@slowestrider Oohh my God, I bought opus ii last month too :) it indeed made a big difference too. 
i am glad you fixed your amplifier issues. That  is one of the reasons i love tube amps. We can just open it and fix it or upgrade it of course if someone is into it. 

Thank you for the update cb3489. Those ACME 300B is not cheap but good to know it improve the X9 much.

I brought a pair of LINLAI 7300B. That pair also tightens the image compared to stock 300b. I didn't listen long enough to see how much those LINLAI tubes can improve over stock ones. Stock 300b is working well after I added the Denafrips Pontus II.


My X9 left channel lost sounds once a while. China HIFI wants me to ship the unit to Michigan for authorize repair shop to check. Instead of shipping, open the unit and solder the socket. The problem disappeared. While the bottom over opened, I checked wiring and noticed some wires and caps were very close to each other. I pushed its part and now very low noise/statics from the unit.

@cb3489 finally upgraded all tubes on X9 :) i got PSVANE Acme 300b and PSVANE 274B Tii. Using Tektons perfect set 15s.  The sound is really good. It improved amazingly. Huge bass sound level and more noticeable details

Congratulations on your successful outcome. I’ve stated before that yes premium 300b tubes are expensive but worth it for the substantial improvement in subsequent sound quality they provide. A good 300b amplifier deserves the use of the higher tier performance tubes. You may as well get the most you can of an amplifier’s potential.

Charles

@charles1dad ​​​​@slowestrider 

i finally upgraded all tubes on X9 :) i got PSVANE Acme 300b and PSVANE 274B Tii. Using Tektons perfect set 15s.  The sound is really good. It improved amazingly. Huge bass sound level and more noticeable details. Every upgrade makes so much difference i wonder if there is any end to spend more money on hifi :) 

 

cb3489. I finally plug it. No issue with the 300B with the ringing noise when I touch it. This amp is so quiet. No noise at all, even turn to 11 o'clock with my 102dB sensitive speakers. So I leave the hum balance at factory setting. Bias were a bit high on both tubes so I adjusted it back to 60mA. I leave NFB at 2 for zero feedback.

Stock tubes with no burn in, it doesn't have any harshness at all, noise floor so much quieter than the R8. High is more extended and bass is not over emphasis as the R8. Vocal and small jazz music gave me the wow even less than an hour burn-in.  It does loose some bogginess compares to the push pull R8 for it doesn't emphasis the upper and mid bass at all.

This will be my quiet morning amp and it will be much better when I start rolling the NOS MEL 6SL7.

Thank you for your help db3489.  
Yes, tubes do have very tight grip and fully seated but it still wiggle slightly. I saw the youtube clip by China-hifi on the  Boyuurange A50 MKIII 300. Those tubes also wiggled as he demonstrate the correct way to install 300B tubes.

One of the 300B tube at V2 position has a ringing sound when I touch and release, not sure if it effects the sound. I still have not plug in and test it yet.

On the Pre-in/OFF toggle switch, is the up position/pre-in for use the X9 as amp and plug in a preamp? and the OFF position is for using the X9 as an intergraded amp? I made out some words in Chinese but not all. Thanks for you help cb3489.
@slowestrider congratulations. My came with Chinese as well :) nfb i liked up position. I don’t know the db difference. 300b and 274 are only 4 pin vs 8 pin kt88 or 6550 so I believe that is why we feel like they are not tight but actually they are and very good grip they have. I doubled checked when you messaged. 
@cb3489. Is your X9 came with Chinese or English manual? My came with Chinese manual. Do you read Chinese?

Are 300B and 274B fit not tightly compares to others? 6SL7 tubes very tight fitting and EL34 and 6550B snuggly fitted on the R8 but these large tub easily moved with slight  finger touching.

NFB 1 means -3db feedback and 2 means no negative feedback?

Thanks in advance.

@cb3489,
After only 18 months in High End audio you became aware of and then acquired a SET amplifier, I’m impressed. It took me much longer to reach that stage but glad I did.

I had a Symphonic Line which is a very good German made solid state amplifier. Moved on to a push pull 40 watt el34 tube amplifier (Which was more musically fulfilling). Next step was a custom 100 watt push pull KT 88/6550 tube mono blocks (Best I’d ever owned up to that point).

