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Official M2 schematic
Official M2 schematic
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Old 12th January 2018, 06:27 PM   #2391
marconi118 is offline marconi118  Germany
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Dac is akm4393 direct output.
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Old 12th January 2018, 06:32 PM   #2392
grimberg is offline grimberg  United States
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Quote:
Originally Posted by Zen Mod View Post
JFet , present production
There aren't many good through-hole devices left in production. Are you relying on surface mount devices? Maybe MMBFJ271...
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Old 12th January 2018, 06:36 PM   #2393
Zen Mod is online now Zen Mod  Serbia
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Official M2 schematic
considering that load resistance (given in datasheet) is 600R , we can assume that you can connect follower stage directly

though , my experience is telling me that proper additional buffer will result in better sound

as with many other things , you can be sure only after trying it all

if you are content with simplest solution , goal is fulfilled - just enjoy in music and forget all technicalities
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Old 12th January 2018, 06:39 PM   #2394
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Official M2 schematic
Quote:
Originally Posted by grimberg View Post
There aren't many good through-hole devices left in production. Are you relying on surface mount devices? Maybe MMBFJ271...
2sk2145
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Old 12th January 2018, 06:49 PM   #2395
marconi118 is offline marconi118  Germany
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Bf862 SMD is acceptable if worth the effort in soldering it.
What is the bias of m2? 1A?
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Old 12th January 2018, 07:16 PM   #2396
Zen Mod is online now Zen Mod  Serbia
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Official M2 schematic
plenty of solutions with BF862 around

M2 Iq is automatically set and , say, between 1A2 and 1A5 , depending of parts you actually have
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Old 12th January 2018, 07:36 PM   #2397
marconi118 is offline marconi118  Germany
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Waiting impatient your solution with 2sk2145
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Old 12th January 2018, 08:38 PM   #2398
KevinHeem is offline KevinHeem  United States
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Official M2 schematic
Quote:
Originally Posted by KevinHeem View Post
To me the M2 sounds a little warmer with slightly softer high end. The F4 doesn't really sound like anything, you just hear whatever comes before it.
I think that's exactly what NP said about the M2's sound. Unfortunately I lost my M2 to a friend and I don't think it's coming back (it's ok, he has some stuff I want to trade with him). I'm listening to the F4 for now and It's preferable to me on some recordings.
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Old 12th January 2018, 08:50 PM   #2399
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as said numerous times - F4 and BA3 OS can't be compared with any other Papamp , simply because they are always paired with some additional gain stage ....... embracing fully (well , 98%) imprint of that stage on sound

OK - yes , in rare occasions , where someone really doesn't need any additional gain , driving source followers directly from source , we can take them as amplifier itself

however , those occasions are unfair to regular (gain-having ) amps
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Old 28th January 2018, 12:26 PM   #2400
blackdod is offline blackdod  Europe
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Quote:
Originally Posted by WalterW View Post
M2 frontend is sounding Mega Giga Super nice, as frontend for a headphone amp
I combined it with the upcoming DIY Headphone amp output stage and it's a keeper...
So I made a quick PCB, found some old Teko TK3710 RF-cases for shielding the Edcor's and the M2 Headphone amp is born

Strange....I always hated the combination of transformers and audio...but I was so wrong... CSX1, F6 and now M2 they all sound so nice.

Makes me wonder how the M2 sounds on my big loudspeakers...
Click the image to open in full size.

A friend and me are working on this HA amp. We have a regulated PSU with B+-15 volt and a trafo with 15volt@2.1A x2 and we used your schematic.

We have two issues:

One is when we connect to our amps, B- rail falls to -14.40volt and B+ rail falls to 14,8volt.

Other is the Offset around 300~400mVolt (very high for a headphone amp).

We instal a 1k trimpot in serie with R6(10K) on the positive rail (similar to M2 design) and now we have a best control of the offset but the voltaje in both rails is still very different.

I readed notes of Nelson about opto, and he says that the both rail needs to have exactly the same voltage for the opto works correctly so obviously our opto doesn´t work because we have a difference about 300~400mvolt between rails.

My amp sounds (I have a little hum but I think that is a ground problem) but is very unstable.

Please, can you think of an idea? Am I missing any detail?

Thanks

Last edited by blackdod; 28th January 2018 at 12:30 PM.
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