Mr Liang amplifier
Hi
If you are located in China would it not be simpler for you to contact Mr Liang and ask if it is ok to publish....or an alternative ask Poor Stoner who is also located in China he has direct contact with Mr Liang....I do not speak Chinese...so might be worth avoiding any troubles if it comes to removing them then that is a simple matter.....
I was not trying to suggest for people to build them merely to share the circuit...you could not build them in the Western world for the price that they are in China.
thanks
steve in the UK
Hi
If you are located in China would it not be simpler for you to contact Mr Liang and ask if it is ok to publish....or an alternative ask Poor Stoner who is also located in China he has direct contact with Mr Liang....I do not speak Chinese...so might be worth avoiding any troubles if it comes to removing them then that is a simple matter.....
I was not trying to suggest for people to build them merely to share the circuit...you could not build them in the Western world for the price that they are in China.
thanks
steve in the UK
Hi to you all.
This is my first post so be gentle.I bought one of these amps on epay a few weeks ago for the princely sum of 155 pounds.
I was wondering if anyone else's differs from the pictures I have seen.Mine has caged EI transformers for the mains,not toroids as in the pics.Also,the bias pots are in front of the 845's,so easier to get to when the valves are hot! Is this a newer version? (it's the 5881 type)
Regards,Ali
This is my first post so be gentle.I bought one of these amps on epay a few weeks ago for the princely sum of 155 pounds.
I was wondering if anyone else's differs from the pictures I have seen.Mine has caged EI transformers for the mains,not toroids as in the pics.Also,the bias pots are in front of the 845's,so easier to get to when the valves are hot! Is this a newer version? (it's the 5881 type)
Regards,Ali
Ali Tait said:
Hi Ali...
Yes, it is a newer version. It has 2 relays for switching the 845 HT and the driver tube HT after a delay. You got it at a good price. I paid a little bit more. Make sure you add an earth wire on the IEC socket to the chassis since it is not earthed.
It may be marked as a 240V version on the back but infact it will be a 220V unit if you check the voltages, esp the heater volts. They will be a little high but inside 10%.
I started to write a Review here. Seems a great buy. Component quality is good and not cheap crap as some suggest.
http://www.triode-systems.com/modules/wfsection/article.php?articleid=30
Hi Swamp,
Thanks for your reply.Yes you are quite correct about the quality of this item.You couldn't have the chassis made over here for that price,never mind the entire amp! I haven't opened it up yet,just been letting it run-in,and it's getting better and better.I'm accquainted with John Caswell(whom I've seen posting on here)from the World-Designs site,and he has advised me on the mods he's done to his,and I'll be following suit when the amp has run-in.I'll also be changing the output transformers for AE amorphous-cores,which are very good and can be had for a very reasonable price.I've just been trying them with a pair of old Technics SB-7000 3-ways that I've just collected after winning them on epay.These are monsters,weighing in at 36kg each.Got them for a song,as one of the tweeters has gone open-cicuit,so i'm trying to source replacements at the moment.They're a phase-linear design,which is what piqued my interest,as I've never heard this type of speaker before.First impressions are very favourable,but of course I'll need to source replacement tweeters to hear what they're really capable of,and then the next job will be to replace all the crossover components,as they're all over 30 years old now.The good thing about these is the 93dB/w/m efficiency,so a very valve-amp friendly design.I forsee a busy few days!
Regards,Ali
Thanks for your reply.Yes you are quite correct about the quality of this item.You couldn't have the chassis made over here for that price,never mind the entire amp! I haven't opened it up yet,just been letting it run-in,and it's getting better and better.I'm accquainted with John Caswell(whom I've seen posting on here)from the World-Designs site,and he has advised me on the mods he's done to his,and I'll be following suit when the amp has run-in.I'll also be changing the output transformers for AE amorphous-cores,which are very good and can be had for a very reasonable price.I've just been trying them with a pair of old Technics SB-7000 3-ways that I've just collected after winning them on epay.These are monsters,weighing in at 36kg each.Got them for a song,as one of the tweeters has gone open-cicuit,so i'm trying to source replacements at the moment.They're a phase-linear design,which is what piqued my interest,as I've never heard this type of speaker before.First impressions are very favourable,but of course I'll need to source replacement tweeters to hear what they're really capable of,and then the next job will be to replace all the crossover components,as they're all over 30 years old now.The good thing about these is the 93dB/w/m efficiency,so a very valve-amp friendly design.I forsee a busy few days!
