Gain
Swamp,
the 6SJ7 is not an exact 6J4P substitute. The later has higher (> 4mS vs. 1.5mS) transconductance which leads to higher gain. That's also the reason why you have to adjust the cathode resistor.
To me it seems quite obvious that the Mr. Liang (at least with the 6SJ7) is not an integrated amplifer even if it is equipped with two inputs and a volume pot. You have to use a preamp to drive it properly.
I personally found the conversion to the 6SJ7 to be an improvement but that's a question of personal taste and might also depend on the type of 6SJ7 you are using.
Best regards,
Norbert
Swamp,
the 6SJ7 is not an exact 6J4P substitute. The later has higher (> 4mS vs. 1.5mS) transconductance which leads to higher gain. That's also the reason why you have to adjust the cathode resistor.
To me it seems quite obvious that the Mr. Liang (at least with the 6SJ7) is not an integrated amplifer even if it is equipped with two inputs and a volume pot. You have to use a preamp to drive it properly.
I personally found the conversion to the 6SJ7 to be an improvement but that's a question of personal taste and might also depend on the type of 6SJ7 you are using.
Best regards,
Norbert
Hi Norbert...
Yes, the metal 6sj7 do sound better in many ways but due to the resulting lower gain a pre-amp is a must. Myself and a friend also found this out from experimenting. With a Pre-amp Mr Liang is much better dynamically and comes back to life. As you say, it may be best to treat this amp as a power amp with a volume control.
Just need a good pre-amp now. Looking at the Aikido as an option ?
Thanks
Swamp
Yes, the metal 6sj7 do sound better in many ways but due to the resulting lower gain a pre-amp is a must. Myself and a friend also found this out from experimenting. With a Pre-amp Mr Liang is much better dynamically and comes back to life. As you say, it may be best to treat this amp as a power amp with a volume control.
Just need a good pre-amp now. Looking at the Aikido as an option ?
Thanks
Swamp
ttan98 said:
I lived in china for awhile and my take on this is the quality of electronics exported to USA, etc.. is of higher quality than what you'll buy in China. I bought several pieces of audio gear while i was there for use in China (i was there awhile... ) and they were of department store quality - nothing special. What I did buy was a great deal of electronic parts to use in my own tube amps that I brought back to the USA. From those there was a high did not work straight out of the box ratio. I bought a bunch of dead parts. Of the ones that did work - they are still working, worked well and were pretty much on spec value wise. So in the end, for a little headache and testing, I got cheap parts. Would I risk that on a transformer though? I don't think so.
A couple of months ago I bought the 6J4P and 6P3P version which does by the way have an earth lead to the chassis.
Can anybody advise me on the best way to remove the driver circuit board as I would like to upgrade the components - it looks to me as if I might have to start with removing the meters?
Also mine has an audible mechanical hum from the mains transformers which really kicks in when the HT supply does. Any ideas to reduce it?
Thanks in anticipation of your reply(ies)...
Can anybody advise me on the best way to remove the driver circuit board as I would like to upgrade the components - it looks to me as if I might have to start with removing the meters?
Also mine has an audible mechanical hum from the mains transformers which really kicks in when the HT supply does. Any ideas to reduce it?
Thanks in anticipation of your reply(ies)...
Remove the front panel by ....
undoing the 4 screws at the front sides and 2 screws on top at the front center.
Pull off volume knob and undo the nut holding volume control on.
Loosen the nuts on the meter back to remove spades.
Front should fall forward, rest it on a book.
unclip the AC heater plugs and led feed plug to board.
undo the board screws and it will tilt up slightly. You need to unsolder the silver wire audio link to 845 grid to lift it more to get to underside.
unsolder the earth and signal wires to remove completely.
I think that's it from memory ?
undoing the 4 screws at the front sides and 2 screws on top at the front center.
Pull off volume knob and undo the nut holding volume control on.
Loosen the nuts on the meter back to remove spades.
