Noisy K1803

Kits Audio Hi Fi Projects
1

I just finished that kit and it’s very noisy I wasn’t expecting much but there’s more noise then audio signal, well 50/50 I’d say It’s like a wind sound, even with no mic plugged in so I would assume it’s the output of the pre-amp that’s noisy. I can roll off the noise with an eq it’s exactly 1.8k by -3db and it’s gone. Also when I touch the bottom of the IC I get pops and crackles.

Here’s the wiring with the xlr connectors

pin 1 & 3 to Neg AF in
pin 2 to pos AF in

pin 1 & 3 to Neg AF out
pin 2 to pos AF out

Here’s some pix

800×600

800×600

800×600

On another forum someone was mentioning to put a 10uF cap right there.

2

Some hints:

Check for obvious wiring mistakes.
Use a regulated supply.
Use shielded wiring.
Put the unit in a metal enclosure.
Use a pin-compatible, better spec op-amp (e.g. 5534)

3

Should I increase the voltage? Right now Iam using a 9 volt.
Also if I use a do I need to midify anything or it would be just a swap?

Thanks

4

No need to increase supply.
If op-amp is pin-compatibe, no need to change anything

5

But for now should I increase the voltage? Is the xlr wiring right? I want to use the pre amp with a dynamic mic

6

No need to increase voltage.
Sorry, I’m not familiar with XLR wiring.
I’m sure there is plenty of info available on the net on XLR pinouts and wiring.

7

Where could I find a 5534? All my search results link me to forums or specs but no sales. Very strange.

Ok I finally found it
search.digikey.com/scripts/DkSea … 4A&x=0&y=0

Which one is the replacement for that kit?

8

Any 8P DIP version will do the job.

9

What about a OPA134?

10

I repeat: if it is pin-compatible with an 741 or 5534, it will most likely work.
I’m afraid I do not have the means nor the time to compare specs or to assist with modifications.

11

Ok and I guess I won’t have to change any of the components on the board?