Assistance in wiring a simple circuit?

[things]

Well basically, it gets the analogue signal from a USB sound card (Before the filter capacitors) and amplifies it. What I want to know is if:

I can bypass everything behind the 1K resistor, and just feed it 5V from the USB there.

Do all the 0V grounds to to the ground on the sound card?

And where the Vdd and Vcc on the op-amp go. (If my 5V idea does work, where will they go then?)

**broken link removed**

Thanks

 

[rjvh]

Your opamp need a power supply in order to work

it needs a positive and a negitive rail in order to give both amplitude sides of the signal in this schematic so yor idea will not work unles you have a separate power suply for you opamp (something you want to delete in this schematic)

Robert-Jan

 

[things]

So, how exactly do you think I could get it to work off USB power? I have seen it done, but not 100% sure how

Thanks

EDIT: ahh, I see how it gets the + and - supply. Well, do you think, if U just removed the 1K resistor, and gave it 2 supplies from the USB, where the 15V is supposed to go, will that work? Or do I need a power supply capable of + and - 5V? (Is USB not?)

 

[Torben]

Well basically, it gets the analogue signal from a USB sound card (Before the filter capacitors) and amplifies it. What I want to know is if:

I can bypass everything behind the 1K resistor, and just feed it 5V from the USB there.

Do all the 0V grounds to to the ground on the sound card?

And where the Vdd and Vcc on the op-amp go. (If my 5V idea does work, where will they go then?)

**broken link removed**

Thanks

Hi Things,

The circuit is a dual-supply op amp inverting amplifier. Your idea will not work (at least, not without further changes) because in this configuration, the op amp requires a positive voltage (Vcc), a negative voltage (Vdd) and a ground exactly halfway between the two. Your idea would leave you with a positive supply and ground.

[Edit: Actually that's not true. It would leave you with ground and *no* positive or negative supply.]

You either need to provide a split supply as shown (which is given in your schematic by the section you want to bypass) or use a single-supply op amp configuration.

An excellent diagram by audioguru to address this issue has been posted as a sticky in General Electronics Chat.

I think you should look at another op amp besides the TL072 as well. The TL072 is spec'd only down to 7V total supply voltage. You have 5V. It will work poorly and unreliably if it works at all. Audioguru has in the past recommended the MC34071 to me, which looks good.

Where did you get get the circuit? Did you design it or download it? Perhaps there is another which would suit your purpose better. It would also be easier to help if you described exactly what you are trying to do, instead of how you think you should do it.


Torben

 

[things]

Hi. Well, I have found a source of + and - 15V I can use. So, would I be able to hook the +15 up to pin 8 on the opamp directly, and the - to the 1K res. directly? Or does it need the dual supply and ground inbetween?

 

[Torben]

Hi. Well, I have found a source of + and - 15V I can use. So, would I be able to hook the +15 up to pin 8 on the opamp directly, and the - to the 1K res. directly? Or does it need the dual supply and ground inbetween?

Hi Things,

Just hook it up as if your +15 supply was the top battery in your schematic, and -15 the bottom battery.

Make sense?


Torben

 

[things]

Hi, that makes sense, thanks.

Now, would the grounds go to the ground of the USB sound card, or the ground of the 15V PSU?


EDIT: WOuld that not create a dead short
??
thanks

 

[things]

Sorry for double post, I made up a little diagram on what I thought was right, but seems like it would create a dead short?

 

[rjvh]

Hi, that makes sense, thanks.

Now, would the grounds go to the ground of the USB sound card, or the ground of the 15V PSU?


EDIT: WOuld that not create a dead short
??
thanks

No every ground conection will be conected to ground so that should not give a problem

although it could get funny if the ground conections are not properly conected

Robert-Jan

 

[things]

So is there even a point of grounding it like that, or will it be fine without it??

It seems pointless, since its just gonna either short, or ground out anyway?

 

[Torben]

Sorry for double post, I made up a little diagram on what I thought was right, but seems like it would create a dead short?

Yes. What you are missing is that the links between +15, gnd, and -15 in your diagram are not links in your original schematic, but batteries.

I believe what you're after is this:

Torben

 

[things]

Okay, gotcha!

Now, for the output, it has a single output. So, i'd use that, but what is the other connection go to? ground? I believe its supposed to output +/-5V or -/+5V

 

[Torben]

Okay, gotcha!

Now, for the output, it has a single output. So, i'd use that, but what is the other connection go to? ground? I believe its supposed to output +/-5V or -/+5V

What is the connector you are trying to connect to? The stereo line in on your sound card?


Torben

 

[things]

I have a 8 channel USB sound card. Basically, I am just using it for its DAC chip. So, I have soldered wires to the direct output of the DAC chip (Right before the filter capacitors)

the circuit is then supposed to amplify it abit, then output it, but at a higher level, so I get a -5 to +5 (I think) output signal. In the circuit, it only shows 1 signal input, and 1 signal output. I was wondering what I hooked the signal out - or gnd to. the usb sound card maybe?

 

[Torben]

I have a 8 channel USB sound card. Basically, I am just using it for its DAC chip. So, I have soldered wires to the direct output of the DAC chip (Right before the filter capacitors)

I was just writing a post to say to ignore my last post since I just went back and re-read your original post. Sorry.

the circuit is then supposed to amplify it abit, then output it, but at a higher level, so I get a -5 to +5 (I think) output signal. In the circuit, it only shows 1 signal input, and 1 signal output. I was wondering what I hooked the signal out - or gnd to. the usb sound card maybe?

I have one question: what filter capacitors? Are there filters on the outputs? What is the name of the sound card?

Anyway, I'd take the output line from the DAC (I'll call that "DAC OUT") and connect that to the input on your amplifier circuit ("AMP IN"). "Gnd" on the DAC board goes to the gnd on your amplifier circuit.


Torben

 

[things]

OK. So all grounds to gnd, then for the output, its the AMP OUT, and GND ?

 

[Torben]

OK. So all grounds to gnd, then for the output, its the AMP OUT, and GND ?

Can you quickly draw out what you mean by that? Your description is too brief and unclear so I'm not going to recommend you wire it like that unless I know exactly what you mean. A picture will work better than words.

Sorry, but it's just that I don't want to agree to something, and find out later I misunderstood you and your sound card melted.


Torben

 

[things]

Okay, here. Basically, I have soldered wires RIGHT after the output from the little chip on the sound card.

What I want to know, is what is the "-" of the output signal.





THanks

 

[Torben]

Okay, here. Basically, I have soldered wires RIGHT after the output from the little chip on the sound card.

What I want to know, is what is the "-" of the output signal.


THanks

I don't know what you mean by 'the "-" of the output signal". The output signal from your amplifier (which presumably you will hook up to some other equipment) is the output from the op amp, and gnd on the amplifier circuit will connect to gnd on whatever you hook it up to.

Again, what do you mean by "filter capacitors"? Do you mean that the sound card outputs are AC coupled and you are referring to coupling capacitors? Are they simply in series directly between the DAC outputs and the physical connectors?


Torben

[Edit: Otherwise, the circuit looks good to me.]

 

[ericgibbs]

Morning Torben,

I believe that 'things' is asking 'where' do I connect my output ground [0v].?

You connect the Output ground [0v] to the Sound Card 0V.