Regards,Ali
Yes. I did the mains filter design. BTW Mr Liang seems to sound better without a mains filter in my system although the filter does have a large choke so maybe it needs the choke by-passing so eliminate the series mains component. Odd that my Korsun v6i sounds better with the filter, so does the cd player !! You have to try with and without sometimes to see what is best.
I added an earth on Mr Liang, on the IEC socket to the chassis at the rear but never bothered with an earth lift resistor at the star point. It did not hum so I think an earth lift is not really required but a real mains earth is for safety !!
I think John changed the tx due to the unit being 2nd hand faulty with an o/p tx short so he had no choice I guess. The standard tx are not that bad IMHO and not worth the cost and effort to upgrade unless you have a faultly one of course.
DC heaters vs AC heaters ?? Don't know which is best but again hum is not an issue on my unit with AC. It is very quiet. The main advantage of going DC for the driver stage would be to get the heater voltage bang on since it is a little high. The 845 is already DC heaters.
I have just changed some caps for Obbligato types off Brian at DiyHS. Major improvement.. miles more open and transparent. Did not expect such a major change. Tubes next ....
I added an earth on Mr Liang, on the IEC socket to the chassis at the rear but never bothered with an earth lift resistor at the star point. It did not hum so I think an earth lift is not really required but a real mains earth is for safety !!
I think John changed the tx due to the unit being 2nd hand faulty with an o/p tx short so he had no choice I guess. The standard tx are not that bad IMHO and not worth the cost and effort to upgrade unless you have a faultly one of course.
DC heaters vs AC heaters ?? Don't know which is best but again hum is not an issue on my unit with AC. It is very quiet. The main advantage of going DC for the driver stage would be to get the heater voltage bang on since it is a little high. The 845 is already DC heaters.
I have just changed some caps for Obbligato types off Brian at DiyHS. Major improvement.. miles more open and transparent. Did not expect such a major change. Tubes next ....
Yes the filter does seem to give variable results with different kit and in different houses!I'll have to try it without the filter.I presume it was the coupling caps you replaced?
I've changed the inputs to NOS GE 6SJ7's,and the drivers for Reflector 5881's.This was worth doing,especially considering how cheaply these valves can be had.Next up is probably some 845M's,or I may save up for KR's if I can find anyone to tell me they are worth the rediculous price!
Agree about the output transformers,but considering how cheap AE amorphous cores are,I think this will be the way to go.I've heard several amps with these,and they are very good indeed,incredible for the money.
I've changed the inputs to NOS GE 6SJ7's,and the drivers for Reflector 5881's.This was worth doing,especially considering how cheaply these valves can be had.Next up is probably some 845M's,or I may save up for KR's if I can find anyone to tell me they are worth the rediculous price!
Agree about the output transformers,but considering how cheap AE amorphous cores are,I think this will be the way to go.I've heard several amps with these,and they are very good indeed,incredible for the money.
Cathode Resistor for 6SJ7
Don't forget to change the value of the 6SJ7's cathode resistor. Without the change anode voltage was about +100V and g2 voltage +50V which is not what a 6SJ7 likes to see. In my amp the stock cathode resistor was only 390 Ohm.
I changed it to 1.5 kOhm and as a result anode voltage came up to 150V and g2 voltage to 100V. Cathode voltage is now 3.4V and anode current is 1.6mA.
The 845 needs about 290Vpp to deliver full power which makes the anode voltage of the first stage >= 150V a must!
Best regards,
Norbert
Don't forget to change the value of the 6SJ7's cathode resistor. Without the change anode voltage was about +100V and g2 voltage +50V which is not what a 6SJ7 likes to see. In my amp the stock cathode resistor was only 390 Ohm.
I changed it to 1.5 kOhm and as a result anode voltage came up to 150V and g2 voltage to 100V. Cathode voltage is now 3.4V and anode current is 1.6mA.
The 845 needs about 290Vpp to deliver full power which makes the anode voltage of the first stage >= 150V a must!
