Background noise - tube amp

Torstensson · 10th December 2012, 12:57 PM

As a newbie I ordered this tube amp kit: Under $25 00 DIY 12AU7 Valve Cmoy Hi Fi Headphone Amplifier Kit Guaranteed | eBay

I've finished it and it's working but there is a lot of background noise.
From what I've found here in the forum it could be the AC-adapter.
It's a regulated 12V / 1A adapter but i still making lot's of background noise.
Tried 2 different ac-adapters I had at home, one from Netgear and one from Yamaha.

Could it be something else or is it most likely the ac-adapter?
Can I build some sort of filter?
Can run it from two 9V batterier in series instead?

I haven't fitted the pcb in a case yet but would this do any difference?

Thanks in advance!

merlin el mago · 10th December 2012, 03:46 PM

Why you don't make a linear PSU for it?

jerluwoo · 10th December 2012, 04:17 PM

Since this has a lm317 regulator on the board already, changing ac adapters will have no real effect. What is said about the ac adapter being regulated is misleading as very few actually are. I would think it is meant that the adapter rating is 12v 1a, its not necessary for it to be regulated with a regulator already a part of the circuit.
A schematic would be very helpful in finding ways to make it quieter.

Torstensson · 11th December 2012, 07:19 AM

How would I make linear PSU?
I will scan the schematic and post it later, no scanner at home.

10th December 2012, 12:57 PM	#1
Torstensson diyAudio Member Join Date: Oct 2012	Background noise - tube amp As a newbie I ordered this tube amp kit: Under $25 00 DIY 12AU7 Valve Cmoy Hi Fi Headphone Amplifier Kit Guaranteed \| eBay I've finished it and it's working but there is a lot of background noise. From what I've found here in the forum it could be the AC-adapter. It's a regulated 12V / 1A adapter but i still making lot's of background noise. Tried 2 different ac-adapters I had at home, one from Netgear and one from Yamaha. Could it be something else or is it most likely the ac-adapter? Can I build some sort of filter? Can run it from two 9V batterier in series instead? I haven't fitted the pcb in a case yet but would this do any difference? Thanks in advance!

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10th December 2012, 03:46 PM	#2
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Catalonia new Europe state	Why you don't make a linear PSU for it?

10th December 2012, 04:17 PM	#3
jerluwoo diyAudio Member Join Date: Feb 2006 Location: Ashland,Ky U.S	Since this has a lm317 regulator on the board already, changing ac adapters will have no real effect. What is said about the ac adapter being regulated is misleading as very few actually are. I would think it is meant that the adapter rating is 12v 1a, its not necessary for it to be regulated with a regulator already a part of the circuit. A schematic would be very helpful in finding ways to make it quieter.

11th December 2012, 07:19 AM	#4
Torstensson diyAudio Member Join Date: Oct 2012	How would I make linear PSU? I will scan the schematic and post it later, no scanner at home.