Hi this is the first video I've ever seen from you - this is really great & I like the careful explanation given. Fender amps also specify a screen resistor of no more than one watt on the 6L6 screens for the same reason. I also have a Leek 10+10 amplifier with a 3 Watt resistor in the HT line. The advice is not to replace it with a 5 Watt device, the 3 Watt is so rated that in the event of overload, it melts the solder & drops off the board:)
Simple and elegant - nice work :) Makes me wonder why the B+ supply is so rarely fused nowadays. Back in the '60s...'80s Polish tube PA amps, main plate supply was fused; even heaters sometimes were. These things were designed by engineers, not accountants :).
Love your videos. Ever think about sharing them with the companies so perhaps they could implement them? I mean, the cost difference between 5W and 1W resistors can't be much, but as you note, it makes the amp much safer.
Thank you so much for this Muzishare X7 series. Have been using solid states equipment since the 70's. This X7 is my very first tube amplifier. The popping noise has been bothering me for some time. You are the only person that have talked about the cause and solution for that problem. This may be a dumb question (from a retired IT guy), does changing the 5 watt resistor to a lower wattage one affect sound quality? Thanks again...Subscribed!
No it won't, but this is the reason I wouldn't lower it below a 1W value even though theoretically a 1/8W resistor would work there. I am a big believer that resisters should be larger than absolutely required for sound quality.
Would you recommend doing the resistor switch if I only have limited soldering experience, it’s limited to soldering electronics in my guitar. On another note, Would changing out the coupling caps have a benefit? I’ve been learning so much through watching your videos and I appreciate all you show us.
Hello, I've had the Muzishare X7 for a week, the sound in combination with my QUAD ESL-988 speakers is not satisfactory. What is your opinion on the tube amplifier today? Regards, Ludovic
Did you replace the tubes? And seriously, if it you don't like the way it sounds and don't want to invest in replacing the tubes (I CLEARLY stated it doesn't sound good with the stock tubes) just return it. Unless the amp has changed, my opinion hasn't changed.
This video was super helpful, and I plan to replace the 4 resistors you referenced. I had a question about your comments about not using the pre-in option. This is my first tube amp, and I may be using it in a bit of an unorthodox way. I'm using the Zone 2 from my receiver and going into the pre-in on the X7. This is because I already have everything hooked up to the receiver and just wanted to replace the "amp" part. I'm under the impression the pre-in input just bypasses the volume control on the X7. Would using that input also somehow impact the sound quality in a negative way? Thanks!!
I enjoy your honest reviews of tube amps. I was about to pull the trigger on Muzishare X7 until you made the comment about the pre-in switch. I have a home theater and I enjoy listening to multi-channel, but I also enjoy 2channel on the phono player. I don't have the space for a separate setup for HiFi. I do have pre-outs on the receiver to make it an integrated amp. Can you tell me in simple terms why you don't recommend using the pre-in on the X7, which my main reason for buying this tube amp. Thank you.
Just use one of the regular jacks going though the volume control, that way you can adjust the input gain. These pre-in jacks are WAY too sensitive and for some reason just don't sound good.
What about quality of headphones amplifier circuit in Muzishare X7? Does it have tubes (what exactly?) or OpAmps (what exactly?) or something else? What headphones impedance range does it fit?
@@SkunkieDesignsElectronics thank you! And what headphones impedance does it fit? Does it use some sort of extra voltage deliverer or something elese to increase the impedance of output?
Honestly I have no idea. On my R8 I tore all that wiring and the headphone jack out. It seems silly to me to run a 45W push pull KT88 amp, with all that extra heat and electricity to drive a pair of headphones.
I have this amp and it works and sounds wonderful, no pops. So you believe the engineers/topology designers overlooked something? Have you talked to anyone at this company about your concerns? Just curious
100% none of the tube amps with "pre-in" bypass the pre-amp, because a tube amp doesn't have a pre-amp. It simply bypasses the volume control and many times will sound worse that using another input and just turning the volume control to the max.
Hello. Thanks for this video. Do I need to change the resistor only for this pair of tubes? Or do the second pair do the same? Anti-interference Vy2 103m? Is it possible to install KT 120 if you change the choke to 250mA and the power cups from 500 to 470?
6:08 Please tell me the exact number of Safety Capacitors Vy2103m. I looked at mouser, there are 12 positions, the difference is one or two letters, part of the number. There is a difference?