Best regards,
Norbert
Mods to Mr Liang 845
Hi all,
Just been catching up on a few things so here is what I have done to my Mr Liang MkI I guess ( 6J4P, 6P3P and 845)
When I first looked at it it belonged to a customer who complained that it was blowing mains fuses. This was traced to an output transformer short circuit primary to secondary. Couldn't source one from China, so measured the other and came to conclusion that a Sowter SE09 (5K:8R) would be suitable. Tried it and it worked very well but the customer didn't want to pay the Sowter price so in the end I bought the amp off him.
Fitted the Sowters roughly but had some hum which diminished when I rotated the OPTX due to hum pickup from power tx field. I then fitted them on a sub plate and rotated them for minimum hum, so far so good, but not enough to lower the hum to inaudible levels.
I then fitted hum bucking controls a la circuit supplied which reduced hum further and finally DC heated the front end (6J4P, 6P3P vlaves) . This took hum levels down to the point where I had to put my ear about 6"/150mm from the LS before anything was audible . Satisfactory conclusion.
I fitted a proper earth from the IEC to chassis and also an earth lift 10R resistor in parallel with a 0.1µF capacitor and removed the input switching and volume ontrol as my amps are always fed from a pre amp
I have taken photos of the work and am quite prepared to copy them to CD and send to people as my broadband here is pretty poor.
I am also prepared to offer advice, comments, or even insults over email or phone should anyone desire assistance and am prepared to do the mods for those lacking the skills but at a cost naturally.
I tried swapping valves 6SJ7 fo the 6J4P ( not quite the same and lower gain) aand a 5881/6L6WGC for the 6P3P (apparently identical). I note Norberts comments re the cathode resistor and will experiment and post results
In the meantime please feel free to email/phone me accordingly.
John Caswell
Hi all,
Just been catching up on a few things so here is what I have done to my Mr Liang MkI I guess ( 6J4P, 6P3P and 845)
When I first looked at it it belonged to a customer who complained that it was blowing mains fuses. This was traced to an output transformer short circuit primary to secondary. Couldn't source one from China, so measured the other and came to conclusion that a Sowter SE09 (5K:8R) would be suitable. Tried it and it worked very well but the customer didn't want to pay the Sowter price so in the end I bought the amp off him.
Fitted the Sowters roughly but had some hum which diminished when I rotated the OPTX due to hum pickup from power tx field. I then fitted them on a sub plate and rotated them for minimum hum, so far so good, but not enough to lower the hum to inaudible levels.
I then fitted hum bucking controls a la circuit supplied which reduced hum further and finally DC heated the front end (6J4P, 6P3P vlaves) . This took hum levels down to the point where I had to put my ear about 6"/150mm from the LS before anything was audible . Satisfactory conclusion.
I fitted a proper earth from the IEC to chassis and also an earth lift 10R resistor in parallel with a 0.1µF capacitor and removed the input switching and volume ontrol as my amps are always fed from a pre amp
I have taken photos of the work and am quite prepared to copy them to CD and send to people as my broadband here is pretty poor.
I am also prepared to offer advice, comments, or even insults over email or phone should anyone desire assistance and am prepared to do the mods for those lacking the skills but at a cost naturally.
I tried swapping valves 6SJ7 fo the 6J4P ( not quite the same and lower gain) aand a 5881/6L6WGC for the 6P3P (apparently identical). I note Norberts comments re the cathode resistor and will experiment and post results
In the meantime please feel free to email/phone me accordingly.
John Caswell
Other Changes
The other changes I did so far:
Best regards,
Norbert
The other changes I did so far:
- Connect earth to chassis ground
- Calibrate the two bias meters
- Replace 6J4P with NOS JAN 6SJ7WGT (Philips), I also tried NOS JAN 6SJ7Y (GE)
- Replace 6P3P with 6L6GC (JJ), I also tried 6L6WGC (TAD), 5881 (Tung-Sol reissue) and KT66 (Valve Art)
- Replace coupling caps with Audio Note tin foil caps
- Replace HV rectifier diodes 1N4007 with BYV96E types
Best regards,
Norbert
Mr Liang 845 amp and Improvements
Hi all
Nice to see all the replies on how peeps have gone about changing this worthy design....
here are somethings I wish to note:
1. if the primary on mains transformer is 220 not 240 volts then it is not just the heaters which are seeing too high a voltage so are the anodes.
