My Integrated GC - Tribute to carlosfm

[juma]

It has been some months since I decided to build me a GC based integrated amp so I went through a lot of reading, gathering info and data and building several types of popular GCs to find out what I like the best. And I found it. It is carlosfm's NIGC with low value resistors in feedback path + AD815 preamp. Of course, all spiced with lots of snubbers. I know it's a subject of many a dispute on this forum, but as carlosfm once said:" yeah, yeah, just try it ". And I did, and I was glad I did. My Epos M5 loudspeakers now really sing.
I've made a web page with schematics, some photos and comments (maybe it might help someone):

http://free.hostdepartment.com/j/jrexton/

Many thanks to carlosfm for his enthusiasm and good will,
Chears all !

[zafira1981]

wow!!! nice work!!! i really like it!! how much time did it take ?

there is only one thing i dont like. why do you use thin cables for PSU rails -> amp and output -> speaker connectors?

in your place, I would use the same thickness cables of the output ones of the transformer for output & psu rails.

[juma]

Thanks zafira,
actually building took 3 days of work, but experimenting, adjusting and searching for the "right stuff" took couple of months.
Those cables are not thin (AWG24 from IBM category 5e SFTP-Shielded, Foiled, Twisted Pair ethernet cable - very, very good conductors, I use them for speaker and interconect cables) and as you can see, for heavy load lines they are doubled (two paralleled) and of course, they are short (5-20 cm).

Cheers

[zafira1981]

Originally posted by juma
Thanks zafira,
actually building took 3 days of work, but experimenting, adjusting and searching for the "right stuff" took couple of months.
Those cables are not thin (AWG24 from IBM category 5e SFTP-Shielded, Foiled, Twisted Pair ethernet cable - very, very good conductors, I use them for speaker and interconect cables) and as you can see, for heavy load lines they are doubled (two paralleled) and of course, they are short (5-20 cm).

Cheers

I didnt noticed that the cables where two paralleled. I have LOT of this cable, i didnt know that they were very very good conductors. I will start using them

[frdchang]

nice,

i was going to make a circuit board for the ad815 preamp, but i guess i don't have to.

[jaudio]

Very Good. That is point to point gone extreme.

Did you get the output for the AD815 down to zero(no cap). The lowest I was able to get it is 25mv(not an issue I have a cap on the output). One thing I notice is that dc offset was not pot position depended,when it settled at 25mv it stayed at 25mv.

[carlosfm]

Originally posted by juma
Many thanks to carlosfm for his enthusiasm and good will,

Thanks for your kind words, Juma.
And to give some credit to a lunatic.

Btw I like your description of how it sounds (from your web site):
"The sound is what I hoped for: it's in a big boys' league! I will not give you the audio magazines' talk (detailed, airy, transparent, tight ...) but I can tell you this: if you know how the good jazz trio (acoustic bass, piano and drums) with singer, sounds in a good room, without any electrical equipment used, yes, that's pretty much it. I'm very satisfied indeed."

Now you need a good source component, and you'll fall off the chair.

[sagarverma]

nice work.

copper heatsink??

its Good looking outside but dirty inside.

in all,what finally matters is how it sounds.u say it sings,nothing more is desired.

Keep it up.

[juma]

Originally posted by jaudio
Very Good. That is point to point gone extreme.

Did you get the output for the AD815 down to zero(no cap). The lowest I was able to get it is 25mv(not an issue I have a cap on the output). One thing I notice is that dc offset was not pot position depended,when it settled at 25mv it stayed at 25mv.

No, it's not extreme. Extreme would be building a PC motherboard point to point
And yes, I did got the output of AD815 to 0mV with Carlos' DC null circuit, but this needs time to settlle. Since this is an integrated amp, it has to be without any DC on power amp's input from the start (I don't want any time delay circuits), so I went for coupling caps solution.
If you can't get it lower than 25 mV, try widening the range of regulation - use 1K or 2K trims insted of 500R ones in DC null circuit. Also, make shure if the polarity of offset voltage is + or - (maybe you need to inject negative voltage).

Originally posted by carlosfm

Thanks for your kind words, Juma.
And to give some credit to a lunatic.

Well Carlos, you were flamed fiercely few times on this forum for defending and promoting a very good concept.
You deserve the credit for that. In my country people say: "When one man tells you that you are a donkey, you shouldn't be upset. But when 10 people tells you that you are a donkey, you better get yourself a saddle".
But you didn't flinch. And you were right. I respect that.

Originally posted by carlosfm

Now you need a good source component, and you'll fall off the chair.

Any suggestions in 500 EUR price range ? Or maybe building something based on PC CD drive unit (I notice that there are some very good ones - Teac, Plextor...)?

Cheers !

[lineup]

juma

what is this?
you have to understand, you can NOT mess like this ...