I just got the TDA1308 boards and it sounds good for the purpose =) I just need to check if its exactly the same as the typical circuit in the data sheet or if its been modified. It has the exact same number of components so hopeful on that.
Heres a close up pic
Here is the typical circuit
Thankfully all the resistors are labeled so the caps will be what I need to check, My multimeter seems to be giving me odd results that im not expecting so may need to tear down the second one I got so I can measure them correctly.
It could do maybe with a touch extra bass?.. just a touch but its not too bad at all. Keep in mind it'l be playing 8 bit music only so it doesn't need to match up with anything huge.
Any suggestions on where I can slightly improve? SMD ceramics ect only.
Heres a close up pic
Here is the typical circuit
Thankfully all the resistors are labeled so the caps will be what I need to check, My multimeter seems to be giving me odd results that im not expecting so may need to tear down the second one I got so I can measure them correctly.
It could do maybe with a touch extra bass?.. just a touch but its not too bad at all. Keep in mind it'l be playing 8 bit music only so it doesn't need to match up with anything huge.
Any suggestions on where I can slightly improve? SMD ceramics ect only.
What's your load impedance? Low, I guess? I am not sure whether you can even get 100 µF MLCC ceramics (they had made it to 47 µF a few years back, not cheap either), and these may well be substantially less. (Not to mention that high-K ceramics make craptacular coupling caps.) Not the best combination with a low-impedance output and 32 ohm or lower 'phones. In the early 2000s there was much hoopla surrounding the iPods of the day and their low bass dropoff - they were using 100 µF output coupling caps. For 32 ohms you really want a minimum of 220 µF.
Do note that you may also be hearing the effect of near-zero output impedance if you happen to be used to higher-impedance outputs, depending on what headphones you were using to test and their impedance response.
Since including big coupling caps in small portable devices is kind of a nuisance and DC coupling would be much preferred, headphone amp ICs for portable use then gravitated to active grounds (at half supply) first and DC-coupled amps with internally generated negative supplies (via a charge pump circuit) thereafter. (Those from Maxim are some of the most advanced you can get, charge pump and class G/H.) The TDA1308 is from the late '90s and predates all of that. I suppose you could run it on a traditional +/-3.3 V split supply just fine (these were 7 V max if memory serves?), but the circuitry and layout would have to reflect that - hacking this particular board may not be feasible.
Do note that you may also be hearing the effect of near-zero output impedance if you happen to be used to higher-impedance outputs, depending on what headphones you were using to test and their impedance response.
Since including big coupling caps in small portable devices is kind of a nuisance and DC coupling would be much preferred, headphone amp ICs for portable use then gravitated to active grounds (at half supply) first and DC-coupled amps with internally generated negative supplies (via a charge pump circuit) thereafter. (Those from Maxim are some of the most advanced you can get, charge pump and class G/H.) The TDA1308 is from the late '90s and predates all of that. I suppose you could run it on a traditional +/-3.3 V split supply just fine (these were 7 V max if memory serves?), but the circuitry and layout would have to reflect that - hacking this particular board may not be feasible.
I connected the board directly to an output on my audio interface to test as the machine Im making it for need repairing before I can test on it, ill try hooking it up to a gameboy to get a close match of my purpose for now.
I have good head room to use larger capacitors but I was hoping not use electrolytic for a marketing reason so tantalum would be fine for this (I may cave and use high end electrolytic). Note that I have a small footprint though.
Im also using a mono speaker amp on the same board. Planning one of the PAM amps for this as I have a well tested schematic to work from.
It'l be run on a 5v power supply.
The reason I planned to use this TDA1308 is because I have a board to work from.
Also seems many of these "Typical circuits" in the data sheets are not up to scratch so maybe I need a newer one that has a good typical circuit design?(with low cost)
I dont need super low-end bass as the machine im making it for will never go that low but having some will be good on the ears.
Alot of this is confusing me, Im not as clued up as you guys as you can tell =) haha.
I have good head room to use larger capacitors but I was hoping not use electrolytic for a marketing reason so tantalum would be fine for this (I may cave and use high end electrolytic). Note that I have a small footprint though.
Im also using a mono speaker amp on the same board. Planning one of the PAM amps for this as I have a well tested schematic to work from.
It'l be run on a 5v power supply.
The reason I planned to use this TDA1308 is because I have a board to work from.
Also seems many of these "Typical circuits" in the data sheets are not up to scratch so maybe I need a newer one that has a good typical circuit design?(with low cost)
I dont need super low-end bass as the machine im making it for will never go that low but having some will be good on the ears.
Alot of this is confusing me, Im not as clued up as you guys as you can tell =) haha.
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Looking back at my LM4808 chips and then looked at the LM4809 for comparison it looks like the exact same amp but with a shutdown mode. Yet the typical use schematic has larger value resistors. Would using this different schematics values do me any good you think?
http://www.ti.com/lit/ds/symlink/lm4808.pdf
http://www.ti.com/lit/ds/symlink/lm4809.pdf
http://www.ti.com/lit/ds/symlink/lm4808.pdf
http://www.ti.com/lit/ds/symlink/lm4809.pdf
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