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Muzishare X7 tube amp owners out there?


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Hello!

 

I wonder if U can check my bias adjustment - the scale in manual is different than in my muzishare X7. Is the value right - 40mA ? Thanks for help. 

 

I am thinking about step up to Genalex Gold Lion KT88.

Is it a good choice ? 

Photo of my bias adj

bias.JPG

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Just a quick update, received the x7 yesterday ! seller took awhile to dispatch(aprox 1 week) , but after dispatch fedex took 5 days to get here.    some photos from my phone , overall the q

Well, after doing some research and looking at my needs, I took the plung and purchased a Muzishare X7 largely by reading multiple web postings and the above comments.  I was also pondering the Willse

Being in Singapore, I am aware of lots of Chinese Tube amps in the market. PrimaLuna and Ayon which claim to be European Brands are "Designed in Europe" are all made in China. So bottom line is that C

Yes - it's 40 mA. Ignore the scale below 20 mA, as its divisions are different - split into divisions of 5 mA between 10 to 20 mA. Between 20 and 60 mA each division represents 10 mA.

Edited by xlr8or
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20 minutes ago, artur56 said:

Thank You! 

 

After 3 hours of playing, bias has changed on V4 to almost 80mA. Is it normal ?

 

No - this is not normal. When checking/adjusting bias make sure that no signal is passing through the circuit. Can you adjust it back down to 40 mA? You want to avoid any red plating of the tubes as this may take out the output transformer or the grid circuit. Let us know how you get along. You may have a faulty tube.

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1 hour ago, xlr8or said:

 

No - this is not normal. When checking/adjusting bias make sure that no signal is passing through the circuit. Can you adjust it back down to 40 mA? You want to avoid any red plating of the tubes as this may take out the output transformer or the grid circuit. Let us know how you get along. You may have a faulty tube.

I have re-adjust all tubes from 0 mA to ~40mA with disconnected all intputs. Will see how manny mA will we get after 2 hours of playing. 

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I think, You are right. Today I have replaced tube from V3 and change its position to V2, and V2 landed in V3 slot. 

I readjusted bias, and after some time the value has increased above 55 mA. If I set bias on this tube lower than 37-36 mA, after some time the value is decreasing, falling to 30mA. 

 

I think it is a time to change KT88 tubes ? 

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4 hours ago, artur56 said:

I think it is a time to change KT88 tubes ? 

 

Unfortunately, yes. It appears the tube is faulty and drifting away from its set bias value. I would recommend getting yourself another single tube if the existing other 3 are still new. If not, get yourself a new quad set. Made in Russia Genalex Gold Lion KT88's are quite reliable.

Edited by xlr8or
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2 hours ago, gapecans said:

Anyone using a pre-amp with the Muzishare X7? 

I do- Lar LPS1 - small polish company, with good quality amps and pre. I use it with denon dl103r. 

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On 05/12/2020 at 8:24 PM, xlr8or said:

 

Unfortunately, yes. It appears the tube is faulty and drifting away from its set bias value. I would recommend getting yourself another single tube if the existing other 3 are still new. If not, get yourself a new quad set. Made in Russia Genalex Gold Lion KT88's are quite reliable.

I have ordered 4 matched genalex tubes today, cant wait to try them. Bias level should be also set close to 40mA ? Or different value ? Thanks 

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3 hours ago, gapecans said:

Anyone using a pre-amp with the Muzishare X7? 

 

Using the Iotavx sa3 as a pre. Better remote, tone controls, and better phono stage. Plus I can power my speakers sans-tube amp with just the sa3 for tv watching with the use of a speaker switcher.

 

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7 hours ago, artur56 said:

Bias level should be also set close to 40mA ? Or different value ? Thanks 

 

Well done on purchasing a new quad set of KT88's. Bias should be set at the same value as prior with the other KT88 tubes - i. e., set at 40 mA.

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On 07/12/2020 at 7:08 PM, artur56 said:

I do- Lar LPS1 - small polish company, with good quality amps and pre. I use it with denon dl103r. 

Thanks for the response. I'm having a very difficult time locating a website got the preamp you are using. I did find a Pic of the internals and it looks very good. Question, do you clearly notice the sonic impact of the the pre-amp? I ask because there is talk out there that the Pre-In inlet only bypasses the volume control of the X7 and not the X7 internal pre-amp. That would bad news if true. 

