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Valab NOS DAC - subjective listening and modifications - Page 105

post #1561 of 1987
1/10/10 at 9:20am
yeah! put it across the v- v+, should of looked more closely at the LM334 Datasheet. still worth a close look at the vreg. Stuck the cap and another across the 7.4v and 5v in from the DC-30W instead, dont know if its sounds better, but it doesnt sound worse, I think?
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post #1562 of 1987
1/10/10 at 9:21am
anyone happens to have a schematic of this thingy, I am trying to assemble my mod kit and would like to order most stuff in one go.

Is the Oscon picking up stray digital signal or do you think you are overloading the LM334?
Perhaps try bypassing the 270uF with something smaller(styroflex, MKP), if you are picking up noise it might be that it gets filtered out that way.
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post #1563 of 1987
1/10/10 at 9:22am
Hi qusp, do you think those .1uf nypasssmd need to still be across the TDA (Gnd, Vdd) at pins 4,5, if you have decent replacements fot the 10uf surface mounts already in place?
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post #1564 of 1987
1/10/10 at 9:31am
On the plastic package the pins go v+ R v-, the R being in the middle, I put it across the V+ and V-. On the datasheet there is only one application they recommend a cap here, for 'low output impedance monitor'.

http://www.national.com/ds/LM/LM334.pdf
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post #1565 of 1987
1/10/10 at 9:35am
Anyone got an opinion on those .1 smd bypass caps on the TDA (Gnd, Vdd) at pins 4,5. Ive got 47uf 16v silmic II on there as well, so do I need those smd's?
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post #1566 of 1987
1/10/10 at 9:54am
Right trying that Lm bypass with a 6800pf stryo, no hiss this time, thanks guys, there is more clarity, is it better overall? Have to live with it a bit first.
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post #1567 of 1987
1/10/10 at 10:08am
By the way, to be clear, I took the sanyo of, so just the stryo is on there.
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post #1568 of 1987
1/10/10 at 10:35am
yeah the idea of a bypass is it should pull the high frequencies away and quick. film caps are better at this than electrolytic.
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post #1569 of 1987
1/10/10 at 10:40am
yes you need the SMDs, or a proper replacement for them and that isnt a larger electro. the SMDs would do a better job by themselves than the silmic II's would by themselves. if you want to get rid of the SMD, you should either replace with a superior SMD like a AVX COG organic polymer cap in 0.1uf or a fast film caps in 0.1uf like your polystyrene, a silver mica or vishay MKP
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post #1570 of 1987
1/10/10 at 11:36am
So is it about charge up time?
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post #1571 of 1987
1/10/10 at 11:40am
that and the fact that a 0.1uf will just skim the top off so to speak, where a larger value will shunt a wider band to ground

you are still talking about the ones from the dac chips to ground arent you? either way yeah its about how fast the cap will react
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post #1572 of 1987
1/10/10 at 12:12pm
Yes the dac ones.

Not sure about the stryo bypass now, seems to compress the sound compared with it off, dont think its because its not burnt in.
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post #1573 of 1987
1/10/10 at 12:19pm
Thread Starter 

two ways

There may be two ways to play bypass at output.

Hang the bypass directly to the main output caps, like I did, or use the spots on the DAC board. If using the small blue Vishays the DAC board is good.

But the difference is that if they sit on the DAC board the signal does not go thru the cap like it would if it was tied directly to the output caps.

So, I think placing a jumper on the DAC board and bypassing directly on the main output caps may be best.


Quote:
Originally Posted by Wood View Post
Yes the dac ones.

Not sure about the stryo bypass now, seems to compress the sound compared with it off, dont think its because its not burnt in.
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post #1574 of 1987
1/10/10 at 12:30pm
Hi pat, the styro bypass is the one I just did on the LM334, better with it off I think now.

But the bypass at output.... not sure what you mean there about hanging the bypass to the main output caps?
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post #1575 of 1987
1/10/10 at 1:41pm
Oh yes I see, thanks!
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