And would that be this?: http://www.diyaudio.com/forums/showthread.php?s=&threadid=48181&perpage=50&pagenumber=1
Wow. What an interesting trip for reading! A passive buffer?
I made something similar, a while back. It didn't do much, but what it did was "in the right direction," and at no cost to clarity.
In comparison, my active preamp is different than this. The active does much more soundstange expansion with somewhat less clarity/authenticity.
Thanks for the fascinating reading and for helping me understand the preamplifier choices.
Wow. What an interesting trip for reading! A passive buffer? I made something similar, a while back. It didn't do much, but what it did was "in the right direction," and at no cost to clarity.
In comparison, my active preamp is different than this. The active does much more soundstange expansion with somewhat less clarity/authenticity.
Thanks for the fascinating reading and for helping me understand the preamplifier choices.
The grounds are connected as in post 68: http://www.diyaudio.com/forums/showthread.php?postid=1517891#post1517891
and in post 77: http://www.diyaudio.com/forums/showthread.php?postid=1518369#post1518369
With dual mono version though, you will run a ground wire from CHG (chassis ground hook up point on each amp board) to chassis.
and in post 77: http://www.diyaudio.com/forums/showthread.php?postid=1518369#post1518369
With dual mono version though, you will run a ground wire from CHG (chassis ground hook up point on each amp board) to chassis.
danielwritesbac said:
More info on preamps, or no preamps:
http://www.goodsoundclub.com/GetPost.aspx?PostID=957
http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=257#257
http://www.high-endaudio.com/RC-Linestages.html
Member
Joined 2006
Thanks Peter for answering my other questions earlier.
And one more here: Was wondering, if there is a need to block DC, which one configuration would you recommend, placing a 10 uF(or 4.7uF) BG N as a coupling cap or using a Ci (10uF) as in the typical application diagram on NS's document? And reasons? Many thanks!
And one more here: Was wondering, if there is a need to block DC, which one configuration would you recommend, placing a 10 uF(or 4.7uF) BG N as a coupling cap or using a Ci (10uF) as in the typical application diagram on NS's document? And reasons? Many thanks!
CFT said:
If you want to block DC a coupling cap is the only option and I like BG N 4.7 or 10uF here.
Ci will not block DC, it will only prevent voltage gain at DC, in other words if you have 100mV DC at the amp input, you will be getting the same 100mV at the output; without Ci you'll be getting close to 3V or so at amp's output (input DC multiplied by amp's gain)
Member
Joined 2006
Hi Peter,
I finished building my first chip amp last night, using your 3875 premium kit , running on 300VA 25V-25V power supply. Thanks to your invaluable instructions here, everything went smoothly and i got it working the first time i turned it on. No humming, no noises. pure silense when no input source connected.
Sound clearly exceeded expectations and i was flabbergasted to hear sheer musical sound produced by this little wonder. Bass is phenomenal and vocals do not loose emotions in reproduction. Overall the sound is very smooth and musical, could listen to it forever without any fatigue.
However, to my ears, i feel it lacks a bit in trebel. I was wondering if theres any possibility to tweak some components to accentuate the trebel a bit more? would appreciate your inputs on this.
Cheers
Mubeen
I finished building my first chip amp last night, using your 3875 premium kit , running on 300VA 25V-25V power supply. Thanks to your invaluable instructions here, everything went smoothly and i got it working the first time i turned it on. No humming, no noises. pure silense when no input source connected.
Sound clearly exceeded expectations and i was flabbergasted to hear sheer musical sound produced by this little wonder. Bass is phenomenal and vocals do not loose emotions in reproduction. Overall the sound is very smooth and musical, could listen to it forever without any fatigue.
However, to my ears, i feel it lacks a bit in trebel. I was wondering if theres any possibility to tweak some components to accentuate the trebel a bit more? would appreciate your inputs on this.
Cheers
Mubeen
Yes, you can further accentuate trebles by adding 0.1uF polypropylene bypasses to main filter caps. You can do it directly underneath the board or by replacing 10uF caps on rectifier board with those (part suggestion from DK): http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=P3104-ND
Thanks for quick response Peter. I understand that i would need to replace or bypass caps on rectifier board only, no changes to amp circuit? Let me know if i am wrong. Sorry, electronics is a bit unfamiliar territory for me. Is there any diagram or instruction on here for this task?
cheers
Mubeen
cheers
Mubeen
That would be correct, but you may also try soldering those small additional bypass caps directly to pins of 1500uF Panasonic caps, underneath the amp board.
