Blown away by YAQIN MC-13S - tube amplifier

A couple weeks ago, I decided to try the YAQIN MC-13S which I could order easily on Amazon. I figure that with the Amazon Prime membership, I could demo the amp for 30 days; and if I do not like it, I could return it easily.

.... My system comprised of the Benchmark DC1 (DAC) which goes into the Parasound Preamp which feeds the Mark Levinson no. 27.5. My speakers is a pair of KEF LS50's. The system sounds great in my room (which has the size of a normal master bed room). The total cost of Amp and preamp is about $5000 at the time I bought my system; and I think it is decent enough for my purpose which is just to enjoy music in the most natural way without too much listening fatigue. My system is connected using AQ cables .

.... Just for curiosity sake, I bought the YAQIN and just plugged it into my system . The YAQIN just basically replaces the preamp and the amp. Everything else stays the same.

When I turned on the YAQIN, I was blown away. The sound is so much bigger. The treble is sweet and has higher roll off then the Mark Levinson. The mid rang is lush and beautiful. The sound stage expandes to the point that I think I am listening to floor standing speakers. I cannot believe that my speakers could be able to produce such sound that is so beautiful.

Now having said that, I also found one flaw of the YAQIN which is the weak bass. The Mark Levinson gave me a strong and tight bass with a full body mid bass, the sound is not lean but leaning a little bit toward the warm side.The YAQIN gives me a weaker bass and some what bloated at the bottom end. I am not a bass head, but it would be nice to have a more refined low frequency production.

So far, I am very impressed with the tube amp. Even my wife notices the different, she even asked me what are the hot light bulbs doing to the sound ? She thinks that music sounds more natural now comparing to the old Mark Levinson. She is now spending more time with my CD than ever before which I found very nice.

I just want to share my experience regarding the YAQIN. If any one used the YAQIN or has any suggestion to improve the YAQIN any further, please let me know. I am actually thinking about selling my Mark Levinson and the Parasound Preamp and just keep the YAQIN, but I still hesitate because Mark Levinson makes such very good amp with good reliability. I am not sure about the YAQIN quality control though.

As all way, in this hobby, we share and discuss ideas. So please share, if you guys have any idea... I will appreciate that.

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Newegg acts as an intermediary for a bunch of Yaqin's from China.  I wonder if you went up their line whether you might find better bass.  Or if by doing so you might compromise the qualities you like so much.
Which taps are your speakers hooked up on?  I believe the LS 50's are a 4 ohm load.  Try them on both the 4 and 8 ohm taps, it won't hurt either the amp or the speakers.  Just make sure you turn the amp off for a while before you change the wires.  Happy listening...   Fritz
The reviewer here, seemed to be pleased as you:

Looks like you may even be surprised rolling the driver tubes with some decent(not pricey)NOS tubes, if your looking for a little audio excitement.

No mention of a power cord swap, but perhaps another area waiting for an upgrade?

I have had a couple of Yaqin amps,  excellent value and very nice sounding. As mentioned,  you may try different tubes. Mine responded well to tube changes. I have recommended Yaqin at least once hear on Agon, seemed to fall on deaf ears.  I'm not using Yaqin now, but wouldn't blink at trying any of their amps or pre's.  
Seem like every body suggested to me to roll tube, what tube should I roll ? Has any one tried it before and what is the result comparing to the OEM tube.

Also, I changed the ohm load, made some db difference but nothing changed in sound quality.
I started my journey into tubes years ago with a Yaqin Tube Buffer,then Yaqin Tube integrated amp and now have downsized to a magnificent Quad AV-One..I could NEVER go back to SS...In my experience if your going to have a problem with a tube amp due to poor quality control it’s going to happen sooner rather than years down the road...Also as mentioned the factory Shaguang power tubes are not the best available..Try a set of the Re Issue Mullard or Genelex tubes.You can get Platinum Matched quads for less than $100.00 on Ebay...The Yaqin uses really good Japanese Steel transformers so I wouldn’t expect loose bass but I seem to remember mine responded really well to a power cable upgrade(nothing crazy though)...You could always sell the SS gear AND the Yaqin and look at something from Raven Audio,Rogue Audio,Cary Audio,Conrad Johnson or PrimaLuna...These amps are built to last a lifetime(with periodic tube replacement) and I’ve never read a word about anyone hearing loose bass in their systems...
Freediver. What speakers are you using with the Quad?  Intriqued by that amp to say the least.  Thanks!

Hi boisty,right now using Dynaudio Excite X14’s...They sound pretty amazing with the Quad.Imaging and Staging is wide and deep,mids are sublime and treble beautifully extended without harshness.They only lack deeper bass and better presence at VERY low listening levels to be fantastic all arounders...I am looking at trying either a set of Spatial Audio M4 TS’s or Reference 3A De Capo BE’s to see what higher up the food chain gets me...
 On the AV-One with only about 30 hours on it I just can't say enough good about it.Coming from the iFi Stereo 50 amp/dac build quality is on another level,sumptuous comes to mind.It feels like an amp that will last several lifetimes.Sound/build and value are off the charts on this amp and that is with factory tubes!
Hi Freediver thanks for the detailed response. Funny as I am using Spatial M2 Turbos at the momemt and was interested in hearing them with the Quad. Hope to check that out soon.  If I get the chance will let you know my thoughts. Currently using a Denon digital amp and I‘m looking to go back to tubes and the Quad caught my eye. Thanks again!

The X14s will sound at a much higher level if/when fed with (much) more than 12 wpc. Spatial is a wise move.