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Old 15th December 2003, 08:50 PM   #1
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Default schematic with 4 or more TDA1541 parallel

Hi,

is there a schematic that uses 4 TDA1541 ?

Is it possible to put more chips parallel ? Like 8 or 16 or 32 or

How is that done ?

I have orderd two S1 today, I will getTDA 1541A N2-S1 they said.

Greetings, Bernhard
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Old 15th December 2003, 10:34 PM   #2
Netlist is offline Netlist  Belgium
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I recall seeing a few approaches while googling.

/Hugo
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Old 15th December 2003, 10:58 PM   #3
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My eyes hurt like hell from "googling" the digital section of this forum.

Please !
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Old 15th December 2003, 11:16 PM   #4
dddac is offline dddac  Germany
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Default Re: schematic with 4 or more TDA1541 parallel

Quote:
Originally posted by Bernhard
Hi,

is there a schematic that uses 4 TDA1541 ?

Is it possible to put more chips parallel ? Like 8 or 16 or 32 or

How is that done ?

I have orderd two S1 today, I will getTDA 1541A N2-S1 they said.

Greetings, Bernhard

Every DAC with a current output (like 1541, 1543, pcm63 etc) can be paralleled for improved linearity. Just tie the outputs together and decrease the load resistor by the number of dacs you parallel.

There is no limit in theory, but for twice the effect you need to quadruple the # of dacs again and again !!! 1 dac=22Ohm, 4 dac=88Ohm etc

Although I am not 100% sure, as I have not tried, but I suspect, you can piggy back the chips and increase the decouple C's value by the number of dacs again... 4 dacs--> 390nF etc This is an easier way to build....

good luck!

doede
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Old 16th December 2003, 11:21 AM   #5
guido is offline guido  Netherlands
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Default Re: Re: schematic with 4 or more TDA1541 parallel

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Originally posted by dddac



Every DAC with a current output (like 1541, 1543, pcm63 etc) can be paralleled for improved linearity. Just tie the outputs together and decrease the load resistor by the number of dacs you parallel.

There is no limit in theory, but for twice the effect you need to quadruple the # of dacs again and again !!! 1 dac=22Ohm, 4 dac=88Ohm etc

Although I am not 100% sure, as I have not tried, but I suspect, you can piggy back the chips and increase the decouple C's value by the number of dacs again... 4 dacs--> 390nF etc This is an easier way to build....

good luck!

doede
Since you say you need to decrease the load resistor, i guess you mean that with 4 DACs the resistor should be 22/4=5.5 ohm.

The reason that you cannot leave the resistor 22 ohm is that it would mean that the voltage over the DAC output would increase by 4. And the 1541 does not like to see a voltage over it's output. Hence the low resistor value in the first place.

So paralleling them is not going to give a lower-gain gainstage, unless you feed halve of them to give an inverted output signal and then add the outputs there.

GuidoB
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Old 16th December 2003, 11:27 AM   #6
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Hi Guido,

is it possible to build your 2-TDA dac without GALs ? Using h-cmos logic ?


Bernhard
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Old 16th December 2003, 11:59 AM   #7
guido is offline guido  Netherlands
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Yes!

You could build all with logic, just make the GAL equasions in hardware. * means "AND", + means "OR", := means clocked output (positive edge iirc). But you have to be carefull with delays due to all the ports (causing glitches etc.).

You can also leave out functionality, like no mute (im not using it either, i'm using the 'mute trick' with the 7210.

And you could remove the choice have differential or not. Then the equasions would be smaller and therefore the amount of logic would be less.

You can also go the other way, use more modern progr. logic to put all into one chip...

As i have a GAL programmer, i used it. It is easy (for me) and a bit flexible. E.g. going to look at DEM reclocking some day and then i probably need to extend the GAL logic further to support it.

For me, i now just use 50 resistors per DAC (two per channel, see the other post) and a 1:15 transformer to get ~2V RMS. After the transformer a buffer is required, AD811 there is crap.

GuidoB

PS, the 1543 can cope with voltage at the output, so there the trick to use multiple of them to get enough output signal without gainstage works.
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Old 18th December 2003, 01:47 PM   #8
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Thanks Guido,

another questions as I am a newbee to DAC circuits...

It is possible to connect the outputs of two or more 1541 directly together ? So that I could stack let's say 7 ?

How about 7 separate 1541 and a transformer on each output.
Connecting the secondaries in series, so that we get 10Vrms which following op amps still can handle.

That would be a great thing:

- Better performance of relais volume attenuators because of large signal swing.

- Less voltage gain required for power amps.

- Improved linearity because of 7 outputs. Does it matter if it is parallel or in series ? I guess not.

The 2x7 decoupling caps, are they for analog or digital ?
I have "glass-k" caps 100n, gold plated leads and small size, but leads are magnetic.

To split the data signal into left and right, I guess I need that I2S ?

Problem for me, because I use Ultra Curve...


Bernhard
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Old 18th December 2003, 04:50 PM   #9
guido is offline guido  Netherlands
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Quote:
Originally posted by Bernhard
Thanks Guido,

another questions as I am a newbee to DAC circuits...

It is possible to connect the outputs of two or more 1541 directly together ? So that I could stack let's say 7 ?

How about 7 separate 1541 and a transformer on each output.
Connecting the secondaries in series, so that we get 10Vrms which following op amps still can handle.

That would be a great thing:

- Better performance of relais volume attenuators because of large signal swing.

- Less voltage gain required for power amps.

- Improved linearity because of 7 outputs. Does it matter if it is parallel or in series ? I guess not.

The 2x7 decoupling caps, are they for analog or digital ?
I have "glass-k" caps 100n, gold plated leads and small size, but leads are magnetic.

To split the data signal into left and right, I guess I need that I2S ?

Problem for me, because I use Ultra Curve...


Bernhard
Think some people combine more then one together, have a look how they do it. If you just put all together, the current is times 7, so the resistor needs to be lower times 7 (approx) so the voltage over the DAC output is not too high (silence is -2mA, so with 7 that would be -14mA).

7 transformers is expensive!

The caps should go to analog GND.
Split into l and r is indeed designed for i2s, but other formats should be possible i think. Dont know you source.

I would recommend to start with one and then go to two in the normal way

Greetings,

Gudo

sorry, in a hurry...
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Old 18th December 2003, 06:47 PM   #10
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7 transformers is for one channel... We have two...

But I could get them eventually.

The caps, do they decouple a digital or analog voltage ?

So are audiophile or "digital" caps needed ?
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