Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Sorry I missed C13 but did change the others as suggested.
Will search fo different mics. I was under impression NOISE CANCELLING meant LOUD noises were shut off.
Going to recheck my entire schematic as I allowed components from my bat project to filter into this one.
I think your opamp is too noisy to be a mic preamp and your maximum gain is way too high at 68,400 (yes, more than 68 thousand when a tone control is at max).
A sensitive mic preamp has a gain of only 200.
But how does anybody except your hearing doctor know how deaf you are? Deaf like a toad?
I have never looked at how much attenuation of sounds occur to a deaf person who can be helped with a hearing aid. 10dB? (3.16 times) 20dB? (10 times).
perhaps lower the pre amp gain by changing R5 which sets the gain on the pre amp?
I will look for a lower noise op amp in TINA as it has LOTS of examples.
Thinking just build as is and I can change the gain seeing how I am using through hole on this unit for testing purposes.
low noise etc https://www.ti.com/product/opa4134
here is the schematic we have so far. NOTE the pots are 200K as that's what I have on hand. The full circuit will use 100k and 500k as noted in the Baxandall.
I noticed the input cap WAS on the wrong side of the input bias. This TINA simulation has it on the correct side.
I changed the input signal for 2.2k internal resistance
Grounding the unused +inputs I assume is correct way to disable the unused portions of the TDA2822 and the OPA4134?
The connection wasn't there . I had to enlarge to see if there was a connection at R5 to C6
here is corrected enlarged pic.
The graph looks better?
I was under impression that R2 provided the bias but I failed to change the J1 to V+
I think the resistor that powers the mic should be supplied through an RC filter so that noise on the power supply is not fed to the input of the preamp.
I don't know where the 5V supply will come from. If it is a battery then it will bounce up and down with the signal which produces "motorboating" when amplified.
Your circuit has two circuits producing a bias voltage but only one circuit can bias both opamps.
EDIT: I forgot to say that since C6 has the huge value of 10uF then it passes frequencies down to one cycle per 6 seconds.
If it is 10nF (0.01uF) then it passes frequencies down to 16Hz.
The battery needs 100uF parallel to it.
The 2.2k resistor that powers the mic should be fed through a 1k ohm resistor from the battery then the two resistors should have a 47uf or 100uF capacitor to ground where they meet.
Hearing aid update
Have all parts purchased but before having PCboard made I want to double check my schematic https://www.electro-tech-online.com/threads/posting-a-two-page-schematic.128132/
I hate to be a bother but I plan to offer a PCboard for assistance in this endeavor. AudioGuru is on my list. Contemplating http://iteadstudio.com/ for boards. Board design is pretty much done but any suggestions are welcomed.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.