how can i increase sound in circuit Opic and opa alice

[amir hossain]

It sounds like you don't have any preamp at all. That thing you showed only uses USB to supply phantom power; it doesn't amplify anything.

This is probably the cheapest thing that will do what you're trying to do:
https://www.amazon.com/channel-interface-Microphone-Headphone-recording/dp/B09YKQVJQP/ref=sr_1_7?crid=11O5DTG2TFJCA&dib=eyJ2IjoiMSJ9.4sQ38GZ5CywDqSM0N-THMSohLwNjgJAJVhbfxxRIJ_895A4e06vmMI6av5Ct8Z3GnnfF5LQSzJwJFnnx7stnx-y-LLyghNoRqPkcrnIw4XsP4aAMT1lRipHRTCoaxyfsuOZtUj3UDwV70zxWUgSGOMlmrfRzgUdiS9s1nXiN_zijMc1Mz78fEBTGIC969xS4Qc-K6g_XtIZ8Suutrxv13g4TKxzobdCDODs_jtokgM6uzbTUZseAzel_ZNNJXZipgouT2fVOnk9Ua_8AbwJnypeSj55fxS73kBkdxn1bDbw.7pNoNeaCd6vTZRCgi__p5PBTXfuDFkYKNhGDWykVI7w&dib_tag=se&keywords=mini+microphone+mixer&qid=1730963341&sprefix=mini+microphone+mixer,aps,231&sr=8-7

Thank you,
So i am guessing there is no way to amplify sound on the circuit with out any audio interface

 

[Khron]

So i am guessing there is no way to amplify sound on the circuit with out any audio interface

Well...

https://sound-au.com/project13.htm

https://sound-au.com/project66.htm

 

[amir hossain]

https://sound-au.com/project66.htm

Interesting, thank you.
Btw, can i replace n5532 with opa1642 (because i have 8 more laying around) or i HAVE To use n5532.

 

[Khron]

Interesting, thank you.
Btw, can i replace n5532 with opa1642 (because i have 8 more laying around) or i HAVE To use n5532.

1642's fine, i'm sure. Especially if it's not a fake one...

 

[amir hossain]

@Khron sorry to bother you again, need some help.

https://sound-au.com/project122.htm

Found this preamp page, i read the whole page but can not understand it fully or have doubts.
Like, is this a pre amp that
1) i need a preamp like opa alice+capsule?
2) opic/opa-alice powering with phantom power then the output from that goes to this preamp.
(Assuming i need no.2)

Also in the schematic (out and ground) is that mic output that goes in audio interface or audio jack?

Sorry for being annoying.

 

[rogs]

The 'single sided' OPIC circuit is simply an impedance converter. It has no gain. The 'differential output' OPIC circuit will provide 6dB of gain.
You can increase that output further by increasing the value of R3 on the OPA1642 schematic. (That will also add a little bit of extra noise as well.)

(That will make the signal levels different on each leg of the output, although that should not affect the impedance balance).

The problem of using that extra gain - when connecting an XLR lead that has a 3.5mm jack at the other end - is that the signal to the jack may only be taken from pin 2 of the XLR. So the differential signal - with it's extra gain - will be lost.

The simplest (and probably cheapest ) way to connect a single sided OPIC mic is to use the type of interface suggested by K. Brown in post #20.
That USB powered device will provide both phantom power and amplification for use with a single sided OPIC.
The phantom power is specified as 48v. In reality it's less than that, but will still power an OPIC circuit OK.
The output can be connected directly into the mic or line input of a computer sound card.
No need for a separate phantom power supply or mic pre amp.

This type of mixer can be found quite cheaply on Aliexpress....... See here: https://www.aliexpress.com/item/1005005925478301.html

 

[amir hossain]

The 'single sided' OPIC circuit is simply an impedance converter. It has no gain. The 'differential output' OPIC circuit will provide 6dB of gain.
You can increase that output further by increasing the value of R3 on the OPA1642 schematic. (That will also add a little bit of extra noise as well.)

(That will make the signal levels different on each leg of the output, although that should not affect the impedance balance).

The problem of using that extra gain - when connecting an XLR lead that has a 3.5mm jack at the other end - is that the signal to the jack may only be taken from pin 2 of the XLR. So the differential signal - with it's extra gain - will be lost.

The simplest (and probably cheapest ) way to connect a single sided OPIC mic is to use the type of interface suggested by K. Brown in post #20.
That USB powered device will provide both phantom power and amplification for use with a single sided OPIC.
The output can be connected directly into the line input of a computer sound card.
No need for a separate phantom power supply or mic pre amp.

This type of mixer can be found quite cheaply on Aliexpress....... See here: https://www.aliexpress.com/item/1005005925478301.html

Thank you for all the informations above, i will definitely look into it.

 

[amir hossain]

the signal to the jack may only be taken from pin 2 of the XLR

Big success, changed R3 resistor with 10k, changed xlr to 3.5mm jack's internal wiring. Previously it was pin2 singnal, (pin3+ pin1 ground)
I changed it to (pin 2 no connection), pin3 signal and (pin 1 ground)
Now its loud, how much loud Don't know. But i am happy with it

I tried my best to explain but my english not good. Sorry if i could not explain it correctly.

 

[rogs]

Big success, changed R3 resistor with 10k, changed xlr to 3.5mm jack's internal wiring. Previously it was pin2 singnal, (pin3+ pin1 ground)
I changed it to (pin 2 no connection), pin3 signal and (pin 1 ground)
Now its loud, how much loud Don't know. But i am happy with it

I tried my best to explain but my english not good. Sorry if i could not explain it correctly.

Changing R3 from 2k2 to 10k will increase the signal on that output by just over 13dB....

