Diamante -a discrete medium power opamp

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MrMajestic

MrMajestic

Member
Joined 2007
Is there still some interest in a group buy of these boards? I havent been doing my part in keeping this thread alive because of other things, but Im ready to proceed if anyone still wants boards. May we have a show of hands please before I put up an official group buy thread and wiki?
 
nelsonvandal

nelsonvandal

Member
Joined 2006
MrMajestic said:
What would have to be changed on the Diamante to make an active ground channel?
Click to expand...
I've been doing some tweaking on my amps, and keeping the small signal grounds from the headphone return grounds seems to be the important step, even if everything is done with passive components.

In most headphone amps a TLE2426 is used to get an "input ground" and it's sinking the small signal returns. Then they connect this IG point to the input of an amp, most often a unity gain opamp (or gain = 2), and you could use a Diamante for this if it's stable at lower gains. If higher gain is used you'll get a higher output impedance and more noise. The headphones ground is connected to the output of this amp and must be kept isolated from "input ground".
 
MrMajestic

MrMajestic

Member
Joined 2007
nelsonvandal said:

I've been doing some tweaking on my amps, and keeping the small signal grounds from the headphone return grounds seems to be the important step, even if everything is done with passive components.

In most headphone amps a TLE2426 is used to get an "input ground" and it's sinking the small signal returns. Then they connect this IG point to the input of an amp, most often a unity gain opamp (or gain = 2), and you could use a Diamante for this if it's stable at lower gains. If higher gain is used you'll get a higher output impedance and more noise. The headphones ground is connected to the output of this amp and must be kept isolated from "input ground".
Click to expand...

The Diamante is unity gain stable from what I understand. But to make an active ground channel I would have to add some kind of circuitry, is that correctly understood?
 
nelsonvandal

nelsonvandal

Member
Joined 2006
MrMajestic said:


The Diamante is unity gain stable from what I understand. But to make an active ground channel I would have to add some kind of circuitry, is that correctly understood?
Click to expand...
I've seen in one of the pictures of your amp that you use some kind of regulated power supply. I guess you're using a center point from this as a ground, right? Then all you have to do is connect this point to the input of a unity gain Diamante board, via a resistor. Lift the ground cable from the headphones out jack and instead make a connection from the output of the "ground channel" amp to the ground of the headphones jack. But... the ground of the headphone jack must be isolated from the input ground. If your jack is all metal, you have to isolate it somehow, or just let it "hang loose" while trying this. Some people like an active ground channel and some don't.

Look at Amb's site (M3, Mini3 and B22) to get a picture of how to properly use an active ground channel.
http://www.amb.org/audio/
Or do some reading at Tangent's site (PIMETA, PPA, PINT).
http://tangentsoft.net/audio/
Tangent has written this article about different grounding methods
http://tangentsoft.net/elec/vgrounds.html
 
MrMajestic

MrMajestic

Member
Joined 2007
nelsonvandal said:

I've seen in one of the pictures of your amp that you use some kind of regulated power supply. I guess you're using a center point from this as a ground, right? Then all you have to do is connect this point to the input of a unity gain Diamante board, via a resistor. Lift the ground cable from the headphones out jack and instead make a connection from the output of the "ground channel" amp to the ground of the headphones jack. But... the ground of the headphone jack must be isolated from the input ground. If your jack is all metal, you have to isolate it somehow, or just let it "hang loose" while trying this. Some people like an active ground channel and some don't.

Look at Amb's site (M3, Mini3 and B22) to get a picture of how to properly use an active ground channel.
http://www.amb.org/audio/
Or do some reading at Tangent's site (PIMETA, PPA, PINT).
http://tangentsoft.net/audio/
Tangent has written this article about different grounding methods
http://tangentsoft.net/elec/vgrounds.html
Click to expand...

Thanks for your reply. I might give this a shot. Given the poor interest in boards I might end up doing a small batch for myself in the meantime.
 
K

korben69

Member
Joined 2006
aparatusonitus said:


Just change R4 to 3k and R3 to 1k and you will have gain of 4.

http://www.diyaudio.com/forums/attachment.php?s=&postid=1550325&stamp=1214705599
Click to expand...

Few words to thank you all !
My Diamante project is finished, it works fine and great !!!! :)
I've modded the gain, a lot of time to desolder 4 resistances and dismount the boards... but it worth the job !
As Aparatusonitus told I've increase the gain to 4.
R4 = 3K3 (no 3K left) and R3=1K, it's better for my HD-650.

Just built and enjoy it.
I'm not skilled, I've done it, so you can.
Thanks to all the forumers :cool:
 
Russ White

Russ White

Member
Joined 2005
twistedpearaudio.com
korben69 said:


Few words to thank you all !
My Diamante project is finished, it works fine and great !!!! :)
I've modded the gain, a lot of time to desolder 4 resistances and dismount the boards... but it worth the job !
As Aparatusonitus told I've increase the gain to 4.
R4 = 3K3 (no 3K left) and R3=1K, it's better for my HD-650.

Just built and enjoy it.
I'm not skilled, I've done it, so you can.
Thanks to all the forumers :cool:
Click to expand...


Excellent!

I have always felt this is an excellent discrete project for people to try. It's challenging enough not to be boring, but within reach of anyone who really wants to do it. :)

The end result is a nice headphone amplifier/preamp. :)

I had mine on my desk yesterday listening to it. :)

Congratulations on your project! Enjoy it!

Cheers
Russ
 
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