12V DC gainclone? - Page 5

wahab · 31st January 2010, 11:06 AM

Quote:

Originally Posted by irishpatrick33

Alright, I have done a horrible job of explaining myself. Perhaps if I draw what I am thinking somebody can correct my errors.

I think it's safe to say I am 100% lost on the TDA2040.

both schematics are right, it will work...
just one thing with the tda2040 used in single supply mode,
you must add two 1N4004 diodes connected in reverse mode
from the output pins of the IC to positive rail and ground...
here a schematic that will help....

wahab · 31st January 2010, 11:13 AM

Quote:

Originally Posted by danielwritesbac

Well, I bought this "significant wall wart plug" for $20.
Toshiba AC Power Adapter Cord for PA2521U-3ACA 15V 6A 9 - eBay (item 170421661028 end time Feb-16-10 02:34:36 PST)

The 15 x 6 = 90va, and that seems workable. Except, that is a switch mode, which is a frail technology, so a good size tank capacitor will be needed as a helper. Its a slightly dodgy prospect, but it was quite inexpensive.
Perhaps it will also be nicely clean power? We'll find out.

The voltage is too high for TDA1558Q; but I couldn't find 14.4v available. Almost all car amplifiers can run on 14.8 volts DC (a car actively trying to charge its battery), so I'm hoping at 15v regulated isn't too much for it.
I'm wondering if I can use diode drop or if that would make additional noise?

For durability purposes, I have 2 chips, so they can run 1 chip per speaker (parallel mode). I'd planned it this way because the thermal interface on that chip appears to be insufficient, due to its small size. This trouble is because I have 4 ohm speakers and have also selected too much voltage (for that size thermal interface).

don t worry daniel, i use a 16.4V switch mode power supply with the 1558,
and it work very well..
anyway, the max power supply is 18v, although i wouldn t go further than the
voltage i m using...
the circuit is made to work with 3.2 ohm loads in bridge mode...
the thermal surface is largely enough, provided you have a decent
heatspreader, i used one that was not very big, and it made no problems.

danielwritesbac · 31st January 2010, 12:24 PM

Quote:

Originally Posted by wahab

don t worry daniel, i use a 16.4V switch mode power supply with the 1558,
and it work very well..
anyway, the max power supply is 18v, although i wouldn t go further than the
voltage i m using...
the circuit is made to work with 3.2 ohm loads in bridge mode...
the thermal surface is largely enough, provided you have a decent
heatspreader, i used one that was not very big, and it made no problems.

Did you test yours with 4 ohm speakers?

The amplifier described is either incredibly efficient or its hooked to 8 ohm speakers.

wahab · 31st January 2010, 03:41 PM

i tested with 3.2 ohm loads at full power,
actually it s used with 4 ohm speakers...
the TDP depend not on the surface of the ic METAL
contact, but firstly fom the thermal resistance between
the chip and the metal surface of the ic.....
just don t forget some thermal past for better heatspriding...
anyway, try, you won t be deceived..

danielwritesbac · 31st January 2010, 03:47 PM

The TDA1558Q is really misbehaving for me.

I build the bridge design from the datasheet.

It seems like something is missing. Input ground seems missing. It has an input ground marked but that doesn't seem to connect to anything whatsoever, according to the multimeter.

With one input channel plugged in there's no output.

With the other input channel plugged in, there's a tiny output plus a great deal of noise.

With both input channels plugged in (stereo) it plays decently on both speakers, but unfortunately. . .

In any condition, the datasheet design draws more than 12 ampers, and my diodes start smoking.

Help!

wahab · 31st January 2010, 05:10 PM

Quote:

Originally Posted by danielwritesbac

The TDA1558Q is really misbehaving for me.

I build the bridge design from the datasheet.

It seems like something is missing. Input ground seems missing. It has an input ground marked but that doesn't seem to connect to anything whatsoever, according to the multimeter.

With one input channel plugged in there's no output.

With the other input channel plugged in, there's a tiny output plus a great deal of noise.

With both input channels plugged in (stereo) it plays decently on both speakers, but unfortunately. . .

In any condition, the datasheet design draws more than 12 ampers, and my diodes start smoking.