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Well, I just tried my first tube rolling over the last 3 weeks.  I exchanged the stock 12AX7 for a NOS RCA 5751 and the pair of 12AU7A for NOS United 5814.  All I can say is WOW.  So much more separation of the instruments.  I went back to the stock tubes and yes, they played slightly louder, but a lot of the higher end was all crunched together.  I listen to everything: Easy listening, Jazz, Rock etc.  I am using just vinyl at this point.  I am going to enjoy this for a time, before I try some other NOS tubes.

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So I have a question...I have a RCA Command 5814A and a regular RCA 5814A in the 12AU7 position.  I read where the Command series were built to last longer.  Is there any issue with pairing the Command and the regular RCA tubes up?  I'm rolling them so far with with a RCA 5751 Command in the 12AX7A position.  Sounds pretty sweet out of the box.  When they burn in, I'm going to compare this set up with the Universal and RCA combo I've tested so far.

Edited by Major_Dundee
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I have been playing on the new Genalex Gold Lion for several weeks. The Bias issue has been resolved and the sound quality has also improved. But this is what I always feel when I upgrade something :)

 

Thanks for help! 

 

tubes.JPG

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On 23/01/2021 at 3:50 AM, Major_Dundee said:

So I have a question...I have a RCA Command 5814A and a regular RCA 5814A in the 12AU7 position.  I read where the Command series were built to last longer.  Is there any issue with pairing the Command and the regular RCA tubes up?

 

There is absolutely no issue with running the two different 5814A tubes together as a pair in the amp. What matters is their internal construction features and if they are the same or differ between the 2 tubes.

 

Can you share some close up photos of the RCA Command 5814A versus RCA 5814A?

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@Major_Dundee The best 5814 to try are the early 1950's white labelled Hytron 5814's or the mid to late red labelled 1950's CBS Hytron 5814A or 5814WA variety. For the 5751, the preferred is the Raytheon 5751 windmill getter from the 1960's. 😁

 

Here are some red labelled CBS Hytron 5814A's from 1956:

 

https://www.ebay.com.au/itm/1pc-CBS-12AU7-5814-Vacuum-Tube-Electronic-Replace-ECC82-6189-HIFI-VINTAGE-Amp-/283403901819

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Here are a couple of shots of the RCA Command 5814A manufactured 6835  and RCA 5814A manufactured 6943.  I hope they are clear enough for you to see what you are looking for.  I am currently running a RCA Command 5751 in the 12AX7 position with this set up.  So far, so good.  I want to give these a couple of weeks to burn in.  I haven't compared it yet to the set up I mentioned in a previous post.  Both of these are definitely a massive improvement over the stock tubes.  Stay tuned and thanks for your thoughts and recommendations on this.

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1 hour ago, Major_Dundee said:

Here are a couple of shots of the RCA Command 5814A manufactured 6835  and RCA 5814A manufactured 6943.  I hope they are clear enough for you to see what you are looking for.  I am currently running a RCA Command 5751 in the 12AX7 position with this set up.  So far, so good.  I want to give these a couple of weeks to burn in.  I haven't compared it yet to the set up I mentioned in a previous post.  Both of these are definitely a massive improvement over the stock tubes.  Stay tuned and thanks for your thoughts and recommendations on this.

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They look identical internal construction to me. Even the shield symbol with the 5814A etched inside and the U.S.A. etched outside and just above it look the same. Although one tube was made in 1968 and the other in 1969 and just over a year apart they can still be used as a matched pair. 👍👍👍

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So while I have my camera out, here are a few shots of the United tubes.  I'm not sure who the original manufacturer is.  These are late run (1977), but sound remarkably good in the Muzishare X7.  I'm going give it a couple of weeks before I compare them to the RCAs.  What is interesting (see picture),  is that there seems to be the number 13 and 18 embossed in the glass at the base of each tube respectively.  Just a curiosity... 

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On 26/01/2021 at 1:31 PM, Major_Dundee said:

So while I have my camera out, here are a few shots of the United tubes.  I'm not sure who the original manufacturer is.  These are late run (1977), but sound remarkably good in the Muzishare X7.  I'm going give it a couple of weeks before I compare them to the RCAs.  What is interesting (see picture),  is that there seems to be the number 13 and 18 embossed in the glass at the base of each tube respectively.  Just a curiosity... 

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I'm considering the Muzishare X7 also. Any update on your experience or any additional information you'd like to share? Thanks!

