Cayin A-300b vs Muzishare x9

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.

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.  

@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 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

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.