 

[zawad_tahmid]

Changing R3 from 2k2 to 10k will increase the signal on that output by just over 13dB....

Greetings Mr. Rogs,
I am planning to do the same as this guy did (for testing). But the OPIC schematic he uploaded has R3= 1k resistor. Changing the feedback resistor?

R3 from 2k2 to 10k

Are you referring to Opa Alice circuit or There an OPIC circuit that has 2.2k as feedback resistor?

Cheers

 

[amir hossain]

R3= 1k resistor

I changed this

 

[rogs]

Greetings Mr. Rogs,
I am planning to do the same as this guy did (for testing). But the OPIC schematic he uploaded has R3= 1k resistor. Changing the feedback resistor?


Are you referring to Opa Alice circuit or There an OPIC circuit that has 2.2k as feedback resistor?

Cheers

The schematic shown in post #9 is an early version of the OPIC project, from around 3 years ago. It shows a differential audio output, similar to the commercial 'Alice OPA' project from JLI Electronics.

As the OPIC project developed, it was simplified to help minimise noise and improve headroom. The audio output became single sided, and was impedance balanced passively.
It is intended for use with a phantom powered balance input microphone preamplifier, not an unbalanced computer sound card input.

If the earlier schematic is to be used then - with R2 fitted as 2k2 - fitting R3 as 10k will increase the gain of audio on pin 3 by c.13dB

If R2 is 1k, then R3 needs to be fitted as 4k7, to obtain the same sort of gain.

If R2 is 1k, then fitting R3 as 10k will increase the gain on pin 3 by 20dB.
(The gain of the differential audio output present at pin 2 will not be increased at all. Note that the the noise level will also be bit higher.)

Instead of purchasing a separate 48v phantom power supply to drive the OPIC circuit, you might like to consider getting one of these USB powered preamp units instead:
https://www.aliexpress.com/item/1005005925478301.html

The costs are similar.

That device will provide phantom power - and a balanced XLR mic pre amp - to connect to an OPIC microphone.
Although the unit is described as providing 48v phantom power, it is actually more like 30v, but that is sufficient to drive an OPIC circuit.

The output from that unit can be connected to a computer sound card input, if required.

 

[zawad_tahmid]

The schematic shown in post #9 is an early version of the OPIC project, from around 3 years ago. It shows a differential audio output, similar to the commercial 'Alice OPA' project from JLI Electronics.

As the OPIC project developed, it was simplified to help minimise noise and improve headroom. The audio output became single sided, and was impedance balanced passively.
It is intended for use with a phantom powered balance input microphone preamplifier, not an unbalanced computer sound card input.

If the earlier schematic is to be used then - with R2 fitted as 2k2 - fitting R3 as 10k will increase the gain of audio on pin 3 by c.13dB

If R2 is 1k, then R3 needs to be fitted as 4k7, to obtain the same sort of gain.

If R2 is 1k, then fitting R3 as 10k will increase the gain on pin 3 by 20dB.
(The gain of the differential audio output present at pin 2 will not be increased at all. Note that the the noise level will also be bit higher.)

Instead of purchasing a separate 48v phantom power supply to drive the OPIC circuit, you might like to consider getting one of these USB powered preamp units instead:
https://www.aliexpress.com/item/1005005925478301.html

The costs are similar.

That device will provide phantom power - and a balanced XLR mic pre amp - to connect to an OPIC microphone.
Although the unit is described as providing 48v phantom power, it is actually more like 30v, but that is sufficient to drive an OPIC circuit.

The output from that unit can be connected to a computer sound card input, if required.

Thanks for sharing the background on the OPIC project’s development. It's interesting to see the progression and how simplifying the design improved performance, especially for professional audio setups. Definitely adds a lot of insight.

Instead of purchasing a separate 48v phantom power supply to drive the OPIC circuit, you might like to consider getting one of these USB powered preamp units instead

I agree. I currently have a decent preamp that's working well. However, I was curious because I recently sent your OPIC preamp to a few of my friends. All of them are happy with it except the one who is still using it with an old 48V Phantom Power Supply

 

[amir hossain]

That is a symmetric output circuit, but a laptop input is single ended, not differential.
How is the XLR output from the phantom power supply connected to the 3.5mm plug?

I found schematic of the phantom power i bought.

Where is power input? Can you help?
Can i make it portable with powering it from battery? Like 9v?

 

[Khron]

I found schematic of the phantom power i bought.

Where is power input? Can you help?
Can i make it portable with powering it from battery? Like 9v?

No, that requires an AC plug-pack / input (despite it saying "DC1" for the input connector).

If you want / need to start from a 9V battery, you'll probably want to look for a boost converter / step-up converter that can go up to at least 50V output.

 

[amir hossain]

No, that requires an AC plug-pack / input (despite it saying "DC1" for the input connector).

If you want / need to start from a 9V battery, you'll probably want to look for a boost converter / step-up converter that can go to at least up to 50V output.

Is there any diy porable phantom power circuit that you know, can you please share it. Thank you

 

[k brown]

Is there any diy porable phantom power circuit that you know, can you please share it. Thank you

These can be powered by a small USB power bank.
https://www.amazon.com/AMOYER-Recor...refix=usb+phantom+power+supply,aps,450&sr=8-7

 

[k brown]

Or, this from a 9v batt.:
https://www.amazon.com/Knox-Phantom...07K3MWGBK/ref=cm_cr_srp_d_product_top?ie=UTF8

Or, DIY:
https://www.electronics-lab.com/project/9v-to-48v-dc-dc-converter/

Simple/crude DIY, with five 9v batt.:
https://www.instructables.com/Phantom-Battery-Power/