1.1 does this or it should mean you need to set bias at a lower level than the recommended 90mA otherwise they will being over run...
1.3 I can not get the bias below 80mA on the righthand amp ...is it the tube? The overvolts or poor bias adjustment?
1.4 I had heard from German Diy site that the 845M the metal type 845 does not work in this amp?
2. 6P3P or I should say the Tung sol 5881s that I have in this amp one went dead a few weeks back swapped the tubes over channels until I found fault left dodgy tube in left hand side and it failed again...got a replacement for free....
2.1 KT66 in my opinion should not be used the 6P3P which has a heater rating of 0.9A and the KT66 is 1.6A...the 5881 and 6L6GC is 0.9A rating as well.
2.2 I suspect that modern valves suffer from lack of testing and a lot more pass through testing than in the old days as take up is smaller now they can not afford to throw away 1000's of tubes to get the reliability factor up to old standards....and of course if a thing has gone out of production or has been mothballed things get forgotten......or lost.
3. I need to be brave and venture inside mine to put or check the earthing.....
3.1 Should I think about replacing those coupling capacitors and with what...I am impoverished student?
3.2 I can testify that by-passing reservoir caps works but have not tried it in this design....usually cleans up top end....
3.3 I think the that when I added the 5881s the gain seems to have dropped...could this be down to the front end tube not operating at correct level.
4...I am thinking of changing the 845s to Shuguang Amperex replicas...the amp comes with these as standard now.....
5. Mine is an earlier version which does not have the second choke or delay in the 5881 supply...
5.1 would it be worth adding these components in?
5.2 It would stop over volts on anodes of input and driver tube.
I must say that I like the sound of the amplifier I do however find that slightly under developed top end a bit noticeable....but I find that that works well with digital sources.....it is a product of the 845 tube itself...it could be compensated for by an overbright pre-amp which would give a bit of a top end lift......
Those are my findings after listening to this amp for about 4 months....
Steve in the UK
Hi all
Nice to see all the replies on how peeps have gone about changing this worthy design....
here are somethings I wish to note:
1. if the primary on mains transformer is 220 not 240 volts then it is not just the heaters which are seeing too high a voltage so are the anodes.
1.1 does this or it should mean you need to set bias at a lower level than the recommended 90mA otherwise they will being over run...
1.3 I can not get the bias below 80mA on the righthand amp ...is it the tube? The overvolts or poor bias adjustment?
1.4 I had heard from German Diy site that the 845M the metal type 845 does not work in this amp?
2. 6P3P or I should say the Tung sol 5881s that I have in this amp one went dead a few weeks back swapped the tubes over channels until I found fault left dodgy tube in left hand side and it failed again...got a replacement for free....
2.1 KT66 in my opinion should not be used the 6P3P which has a heater rating of 0.9A and the KT66 is 1.6A...the 5881 and 6L6GC is 0.9A rating as well.
2.2 I suspect that modern valves suffer from lack of testing and a lot more pass through testing than in the old days as take up is smaller now they can not afford to throw away 1000's of tubes to get the reliability factor up to old standards....and of course if a thing has gone out of production or has been mothballed things get forgotten......or lost.
3. I need to be brave and venture inside mine to put or check the earthing.....
3.1 Should I think about replacing those coupling capacitors and with what...I am impoverished student?
3.2 I can testify that by-passing reservoir caps works but have not tried it in this design....usually cleans up top end....
3.3 I think the that when I added the 5881s the gain seems to have dropped...could this be down to the front end tube not operating at correct level.
4...I am thinking of changing the 845s to Shuguang Amperex replicas...the amp comes with these as standard now.....
5. Mine is an earlier version which does not have the second choke or delay in the 5881 supply...
5.1 would it be worth adding these components in?
5.2 It would stop over volts on anodes of input and driver tube.
I must say that I like the sound of the amplifier I do however find that slightly under developed top end a bit noticeable....but I find that that works well with digital sources.....it is a product of the 845 tube itself...it could be compensated for by an overbright pre-amp which would give a bit of a top end lift......
Those are my findings after listening to this amp for about 4 months....
Steve in the UK
Meter Calibration
Hi Steve,
the procedure is as follows:
Sadly there is no way round opening the bottom and connecting a voltmeter across the two 15 Ohm resistors (located on the power supply board) which is part of the 845 cathode ground path.