Decided to try an 8 watt 300b SET mono blocks  in 2009 and immediately knew this was what I’d been seeking . 12 years later I’m as happy and satisfied as I was on day 1.
Most musically and emotionally engaging amplifier I have ever owned. It brings the music alive. This journey far exceeded 18 months 😊.
Charles
@slowestrider i am new to hifi i only experiment 18 months in this hobby. But what you said sounds correct. Kt88 push pull to my taste won against Cambridge audio azure 851a. So i sold azure. Now between kt88 push pull vs 300b set i kind of feel like  the same comparison as azure but not as much. So i feel lucky to have both x7 and  X9. 
How bass different from X7? Not as emphasized and more definition since it is SET compares to PP? Mid warmer and more holographic with X9?
@cb3489, 
 I thought that the Tekton Perfect SET speakers would be a wonderful match with your 300b SET and happy to know this is the case. I'm sure your music reproduction is gratifying and very engaging. 
Charles 
@charles1dad 
KEFs are amazing but Tekton is more detailed and more wider sounding. old vs new perfect example. KEFs each crossover has 13 capacitors and multi stage filtering vs simple crossover with 3 mundorf oil capacitors. My friend brought 1w old Decware amp. These power hungry KEFs both 104/3 and 105/3 did really good too we were surprised. But again Tekton was little more detailed and natural. I also added Tekton 4-10 sub to tekton perfect set 15s. I love lots of bass low volume :)
Cool cb3489. I am not far, in San Gabriel area. Thanks for the offer. I will surely swing by one of these days. 
@cb3489, 
I have to believe that the Tekton Perfect SET speakers are a better match with your X9 300b SET compared to the less efficient and sensitive KEFs. What has improved sonically in your opinion (Or am I being presumptuous?).
Charles 
No power tube rolling. It has been confirmed that they muzishare branded psvanes 300b. Changed preamps with tungsols. Made huge difference. Bass is very different than x7. If you are in los angeles area you can come and listen:) 
Thanks cb3489. I am very close to getting the X9 to drive my CW IV. How is the X9 bass control compares to your X7? Roll any tube yet?
No. I like manual anyway it feels like i have the control. By the way Tekton perfect set 15s came a couple of days ago. I am really happy with the great match. 
The Cayin brand is owned and manufactured entirely by the Chinese government.  Personally, this would be a deal breaker for me though I know for others it is not an issue.(Yes, I know where my iPhone is manufactured, thank you.)
@cb3489,
You have 2 very capable amplifiers, however I do understand the allure of the SET and why you are drawn to it. This type of amplifier if executed properly stirs much musical emotion and gets you more involved/connected with the music. I would be surprised if things do not further improved once you receive the more efficient  Perfect SET speakers. It’s impressive your SET is doing this well with the KEFs.
Charles
@charles1dad 
thank you. Using 105/3s in 4ohm mode. 8ohm mode some how generated distortion after 11oclock level. As expected Kefs wants lots of current i assume. Tekton perfect set 15 i ordered,  12 weeks wait time so another 9 weeks to go. That would be a great test. I also test audioquest and requisite cables. Ares ii and raspberry pi streaming stays same. X7 is really good too but X9 sound debt and larger sound is good. Big price difference though X9 is 1k more. I guess we get what we pay for. Both are amazing value. I need to figure out how to share photos here. 
@cb3489, 
Congratulations!
As long as the 300b SET is paired with appropriate speakers I believe that you'll be quite happy with it. Are you using the KEF or have you received the Tekton Perfect SET?
Charles 
I received the Muzishare X9 today..It is very good and comparing to X7 it is bigger in every size, dimensions, tubes, transformers, knobs etc...and sound bigger too. First day test I noticed that X9 as SET is more picky on the speakers and the speaker ohms. I will keep testing and roll some 6sn7 and 6sl7s first etc...
Yep, the KEF is rated at 93 db sensitivity so with even modest power, reaching high volume would not be a problem. And no doubt that the push-pull KT88 amplifier is more suitable than an 8 watt SET  amp.
Charles
Also let me give some more info about kef 104/2 and 105/3 and tube amp triode mode 24, ultra linear 45w kt88s. In triode mode 1 or 2 o’clock area i assume 12 14 watt kefs and muzishare x7 shakes the house and i feel the bass in my lungs. But i like low watts with full air music so that is why i am still experimenting to go to 8 wattsh set and tekton 15 inch woofer 8 ohm stuff. For someone wants loud music these amps and speakers combinations seems to be pretty satisfactory. 
i agreed. I ordered Tekton perfect set 15 a couple of days ago. 8 to 10 week delivery estimate. I am  also planning to buy Muzishare X9 as well soon. 
@cb3489,
I’m a very happy owner of an 8 watt 300b SET amplifier. The KEF  is a 4 ohm speaker that dips to 3 ohms in the bass frequencies. They recommend 50 watt minimum to drive them. In addition it’s a 4 way speaker with multiple crossovers. In my opinion this is not an ideal choice for a low power SET.

I believe you’ll get much more of the capability and attributes from a 300b SET paired with the Tekton Perfect SET 15 speakers. They are intentionally designed to work very well with low power tube amplifiers.
Charles
I also learned that Cayin is mostly 220v...I am in the USA so 120V is on Muzishares...
Team, i am kind of new to tubes comparing to others, only involved last 8 months or so. I started with Muzishare X7...Push-Pull 4xKT88s.
I also have KEF 105/3 that I renewed painfully, all donuts and capacitors.
I keep reading about SET...so I wanted to try SET and compare.
I am also planning get Tekton perfect 15s if KEFs would be hard to drive with 8W 300Bs etc...
I also build raspberry stream with HAT digital out, trying Ethernet to Digital streaming source.
I have Ares II as R2R DAC.

Muzishare has 2x300bs...I believe those 2 more looks like 300b but they are 274b i think...used as rectifiers. 
I never heard of Muzishare, but that doesn't mean much since I haven't been shopping in this range.  But why does it have four 300Bs if it is a single ended design?

Some years ago I owned a Cayin 300P, a push-pull version producing 20 wpc.  Apparently that was an earlier version of this model -  https://www.china-hifi-audio.com/en/cayin-audio-hi-fi-tube-amp-c-47/cayin-a-300p-mk2-class-a-power-a...

I found that to be of high build quality, good sonics, and reliable.  Oddly that is listed for less than the model you linked?
it depends on what kind of tubes you like to roll....is this your first tube amp? Some folks are very picky; others are not.

Also take in to consideration weight, size, and overall appearance. What does your heart say?