I just received a pair of MX50 SE complete boards. Al info and pictures I have found on the Net show the usual versions with 669 a 649 drivers. The pcb heatsink shows the 3 drivers.
The one I received has substituted 2 2sa1704's and a 2sc2803. Also, the emitter resistors are .1 ohm verses the usual.22 ohm. 5551 and 5401 are also replace the BC556 and BC546 in the drive stage. The 1704's and 2803 are mounted a bit differently than the 669 / 649 drivers indicating a slight change to the pcb. layout.
I'm just wondering if this is a latest version or older. What I received is not what was pictured in the Ebay listing.
With that said... I tested both boards with 36V DC rails and they both looked great up to clipping at about 55 wrms. They both ran cool with DC balance less than 5mv both channels.
I can't seem to find (on the net) a schematic indicating the use of the 2sa1704 or 2sc2803. I have included what I received and the usual suspects from Ebay.
Pic 2 is the pcb I received and Pic 3 is the Ebay listing.
The one I received has substituted 2 2sa1704's and a 2sc2803. Also, the emitter resistors are .1 ohm verses the usual.22 ohm. 5551 and 5401 are also replace the BC556 and BC546 in the drive stage. The 1704's and 2803 are mounted a bit differently than the 669 / 649 drivers indicating a slight change to the pcb. layout.
I'm just wondering if this is a latest version or older. What I received is not what was pictured in the Ebay listing.
With that said... I tested both boards with 36V DC rails and they both looked great up to clipping at about 55 wrms. They both ran cool with DC balance less than 5mv both channels.
I can't seem to find (on the net) a schematic indicating the use of the 2sa1704 or 2sc2803. I have included what I received and the usual suspects from Ebay.
Pic 2 is the pcb I received and Pic 3 is the Ebay listing.
Just look at the back of the board and verify that there is usual LJM logo at the back - panda drawing. Regarding transistors: they usually substitute them without notice with what they have on stock and claim that the board is new, better version. Get used to it. 😉
..,.but such substitutions aren't necessarily wrong nor they degrade the operation. They know what should or could be replaced and how.
For example, a couple of weeks ago I've tested an amplifier where MJE340 and MJE350 were substituted with MJE243 and MJE253 repectivelly. I have revamped the board by replacing everything with all original components. Everything. I have found out that their replacement transistors were quite adequate in that case.
So, nothing wrong with substitutions if adequately done.
maybe you will find additionally answers here:
here
compensation
signal output
ivanlukic is the "expert" for these boards
here
compensation
signal output
ivanlukic is the "expert" for these boards
I have the new MX50SE as well and assembled it from a CKD kit - it is similar to member @a10195us and has the LJM logo on the reverse. Mine are 649/669 with output as D1047 & B817. There seems to be a major change in the in the input coupling (from the circuit posted) with a single 3.3uf in series.
Musically, I found the sound to be good and non-fatiguing, but lacking in low end reproduction. Wonder if any members felt the same and/or done any modifications?
Musically, I found the sound to be good and non-fatiguing, but lacking in low end reproduction. Wonder if any members felt the same and/or done any modifications?
