradi)]

Hi, we are StradiTube.

1. >> In relation to bigjako(ID)’s Stradi 5U4G post :
According to our policy, we asked him to send us the tube so we could investigate the issue with his Stradi 5U4G.
He refused, however, and continued to demand a refund while verbally abusing us.
We don't accept requests from customers that fall outside of our policy.
Due to his continued verbal abuse, we also stopped providing customer service to him.
He claims there is a problem with the tube, but since he did not send us the tube, the issue is still unknown.

2. >> GE premium line is five stars, and the target defect rate for this line is less than 5%.
Until now, Stradi 5U4G's post-sale defect rate is lower than the five star line's target defect rate.

3. >> To ensure safe use of the Stradi 5U4G, it is necessary to check not only the size of the first capacitor but also effective plate supply resistance of the circuit.
However, it will be difficult for the end user to know the value of the effective plate supply resistance, so please contact the amp manufacturer.

p.s., There is no record of mariovalvola(ID)’s purchase of StradiTube.

- John

 

[mariovalvola]

Hi, we are StradiTube.

1. >> In relation to bigjako(ID)’s Stradi 5U4G post :
According to our policy, we asked him to send us the tube so we could investigate the issue with his Stradi 5U4G.
He refused, however, and continued to demand a refund while verbally abusing us.
We don't accept requests from customers that fall outside of our policy.
Due to his continued verbal abuse, we also stopped providing customer service to him.
He claims there is a problem with the tube, but since he did not send us the tube, the issue is still unknown.

2. >> GE premium line is five stars, and the target defect rate for this line is less than 5%.
Until now, Stradi 5U4G's post-sale defect rate is lower than the five star line's target defect rate.

3. >> To ensure safe use of the Stradi 5U4G, it is necessary to check not only the size of the first capacitor but also effective plate supply resistance of the circuit.
However, it will be difficult for the end user to know the value of the effective plate supply resistance, so please contact the amp manufacturer.

- John

Messrs John, good morning.
Why does the filament tension have to be so precise? To turn on AC these tubes, you have to stabilize the mains voltage or you have to have continuous monitoring along with a multitap transformer to compensate for variations in AC voltage.

Thanks
Mario

 

[boy_lah]

hi everyone! just signed onto WBF to cross post this....thought folks maybe interested in my initial impressions. As way of quick background, I am a 1-3watt SE DHT, 100db+ open baffel guy. My amp is a custom dual rectified, direct coupled (no caps) 417a drive 71a amp with japanese finemet output transformers. I am quiet familiar with 71a, 45, 46, 2A3 and 300B. My fav/bias are for the 71a and 45 then 2A3 finally much later 300B. Less keen on PP, KT88, 66/150, EL34, 211, 845 etc.... of the pentodes my fav is probably EL84.

I'm came home with a pair of S300b (the Valvo Ed) and 45 which I am running in. I have done some brief comparisons with 45 globes incl RCAs and also WE300b 1988 and WE 2022 reissue and I am more than impressed. I'll do a followup once I've had more time. I will also get my hands on some Elrog and Takasuki shortly and some 1960s WE. I am also very familiar with EML, Psvane ACME as well as LinLai Elite. Best!


---------------------
I recently met Jay Jung (StradiTube's co-founder and chief designer) in Seoul and got to listen to their AD1 (European 2A3), 300B (STC4300/EU 300b), S300B (Valvo Ed in a 300b drop in) and their hotly anticipated 45 and here's my impression...(caveat it was on multi-tap test amp, an unfamiliar system etc.)







What is their house sound?

• Linear and extended - this striked me immediately, you get a much more even and extended top to bottom than other brands. E.g. their 300b/45 mid band emphasis is less than other/vintage 300b/45.
• Low noise floor - StradiTube talks about their low microphics ladder type frame grid which means you hear a lot more nuance of the performance (instead of micrphonics of the tube itself). These are subtle micro details, not etched hyper/leading edge details (which i sometimes associate with chinese tubes).
• Harmonically and tonally it is more correct/neutral vs overly rich - this is different to more classic 300b or 45 which is on the coloured side. It's not sterile (thank god). Folks may need to give it a chance to get used to what this has to offer. I personally really liked it then again I'm a fan of the 71a tube - which I find more correct tonally and yet very satisfying.

How do they compare with other brands?
Stradi offers a sound signature different to the chinese tubes (which I find tend to favour mid highs (great for female vocals), sparkling top end/details but typically lack mid lows and fullness) or even Emission Labs/KR/ElectroHarmonix (more classic linearity/slightly more linear, but fuller/bolder/mid low weight vs chinese). WE or Takasuki is more classic WE300b sound, these will be different. They are also recreating their favoured EU tubes vs the more common US ones, which offers us the consumer, more options.

How do StradiTubes compare amongst themselves?
Their 300b and 45 are their most coloured/rich tubes amongst their line up (but compared to classic 300b/45, they are still more correct/linear). Their AD1/2A3 and S300b is more correct and linear and would be their typical house sound. The S300b is to me, more of a 71a in a 300b drop in - which turns out to be Jay's fav tube as well.

 

[mariovalvola]

Hi, we are StradiTube.