Hi, I have two of these amps, so very interested in your comments about them and enjoying and learning so much from your videos! I want to take your advice and replace those resistors on the KT88’s , can you give me the value and type of resistor to use, carbon or metal film and tolerances so I can order from here in the UK. Many thanks and keep up the very interesting vids! Alex.
Hi - I've been asked to replace a failed OPT on one of these. Maybe because the 5w resistor didn't pop to save the Tx. Do you happen to know what the Tx specs are and where I can get one from? Probably, I would replace both. I think it might also be sensible to add fuses in series with the resistors?
Thanks for the capitor tip to stop the popping sound when switching off, been dealing with that "pop" for too long. I have an amp with "Standby" , power switch on then wait 20 seconds and flip the stanby on for full power. When switching off I flip standy and "pop" so I just flip the power switch instead to avoid the pop(loud). Only does it on "switch off" otherwise fine. Do you think I should use the .1uf cap on the Standby or on the Power terminals? Thanks again...your soldering skills are A-1.
@@moodyga40 Fuse holders and fuse caps tend to oxidise and corrode over time creating non linear contact resistances, not so good for audio quality. I guess you could find solder lead style fuses, but remember they don't actually blow at the rated current.
@@mfr58 that's not true use good fuse holder. In every bit of valve audio gear I've built I have never seen this. My last 300B stereo amp I built I have a fuse on the centre tap of the HT transformer to the star ground. Never had any issues. As for the fuse not blowing I'm not sure what topography you have been reading, by using ohms law and testing the circuit to ensure that the correct fuse is fitted etc.
China syndrome meltdown..... really? With due respect, how was it tested as 5 watts version? The idea of using smaller watts resistor as a fuse, is understandable, still is controversial! Use of higher watts resistor is quieter, so its a balance.
Just going by the physical size vs the other resistors in the amp, which are the same type. might be a 3W? I'm just guessing but it's not small enough to act as a fuse. Higher W resistors are quieter, but given the tiny ma of current going though this one, a high quality metal film 10 ohm 1W isn't going to introduce any audible noise. And here is what can happen if the resistor doesn't pop. drive.google.com/file/d/1SOXHfqk7DyPFH2nHlRwXduWSzmmFk0Ff/view?usp=sharing
@@SkunkieDesignsElectronics not sure you will accept, but small metal film resistors does change the sound, in such critical areas. It will sound a bit dry, that's my experience. I would expect the HT fuse will pop if red plate or failure issues in hifi amp. Appreciate yr work, just want us hifi community to realise there are compromises, but the sound is most important.
Sadly the main fuse will not pop when a power tube starts to red plate. If it did, I wouldn't see the major damage I see in amps that have a red plate event. I heard no change in the sound of this particular amp reducing the wattage of this 10 ohm "meter shunt" resistor, but I do agree if this was a 1K or higher resistor, you might hear something. BTW these amps have no "HT fuse", they just have a fuse on the AC input jack.
Hi this is the first video I've ever seen from you - this is really great & I like the careful explanation given. Fender amps also specify a screen resistor of no more than one watt on the 6L6 screens for the same reason. I also have a Leek 10+10 amplifier with a 3 Watt resistor in the HT line. The advice is not to replace it with a 5 Watt device, the 3 Watt is so rated that in the event of overload, it melts the solder & drops off the board:)
Exactly!
Been loving this series on the X7, thanks so much for putting it together. Can’t wait to hear the results from the listening test.
Simple and elegant - nice work :)
Makes me wonder why the B+ supply is so rarely fused nowadays.
Back in the '60s...'80s Polish tube PA amps, main plate supply was fused; even heaters sometimes were. These things were designed by engineers, not accountants :).
This is such a great series. Thank you 👍
Thanks for your modifications, I have implemented some, it sounds better now, thanks
Great to hear! I may be doing a revisit on this amp soon!
Love your videos. I will definitely upgrade my R8. Still waiting to hear your comparison of the two amps. I am really curious.
Love your videos. Ever think about sharing them with the companies so perhaps they could implement them? I mean, the cost difference between 5W and 1W resistors can't be much, but as you note, it makes the amp much safer.
Well, what I do to them is public domain.
