TDA1543 DC connect to TA2024 amp - diyAudio
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Old 8th August 2009, 05:04 PM   #1
jkeny is offline jkeny  Ireland
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Default TDA1543 DC connect to TA2024 amp

I'm playing around with a TDA1543 DAC & thinking of connecting it to a Tripath TA2024 amp. Now before I blow up everything I wanted to get some opinion on whether this idea is stupid, fanciful or might work?

The TDA1543 outputs are biased to something like 3V so a capacitor is put on the O/P to block this DC. The TA2024 has something like 2.5V DC on it's input so a cap is used here to block DC from feeding back to anything connected to it's input. You see where I'm going with this, don't you?

Can the TDA DAC be DC connected to the Tripath amp? No caps in the signal path in theory should be better sounding? Could this work somehow? Has anybody gone here before?
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Old 10th August 2009, 04:54 AM   #2
dddac is offline dddac  Germany
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I did not try and temping as it looks it seems not doable

The 2,5 Volt is the Bias voltage generated inside the chip amp as mid voltage for the opamp input stage

If you do not decouple DC at the input, the Opamp will see, lets say, 3 Volt

Meaning with a gain of 12 you will have an output of 0,5 * 12 = 6 Volt DC at the output. not so nice for your speakers plus the amplifier clips

but at least you can choose One couple C only if it goes in one chassis
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Old 10th August 2009, 08:52 AM   #3
jkeny is offline jkeny  Ireland
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Thanks DDac,
So without anything connected to the Tripath input & with no cap on the input we get large DC on the output? Have you tested this?
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Old 10th August 2009, 08:59 AM   #4
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I see a simple solution for this matter.

But I doubt it will be useful as long as you can not arrange for a volume-control in the signal-chain.
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Old 10th August 2009, 09:15 AM   #5
jkeny is offline jkeny  Ireland
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Tell more, Lars!
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Old 10th August 2009, 09:20 AM   #6
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Hey Jkeny,
First you tell me, where you planned to place the volume-control ?
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Old 10th August 2009, 09:45 AM   #7
jkeny is offline jkeny  Ireland
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I'm totally flexible - from PC digital control to vol control on the speaker cables & anywhere in between.

Probably PC control.
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Old 11th August 2009, 01:27 AM   #8
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Dear Jkeny,

I did something liek this before. I can't quite remember the full details of the circuit off hand.

I wanted to minimize the op-amp signal has to go through, so I used the op-amp of the TA2022 as the I-V stage. The key is to let only the AC through. That way you save on an I-V stage.

http://diyparadise.com/web/index.php...d=67&Itemid=26

The difficulty was the volume control. I think i placed a small VR in series about 1 kohm from the output, so it is the same as the resistor to DC on the actual circuit. I also reduced the resistor of the negative feedback loop of the tripath op-amp stage significantly. So it just behaves like an I-V stage. The VR + resistor to DC serves as a current divider, between I-V and virtual ground for the AC. So when the resistance is low, you would get a most of the AC current to the I-V.

I don't think PC remote control is a good one, it just reduces the resolution of the music by reducing the number of bits....

Oon
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Old 11th August 2009, 01:53 AM   #9
jkeny is offline jkeny  Ireland
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Quote:
Originally posted by oon_the_kid
I wanted to minimize the op-amp signal has to go through, so I used the op-amp of the TA2022 as the I-V stage. The key is to let only the AC through. That way you save on an I-V stage.
I don't know what op-amp you mean?
This reminds me that diyparadise have announced that their TA2020 amp (Charlize?) now has no cap on the input! How do they do this? I don't see a schematic.

Quote:
The difficulty was the volume control. I think i placed a small VR in series about 1 kohm from the output, so it is the same as the resistor to DC on the actual circuit. I also reduced the resistor of the negative feedback loop of the tripath op-amp stage significantly. So it just behaves like an I-V stage. The VR + resistor to DC serves as a current divider, between I-V and virtual ground for the AC. So when the resistance is low, you would get a most of the AC current to the I-V.
I'm not really following you here - can you post a rough & ready drawing?

Quote:
I don't think PC remote control is a good one, it just reduces the resolution of the music by reducing the number of bits....
I agree but it depends on whether you have the bits to throw away? I was just giving revintage all vol control options!
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Old 11th August 2009, 02:13 AM   #10
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Hi Jkeny,

As you know TDA 1543 is an current sink DAC. So you would need an op-amp for an I-V stage first unless you are using a resistor as I-V. Alternatively there are discrete I-V stage. I am using the op-amp stage on the TA2022 as the I-V stage.

I I can't draw a circuit out now, but might scrible it on a piece of paper and scan it in later.

Oon
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