Have you looked up the specs of the "older Kenwood amp"? It might just be a relatively noisy design.
That might be a clue...
Over on the parts express forums other people seem to be having the same problem as I am having. Seeing how the hiss went away once I disconnected the DSP unit I'm starting to believe the problem lay in the DSP and not the amp. But thanks for all of the suggestions.
It could still be the combination, either the amplifier being too sensitive for the levels coming out of the DSP or my far fetched hypothesis from post #15. How did you arrive at the conclusion that everything but the amplifier is good in post #8?
Last edited:
If your amp hisses at you, it's signalling that it's frightened, defensive and warning you to not approach, lest you be attacked. Even if not, you don't want your new amp cowering behind the subwoofer. Instead, we recommend you keep your distance. Let the amp get accustomed to his new surroundings and to you. Bring it toys such as expensive interconnects, or perhaps a saucer of milk. Eventually it should let you approach, perhaps even touching its controls and gently stroking it. With time, the amp may become comfortable enough to sleep quietly in your lap or next to you on the sofa.
My apologies, perhaps I've been volunteering at the animal shelter for too long! 😺
On a bit more serious note, yes I've had hissy components. It became a big problem with active EQ situations. My solution? If a PC is involved, a wireless or optical (TOSLINK) connection eliminates any noise issues as the PC is often at fault. When possible, the rest of the chain is all balanced connections. Need not be expensive either. I've been quite happy for several years with Behringer gear used for line-level amp and power amps. Even then, there is some faint hiss with an active system.
My apologies, perhaps I've been volunteering at the animal shelter for too long! 😺
On a bit more serious note, yes I've had hissy components. It became a big problem with active EQ situations. My solution? If a PC is involved, a wireless or optical (TOSLINK) connection eliminates any noise issues as the PC is often at fault. When possible, the rest of the chain is all balanced connections. Need not be expensive either. I've been quite happy for several years with Behringer gear used for line-level amp and power amps. Even then, there is some faint hiss with an active system.
If I press my ear to the speaker, I can hear a faint hiss in a quiet room.
I estimate an s/n of 110 to 115 dB from its 80 watt max.
I estimate an s/n of 110 to 115 dB from its 80 watt max.
I think it has to do with the DSP outputs almost 4 volts, I think it is 3.7 or somewhere in that range and the amp is expecting 2 volts. I've been reading a lot of complaints on different forums about this DSP (Dayton Audio 408) in regards to it having a hiss and I haven't found any definitive reason for it or any work arounds for it. Although I did read somewhere that the power supply that comes with it, which is 12 volts doesn't supply enough voltage and is noisy and that a 17 or 18 volt power supply is what it really needs to bring the noise floor down and clean it up. I don't know if that is true.
I know this is older thread, but I just wanted to chime in. I also bought a Dayton 408, and I got noticeable hiss when I turned up the gain. So as a rule I'd say do not turn gain up above zero.
If you keep the gain down, it really isn't that noisy. But I replaced it because it really is not suited for home theater. It would be great for car audio, which is where it belongs. I had issues with it's auto shut-off on RCA mode--it sometimes shuts off in the middle of a song. It shuts off when signal input drops below an arbitrary number, and a quiet portion of a song can drop below that number. Or it turns off when I hit pause, and takes awhile to turn back on. So I set it to REM mode, which is always on when used with the included power supply.
I upgraded to the Peavey 48e. It has balanced inputs and has more delay adjustment, plus EQ on input and output. I prefer balanced connections, and the delay and input EQ have come in handy.
I'm also building a fully active system, 4 way, and I'm also running into hiss/ noise. I'm 99.9% sure it is caused by high speaker sensitivity exaggerating a nominal noise floor that wouldn't be noticed with less sensitive speakers. I have 12" coaxial drivers, and the HF horns are 107db sensitivity. At this point I think I just need to add an L-Pad to kill the noise. But I'm still open to suggestions.
But yeah, it seems to me that all amps have some noise despite spec sheets claiming impressively low numbers.
It depends how the amp is designed.
Some designers insist on MHz bandwidth and so HF is amplified and let through.
Resistors can introduce noise.
I tend to add small pf feedback caps to kill off any out of band HF.
My amps hiss is inaudible.
Some designers insist on MHz bandwidth and so HF is amplified and let through.
Resistors can introduce noise.
I tend to add small pf feedback caps to kill off any out of band HF.
My amps hiss is inaudible.
If a circuit in your amp becomes unbalanced such that it has a stressed transistor like Q1 in the White Noise Generator, it might have a "hissy-fit". The base-emitter junction acts like a zener.
Yea I was having the same problem with it shutting off during quite passages in the audio. It was especially bad at night time when the volume is low. But I changed the power supply and it now resides inside my amplifier case and it uses the REM setting. We will find out if it is still hissing once I finish my speakers. They will be using the SB Acoustic's Textream tweeter that will play the hiss if it is present. There is no more hiss playing back through my two ways with a fabric soft dome tweeter though. We will see.
The hiss is masked when there is signal? If so you need a noise gate or downward expander. Hiss is a fact of living in the real world but of course certain pieces of gear are worse/better than others. DSPs are notorius for adding hiss..kind of the nature of the beast. Proper gain structure is very important throughout your whole system.
Any semiconductor junction or resistor in an early gain stage can cause hiss with sufficient voltage drop snd current flow across it. The input differential pair is a known culprit, especially if the transistors are of sufficient high gain. The noise will increase with every extra stage of amplification further downstream.
All of my Parasound stuff is very low noise, even with high efficiency drivers. You have to stick your ear right next to the HF driver to hear any noise.
The Roland 808 drum machine used a defective (noisy) transistor as a sound source.
All of my Parasound stuff is very low noise, even with high efficiency drivers. You have to stick your ear right next to the HF driver to hear any noise.
The Roland 808 drum machine used a defective (noisy) transistor as a sound source.
Attachments
Just a few suggestions:
I have absolutely zero noise/hum/hiss in my system... that follows all of the above. I can not tell if the system is on or off... even with my ear right next to the tweeter.
- try to always use a balanced signal chain
- a (very) low noise power supplies
- amplifiers with the least amount of gain stages
- if used with DACs... try to find ones that have galvanic isolation between the PC (source) and the USB module
- lowest possible source output impedance
I have absolutely zero noise/hum/hiss in my system... that follows all of the above. I can not tell if the system is on or off... even with my ear right next to the tweeter.