Chip amp modification to current drive

[Freedom666]

Preparation of the next one

 

[Freedom666]

Heat sinks get a bit hot. Will add maybe a 12volt computer fan working with 9volts to be quiet.

Sound is high end. Now using Fiio X1 player as source playing wav files.

Astonishing: with current driven amps I never feel need for frequency linearization with fullrange drivers.

On the box: no tweeter active! Only fullrange at work

 

[Freedom666]

Had to remove the direct decoupling from the chips. It was only 25volt electrolytic but I need here a 50v type.


After an hour one died away with smoke protesting against volt torture.

 

[Freedom666]

Added 470uF 100volt across the pins 3 and 5 of LM1875.

Without this decoupling directly on the chip it sounds less precise and mellow on transients.

 

[Freedom666]

I would like to make a headphone amp with TDA2003 but as a current driven amp.

Found this topic in diy audio forum:

https://www.diyaudio.com/community/threads/old-school-tda2003-headphone-amp.257582/

Also found in the web archive some more information on it with measurements.

https://web.archive.org/web/20170103032351/http://g4oep.atspace.com/headamp/headamp.htm

Any idea if the basic current feedback can be applied to this TDA2003 headphone amplifier?

I added the previous schematic of a TDA2003 converted to current drive as attachment.

 

[Freedom666]

That would be too easy?

 

[JMFahey]

All the discussion above applies to chipamps driving speakers, and the standard easy/practical solution is to make the NFB network out of the speaker in series with a grounded low value resistor, then taking NFB signal from their junction.

So far so good, also applies to Stereo amps, where each speaker has its own ground reference resistor .
2 speakers: 4 wires.

BUT with headphones norm is 3 wires : +Right, +Left and common ground.

You can open the plug , split wires and turn it into a 4 wire system, but then you will need an incompatible connector, both at headphone and amplifier.

That said , my experience (and most everybody else's) with headphones driven from a high impedance is ugly raspy tiring sound, not sure that is a worthy goal.

 

[Freedom666]

Thank you for your advice.

So the simple change in 266 post would work. Was not sure for this as pin 2 on the TDA2003 for headphone is wired a bit different than usual.

With the TDA2003 in voltage mode the stereo grounds can be connected to Mono but in cfa mode not?

However changing / separating output at the headphones could be possible and maintaining compatibility by making an adaptor combining it back again for standard amplification if needed.

Concerning Sound of cfa for headphones - is it ugly on all headphones?

As there is already discussion on projects for such amplification

https://www.diyaudio.com/community/...ne-amplifier-easy-project.393888/post-7452278

 

[Freedom666]

Would like to find out about how this TDA2003 based headphone amp was wired for practical use.

On the design here is more to be found

https://www.gammaelectronics.xyz/ax_03-2008_flea-headphone-amp.html

The man who published it was Andrew Smith

 

[Freedom666]

@JMFahey

On this schematic the TDA2003 share the common ground.

In cfa mode there would be only one resistor 0.1 ohm to ground, but it would not work, right?