the op amp output can drive added load - up to ~20 mA (I use ~ 1/2 the short circuit current as a practical max linear output)
you also have to consider the V required - opa2134 can't swing much current at Vout within 2 V from the rail
a single op amp I/V used as output doesn't give much choice for the required low pass filtering
you also have to consider the V required - opa2134 can't swing much current at Vout within 2 V from the rail
a single op amp I/V used as output doesn't give much choice for the required low pass filtering
Not sure low-pass filtering is required when only driving headphones? Certainly if driving an amp, an LPF will minimize IMD but headphones are generally going to be better than amps for IMD.
@maxw You don't say what impedance your headphones are? I've done this but I didn't use OPA2132, rather I used AD8016 which has a lot more current output. More akin to jcx's TPA6120.
@maxw You don't say what impedance your headphones are? I've done this but I didn't use OPA2132, rather I used AD8016 which has a lot more current output. More akin to jcx's TPA6120.
Thanks for the replies.
I'm not sure I need any filtering. This is not a standard DAC, this is a multiplying R2R DAC being used as an attenuator:
My headphones are 32Ω.
Basically, I don't care too much about the opamp, I can change it later but I'm just curious if I can damage the DAC? Is there any way that using the opamp to drive a 32Ω load would cause that DAC to output more than 2.5mA? I'm not sure how to calculate this!
I'm not sure I need any filtering. This is not a standard DAC, this is a multiplying R2R DAC being used as an attenuator:
An externally hosted image should be here but it was not working when we last tested it.
My headphones are 32Ω.
Basically, I don't care too much about the opamp, I can change it later but I'm just curious if I can damage the DAC? Is there any way that using the opamp to drive a 32Ω load would cause that DAC to output more than 2.5mA? I'm not sure how to calculate this!
You cant damage the DAC, cause the output is current source. It is not a voltage source that is sensible to the load (that is how I understand the theory) Any current source has its own internal resistance, so even if you bridge it, it still has load to work out the current.
But what you can do is overheat OpAmp and make his life very hard. But you no need it, do you? So put in place TPA152 or TDA6120 and thing is done=)
But what you can do is overheat OpAmp and make his life very hard. But you no need it, do you? So put in place TPA152 or TDA6120 and thing is done=)
I'll echo the comments above. You won't hurt the volume control, but the I/V opamp isn't going to be ideal for driving the headphones. The TPA152 suggest by Devilsdance seems a good, easy solution.
If you want to kick it up a notch, try the TPA152 headphone amp. I've used it with very good results. I've only used it with differential inputs, but it can be used single ended, too.
If you want to kick it up a notch, try the TPA152 headphone amp. I've used it with very good results. I've only used it with differential inputs, but it can be used single ended, too.
I did by myself ( I mean TPA152 ). Just recently and was surprised by quality of output sound. Than I started to read more and more and realized that all community is crazy about TDA6120. So I went crazy, took my time and decided to have it done =) ( Accidentally I did managed to damaged my right knee while riding my Rayen skatebaord in Sydney) Well, by sitting home alone and getting sick I designed USB DAC, PCM2704+DIR9001+PCM1792+OPA134+TDA6120... And I can tell you for sure, it worth it. TDA6120 does its job very well. So, dont be afraid to invest some time into your future
Thanks for the input folks.
This isn't to drive headphones permanently, I just sometimes use headphones for testing. So I'll stick with the opamp.
Now I have to look for other reasons why my DAC ICs seem to randomly stop functioning after a period of time
What is happening when it stops? What your PC says? and what are you getting as a output sound?
Nothing to do with a PC. This DAC IC is not like a normal DAC most people talk about in here, it's basically a serial controlled R2R resistor ladder. It's a DAC8812.
Basically, after a period of time, the IC just stops responding to serial control (SPI from an Arduino). It powers up and lets sound through but just won't change settings. No distortion, no DC, no other issues, it just stops responding to the serial control. I've had a few do this too. Strange. I must be doing something wrong...
It is something that I am not familiar with at all. I bought ARDUINO recently to keep it lying on my table for future projects ( than I got stuck learning C++ to manage the code)... But, it seems like it will take more time than I expected to start with it. Why don't you get yourself a decent USB-DAC and get rid of such a torture? Is it part of your job or educational program?
By the way, I do read some books about software development occasionally and when it happens like this ( JUST STOPS) more and more people say you have a problem with STAKE. Have you got any control over serial interface? Maybe you need to change the code to have some debbuging message to be sent to you for analysis? Well. it is just my thoughts. But if I were you, I would start from managing my source code to tell what is going on right now and where my stack pointer is upload all vital registers status.
p.s. sorry for my poor English ))) it is my second language
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Why? They are VERY easy to use and get started with! I recommend it.
Again, this is not a normal DAC. In this application I am using the DAC for precision attenuation, volume control. I already have a number of USB DACs
Not a problem. At least you speak more than one language!
I think I will start a new thread about the issue I'm having.
The irony of this story is - in my understanding, the TPA6120 was originally designed as an ADSL driver, and re-badged for audio
The irony of this story is - in my understanding, the TPA6120 was originally designed as an ADSL driver, and re-badged for audio
Well. it is a amp with current feedback, nothing else. Powerful, wideband and successful. The problem is that a lot of people do not understand how it works and what it is for =) A lot of pressure from those who advocate voltage feedback over current. Well, it is how it is. I dont really care as long it satisfiy my human being needs.
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Why? They are VERY easy to use and get started with! I recommend it.
Again, this is not a normal DAC. In this application I am using the DAC for precision attenuation, volume control. I already have a number of USB DACs
Not a problem. At least you speak more than one language!
I think I will start a new thread about the issue I'm having.
I have been heavily involve in plastic injection molding machinery business for last 6 years, but originally my background is military radars developments =) So it takes time to learn C, than C++ .. that is something new to me. I do agree, second language is a great opportunity to walk away from where you were burn, specially when it comes to places like Australia =))) more languages you talk, wide road for you is
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