I completed this amp today (L12-2 v 4.2) and left the whole amp untouched as bought. My thinking was that I'll do the "Mods" at a later date as I have room to easily remove the amp boards from the enclosure. My initial reaction was a disappointment to me. I have used the LJM L20 V9.2 boards with film input capacitor being the only mod. To me the L20 amp was pretty well perfect. Very neutral with no overall audio signature, just as if the input was driving the speakers with nothing in between (yes, I know it's impossible, just a sort of illusion) However the L12-2 is definitely brighter making all music styles just seem colder and unnatural. The bass is a little odd too.... seemingly less controlled and fatter. Yes, so far, a disappointment but the ads do carry a "Warning" saying the amp is bright!... There is a YouTube video showing a subtle rise in the frequency response. It seems very strange to have a non-flat frequency response in a modern amp, but I reckon this is enough to explain what I can hear, as it's over a wide upper response area. I would be VERY interested to hear what others think of their L12 amp used with highly neutral and detailed speaker. Thanks
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Yes, maybe I'll get used to it, or ultimately, I might have to add some resistance to the tweeter section of the Bragi speakers I use, perhaps 0.5R might be enough. From memory, the sound seems to be similar to the Pioneer A400X I have. Perhaps I'll get round to trying a comparison one day. I would still like to get some other user's opinions on how they judge the tonality of their L12 amp.
The input of the L12-2 is very similar to the L20.5. On the L12 board two things are missing. One 3,3 uf capacitor and one 100 k resistor. It is nearly the same then...(groundliftresistor is missing, as on all boards of LJM)
Perhaps it will force the sound to more, how can i say, lovely sound, without hardness, if using a input capacitor...
I always found the bass is missing a little bit, to flat sound..the rest is ok...
I think ljm wanted to change that with Vers.5. He had no luck with the new design...
Perhaps it will force the sound to more, how can i say, lovely sound, without hardness, if using a input capacitor...
I always found the bass is missing a little bit, to flat sound..the rest is ok...
I think ljm wanted to change that with Vers.5. He had no luck with the new design...
Thanks for your reply Kleinhorn. At the moment I am using the input directly with NO capacitor as my pre-amp has no DC on it. I was thinking I will also try WITH a capacitor and resistor to see if that makes it sound "sweeter" On my first post here, I said the bass was too full, but after it has "burnt-in" I think the bass is too lightweight as you have also found. The L20 V9.2 has a much better bass sound. With more bass it would sound better balanced sonically. I also have not done the BIAS mod. Berlusconi has told me the bias adjustment will "tame" some of the brightness and I will be doing this very soon. Obviously a less bright sound will also make the bass seem a bit more powerful too. Thanks again...
Hi,
bias adjustment is necessary for the different voltages the board can get. But i dont think it is a great change in sound. I have the older version L12-2 Vers. 4 and choosed 40 ma bias. Bass remains flat...
If the L12-2 is made for monotoring, as wrote, but the bass is too flat for any monitoring.
It was new to me that the inputs of different boards ljm has designed are very similar. LJM should stop to advertise his goods in this forum and read as often he can...(to learn about designing amps)
You can't compare the L12 with the L20 or L20.5. That are the best boards ljm has made.....the rest..mhmmm, don't like them.
Good luck with your changes...
Peter
bias adjustment is necessary for the different voltages the board can get. But i dont think it is a great change in sound. I have the older version L12-2 Vers. 4 and choosed 40 ma bias. Bass remains flat...
If the L12-2 is made for monotoring, as wrote, but the bass is too flat for any monitoring.
It was new to me that the inputs of different boards ljm has designed are very similar. LJM should stop to advertise his goods in this forum and read as often he can...(to learn about designing amps)
You can't compare the L12 with the L20 or L20.5. That are the best boards ljm has made.....the rest..mhmmm, don't like them.
Good luck with your changes...
Peter
I don't see a wiring diagram.
What are the values of the input RC filter?
It can help to lower its cutoff frequency. So increase the value of the resistor or capacitor.
Adding a DC blocker to the power supply can also reduce the clarity of the sound and soften the presentation a little.
What are the values of the input RC filter?
It can help to lower its cutoff frequency. So increase the value of the resistor or capacitor.
Adding a DC blocker to the power supply can also reduce the clarity of the sound and soften the presentation a little.
If a combination of 2k2 and 330pF is used at the input, there is no room for increasing these values, so the sound cannot be adjusted appropriately.