Incredible channel
Thank you so much for this Muzishare X7 series. Have been using solid states equipment since the 70's. This X7 is my very first tube amplifier. The popping noise has been bothering me for some time. You are the only person that have talked about the cause and solution for that problem. This may be a dumb question (from a retired IT guy), does changing the 5 watt resistor to a lower wattage one affect sound quality? Thanks again...Subscribed!
No it won't, but this is the reason I wouldn't lower it below a 1W value even though theoretically a 1/8W resistor would work there. I am a big believer that resisters should be larger than absolutely required for sound quality.
Would you recommend doing the resistor switch if I only have limited soldering experience, it’s limited to soldering electronics in my guitar. On another note, Would changing out the coupling caps have a benefit?
I’ve been learning so much through watching your videos and I appreciate all you show us.
Coupling caps do impact the sound and honestly I can't really comment on if you have the skills for this or not.
Great video.
Excellent! 😀👍
Thank you❤
the sensitivity of the volume control is annoying, I have installed a voltage divider directly after the control to the tube
Hello,
I've had the Muzishare X7 for a week, the sound in combination with my QUAD ESL-988 speakers is not satisfactory.
What is your opinion on the tube amplifier today?
Regards,
Ludovic
Did you replace the tubes? And seriously, if it you don't like the way it sounds and don't want to invest in replacing the tubes (I CLEARLY stated it doesn't sound good with the stock tubes) just return it. Unless the amp has changed, my opinion hasn't changed.
This video was super helpful, and I plan to replace the 4 resistors you referenced. I had a question about your comments about not using the pre-in option. This is my first tube amp, and I may be using it in a bit of an unorthodox way. I'm using the Zone 2 from my receiver and going into the pre-in on the X7. This is because I already have everything hooked up to the receiver and just wanted to replace the "amp" part. I'm under the impression the pre-in input just bypasses the volume control on the X7. Would using that input also somehow impact the sound quality in a negative way? Thanks!!
Both the pre-jacks and another port with the volume control wide open and go with what sounds better.
I enjoy your honest reviews of tube amps. I was about to pull the trigger on Muzishare X7 until you made the comment about the pre-in switch. I have a home theater and I enjoy listening to multi-channel, but I also enjoy 2channel on the phono player. I don't have the space for a separate setup for HiFi. I do have pre-outs on the receiver to make it an integrated amp. Can you tell me in simple terms why you don't recommend using the pre-in on the X7, which my main reason for buying this tube amp. Thank you.
Just use one of the regular jacks going though the volume control, that way you can adjust the input gain. These pre-in jacks are WAY too sensitive and for some reason just don't sound good.
Thanks, I will try your recommendation.
Is it A-class amplifier? AB? Or mixed-class depending on the required power?
AB is a "mixed class", it's class A up to a certain output level.
What about quality of headphones amplifier circuit in Muzishare X7? Does it have tubes (what exactly?) or OpAmps (what exactly?) or something else? What headphones impedance range does it fit?
There are no opamps, the headphone jack runs off the same output as the speaker jacks, all the tubes are used.
@@SkunkieDesignsElectronics thank you! And what headphones impedance does it fit? Does it use some sort of extra voltage deliverer or something elese to increase the impedance of output?
Honestly I have no idea. On my R8 I tore all that wiring and the headphone jack out. It seems silly to me to run a 45W push pull KT88 amp, with all that extra heat and electricity to drive a pair of headphones.
I have this amp and it works and sounds wonderful, no pops. So you believe the engineers/topology designers overlooked something? Have you talked to anyone at this company about your concerns? Just curious
Honestly, in normal use this isn't a huge deal, but if I owned one of these I would do this. It has no impact on the sound.
May be you should suggest such mod to the manufacturer? Have you tried to contact them?
I have no idea who even actually makes them lol.
@@SkunkieDesignsElectronics i guess the same manufacturer which produces "line magnetic". They have official website with contacts (youtube censored)
Dear Skunkie, could you pls check if pre-amp gets bypassed when using the pre-in inputs? Thanks
100% none of the tube amps with "pre-in" bypass the pre-amp, because a tube amp doesn't have a pre-amp. It simply bypasses the volume control and many times will sound worse that using another input and just turning the volume control to the max.
Hello. Thanks for this video. Do I need to change the resistor only for this pair of tubes? Or do the second pair do the same? Anti-interference Vy2 103m? Is it possible to install KT 120 if you change the choke to 250mA and the power cups from 500 to 470?