This is probably most recomended approach and depending on final result, you may as well remove 10uF caps from rectifier board, whatever works best for you.
This is probably most recomended approach and depending on final result, you may as well remove 10uF caps from rectifier board, whatever works best for you.
Thanks mate 
that worked like a charm. Though the effect is subtle, or may be its not but i would not be able to know as i cant do A-B comparison at the moment. So i am content with 0.1uF caps for now.
I just cant stop music once i start playing through this amp its so much 'alive'. I became a believer in simplicity and minimalist approach when i first heard a NOS DAC and this is the second time i have been amazed and it has only firmed my belief further, rather it has become my guiding philosophy in hi-fi now
Mubeen
that worked like a charm. Though the effect is subtle, or may be its not but i would not be able to know as i cant do A-B comparison at the moment. So i am content with 0.1uF caps for now.I just cant stop music once i start playing through this amp
its so much 'alive'. I became a believer in simplicity and minimalist approach when i first heard a NOS DAC and this is the second time i have been amazed and it has only firmed my belief further, rather it has become my guiding philosophy in hi-fi now Mubeen
Re: LM3875 rocks!
Thanks mate! Its already beaten my 450 quid worth of 'commercial' amp
'commercial amp' definitely has clearer trebel and thats where it excels, buts thats where its excellence ends. It lacks everything else. It clearly does not have the flow and dynamics of chip amp. It seems rather 'choked/clogged' compared to chippy. I am simply amazed!
This despite the fact that i used ordinary wires and volume pots for assembly, with bit longer signal path due to large case.
lanchile07 said:Well done Mubeen!.and yes,these fellas when they are build properly they sound really good. They produce very clean and fast sound.They can beat easily some of the good "commercial"ones out there. Enjoy your LM3875 amp!
Thanks mate! Its already beaten my 450 quid worth of 'commercial' amp
'commercial amp' definitely has clearer trebel and thats where it excels, buts thats where its excellence ends. It lacks everything else. It clearly does not have the flow and dynamics of chip amp. It seems rather 'choked/clogged' compared to chippy. I am simply amazed!
This despite the fact that i used ordinary wires and volume pots for assembly, with bit longer signal path due to large case.
Lm3875!
'commercial amp' definitely has clearer treble and thats where it excels...
Well,I have noticed and compared that these amps are NOT fatiguing as some commercials ones.You can listen to them all day long. I believe is because it's "delicate" trebles.
Some people like a lot treble,but if you are going to listen to it for a long period of time the sound becomes fatiguing.
I had so many amps like:
Marantz,Luxman,Adcom,Arcam,portal panache etc. but I still like the LM3875 GC better.
'commercial amp' definitely has clearer treble and thats where it excels...
Well,I have noticed and compared that these amps are NOT fatiguing as some commercials ones.You can listen to them all day long. I believe is because it's "delicate" trebles.
Some people like a lot treble,but if you are going to listen to it for a long period of time the sound becomes fatiguing.
I had so many amps like:
Marantz,Luxman,Adcom,Arcam,portal panache etc. but I still like the LM3875 GC better.
Source selector
Hi Peter,
finally I can start to build my first amp with the kit you sent me.
But I am a real beginner so please, can you address me where I can find instruction on the net about how to connect the input selector you sent me together with the kit? Even Decibel Dungeon on his beautiful pages dedicated to gainclone beginners shows a rotary input selector but seems that he did not explain how to do it.
The switch has 4 position and 12x3 pins but how to connect them?
Thank you
Renato
Hi Peter,
finally I can start to build my first amp with the kit you sent me.
But I am a real beginner so please, can you address me where I can find instruction on the net about how to connect the input selector you sent me together with the kit? Even Decibel Dungeon on his beautiful pages dedicated to gainclone beginners shows a rotary input selector but seems that he did not explain how to do it.
The switch has 4 position and 12x3 pins but how to connect them?
Thank you
Renato