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Old 17th March 2004, 06:02 PM   #1
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Lightbulb Some 1541 ideas

Hi,

what about a

_ 16 bit switched-I/V-resistor volume control ?

_ 16 bit switched 1541-output volume control ? ( 16 x 1541 chip )
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Old 17th March 2004, 06:13 PM   #2
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intersting, only No.2 may be a little expensive since Reichelt doubled the price of TDA1541
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Old 17th March 2004, 08:18 PM   #3
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16xS1 would be expensive

Just compared 1541, 1541 A and 1541 A S1.

Philips was so nice to put sockets on the CD650 board

Very very difficult...
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Old 17th March 2004, 08:19 PM   #4
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und? tell the truth, more difference than between metalfilm and carbon resitors in signalpass?
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Old 17th March 2004, 11:37 PM   #5
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Quote:
Philips was so nice to put sockets on the CD650 board
There are no sockets on mine!

Quote:
und? tell the truth, more difference than between metalfilm and carbon resitors in signalpass
Quite similar,maybe bigger.

Bartek
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Old 18th March 2004, 12:08 AM   #6
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ok, for the switched I/V resistors you will need a wide range from lowest to highest value. I did measuremt THD against value of resistor only with TDA1543 because for me TDA1541 is expensive, and i found the value is very critical for minimal THD. I doubt this is different with the 41. So we would have only one volume setting (the lowest ?) with good THD figure. The more voltage we get out, the worse the DAC would perform. So we need a lot of gain behind, and more gain means more trouble...

For the switched DACs: beside its expensive, about 100 for DACs, the main benefit of parallel DACs would only be used at full volume - a waste of ressource.

I think the D1 stage were the DAC drives about no resistance and may be happy with this very low value, and the D1 volume control by switched resistors between positive and negative side of the differential pair would bring much more benefits. And there is still the option to drive the D1 stage with 16 parralel DACs, and if you want 16 for positive and 16 for negative half...

If i only had the money and the parts i need.....

So i propose balanced DAC with D1 and volume control by relays switched resistors in the D1 stage like Nelson did. And for next step instead of the TDA the 1865NK.
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Old 18th March 2004, 07:42 AM   #7
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What about the tube output stage ?
This one got a resistor which's value can be reduced for lower output voltage ?
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Old 18th March 2004, 08:26 AM   #8
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which tube output stage? resistor with cathode follower?

it would also be possible to build D1 with tubes, without resistor.
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Old 18th March 2004, 05:13 PM   #9
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I don't know too much about tubes.
The schematics that are around in this forum.

What about driving a load directly by multiple parallel DACs ?
Or current amps ?
Or built a high power DAC ?
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Old 18th March 2004, 05:21 PM   #10
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driving the load directly would mean we need enogh current - no prob with massive parallel them, and enough voltage. In case the DAC gives us 1V and we have a 1Ohm speaker we need 1A so about 200 or 300 DACs? and we have 1W. Enough for a high efficent System. Current amp is nothing but the follower, if cathode, emitter or source depends on taste.Will do the same but with less parallel DACs. But without voltage gain and about 1V we will never reach real power levels... High power DAC would mean we need switchabel current sources with very high precision relative to each other. Will not reach 16 Bit resolution if precision is not good. Precision would mean we need a thermal stbilized system and so, will be difficult i suspect. I suggest you have a look on the D1 stage, the outer 2 transistors are only buffers and not really needed if you drive normal impedances. The stage of corse should be also doable with triodes instead of FETs, but we need higher voltage.
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