Front should fall forward, rest it on a book.
unclip the AC heater plugs and led feed plug to board.
undo the board screws and it will tilt up slightly. You need to unsolder the silver wire audio link to 845 grid to lift it more to get to underside.
unsolder the earth and signal wires to remove completely.
I think that's it from memory ?
Mr Liang 845-3
Hi well it seems to be a while since anyone responded further to this subject. Yesterday, I was asking about Svetlana 811 valves and if anyone knew of a good design for the 811. Well as it turns out 1. my post hasn't posed (still in moderation?) and 2. looking at circuits previously posted the 811 will pump out about 11 watts max in SET mode. OK so now to Mr Liang.
I got really excited about this 845 amp and decided to try and build it.
In hind site I think I made a mistake. However, I had already ordered the Chokes and Transformers. As fortune would have it T2 was to be built last due several design considerations. At one point we were going to split it into two separate trans. T2a and b.
While this was going on, we took a closer look at the 845 bias circuit, and made some obvious safety mods in case we ever lost bias pot. wiper contact. We then decided that the whole thing was a potential major melt-down waiting to happen (Chernoble move over!). So we are currently looking at a major a redesign to use self-bias on the 845's, do away with the 120V T2 winding, and install valve diodes in the HT supply and do away with the timer device. (Valve diode warm up and a 20W resistor will take care of that). Also we need an anti-surge circuit on the AC.
So to the point, has anyone 1. built this amp from scratch and if so what experience re above problems (if any) and 2. Can anyone offer suggestions (or comments) on the proposed self-bias.
In retrospect I wish I had never started this, but who knows maybe a silk purse can be made from a Pig's ear!!
Hi well it seems to be a while since anyone responded further to this subject. Yesterday, I was asking about Svetlana 811 valves and if anyone knew of a good design for the 811. Well as it turns out 1. my post hasn't posed (still in moderation?) and 2. looking at circuits previously posted the 811 will pump out about 11 watts max in SET mode. OK so now to Mr Liang.
I got really excited about this 845 amp and decided to try and build it.
In hind site I think I made a mistake. However, I had already ordered the Chokes and Transformers. As fortune would have it T2 was to be built last due several design considerations. At one point we were going to split it into two separate trans. T2a and b.
While this was going on, we took a closer look at the 845 bias circuit, and made some obvious safety mods in case we ever lost bias pot. wiper contact. We then decided that the whole thing was a potential major melt-down waiting to happen (Chernoble move over!). So we are currently looking at a major a redesign to use self-bias on the 845's, do away with the 120V T2 winding, and install valve diodes in the HT supply and do away with the timer device. (Valve diode warm up and a 20W resistor will take care of that). Also we need an anti-surge circuit on the AC.
So to the point, has anyone 1. built this amp from scratch and if so what experience re above problems (if any) and 2. Can anyone offer suggestions (or comments) on the proposed self-bias.
In retrospect I wish I had never started this, but who knows maybe a silk purse can be made from a Pig's ear!!
Attachments
I haven't built one of these, but I would not get rid of fixed bias in favor of cathode bias for three reasons:
1. You will need a very high quality cathode bypass cap on the 845, and frankly there is nothing better sounding than no capacitor at all.
2. The B+ will have to increase by a commensurate amount to compensate for the loss across the cathode resistor.
3. With fixed bias you can easily tune the operating point for lowest thd or any sonic compromise that you prefer within the dissipation limits of the output tubes you are using.
Finally a fuse in the cathode circuit will protect against bias failure. (Usually that pot is more reliable these days than the tube it is associated with anyway. I expect the pot to outlast many output tubes. I've worn out plenty of tubes - I've yet to see a modern high quality pot fail, although it does happen. )
Almost without exception every amplifier I have ever design, built or sold to a client has used fixed bias, and I have never had a failure attributable to its use. That's not to say it can't happen - and there are certain very high transconductance/high perveance types were fixed bias is ill advised like the 6AS7 for example.
There are lots of other reasons I can think of not to build this particular design, not the least of which is that mediocre cathode follower circuit. I'd look for a Sakuma or other similar Japanese design instead.