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On 27/01/2021 at 5:31 AM, Major_Dundee said:

So while I have my camera out, here are a few shots of the United tubes.  I'm not sure who the original manufacturer is.  These are late run (1977), but sound remarkably good in the Muzishare X7.  I'm going give it a couple of weeks before I compare them to the RCAs.  What is interesting (see picture),  is that there seems to be the number 13 and 18 embossed in the glass at the base of each tube respectively.  Just a curiosity... 

20210126_131207.jpg

20210126_131231.jpg

20210126_131749.jpg

20210126_131433.jpg

20210126_131618.jpg

 

I'm coming in late here as I've just seen these photos. I'm not at all surprised that you like these 5814's a lot. They're from the early 1950's pre triple mica construction. Both tubes were made by GE and possibly Ken-Rad for the one on the right with the shiny carbonised anode plates.

 

These are one of the most desirable 5814's to own. The first vesion of the 5814's pre 5814A are the most sort after tubes to collect. The use of the 4 silver clamp clips on the top mica plate is a dead give-away it's a GE manufactured tube.

 

Between the newer United Electronics tube boxes and the older GE tube boxes you can also see a similarity in the same colour banding that has been used. United Electronics in the USA acquired many older tubes from GE, RCA and Sylvania and relabelled them in the 1970's as their own.

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  • 1 month later...

Hi, I am seriously considering the X7 as my next amp as I plan to move my current amp into a second setup. A few questions: 

 

- I am still debating between the X7 and the R8. I can get the Muzishare delivered from Europe for 1200 EUR, while the R8 is much cheaper ordered in China Audio (770 EUR), but with import tax will cost probably about 1000 EUR. X7 has a phono stage which is interesting as I plan to re-introduce a turntable into my stereo setupsoon. Anyone tried the phono on the X7? Also more comments on how the R8 and X7 compare are welcome. 

- I am now firmly into TDA1541 DACs and will recieve in a couple of weeks a new MHDT Orchid with Tube buffer. Anyone with such a combo? My current amp is an Exposure 3010s which I like quite a lot, but am more and more attracted to a "tube" sound. 

  

 

 

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1 hour ago, al2813 said:

Hi, I am seriously considering the X7 as my next amp as I plan to move my current amp into a second setup. A few questions: 

 

- I am still debating between the X7 and the R8. I can get the Muzishare delivered from Europe for 1200 EUR, while the R8 is much cheaper ordered in China Audio (770 EUR), but with import tax will cost probably about 1000 EUR. X7 has a phono stage which is interesting as I plan to re-introduce a turntable into my stereo setupsoon. Anyone tried the phono on the X7? Also more comments on how the R8 and X7 compare are welcome. 

- I am now firmly into TDA1541 DACs and will recieve in a couple of weeks a new MHDT Orchid with Tube buffer. Anyone with such a combo? My current amp is an Exposure 3010s which I like quite a lot, but am more and more attracted to a "tube" sound. 

  

 

 


The phono stage on the X7 is seriously lacking. Someone else pointed it out so I tested it against the IOTAVX SA3 and he was right, the latter is miles better. I released a video with my thoughts on the X7:
 


The next one will compare the phono stages, hope to release it soon

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Hi,

 

I use the built in phono stage in the Muzishare X7 and ALWAYS have it set in the Ultralinear position.  My phonograph is a vintage Empire  Troubador 598 III and my cart is a Empire 4000 D/III frequency response: 5 - 50,000Hz.  My speakers are DCM Time Windows 7:  4 Ohms Frequency Range - 20 Hz -25,000 Hz.  I pass through a DCM powered Sub - 712 Frequency Range 28Hz - 80Hz to control as much bass as I want.  I can honestly say that I have been totally blown away by the sound stage.  Now, the one huge upgrade is that I swapped out the stock 12AU7 to 5814 and the 12AX7 to 5751 as mentioned earlier in this thread.  I would consider tube rolling before jumping to the conclusion that the phono stage in inadequate IMHO.  I listen to all genres of music including live stage shows, jazz, swing and rock.  I am more than content.

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Awesome sounding cart that Empire 4000 D/3 as long as the load is 100k.

 

@Major_Dundee if It's not loaded at 100k, you will be amazed at the difference if you change it to 100k. I had one and had it loaded at 50k and it was OK but at 100k it was another level.

