Amps static too loud

Hey guys.
Is there any way of getting rid or lowering the static that comes from an amp? When you have the volume at 0 it has a static like ssshhhhh basically white noise kind of sound and it gets slightly louder as the volume gets turned up to full. I'm running it of a laptop power supply and it does the same if I run it off battery. I know the problem is probably due to it being a cheap amp or poorly designed circuit but hey it's worth a try if there is a simple fix hahaha.
I know it's cheap and nasty... This is the amp:
Cheers

s-l400.jpg
 
Many amplifiers have no filtering at the input.

I am an advocate for effective input filtering
I recommend two filters. A high pass filter to attenuate excessively low frequencies and remove the risk of DC damaging your equipment and a low pass filter to attenuate Radio Frequency interference and to reduce out of band non audio information.

The Low Pass is a series resistor in the signal flow/hot line followed by a small capacitor connected between the signal flow/hot and the signal return/cold.

The High Pass is a series capacitor in the hot followed by a resistor between hot and cold.

Eight components that usually cost less than £1 ($1.50) for two channels.
 
There is a faint hiss when the volume is at its lowest but I’m not too concerned about that as it’s only when the volume is turned up a lot that I get a real hiss.
I have connected the ground of the input to the left and right of the input so they are all shorted to one another and that cuts the hiss down to about half.

Thanks AndrewT what values are those components? Is it something that I just have to experiment with values?
Cheers guys
 
the low pass can be set to around one octave to two decades above 20kHz, i.e anywhere from 40kHz to 2MHz. There is a lot of leeway.
I choose ~200kHz to 250kHz.
The high pass can be set similarly below 20Hz, i.e. anywhere from 10Hz to 0.2Hz.
I use 1.5Hz to 2Hz.

The formula that predicts the passive filter frequency turn over (roll off) is:
F-3dB = 1/ 2 / Pi / R / C

eg. for 1nF and 1k0 low pass filter the F-3dB = 1/2/3.14/1000/1*10^9 = 159kHz
The 10^9 is for the nanoFarads
 
Hey Arty yes I have connected the ground of the input to the left and right of the input so they are all shorted to one nother and that cuts the hiss down to about half. The source is a cd player, phone, PC, iPod or a Bluetooth modual (I use various sources) and they all have that hiss even when there is nothing connected to the input of the amp so it's not the source I guess. There is a hiss when the volume is at 0 which is bare able but it's when I turn up the volume that the hiss gets louder. When there is a quiet part in music you can hear it or if you're listening to an audio book then it just annoys me. Over the next day or 2 I'll try those resistors and cap that others suggested :)
Thankyou

Oh by the way it's not a ballenced input it is just a standard left/right and ground connection (stereo)
 

mrWagner

Member
2006-10-27 1:34 pm
I already mentioned before that the TPA3116 amps have hiss because of the layout.
And you should read about it in the class D section. Using high and low pass filters will not help as those only affect signals out of hearing range, but hiss is in the audio band. As I read it is partially because the analog and digital supply is directly connected.
 
Thanks for all your input, I work with professional audio all day every day and even a $100,000 system I use has some shhhh in it when the volume is at 0. Even speakers like the ART 725-A MK II do it. I hear shhh in various systems from professional audio to home hifi to at the cinemas to ipods etc…. some are louder than others but still at very acceptable levels. From my knowledge this is normal but it seems like this cheap little amp has a lot more than I expected, I’m not looking at making it 100% silent as it’s probably impossible (it would be good tho….*dreaming* hahaha) but I’m yet to try what was suggested above with resistors and caps as I have been so busy lately hopefully I can get back to the project sometime soon... tomorrow or when ever. I’ll keep you guys up to date.
Thankyou so much!!
 
Look forward to your report of your progress with it.

I found I was getting hum and electrical noise from household switches etc. I got a filter as suggested for main AC input. That didn't help.

Turned out to be a defective RCA cable. Changed that out and it's now perfect.

I just built an LM3886 with the help of AndrewT and others, and I get no "shhh" unless I crank the amp all the way to max and have ear 1 1/2" away from tweeter. And that could be coming from the DAC or Pre ? Maybe the AC filter did help? Perhaps it could have more "sshh" without it? will never know now.
 
Last edited:

Arty

Member
2011-02-24 5:04 pm
Look forward to your report of your progress with it.

I found I was getting hum and electrical noise from household switches etc. I got a filter as suggested for main AC input. That didn't help.

Turned out to be a defective RCA cable. Changed that out and it's now perfect.

I just built an LM3886 with the help of AndrewT and others, and I get no "shhh" unless I crank the amp all the way to max and have ear 1 1/2" away from tweeter. And that could be coming from the DAC or Pre ? Maybe the AC filter did help? Perhaps it could have more "sshh" without it? will never know now.

just get some really high efficiency speakers, and you will get a lot more ssshh sound.
sometimes too sensitive speakers are not that desirable at all.
 
just get some really high efficiency speakers, and you will get a lot more ssshh sound.
sometimes too sensitive speakers are not that desirable at all.

The sensitivity of my RS 2001 speakers are 89db @ 6 ohms.

Was thinking about buying a pair of $200 Kilpsch bookshelf speakers that have gotten good reviews. But the midrange is only 5.25" in them -- the Rs2001 I have they are over 6 inches.

I am just curious how much better I can do than these infinities. They went for like $238 back in the early 80's I believe. I've re-foamed the midrange speakers (are they called surrounds?)

If you only had $300 to spend, and could only have bookshelf speakers (say 12-16 inches tall), how would you spend it? What's the best sound one can get for $300?

The RS2001 I have are good enough that I can hear a HUGE difference between the Adcom 535 and LM3886 I have. And can hear a gigantic difference between the FIIO D3 V1 dac and the Sony XE-500 (1999) cd player's dac (which sounds muddy in comparison). Cymbals and vocals sound clear and crispy with the FIIO D3 V1 on these speakers. I hear more separation of instruments. Listening to David Gilmore's On An Island album right now -- great sound.
 
Last edited:

Arty

Member
2011-02-24 5:04 pm
depends on a lot, i might even hazard some fullrangers. it really depends.
thing is, i would never go with bookshelf speakers.
2 way, 6,5 " midbass with a proper 1" tweeter.
and verry naturally a subwoofer.
i absolutely do not prefer pre-fabricated speakers at all.
i prefer to design and build them on my own. along with the xovers.