1. >> In relation to bigjako(ID)’s Stradi 5U4G post :
According to our policy, we asked him to send us the tube so we could investigate the issue with his Stradi 5U4G.
He refused, however, and continued to demand a refund while verbally abusing us.
We don't accept requests from customers that fall outside of our policy.
Due to his continued verbal abuse, we also stopped providing customer service to him.
He claims there is a problem with the tube, but since he did not send us the tube, the issue is still unknown.

2. >> GE premium line is five stars, and the target defect rate for this line is less than 5%.
Until now, Stradi 5U4G's post-sale defect rate is lower than the five star line's target defect rate.

3. >> To ensure safe use of the Stradi 5U4G, it is necessary to check not only the size of the first capacitor but also effective plate supply resistance of the circuit.
However, it will be difficult for the end user to know the value of the effective plate supply resistance, so please contact the amp manufacturer.

p.s., There is no record of mariovalvola(ID)’s purchase of StradiTube.

- John

It's very exciting to have Stradi on the forum. It's a shame that he doesn't respond to questions and invitations.
I asked for information about the powering up of the filaments and their tolerance, and why it was so low, especially on rectifier tubes.

I am very intrigued, but it would be nice to have more data. If I don't have real information, even if the tubes look beautiful, I am very hesitant.

Subjective aspects and perception are very important when listening to music, but some measurements help to understand the quality of the tube's construction. In a single-ended amplifier, the quality of each component is extremely important. Since there are usually no feedback loops in these amplifiers, the actual linearity of the tubes is a necessity, not a quirk.

Thank you.

 

[boy_lah]

Congrats @Treehaus Audiolab @John(Stradi) on the latest review.
https://twitteringmachines.com/review-treehaus-audiolab.../

This pretty much mirrored my own experience with the Stradi tubes - vs 45 globes incl RCAs and WE1988+2022 300B, Psvane, LinLai, JJ, EH.
...."[the reviewer] preferred the Stradi 300s by an obvious margin. The WE 300Bs made music sound softer, fatter, and fuzzier than the Stradi tubes, all qualities I found less compelling. Perhaps you could say the WE 300Bs are ‘richer’ sounding, and they glow prettier purple to put a positive spin on it, but the Stradi tubes were not only as rich but they also brought with them better bass control, more refinement, increased dynamics, and better resolution."

 

[Treehaus Audiolab]

Congrats @Treehaus Audiolab @John(Stradi) on the latest review.
https://twitteringmachines.com/review-treehaus-audiolab.../

This pretty much mirrored my own experience with the Stradi tubes - vs 45 globes incl RCAs and WE1988+2022 300B, Psvane, LinLai, JJ, EH.
...."[the reviewer] preferred the Stradi 300s by an obvious margin. The WE 300Bs made music sound softer, fatter, and fuzzier than the Stradi tubes, all qualities I found less compelling. Perhaps you could say the WE 300Bs are ‘richer’ sounding, and they glow prettier purple to put a positive spin on it, but the Stradi tubes were not only as rich but they also brought with them better bass control, more refinement, increased dynamics, and better resolution."

View attachment 157840

I appreciate you posting up the review!

 

[TKK]

a data point from my end regarding stradi's 242 and 242H. Rich (Treehaus Audiolab) was kind enough to lend me his own experimental preamp using a pair of Stradi 242 (non-H version). The sound was very good, very evolving, has great dimension and soundstage, a bit on the relaxing side and I loved it very much when it gets paired with my solid state DAC. Great quality tubes (and great preamp of course).

It made me wonder about their 242H on my Lampi Pacific -- as one of my PX25 is half dead. So I purchased a pair directly from Straditube, John made a pair with black UX4 base, awesome looking, and awesome sounding with my Pac. I was expecting 242H to sound a bit more exciting and indeed unlike how I felt about Rich's 242 preamp, these 242H sounded super dynamic, detailed, strong and powerful on my Pac compared of RK PX25 and TAK300Bs -- pretty much like how most people described KR242 paired with Pac. Just saying --- if people like KR242 on Pac, maybe also take a look at stradi's 242H, they can be made with UX4 base (and in black if requested), which saves you from adaptors.

 

[cpcat]

I got a Stradi 5u4G for my birthday- tried it tonight on my Lampi Big 7 MKII.

Not for me. Sounded immediately like it was out of phase or just” not right”
Someth8ng was off and I coukd hear it immediately. I was not willing to risk it.

It is also backwards in its installation -tab facing rear -wards instead of forward- which was a little unusual as well. So the tube faces backwards?

Maybe I don’t have the “right capacitor”

Anyway, switched back to RK 5u4G and all is well.

 

[mariovalvola]

I got a Stradi 5u4G for my birthday- tried it tonight on my Lampi Big 7 MKII.

Not for me. Sounded immediately like it was out of phase or just” not right”
Someth8ng was off and I coukd hear it immediately. I was not willing to risk it.

It is also backwards in its installation -tab facing rear -wards instead of forward- which was a little unusual as well. So the tube faces backwards?

Maybe I don’t have the “right capacitor”

Anyway, switched back to RK 5u4G and all is well.

I think that any tube rolling without careful analysis of the circuit diagram is always a gamble. In particular, blindly replacing the rectifier exposes us to major risks. It's not difficult, but the anode power supply diagram makes all the difference.