Edited by muon*
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Well pulled the trigger on the X7. It's the last unit available for delivery from Belgium and as I hear of significant delays in amp deliveries from China, decided to pull the trigger.

A lot of money spent the past days so will have to sell out some items but well yet again Easter holidays with no travel due to Covid so might as well have some fun 🙂 

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Got my X7 yesterday. Just trying it out all default as this stuff is new to me. One strange thing, the left channel meter is showing much higher values than the right hand one. Is there anything faulty? How can I troubleshoot this? 

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47 minutes ago, al2813 said:

Got my X7 yesterday. Just trying it out all default as this stuff is new to me. One strange thing, the left channel meter is showing much higher values than the right hand one. Is there anything faulty? How can I troubleshoot this? 

 

Try re-adjusting each tube's bias to 40mA and let us know how you go. I suspect the power tubes that have been used in each channel pair haven't been matched at the factory, which is understandable for a mass produced unit such as this..

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1 hour ago, xlr8or said:

 

Try re-adjusting each tube's bias to 40mA and let us know how you go. I suspect the power tubes that have been used in each channel pair haven't been matched at the factory, which is understandable for a mass produced unit such as this..


hi, thx. I adjusted the bias to 40 mA plus switched speaker cable. No change.  Needless to say I try two different sources with different connector cables. 

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Can you share photos of the left and right channel meters?

 

You can try swapping the pairs around - left to right and right to left, and see if that changes anything.

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28 minutes ago, xlr8or said:

Can you share photos of the left and right channel meters?

 

You can try swapping the pairs around - left to right and right to left, and see if that changes anything.


let me take some photos and post. I tried multiple things. Swapped the pairs, changed speakers (my usual speakers are 4 ohm but I have a second pair which is 8 ohm). Same issue. I wrote the store. I suspect a faulty unit. 
 

 

 

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It's a problem related to the dual meter. Initially, I thought the problem was related to the tubes but youve confirmed that isn't the case.. The rest of the swaps won't change anything as they're unrelated.

 

You've confirmed bias can be set correctly. I would feel more comfortable purchasing a cheap bias meter on eBay to confirm the plate current values. If the VU meter is playing up then all that is needed is a new meter to be fitted in its place. Whether it's the left or right VU meter playing up is going to be challenging to call.

 

Sorry to hear you've experienced such a problem. You would've hoped that QA/QC would've picked this up.

 

Edit: The VU meter is just an aesthetics thing. If the tubes are properly biased to 40mA you can ignore the VU meters and sit back and enjoy the sound. That's what really counts. 👍

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1 minute ago, xlr8or said:

It's a problem related to the meter. Initially, I thought it was related to the tubes but youve confirmed that isn't the case.. The rest of the sways won't change anything as they're not related.

 

You've confirmed bias can be set correctly. I would feel more comfortable purchasing a cheap bias meter on eBay to confirm the plate current values. If the VU meter is playing up then all that is needed is a new meter to be fitted in its place.

 

Sorry to hear you've experienced this problem. You would've hoped that QA/QC would've picked this up. I guess they are mass produced, boxed and shipped out with this important step skipped.


I probably forgot to mention the fact that the speaker matching the “higher” meter is playing louder. And I swapped the wiring to make sure I am not imagining. I will test with a second amp I have tomorrow. 

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50 minutes ago, al2813 said:


I probably forgot to mention the fact that the speaker matching the “higher” meter is playing louder. And I swapped the wiring to make sure I am not imagining. I will test with a second amp I have tomorrow. 

 

Cool. I think the bias is not also reading correctly on the left channel. The spring in the dual meter appears to have lost some of its full scale deflection capability or the zero point hasn't been adjusted accordingly on the meter and is offset. The tubes are probably under biased and sounding lower in volume output. One of these would help to dial in 40mA for all 4 tubes.

 

https://www.ebay.com.au/itm/Dual-Bias-Current-Probe-Tester-VU-Meter-for-EL34-KT88-6550-Vacuum-Tube-Amplifier-/392702491739

Edited by xlr8or
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My own personal opinion is to send it back for another unit.  I just had an issue with one of the KT-88 tubes popping.  I switched the tubes around until I isolated the culprit.  After talking to the manufacturer,  I had to make a video showing what the issue is.  Now they want me to mail the tube back to them.  I haven't done it yet, because I'm not convinced it is worth the postage and time from the USA to China for a lousy stock tube.  I think I'm going to slowly replace them.

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