For a CMOY amp, is there any worthiness to Class-A bias using just resistor?

you cant do that for the CMOY amp mainly due loading effect(which will screw up output) and there is not enough output current for you to pull Class A on the NPN side of the output stage.

You need a two block stage for it to work, usually followed by a high input impedance output stage.

You also need to take note that resistor biasing has impedance issues across the bandwidth and limits voltage swing, not a good choice to "force" bias the opamp.

I personally dislike this method . If you want real Class A, just use Ad744/AD829 with compensation pin output method.

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Added on January 23, 2011, 11:11 pmon a side note, I am jelly of people related to aviation do you fly jets jazzy?

if you do i jelly T_T

This post has been edited by LittleGhost: Jan 23 2011, 11:11 PM

LittleGhost,
Fortunately I don't fly them.. I just make sure that they continue fly as they were designed to..
Still feeling jelly-ish..?

This post has been edited by jazzy939: Jan 23 2011, 11:44 PM

gonna scavenge parts to make one of these later..uehehehe
got the D2822A from an USB Speaker...

That TDA is quite a performer for a 1 watter. I have one for a general purpose bench amp

Thanks to littleghost's guidance, I have my first complete amplifier with a case. Many thanks for his afternoon on Saturday.



Quite a looker isn't it. Thanks to littleghost's Jujubes box.



Work log, schematic and other details: http://mengsuan.blogspot.com/2011/02/project-ubercmoy.html

wuah, it look so beautiful!

Thanks for your compliments. Truly encouraging.

Hopefully one day soon I could progress as far as you and littleghost are.

p.s. littleghost even helped me punch holes through the case.

This post has been edited by mengsuan: Feb 1 2011, 09:50 PM

Looking good mengsuan! Welcome to the club!

This post has been edited by jazzy939: Feb 1 2011, 10:17 PM

What tool is used for punching holes through the case, dremel?

trade secret.

No drilling involved.

Dual opamps???

Why not dual the power supply

One of the chip is OPA2132. Another chip is TLE2426, a virtual rail splitter.

You just reminded me that, I should also try dual op-amp like A47 design. Well, maybe I should progress further than that

LOL

just noticed...why is your resistors all 'tegak' one???

I put it in tombstone orientation because I want to make the board as compact as possible. The laid-flat resistor, is however, out of the view in the photo.

Rather not tombstone, double siding component placement is probably better. Them raised leads act like antennas and if in the feedback loop tend to make things worse.

I'm not sure if you did, but you can install a better compensation capacitor with that TLE2426 for extra performance. Although I'd prefer a 2 opamp servo.

This post has been edited by empire23: Feb 2 2011, 11:41 AM

hey thanks!

This post has been edited by wongpeter: Feb 2 2011, 01:54 PM

How much does it cost you?

Hard to reply. None of the components costs a lost. Some components were from my toolbox, some were from littleghost. Nevertheless, it's the effort that costs. I took several visits to Jalan Pasar to get the materials for breadboard prototype testing.
I did not spend the money very efficiently. Moderate amount of wastage.

I'm getting interested with this DIY stuff, but dunno where to start. I got some very little knowledge on curciut. Just don't know where to start.. Seeking guidance