[shlomomofo]

Quote:

Hmm, bass isn't as present as it was before.

i agree that the bass is not as present after the bypass, but it just makes it seem cleaner and more well-balanced in my system...

 

[dsavitsk]

Quote:

Originally Posted by tilt i wonder what c37's value is... i have some wima 100nf's just laying around maybe i could stack them no seriously tho, can I?

C37 (and actually C28 which feeds the other half of the chips), from the schematic above, is 220000nF, so the 100nF wimas won't do much as a replacement, though they might work as a decnet replacement for the bypass caps. My own tda1543 based dac has tons of bass, so lack of bass is not inherent in a NOS design. I use a high quality 680uF cap for one chip, this dac uses a low quality 220uF cap for 4 chips.

 

[Samgotit]

We have to stick to ~8mm diameter here.

Would this be a decent upgrade for C37, 28:


470uf 25v Panisonic FM
http://www.digikey.com/scripts/DkSea...479054&Site=US
P12389-ND

Thanks,
Sam

 

[dsavitsk]

No reason to use 25V here as the cap will only see 8V. But, the Panasonic FM range is a good choice. It looks like the 680uF or 1000uF 10V or the 680uF 16V will fit, though you need to be sure you get the L version

 

[Samgotit]

Finished the bypass! (thanks for the hand holding everyone). I too have lost bass, but It seems significantly less grainy. I'll reseve judgement until I replace the other caps per dsavitsk. If the bass is restored I'll be one happy camper, if not I guess I'll just have to build the one on his web site.

I used 3uF Aerovox caps. Pics to come.

Thanks all,
Sam

 

[Samgotit]

Quote:

Originally Posted by dsavitsk No reason to use 25V here as the cap will only see 8V. But, the Panasonic FM range is a good choice. It looks like the 680uF or 1000uF 10V or the 680uF 16V will fit, though you need to be sure you get the L version

Thanks!

Updated Digikey part numbers C37, 28 :
P12354-ND 1000uF 10V
http://www.digikey.com/scripts/DkSea...479009&Site=US

or

P12378-ND 680uF 16V
http://www.digikey.com/scripts/DkSea...479042&Site=US

Replacements for C5, 6, 7, 8, 12, 13, 14, 15:
BC2054-ND
http://sales.digikey.com/scripts/sal...emseq=34443076

 

[shlomomofo]

thanks for the info and links on the other caps. i just ordered a couple 1000uf's from digikey. i've also got some of those aerovox film caps coming. i'll be sure to post impressions and pics when i'm done.

 

[dsavitsk]

Quote:

Originally Posted by Samgotit If the bass is restored I'll be one happy camper

Altering R35 and R36 can change the tonal balance a bit. You can do this either by using different types of resistors or by altering the value. Higher values will be warmer and fuller, but will also add distortion. Too high will be all distortion.

How to calculate these can be seen here: http://www.diyaudio.com/forums/showt...ht=#post173483

and some other background info is here: http://pinkfishmedia.net/forum/print...?threadid=9739

 

[Samgotit]

Taken from the post linked by dasavitsk:

Quote:

"Anyway, our absolute, maximum output swing is 1.8V to +V -1.2V. So for 5V this is 5V -1.2V -1.8V = 2V"

Is the 5V supply voltage in the above statment a measured value between pins 4 and 5 on the TDA1543 or is he using typical supply voltage as shown in the data sheet?

I get 6V at VDD on all of the DACs. This gives me 3V/2.3mA (R=V/I) = 1304 ohms. So I could "safely" the replace the 270ohm resistors with ~1.2kohm?

edit: forgot to add a picture of the bypass.

Thanks,
Sam

 

[dsavitsk]

You've got 8 chips there, not one. The currents aggregate.

 

[Samgotit]

Ok..

May I try again:
So I've got 2 banks of 4 chips per resistor? With current being additive from each bank?

3V/((2.3e-3A(4)) = 326 ohms for each resisitor? Is this any better.

Thanks,
Sam

 

[dsavitsk]

Quote:

Originally Posted by Samgotit Is the 5V supply voltage in the above statment a measured value between pins 4 and 5 on the TDA1543 or is he using typical supply voltage as shown in the data sheet?

According to the schematic, you should have 8V. Try measuring again, or see why the LM7808 isn't giving you 8V, or if your dac has different regulators.

 

[tilt]

ohh, take a picture after you've replaced the other caps too!

 

[Samgotit]

Hmm, Regulators are 7808 so I should get 8V (as you stated) between pins 4 (gnd) and 5 (vdd) on each dac...correct? I still get 6V. Thers is nothing in the path to cause a drop in voltage I can see. Is this the whole story: 8V output from 7808 = 8V at Vdd on the DAC? I can't get to the pins on either 7808 from the top for a measurement

. The regulators are NEC. Are Fairchilds a better option?

Could someone else measure the voltage at the DACs for a comparison. Here is the data sheet for pin reference:

http://www.diyparadise.com/TDA1543.pdf

One more barrage of quetions,
Sam

 

[Samgotit]

I just pulled the board off and I am only getting 6V out of the regulators. Oddly, I'm getting 16.5V in! Schematic reads In voltage at 10.5AC? The heat sinks on the the regulators are very hot. If I got new (or real) LM7808s that would be MAX supply voltage to the TDA1543's

. Good for sound?

Sam