A600 now playing MP3 on vampire... yes, you read it right

[8bitbubsy]

Originally Posted by Akira

All I do is remove these two. Works fine. No replacements, no touching of the components on the top of the board, sounds like my A1200.

They're in there even in the A1200, for a reason.
I wonder if removing the capacitors in the RC low-pass filters changes the impulse response in any way, it could leave more hard edges in the waveform, resulting in audible aliasing, but I'm not sure...

[Amiga1992]

I've had this modification in for years with no problems. Sound is fine. I dunno why they are there but removing them causes no troubles, rather fixes the muddy shitty audio.

[8bitbubsy]

They're in there to complete the 27kHz (A1200/CD32) RC low-pass filter. Just removing the capacitors is NOT the way to do it at all, even if it sounds the same. I wouldn't be surprised if this has some bad effect on the audio in a way.
But what I meant is that the 27kHz low-pass is there for a reason, even if the cutoff is so high that you won't hear a difference. The component costs would be reduced if you removed that filter stage in itself, so there has to be a reason why they decided to keep the filter instead of removing it. Anyways, enough of this, I'll not go anymore off topic for now.

[TuKo]

[09:45] <BigGun> igor and Brian started shipping or will ship today ..

[grond]

Originally Posted by 8bitbubsy

But what I meant is that the 27kHz low-pass is there for a reason

The reason is probably that they never cared enough to do it properly. Aren't there those electrolyte caps in there, too?

I don't see much sense in a 27 kHz aliasing filter in audio hardware. I mean, your speakers would have the same effect on the signal.

[pandy71]

Originally Posted by grond

The reason is probably that they never cared enough to do it properly. Aren't there those electrolyte caps in there, too?

I don't see much sense in a 27 kHz aliasing filter in audio hardware. I mean, your speakers would have the same effect on the signal.

This is reconstruction filter to perform two things.
First to average sample values as Puala use PWM to control signal level.
Second to reduce signal bandwidth (IMHO this should be passive LP filter before operational amplifier as most of OPAMP require to reduce signal bandwidth before feeding it to input - they are to slow and they distorting signal - unless you use fast OPAMP it is recommended to reduce signal bandwidth bellow 50kHz anyway).

[grond]

Originally Posted by pandy71

This is reconstruction filter to perform two things.

I know what a reconstruction filter is. Unless you have a quite non-linear amplifier, you usually don't need it as you have enough bandwidth limitation on the way to your speakers. The most important aspect in an Amiga would probably be to not interfere with badly shielded electronic devices due to emission from the audio cables connecting the Amiga to your speakers.

[eXeler0]

Maybe move this Audio-filter discussion to its own thread? ;-)

[Lord Aga]

Yup. It's not that interesting + it doesn't have much to do with Vampire cards.
I see couple of new posts in this thread and think I'll see some news about the card. Instead I get audio filter talk.