1. You will need a very high quality cathode bypass cap on the 845, and frankly there is nothing better sounding than no capacitor at all.
2. The B+ will have to increase by a commensurate amount to compensate for the loss across the cathode resistor.
3. With fixed bias you can easily tune the operating point for lowest thd or any sonic compromise that you prefer within the dissipation limits of the output tubes you are using.
Finally a fuse in the cathode circuit will protect against bias failure. (Usually that pot is more reliable these days than the tube it is associated with anyway. I expect the pot to outlast many output tubes. I've worn out plenty of tubes - I've yet to see a modern high quality pot fail, although it does happen. )
Almost without exception every amplifier I have ever design, built or sold to a client has used fixed bias, and I have never had a failure attributable to its use. That's not to say it can't happen - and there are certain very high transconductance/high perveance types were fixed bias is ill advised like the 6AS7 for example.
There are lots of other reasons I can think of not to build this particular design, not the least of which is that mediocre cathode follower circuit. I'd look for a Sakuma or other similar Japanese design instead.
I found this threat by way of a search on Liang amps on yahoo.
I purchased a Mr Liang 2002 Stereo amp off eBay. it is not the same model as the amp you were discussing but it is a very well made, very solid, rich amp with ample headroom. I have only used it for a few hours so its not even close to being broken in but it arrived here from China superbly packaged, with not a scratch on it nor were the tubes anything less than ready to go to work.
I would be happy to post photos if I can find a host source for them, but its an attractive piece of work that combines contemporary looks with age old tube technology.
I purchased a Mr Liang 2002 Stereo amp off eBay. it is not the same model as the amp you were discussing but it is a very well made, very solid, rich amp with ample headroom. I have only used it for a few hours so its not even close to being broken in but it arrived here from China superbly packaged, with not a scratch on it nor were the tubes anything less than ready to go to work.
I would be happy to post photos if I can find a host source for them, but its an attractive piece of work that combines contemporary looks with age old tube technology.
You need to treat most china made tube amps as a starting point for DIY work. Also many tube amps from china are not in the same league as the Mr Liang. Some are crap with poor quality iron and very poor build inside.
The Mr liang is quite the opposite with massive output tx, 2 mains tx and 2 chokes. It weighs over 100lb compared to the music angel 845 at less than half that. The weight is due to the iron used. This makes it a great starting point to build a very high quality 845 amp. Inside it is also well put together on good PCB's with a very nice PSU and no voltage doubler crap like the MA845. Out of the box it is good but needs work to make it great and true hi-end.
I don't think Mr Liang's circuit design is the best but so what ? It is easy to replace the driver stage with something like an AN design. Cost is less than 500 GBP and once finsihed should equal 845 amps at silly prices. However not everyone is into diy audio or wants to mess about with 900V HT. If not and you have the cash to blow just go any buy something else and leave the chinese amps to the diy'ers.
The Mr liang is quite the opposite with massive output tx, 2 mains tx and 2 chokes. It weighs over 100lb compared to the music angel 845 at less than half that. The weight is due to the iron used. This makes it a great starting point to build a very high quality 845 amp. Inside it is also well put together on good PCB's with a very nice PSU and no voltage doubler crap like the MA845. Out of the box it is good but needs work to make it great and true hi-end.
I don't think Mr Liang's circuit design is the best but so what ? It is easy to replace the driver stage with something like an AN design. Cost is less than 500 GBP and once finsihed should equal 845 amps at silly prices. However not everyone is into diy audio or wants to mess about with 900V HT. If not and you have the cash to blow just go any buy something else and leave the chinese amps to the diy'ers.
Tis the season to start my DIY Mr Liang . My iron is in shipment, having been hand made for me in HK at a very good price. I have pics if anybody would like a peek, the quality to judge by weight and looks is excellent. As for the valves/tubes;-300b's and 2 sets (one cheap the other set more expensive in case of screw-ups) of 845's on order.
Some modifications....
