Preamp Kit Project

[audiorules]

Hi, first posting on this cool site.

Basically, I bought a Vellman Preamp Kit and I have no idea how to power it? It says between 10 and 30 volt DC, but on the PCB is says 12. Could I just plug in a DC adapter with 12 volts and connect tip and sleeve respectively?
I'm new to electronics, so go easy on me . Any help appreciated.

Thanks!

 

[Mooly]

What is the kit number etc. Any supply must have the correct polarity i.e plus and minus must be correct.

 

[audiorules]

K1803 is the #.

Specs are: Power - 10-30VDC/ 10mA.
Output impedeance: 1kohm
Max. input signal: 40mV

 

[Mooly]

OK, its a simple opamp based preamp with no on board power supply regulation. You could actually use a 9 volt battery to test this. Whatever you connect make sure that the positive voltage is going to pin 8 on that opamp and the "0 volts" to pin 4. And any voltage up to the working voltage of the caps or a maximum of 36 volts (the opamp max voltage) is OK

 

[audiorules]

So, wire directly to the op amp? I would've thought the 2 terminals on the PCB for power would've been set up correctly. I'll try it anyway.

 

[Mooly]

No... wire it up to the PCB as its marked but the real confirmation is that pin 8 must have the positive supply to it. You will find pin 8 goes to the DC input pin anyway.

 

[KatieandDad]

The PCB is clear as day as to which is + and which is -.

 

[audiorules]

I know that, I had an adjustable 12volt DC adapter (adj. from +3 to +12volts) and everytime I wired it to the kit nothing would change. The volume would only go down, not go up.

 

[Mooly]

I know that, I had an adjustable 12volt DC adapter (adj. from +3 to +12volts) and everytime I wired it to the kit nothing would change. The volume would only go down, not go up.

That is the first time you have mentioned "volume". Do you mean the volume control on the amp doesn't work ?

 

[audiorules]

Yes. The little volume control didn't change the level at all. Well it did change it. It changed it as if it were a passive volume, not a preamp volume. Which leads me to believe I either have a cold solder somewhere or my power source was incorrect.

 

[Mooly]

It sounds like a ground connection is missing to the little preset control. I would expect one of the end legs of the control to go to the GND pin. Those things are somewhat fragile and actually have a very limited number of cycles. You could wire a normal full size pot in its place if you wanted.