Purpose of the resistors and capacitors on output here?

[Garbz]

Well above is the output of the M-Audio transit. Just wondering what each part after the 10uf cap does?

the 10uf cap is to stop DC offset, that's plainly obvious and in my case it has been modified with a 2.2uf black gate cap.

Anyway i'm assuming the parallel resistor after it has something to do with charging the cap on powerup.

But what are the folling series resistor and parallel cap for?

The point of this is i'm trying to reduce the output impednace of the transit as close to 0 as possible and I was thinking of removing things.

If it makes a difference the following amps have input impedances of 50k and 330k. So in the words of our gloriously failed one nation political candidate
"Please explain"

 

[Pars]

Low pass filter, to filter off any residual ultrasonic hash coming out of the DAC? Can't read the component values, but I would guess maybe around 30KHz or lower.

 

[rellik]

yup the last resistor and cap are low pass filter

cutoff freq(-3db) is defined by F = 1/(2*pi*R*C)

http://en.wikipedia.org/wiki/Low-pass_filter

 

[flecom]

since your coming from a DAC also its probably DC blocking too

 

[Garbz]

10uf cap does dc blocking. Ok i'll leave it as is. Looks important.

 

[xchagg]

Thanks a lot . . . . not

I've just gone and ordered some BGs to mod my Transit with grrr . . .

And than I'll have to grab some Ratshack soldering tools to to the mod, my tools are back in my home country haha (international student here)

Anything for better sound heh?

 

[Garbz]

hahah lol. The BG mods make a lovely difference. I put 2 NX-HiQ 2.2uf caps in there, worked very well.

The reason i was looking to drop the output impednace was because following the transit is a Transformer to convert the signal to balanced. The input impedance makes a bit of a difference to it's performance.

 

[flecom]

well someone correct me if im wrong but if your using an output tx you could drop the DC blocking cap since the tx will block the dc anyway

 

[Garbz]

Nope DC is bad for transformers. It's plastered all over the application details that DC across audio transformers is to be avoided.

 

[rickcr42]

Notice the power supply ? Single polarity and that means big time DC offset that must have a blocking capacitor.Use a better cap here to improve the sound (something with oil

).Next inline for "improvement" would be the resistor part of the low pass filter.It is directly in the signal path so everything goes through and that means should be the best you can find.Maybe a tantalum here would sound good.
The rest of the passive parts are "shunts" so have less sonic importance though never hurts to use the right parts in the right spot.

 

[flecom]

Quote:

Originally Posted by Garbz Nope DC is bad for transformers. It's plastered all over the application details that DC across audio transformers is to be avoided.

so then how do tube amps work?

 

[flecom]

Quote:

Originally Posted by rickcr42 Notice the power supply ? Single polarity and that means big time DC offset that must have a blocking capacitor.Use a better cap here to improve the sound (something with oil ).Next inline for "improvement" would be the resistor part of the low pass filter.It is directly in the signal path so everything goes through and that means should be the best you can find.Maybe a tantalum here would sound good. The rest of the passive parts are "shunts" so have less sonic importance though never hurts to use the right parts in the right spot.

no matter what there is gonna be a dc offset cause most dac's have dc on their output...

 

[rickcr42]

Quote:

no matter what there is gonna be a dc offset cause most dac's have dc on their output...

which you make large by any gain factor of the active stage that follows.

Quote:

so then how do tube amps work?

look at the schematic of a tube amp and it will be obvious

 

[JahJahBinks]

DC in transformer means infinite current, which is bad for transformer itself.

 

[flecom]

i have seen some transformers specifically designed to go on the output of common dac chips with the idea of blocking dc without using caps... maybe put your transformer after the dac and put a balanced preamp or something after the tx?