Hi!
I will be building a cmoy-type headphone amp to be embedded inside a retropie console powered by a LiIon battery (3.7V). That voltage is then converted with a DC/DC-converter up to 5V and used to power the system.
So, 5V is what I have to play with for the audio section which is comprised of two parts, a speaker amp (PAM8403) and a headphone amp. My aim is to use a switched jack to sense when the plug is inserted, and simultaneously switch the PAM8403 OFF, and the headphone amp ON. This can be done with enable/shutdown pins in the devices. The PAM8403 already has an enable pin, but finding an opamp usable for headphone drive, operating at 5V, being diy-friendly and having reasonable specifications is a bit daunting.
My options that I have landed in includes:
Also, neither of these are specifically aimed at low voltage use. But they are within specs at 5V. Problems?
Are there other options of opamps that has shutdown builtin already that I should consider?
I will be building a cmoy-type headphone amp to be embedded inside a retropie console powered by a LiIon battery (3.7V). That voltage is then converted with a DC/DC-converter up to 5V and used to power the system.
So, 5V is what I have to play with for the audio section which is comprised of two parts, a speaker amp (PAM8403) and a headphone amp. My aim is to use a switched jack to sense when the plug is inserted, and simultaneously switch the PAM8403 OFF, and the headphone amp ON. This can be done with enable/shutdown pins in the devices. The PAM8403 already has an enable pin, but finding an opamp usable for headphone drive, operating at 5V, being diy-friendly and having reasonable specifications is a bit daunting.
My options that I have landed in includes:
- OPA1622, has a shutdown pin, but is not possible to solder with my current equipment. It is a SON-10 package. (EDITED: wrote OPA6122 my mistake first)
- OPA1688, does not have a shutdown pin, but is great otherwise
Also, neither of these are specifically aimed at low voltage use. But they are within specs at 5V. Problems?
Are there other options of opamps that has shutdown builtin already that I should consider?
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Probably because it's not necessary with a quiescent current of only 1.6mA? How many hours of battery power will that eat away? Just thinking...
The SOIC package is very easy to hand solder, and no special equipment is needed.
Don't be afraid of it. Tack solder a corner pin first to align, then solder the rest,
and last come back to the first pin.
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I agree with this, except I'd get a few inexpensive SOIC chips to practice with first.
Sure, but it's easy. I'd not install other components near the SOIC until it is soldered in place,
at least not until you're used to doing this. Now for say 0603 parts, those aren't so easy to do
by hand, even if you can see them.
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Probably because it's not necessary with a quiescent current of only 1.6mA? How many hours of battery power will that eat away? Just thinking...
I need a shutdown function as I am to switch between the headphone and speaker amps. And since shutdown isn't available in most amps I've seen, and if it is it is most often a very small smd package size and thus not possible by DIY means. I was thinking that I could make my own shutdown function with a MOSFET as a switch. But I guess a built-in shutdown function in the amp is better - if I can find a good opamp. Hence the thread...
I have no problems with soldering SOIC. Sorry, I had the wrong reference in the post, what I meant was the OPA1622 that is in SON package. That one would otherwise be a perfect candidate since it has shutdown mode, but it is a bit too hard to use.
Yes, it would work. But it is a device from 1997 and a bit dated. Specwise it is nowhere near the more modern stuff. I'm looking for some decent audio quality at least.
Here's a schematic of the amp switching circuit I want to build. Well, mayby not exactly like that, but someting similar. For instance by using a 4-pole headphone jack where one pole is used for the sense circuit alone, by tying it to Vcc, grund or whatever signal level is needed.
An externally hosted image should be here but it was not working when we last tested it.
I also recommend OPA1688 without On/Off switch. Its quiescent current is so low that it has practically no influence on power consumption of your setup.
Probably because it's not necessary with a quiescent current of only 1.6mA? How many hours of battery power will that eat away? Just thinking...
Ah, what you are proposing is to have the headphone amp On at all times even when no plug is inserted? Didn't think of that really! But is the power draw really equal to quiescent current levels when input has audio playing?
The OPA1688 (consuming 1.6mA idle current per side) when linked with the new and extremely efficient TI TPS3701 comparator drops that down to just ~7-8uA of idle current... it would take over 30,000 hours to run down a lithium 9V cell on idle! By the way, this comparator supplies voltages down to 1.8V!
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WoodyLuvr, I'm not sure how you propose this device will solve the problem. And it is in a not-so-friendly SOT-6 package of about 3x1.6mm in size...
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