Once done that you adjust the bias pot for a reading of 675mV on your voltmeter.
Perhaps you have noticed that tiny black screw on the meter which usually serves the purpose of nulling the meter. For our purpose (exact reading of one single value) you can calibrate the meter to show exactly 90mA. Nulling might be spoiled now but who cares?
BTW, with the Philips 6SJ7 and all driver tubes I have tried I never encountered anything like an underdeveloped top end, especially the JJ 6L6 provides a really extended and liquid top end.
Best regards,
Norbert
Hi Steve,
the procedure is as follows:
Sadly there is no way round opening the bottom and connecting a voltmeter across the two 15 Ohm resistors (located on the power supply board) which is part of the 845 cathode ground path.
Once done that you adjust the bias pot for a reading of 675mV on your voltmeter.
Perhaps you have noticed that tiny black screw on the meter which usually serves the purpose of nulling the meter. For our purpose (exact reading of one single value) you can calibrate the meter to show exactly 90mA. Nulling might be spoiled now but who cares?
BTW, with the Philips 6SJ7 and all driver tubes I have tried I never encountered anything like an underdeveloped top end, especially the JJ 6L6 provides a really extended and liquid top end.
Best regards,
Norbert
Mr Liang 845 amp and meter calibration
Hi Norbert
Thanks so much for that... I am competant enough to carry out such a task but I am rather loathsome to do so...of course the easy option is to connect it all up with the power disconnected of course.....
I have a Leader LMV 181 or some such millivolt meter which I can use for this purpose......
Like you say who cares about the nulling would much rather that the meter was reading accurately.....
one final thing or two actually where did you you get the philips(Mullard) 6SJ7s? Secondly does this procedure need to be done again when you change the 845s ?
Thanks for your help
Steve
Ps when I said under developed I meant not overly extended or sharp as in many amps cases
Hi Norbert
Thanks so much for that... I am competant enough to carry out such a task but I am rather loathsome to do so...of course the easy option is to connect it all up with the power disconnected of course.....
I have a Leader LMV 181 or some such millivolt meter which I can use for this purpose......
Like you say who cares about the nulling would much rather that the meter was reading accurately.....
one final thing or two actually where did you you get the philips(Mullard) 6SJ7s? Secondly does this procedure need to be done again when you change the 845s ?
Thanks for your help
Steve
Ps when I said under developed I meant not overly extended or sharp as in many amps cases
Meter Calibration
Hi Steve,
you don't have to repeat that calbriation procedure when you change the 845. Only when changing the bias point significantly (e. g. to 75mA for the 845B) I would repeat the procedure for the new bias point.
I did buy my Philips 6SJ7WGT from Angela Instruments. They also sell in the bay.
Best regards,
Norbert
Hi Steve,
you don't have to repeat that calbriation procedure when you change the 845. Only when changing the bias point significantly (e. g. to 75mA for the 845B) I would repeat the procedure for the new bias point.
I did buy my Philips 6SJ7WGT from Angela Instruments. They also sell in the bay.
Best regards,
Norbert
Mr Liang 845 and the 845B
Hi Norbert
Forgive me for picking your brains .....so I am to understand that I need to re-measure the volts across the 15 ohm resistors which would in the case of the 845B be 75mV...did I get that right?
That means they are a bit beefier than the standard Shuguang 845s?
Thanks you've been a great help and of course if you adjust bias or calibrate in this way it matters not that the ht is a bit high as you are adjusting the meter and bias pot for the correct dissipation in the output tube?
Will go look up 6SJ7s philips....anyone tried RCA or some such 5693 which is mil-spec version?
steve in the uk
Hi Norbert
Forgive me for picking your brains .....so I am to understand that I need to re-measure the volts across the 15 ohm resistors which would in the case of the 845B be 75mV...did I get that right?
That means they are a bit beefier than the standard Shuguang 845s?
Thanks you've been a great help and of course if you adjust bias or calibrate in this way it matters not that the ht is a bit high as you are adjusting the meter and bias pot for the correct dissipation in the output tube?
Will go look up 6SJ7s philips....anyone tried RCA or some such 5693 which is mil-spec version?
steve in the uk
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