Help!

the input ground must be connected to the other grounds,
not only to the source ground...

danielwritesbac · 31st January 2010, 08:36 PM

Okay, have mute to v+ via a 10k resistor. The mute switch didn't need to pull full current--it only needs voltage. Stupid datasheet. lol!

It sure does run cool now!

Next problem:
There's a little buzz
Now trying to find out how to impose an input load without also increasing noise. Any attempt to put a load between ground and input makes a noise. darnit! Can't use a potentiometer?

However, pin15 with about 2k to input does make an input load (amp goes silent and I had to increase the input cap size too). Pin 15 doesn't work for input ground though. OH, this is one weird little chip!

wahab · 31st January 2010, 09:39 PM

pin15 is to be let unused...
you can add a 100uF cap from pin4 to ground to improve
the supply ripple rejection...at first , i didn t add it, and it
also worked...
the little buzz is surely due to a ground loop from the
earth connection of the switch mode supply to the earth
connecction of your source if this latter has also a earth
connection...
i use a potentiometer at the input,
as the amp has high gain, it s mandatory..

irishpatrick33 · 1st February 2010, 03:31 AM

Quote:

Originally Posted by wahab

both schematics are right, it will work...
just one thing with the tda2040 used in single supply mode,
you must add two 1N4004 diodes connected in reverse mode
from the output pins of the IC to positive rail and ground...
here a schematic that will help....

I am not sure I understand. There's a bunch of stuff from the data sheet missing, like C5, C3, R1, and R5. I assume your C1 and R1 replace the data sheet's C6 and R6. Also not sure what the TLO72 is mentioned for.

Am I eliminating the R5 connection between pins 4 and 2; as well as eliminating the C3 and R1 connection between pins 5 and 1; and eliminating C5? Because that's what I got out of it.

irishpatrick33 · 1st February 2010, 03:38 AM

Quote:

Originally Posted by wahab

the input ground must be connected to the other grounds,
not only to the source ground...

So the signal grounds connect to pin 3... and pin 3 also connects to the other grounds?

Here a picture of what I understanding.

By the way, did I actually get polarity or phase of speaker correct?

31st January 2010, 03:47 PM	#45
danielwritesbac diyAudio Member Join Date: Nov 2007	Bad design The TDA1558Q is really misbehaving for me. I build the bridge design from the datasheet. It seems like something is missing. Input ground seems missing. It has an input ground marked but that doesn't seem to connect to anything whatsoever, according to the multimeter. With one input channel plugged in there's no output. With the other input channel plugged in, there's a tiny output plus a great deal of noise. With both input channels plugged in (stereo) it plays decently on both speakers, but unfortunately. . . In any condition, the datasheet design draws more than 12 ampers, and my diodes start smoking. Help!

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31st January 2010, 03:41 PM	#44
wahab diyAudio Member Join Date: Nov 2009 Location: algeria/france	i tested with 3.2 ohm loads at full power, actually it s used with 4 ohm speakers... the TDP depend not on the surface of the ic METAL contact, but firstly fom the thermal resistance between the chip and the metal surface of the ic..... just don t forget some thermal past for better heatspriding... anyway, try, you won t be deceived..

31st January 2010, 08:36 PM	#47
danielwritesbac diyAudio Member Join Date: Nov 2007	Okay, have mute to v+ via a 10k resistor. The mute switch didn't need to pull full current--it only needs voltage. Stupid datasheet. lol! It sure does run cool now! Next problem: There's a little buzz Now trying to find out how to impose an input load without also increasing noise. Any attempt to put a load between ground and input makes a noise. darnit! Can't use a potentiometer? However, pin15 with about 2k to input does make an input load (amp goes silent and I had to increase the input cap size too). Pin 15 doesn't work for input ground though. OH, this is one weird little chip!

31st January 2010, 09:39 PM	#48
wahab diyAudio Member Join Date: Nov 2009 Location: algeria/france	pin15 is to be let unused... you can add a 100uF cap from pin4 to ground to improve the supply ripple rejection...at first , i didn t add it, and it also worked... the little buzz is surely due to a ground loop from the earth connection of the switch mode supply to the earth connecction of your source if this latter has also a earth connection... i use a potentiometer at the input, as the amp has high gain, it s mandatory..