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Praise! 14th November 2003 05:33 PM

Capacitor sound
 
Hi all DIYers and Audio lovers

Please help!

I design many amplifiers but they are all DC-coupled.
Recently, I have been trying to design some good
quality car audio systems and find it very difficult not
to put a capacitor in the signal path. I don't know of
any good sounding caps as caps in the signal path is
against my design philosophy.

Could anyone INTRODUCE me to the world of capacitors?
I would appreciate much for your help. Please tell me
the type (MKP, Ceramic .....), where to source them,
how much and popularity.

I don't mind "subjective" opinions as listening to sounds
and enjoying it is subjective in essence anyway.

Go on, share your opinions!

James Yung
:smash:

analog_sa 14th November 2003 06:10 PM

Just curious - how did you come up with the 'no cap' design philosophy if you don't know about cap types at all?

JOE DIRT® 14th November 2003 06:50 PM

quote>>I design many amplifiers but they are all DC-coupled.
Recently, I have been trying to design some good
quality car audio systems and find it very difficult not
to put a capacitor in the signal path. I don't know of
any good sounding caps as caps in the signal path is
against my design philosophy.

If you design audio systems then you must know about the question you have asked??????

Praise! 14th November 2003 09:07 PM

Quote:

Originally posted by analog_sa
Just curious - how did you come up with the 'no cap' design philosophy if you don't know about cap types at all?
To be honest, I don't really know how I got to the present
no-caps design approach. But of course, I can give you many
reasons:

1 If you don't need a component in the signal path, scrap it.

2 phase shift, worse: different phase shift at different frequency.

3 subjective: my love of JFETs --- depletion mode devices.

I don't know ..... Since I don't normally use caps, I don't reserach
for them. That's why I don't even know which type of caps
are suitable for audio.

James

Praise! 14th November 2003 09:11 PM

If you design audio systems then you must know about the question you have asked?????? [/B][/QUOTE]


Hi Joe,

See my reply to analog_sa

James

Richard C 14th November 2003 09:22 PM

Why is it more difficult to avoid putting capacitors in the signal path of an in-car amplifier than any other type of amplifier?

Praise! 15th November 2003 12:46 AM

Quote:

Originally posted by Richard C
Why is it more difficult to avoid putting capacitors in the signal path of an in-car amplifier than any other type of amplifier?

Because I'm trying to use application specific ICs to make
up the whole system. Inside the ICs, they probably use
BJTs instead of JFETs in the input stage. There is a DC offset
at the input which makes a input cap complusory.

James

fdegrove 15th November 2003 01:27 AM

Hi,

Quote:

I don't know ..... Since I don't normally use caps, I don't reserach
High time you should, both as an RC coupling element as in the PS....

Designs that don't use caps are far and in between, although it can be done with lots of iron...:angel:

Let's face it, you do use caps, in the PS at least and these too are candidates for sonic degradation.

We're a PITA, aren't we?:D

Cheers,;)

theChris 15th November 2003 01:51 AM

"Why is it more difficult to avoid putting capacitors in the signal path of an in-car amplifier than any other type of amplifier?"
-probably because the car amp is run from a single supply battery and must be run in such a manner to function.

i'd avoid ceramics for the signal path. i'd probably reccomend - polycarbonate, polystyrene (make sure the amp's insides don't get hot enogh to damage them), or polyproplyene. if you are worried about the phase shift, try for a lower cutoff frequency, likely meaning a high input impedance. Fets could be used here.

note that cap differences aren't as night and day as other things and if the car is in motion the noise floor will likely swamp any capacitor's sound.

also, you can use a signal level transformer to interface the signal. this will also allow you to add a single resistor and get an approximation of a balenced transmission system. likely not good for a CMRR over 30dB.

claudio 16th November 2003 09:50 PM

Hello James,
I think that reading thishttp://www.capacitors.com/picking_ca...rs/pickcap.htm will give you a lot of informations about caps.

Regards

Claudio


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