The power transformer likely can't handle KT120 heaters. And any mod done to one channel should be done to the other.
Thank ❤
It is recommended that I replace the shunt capacitor with a good film capacitor. remove the shunt resistor from the capacitor. How do you like it?
6:08 Please tell me the exact number of Safety Capacitors Vy2103m. I looked at mouser, there are 12 positions, the difference is one or two letters, part of the number. There is a difference?
The last ones I ordered were VY1472M51Y5VQ63V0 I don't think it's that critical, you just want some style of this type of cap across the switch.
Thanks
Hi, I have two of these amps, so very interested in your comments about them and enjoying and learning so much from your videos! I want to take your advice and replace those resistors on the KT88’s , can you give me the value and type of resistor to use, carbon or metal film and tolerances so I can order from here in the UK. Many thanks and keep up the very interesting vids! Alex.
Metal film, 10 ohm, 1W 0.1%
My lovely video! Yoy are best.
Hi id like to know what value of the ceramic cap you put on the switch to eliminate pop noise .Thanks
4700pF XY cap specifically mou.sr/49QROcb
ok thanks a lot
@@SkunkieDesignsElectronics
@@SkunkieDesignsElectronics This is a link to a 4700pf cap. You call out in the video a .01uf. Just want to be sure I put in the right one. Thanks
👍👍
I replaced my resister from 5w to 1 w end up the bias dead can’t adjust the bias!
Sounds like maybe a bad solder joint?
Hi - I've been asked to replace a failed OPT on one of these. Maybe because the 5w resistor didn't pop to save the Tx. Do you happen to know what the Tx specs are and where I can get one from? Probably, I would replace both. I think it might also be sensible to add fuses in series with the resistors?
👍
Thanks for the capitor tip to stop the popping sound when switching off, been dealing with that "pop" for too long. I have an amp with "Standby" , power switch on then wait 20 seconds and flip the stanby on for full power. When switching off I flip standy and "pop" so I just flip the power switch instead to avoid the pop(loud). Only does it on "switch off" otherwise fine. Do you think I should use the .1uf cap on the Standby or on the Power terminals? Thanks again...your soldering skills are A-1.
You can try a cap on the standby and see if it helps.
put fuse on the HT even better
Folks could, but wiring in a fuse holder able to deal with 440VDC is a lot more complicated.
@@SkunkieDesignsElectronics it will be fine been done in tube gear for years put it on the centre tap of the transformer.
@@moodyga40 Fuse holders and fuse caps tend to oxidise and corrode over time creating non linear contact resistances, not so good for audio quality. I guess you could find solder lead style fuses, but remember they don't actually blow at the rated current.
@@mfr58 that's not true use good fuse holder. In every bit of valve audio gear I've built I have never seen this. My last 300B stereo amp I built I have a fuse on the centre tap of the HT transformer to the star ground. Never had any issues. As for the fuse not blowing I'm not sure what topography you have been reading, by using ohms law and testing the circuit to ensure that the correct fuse is fitted etc.
China syndrome meltdown..... really? With due respect, how was it tested as 5 watts version? The idea of using smaller watts resistor as a fuse, is understandable, still is controversial! Use of higher watts resistor is quieter, so its a balance.
Just going by the physical size vs the other resistors in the amp, which are the same type. might be a 3W? I'm just guessing but it's not small enough to act as a fuse. Higher W resistors are quieter, but given the tiny ma of current going though this one, a high quality metal film 10 ohm 1W isn't going to introduce any audible noise.
And here is what can happen if the resistor doesn't pop. drive.google.com/file/d/1SOXHfqk7DyPFH2nHlRwXduWSzmmFk0Ff/view?usp=sharing
@@SkunkieDesignsElectronics not sure you will accept, but small metal film resistors does change the sound, in such critical areas. It will sound a bit dry, that's my experience. I would expect the HT fuse will pop if red plate or failure issues in hifi amp. Appreciate yr work, just want us hifi community to realise there are compromises, but the sound is most important.
Sadly the main fuse will not pop when a power tube starts to red plate. If it did, I wouldn't see the major damage I see in amps that have a red plate event. I heard no change in the sound of this particular amp reducing the wattage of this 10 ohm "meter shunt" resistor, but I do agree if this was a 1K or higher resistor, you might hear something. BTW these amps have no "HT fuse", they just have a fuse on the AC input jack.