today I ordered the 5 volt reg. and some of the 2073 chips,
what I am wondering is there any one know if there is any problems with installing a socket for the audio chip.
I don't want to create any more problems with this rig.

I disagree.
Both are spec'd for operating voltages of 1.8 to 15v.
Look like TDA2822 clones to me, in spite of the different part numbers.

And like all the TDA2822 datasheets, they spec distortion by way of
giving specific supply voltages and speaker impedances and power levels
for some max distortion level.
And none of them including the TDA2822 bother to do so for a 12v supply.
I guess that's what John is complaining about.

I believe ST (was SGS-Thomson) was the originator of the TDA2822.
They still make the TDA2822D, which is the SOIC version.
Mouser sells it.
Max dissipation is only 1/2 watt though, as one might expect, a problem
for us.
They probably gave up on the DIP after the first dozen clones showed up.
And all the manufacturers of miniature audio gear wanted to give up on
DIP's as well.

It ain't dead yet.

Jerry, KE7ER


On Tue, Mar 6, 2018 at 09:22 pm, John Backo wrote:

Neither of Jerry's recommendations are pin for pin replacements.
Both of them are recommended for relatively low voltage
applications, even though the maximum voltage is given as
15v or so.

Ash and all,

Jerry Gaffke provided a valuable link:



the second circuit (without crossover distortion compensation) seems to me to be more than adequate, with extremely low? THD.

Uses fairly common parts, and not very complex.


Rod KM6SN




On 03/07/2018 01:01 AM, Ashhar Farhan wrote:

John, others,

Given our experience of the non-generic ICs going out of production, it is best to stick to either discrete or generic ICs. The bitx20 will soon be a 15 year old design. The NorCal is probably older and still being built. We will have to choose parts that are going to be around for a long time, that are easily substituted. This means, we must work with large design margins, discrete or generic ICs.

Given these limitations, we are pretty much limited to either op-amps or discrete devices.

Opinions?


- f

I did some experiments with the chip failure.

FCI chips were sourced locally and plugged in. No failure with normal volume.
I raised the volume to a high level and the chip failed immediately!

Solutions

1: Add a resistor in series with the 12V line maybe 10-15 ohms to drop the voltage.

2. Simple solution is to use only a 16 Ohm speaker or add a series 8-10 Ohm resistor with the 8 ohm speakers.

3. Cut the power track to the TDA and insert a 78L08 or 9 to reduce the voltage. There is a track which can be cut
??? and a SMD or leaded regulator can be soldered on the board. This track leads directly to the chip and filter cap.

The second solution may be the simplest.

Further experimentation scheduled for tomorrow!

John, others,

Given our experience of the non-generic ICs going out of production, it is best to stick to either discrete or generic ICs. The bitx20 will soon be a 15 year old design. The NorCal is probably older and still being built. We will have to choose parts that are going to be around for a long time, that are easily substituted. This means, we must work with large design margins, discrete or generic ICs.

Given these limitations, we are pretty much limited to either op-amps or discrete devices.

Opinions?


- f

On Mar 7, 2018, at 00:11, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

NJM2073D