The bias circuit has been modified in my proposed build; - R114 47K, VR102 10K, added 100K from wiper of VR102 to junction of R314/C310 for protection.
I propose to do away with the delay circuit; by placing thermionic diode valves in series with the HT rectifiers. Diode warm-up time should provide the required delay. (anyone had experience with this, what diodes would be best for the job, also probably need a resistor (value?) in there as well ??)
Someone in another related Liang post (July?)had a suggestion to redo the front end. What was it or anyone care to comment??
This project will be my first build for many many years and I'd appreciate any help.
Some modifications....
The bias circuit has been modified in my proposed build; - R114 47K, VR102 10K, added 100K from wiper of VR102 to junction of R314/C310 for protection.
I propose to do away with the delay circuit; by placing thermionic diode valves in series with the HT rectifiers. Diode warm-up time should provide the required delay. (anyone had experience with this, what diodes would be best for the job, also probably need a resistor (value?) in there as well ??)
Someone in another related Liang post (July?)had a suggestion to redo the front end. What was it or anyone care to comment??
This project will be my first build for many many years and I'd appreciate any help.
Lukasz Fikus has done this new front end....
http://www.lampizator.eu/AMPLIFIERS/CHINA/845/new845sch.jpg
My mate has built and fitted it in his Liang and in someways it is better (very clean, smooth) but in others not. Too me it now sounds very polite and safe. More of a sideways step really.
If it was me making a 845 diy I would try and use a DHT like a 205,45 driving the 845 after some voltage gain tube like a 6sl7 maybe in SRPP or MU. The 845 shows the sound of the driver stage so it is very important.
http://www.lampizator.eu/AMPLIFIERS/CHINA/845/new845sch.jpg
My mate has built and fitted it in his Liang and in someways it is better (very clean, smooth) but in others not. Too me it now sounds very polite and safe. More of a sideways step really.
If it was me making a 845 diy I would try and use a DHT like a 205,45 driving the 845 after some voltage gain tube like a 6sl7 maybe in SRPP or MU. The 845 shows the sound of the driver stage so it is very important.
Yes, it is a waste using expensive tubes like 300B's as a cathode follower. Better to keep them for another project / amp
Much better to use something cheaper and more common like the 6sn7's or a cheaper power tube as a driver.
That 6sn7 front end is certainly very easy on the ear and quite musical if not the last word in speed and dynamics.
David
Much better to use something cheaper and more common like the 6sn7's or a cheaper power tube as a driver.
That 6sn7 front end is certainly very easy on the ear and quite musical if not the last word in speed and dynamics.
David
ONKYO CD PLAYER DX-C311
DOES ANYONE HAVE A SERVICE MANUAL FOR THE DX-C311.
I NEED TO KNOW WHAT THE DAC IS ON THIS UNIT. IT IS LOCATED UNDER THE DISC CHANGER MECANISIM AND A REAL SOD TO GET AT. I'M THINKING I MIGHT "LAMPIZISE" (SEE LUKAZS FIKUS SITE). BUT BEFORE I TAKE THE WHOLE THING APART I NEED TO KNOW WHAT TYPE OF DAC IT IS.
IT WOULD BE GREAT IF IT IS THE CURRENT OUTPUT TYPE.... BUT UNTILL I KNOW.....DUH.
CAN ANYONE HELP PLEASE.
DOES ANYONE HAVE A SERVICE MANUAL FOR THE DX-C311.
I NEED TO KNOW WHAT THE DAC IS ON THIS UNIT. IT IS LOCATED UNDER THE DISC CHANGER MECANISIM AND A REAL SOD TO GET AT. I'M THINKING I MIGHT "LAMPIZISE" (SEE LUKAZS FIKUS SITE). BUT BEFORE I TAKE THE WHOLE THING APART I NEED TO KNOW WHAT TYPE OF DAC IT IS.
IT WOULD BE GREAT IF IT IS THE CURRENT OUTPUT TYPE.... BUT UNTILL I KNOW.....DUH.
CAN ANYONE HELP PLEASE.
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