basic preamplifier/unity gain buffer

But audio is AC coupled so its usually unimportant
You can't count on that if 'equipment modders' are at work removing output coupling caps in source components. Worst case the DC offset from a unity gain 5532 stage with something as low as 47k input resistor can still be quite a few tens of millivolts.

Looks like we think alike in suggesting FET is the way to go here.
 
I wouldn't count on that. I always put an input cap on the input. You never know what you're connecting to. And you can get a super good quality film cap that's not going to degrade anything at all, one or two microfarads, and then you'll always be safe no matter what the source is. I always use a 2.2 uf Wima on the input, and make sure I have ultralow DC coupled offset on the output.
 
What are you assuming is at the output of the preceding stage? Assume it is another 2.2 uF, which is very low and very safe to assume. It is probaly quite a bit more in most cases, if present.

So 2.2uF in series with 2.2 uF on your input yields 1.1uF total. With a 47k impedance that yields an f3 at 2.8 Hz. That is in the weeds and neither your speakers nor headphones will ever get close to that frequency. I don't see a problem at all with a 2.2 uF coupling cap in this instance. It will work fine AND protect whatever follows it from unwanted DC or voltage offset. It's safe thing to do.

Play with the math yourself.
f = 1/(2*pi*R*C ) Don't forget R is in ohms and C is in farads. so 2.2uF =s 2.2/1000000.
 
What are you assuming is at the output of the preceding stage? Assume it is another 2.2 uF, which is very low and very safe to assume. It is probaly quite a bit more in most cases, if present.

So 2.2uF in series with 2.2 uF on your input yields 1.1uF total. With a 47k impedance that yields an f3 at 2.8 Hz. That is in the weeds and neither your speakers nor headphones will ever get close to that frequency. I don't see a problem at all with a 2.2 uF coupling cap in this instance. It will work fine AND protect whatever follows it from unwanted DC or voltage offset. It's safe thing to do.

Play with the math yourself.
f = 1/(2*pi*R*C ) Don't forget R is in ohms and C is in farads. so 2.2uF =s 2.2/1000000.
this is my general idea
1733434649228.png
 
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Here is what i built:
1000002391.jpg
im also intrested in the value of the biasing and if 100k is too much and if i could add an 100k resistor on the input or even add an switch to switch between diffrent input resistors.
1734449097302.png

I found this schematic on google images becuse i was too tired to make my own, the changes i made is no R9 100k R6 and R5 and 100uF C6.
 
Here is what i built:View attachment 1394996im also intrested in the value of the biasing and if 100k is too much and if i could add an 100k resistor on the input or even add an switch to switch between diffrent input resistors.
View attachment 1394997
I found this schematic on google images becuse i was too tired to make my own, the changes i made is no R9 100k R6 and R5 and 100uF C6.
You are using a single ended supply here so should add a blocking cap to the output or else you will be feeding DC to your power amp.
 
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i will you can even see two of these blue capacitor things in the picture with one of them being the output cap, im probably gonna add an volume control potentiometer before the output decoupling capacitor like this: (asuming the first triangle is the buffer/preamp and the 2nd one is an unspecified power amplifier [ignore values])
1734451685977.png
 
The Toslink DAC probably needs the output capacitor to block DC voltage. But, it was setup for an input resistance of 100k minimum (15.9 Hz cutoff). That would even be marginal. Use this high pass filter calculator . You want the cutoff frequency to be much lower than 20 Hz, because you want phase shift in the audio band to be minimal. For usual solid state 10k loads, they typically use a 10uF coupling cap, which gets the cutoff frequency down to 1.59 Hz. It doesn't need to be that low.

With pots, there is a fixed resistance facing the coupling capacitor, when AC coupled. The high pass filter will then have a fixed cutoff frequency. The wiper connects to the following stage. Buffers after the pot do help a great deal, in my experience.

If you want to DC couple, as in your original idea, you would use JFET input op amps and dual supplies for lowest DC offset. I would also use adjustable regulators (e.g. LM317/LM337), so that you can get the rail voltages symmetrical. Buffer-pot-buffer arrangement.

I just use a PGA2310 based volume control. I like it. They are not available on Ali any longer. They now have the improved (assuming) MUSES72320 units. You get remote control. Not very DIY. There are some DIY projects here using the MUSES72320 or MUSES72323.
 
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it was this uninspiring piece of 5$ audio gear
1734457123763.jpeg

i should invest in something nicer even maybe with an hdmi out, or just sell these tower speakers from someones trash bin and invest in near field gear becuse i dont spend any time near my tv and said speakers.