TDA7393 design help

[whammoed]

I have a few questions on building an amp using TDA7393.
I am starting with the application circuit from the documentation attached.
I will be using in stereo mode and have no need to use the chips mute or st-by functionality. This doesn't have to sound spectacular, but I would like it to be as good as possible.
1. I understand that the round capacitors where the polarity is designated are to be electrolytic. Should they be any special kind of electrolytic?
2. What kind of caps are the ones represented by a rectangle? Ceramic disc?
3. Are there any components I can disregard since I won't be using mono, mute, or st-by?
4. Depending on answer to #3: Do I need to tie the st-by pin to +5vdc to have the amp operational? What about mute pin(s)...tie to ground, 12vdc, 5vdc?

[Mooly]

The caps drawn as rectangles are non polarised such as polystyrene or polyester etc. You won't find ceramics in those values I would imagine (1uf).
C3 and C4... can't see why an electroylitic won't be OK... just choose good quality parts such as 105 degree rating low E.S.R. types.

Am guessing that for the mute function to be active require the transistor/s to turn on in which case if not needed just omit R1 and R2 but keep the caps of course.

[whammoed]

Thanks, I was thinking they should probably be polyester film after I posted.
Should any other caps be low ESR, like the main filter cap C1?
Also, what voltage rating should I be looking for for the caps?

[Mooly]

Low ESR types are so common these days I personally wouldn't use anything else. So that includes C1 of course... and you might find 4700uf a more common value.
Choose a voltage rating that gives a reasonable safety margin. For a 12 volt supply, 16 volts caps are fine, if it's nearer 14 or 15 volts then go for 25 volt working.

[whammoed]

OK, I will go low ESR on all of them.
I will preferably be running 12vdc however I want the ability to play around with different supplies if need be, so I will choose a 25v rating.
Is carbon film ok for the resistors in this circuit or should I go with metal film?

[Mooly]

5% carbons are fine... lol 20% pieces of wet string are fine, as those three resistors have no audio on them

The main advantage of metal film is long term stability (the noise level is lower but you would be hard pushed to say it made an audible difference in 99.9% of designs)

[whammoed]

Originally Posted by Mooly

5% carbons are fine... lol 20% pieces of wet string are fine, as those three resistors have no audio on them

The main advantage of metal film is long term stability (the noise level is lower but you would be hard pushed to say it made an audible difference in 99.9% of designs)

Great, that's what I figured. I think it's about time to order some parts and etch a pcb. I've assembled amp kits before but this will be my first scratch build. Should be fun.

[Mooly]

That sounds like a plan

[gfiandy]

Hi,

Just a quick observation, you say you don't need the mute. Are you planning to use relays to mute the speakers at power up as if you don't use the mute those amps are likely to make quite a thump at power on. I would put an RC circuit on them to mute the amplifer for the first few seconds after turn on.

Regards,
Andrew

[whammoed]

Originally Posted by gfiandy

Hi,

Just a quick observation, you say you don't need the mute. Are you planning to use relays to mute the speakers at power up as if you don't use the mute those amps are likely to make quite a thump at power on. I would put an RC circuit on them to mute the amplifer for the first few seconds after turn on.

Regards,
Andrew

Thanks, that is definitely somthing I'll be looking out for. I plan to make my proto pcb with space for all components so I will be able to test this kind of scenario.