Hi, I recently got a pair of Luxman B12 mono amps on Ebay.
I restored them with new electrolytes,input and output terminals,control lights,output relays and fresh heatsink compound on all the power trannies.
They function perfectly with about 4mV of offset at the output.
The only difference between the two is the bias current.One has 115mA and the other 200mA.
Neither get very hot in iddle.
Does anybody know the correct bias setting for these amps?
Any suggestion are welcome.
kro5998.
I restored them with new electrolytes,input and output terminals,control lights,output relays and fresh heatsink compound on all the power trannies.
They function perfectly with about 4mV of offset at the output.
The only difference between the two is the bias current.One has 115mA and the other 200mA.
Neither get very hot in iddle.
Does anybody know the correct bias setting for these amps?
Any suggestion are welcome.
kro5998.
Hi kro5998,
Cool! I've never heard of those ones. Got a picture?
Anyone have a diagram for this??
-Chris
Cool! I've never heard of those ones. Got a picture?
Anyone have a diagram for this??
-Chris
Hi Chris.
They look just the same as the M12 amp from the outside.The only difference is at the back.(the M12 is stereo 2 x 85 Watt)
They are rated at 150 Watt into 8 ohm but i measured 176 Watt with 0.70 Volt.
I you don't know the M12 either i'll post some pictures.
kro5998
They look just the same as the M12 amp from the outside.The only difference is at the back.(the M12 is stereo 2 x 85 Watt)
They are rated at 150 Watt into 8 ohm but i measured 176 Watt with 0.70 Volt.
I you don't know the M12 either i'll post some pictures.
kro5998
Hi kro5998,
Okay, that I know. The bias current is measured by pulling off the gray wire on lug #2 and using an ammeter. The target was 60mA (+10, - 0 mA), or 60~70 mA. This model had two pair of outputs, so that would be 30~35 mA per device (0R18 emitter resistors).
I don't know how close that is to yours. I hope this helps.
-Chris
Okay, that I know. The bias current is measured by pulling off the gray wire on lug #2 and using an ammeter. The target was 60mA (+10, - 0 mA), or 60~70 mA. This model had two pair of outputs, so that would be 30~35 mA per device (0R18 emitter resistors).
I don't know how close that is to yours. I hope this helps.
-Chris
Hi Chris. Although they look similar on the outside they are not the same inside.
The endstage of the M12 runs on 48-52 Volts (driver stage 58 V) and uses two pairs of 2SD551/2SB681
The endstage of the B12 runs on 76 Volts (driver stage 95 V) and uses three pairs of 2SD665/2SB645
The emitter resistors are 0R18 ohm.
kro5998
The endstage of the M12 runs on 48-52 Volts (driver stage 58 V) and uses two pairs of 2SD551/2SB681
The endstage of the B12 runs on 76 Volts (driver stage 95 V) and uses three pairs of 2SD665/2SB645
The emitter resistors are 0R18 ohm.
kro5998
Hi kro5998,
Okay, however the bias current per device may be the same. I'll assume the heatsink for the B12 is larger than the M12.
What was the bias measured at? If it was close to the figure (30~35mA per device) you are probably safe to trim it to those values.
-Chris
Okay, however the bias current per device may be the same. I'll assume the heatsink for the B12 is larger than the M12.
What was the bias measured at? If it was close to the figure (30~35mA per device) you are probably safe to trim it to those values.
-Chris
Chris, the heatsinks are the same size on both amps (for a class AB amp the're big).
One amp was set at 115 mA and the other at 200mA. Neither did warm up much though. Only a few deg above room temp.
kro5998
One amp was set at 115 mA and the other at 200mA. Neither did warm up much though. Only a few deg above room temp.
kro5998
Hi kro5998,
That would be handy, and thank you. The link Jacco kindly provided is a type of look but don't download kind. 😡
Please send it to bhomester at gmail dot com. You can send a very high resolution file to that one.
Looking at your numbers, 115 mA is 10 mA higher than 35 mA per device. So that is close. I don't see any value in running the outputs higher than that at idle. 40mA per device would run at 120 mA. I think your 200 mA channel might be running a little warm. Mosfet it isn't!
-Chris
That would be handy, and thank you. The link Jacco kindly provided is a type of look but don't download kind. 😡
Please send it to bhomester at gmail dot com. You can send a very high resolution file to that one.
Looking at your numbers, 115 mA is 10 mA higher than 35 mA per device. So that is close. I don't see any value in running the outputs higher than that at idle. 40mA per device would run at 120 mA. I think your 200 mA channel might be running a little warm. Mosfet it isn't!
-Chris
anatech said:
-Punch the type number of the model at search gallery and push enter.
-click the picture.
-click the white printable text block at the row on the bottom, 5th from left.
Then you can download the image, easy peasy.
Hi Jacco,
Thank you. I didn't see the bottom boxes. You were right, aftre you get to a printable version the download is easy.
-Chris
Thank you. I didn't see the bottom boxes. You were right, aftre you get to a printable version the download is easy.
-Chris
Chris,
let me explain to you how long it took me to figure that one out some other time.
The front heatsink/mesh design of these B/M Luxman models is still remarkable. Strangest heatsinks i've ever seen, and first amp i've seen with TO3s wearing hats. All those tropical wood side 1980s Japanese power amplifiers were sooooo boring.
let me explain to you how long it took me to figure that one out some other time.
The front heatsink/mesh design of these B/M Luxman models is still remarkable. Strangest heatsinks i've ever seen, and first amp i've seen with TO3s wearing hats. All those tropical wood side 1980s Japanese power amplifiers were sooooo boring.
Hi Jacco,
Lux made some pretty neat stuff. Except for the new high end Marantz, I haven't seen too much out there as nice looking as the C-02 / M-02 pair.
You may never have enough time to tell me how hard that site was to figure out. I may forget the next time I need something!
-Chris
Luxman was still into formal wear. 😉 😀
Lux made some pretty neat stuff. Except for the new high end Marantz, I haven't seen too much out there as nice looking as the C-02 / M-02 pair.
You may never have enough time to tell me how hard that site was to figure out. I may forget the next time I need something!
-Chris
I think the design of the B12/M12 is stunning in it's simplicity.
The build quality of these amps is also remarkable.Not a piece of plastic in sight.I had to take them (partially) apart and still had to remove approx 50 screws.
The only drawback is that the pcb's aren't epoxy.The pertinax is of a good quality though.
As for the sound. I had a chance to compare my C12/M12 combo against a Marantz PM17mk2 and i strongly prefer the Lux. I think it's the current feedback that i don't like very much.Compared to the Lux the Marantz has a harsh middle and over emphazised low.
But as always it's a matter of taste and the type of loudspeakers you use.The listening material has also something to do with it.
kro5998
The build quality of these amps is also remarkable.Not a piece of plastic in sight.I had to take them (partially) apart and still had to remove approx 50 screws.
The only drawback is that the pcb's aren't epoxy.The pertinax is of a good quality though.
As for the sound. I had a chance to compare my C12/M12 combo against a Marantz PM17mk2 and i strongly prefer the Lux. I think it's the current feedback that i don't like very much.Compared to the Lux the Marantz has a harsh middle and over emphazised low.
But as always it's a matter of taste and the type of loudspeakers you use.The listening material has also something to do with it.
kro5998
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