Hiss from preamp

Ronnie Myers · Post by **Ronnie Myers** » 26 Jul 2020 8:58 am

What can cause annoying hiss and noise from preamp

Fred Treece · Post by **Fred Treece** » 26 Jul 2020 9:39 am

It would help to know what make and model preamp, tube or solid state or hybrid, and if you checked without an instrument plugged in.

Best I can do is take a guess.

The noise could be from having a gain setting too high, or an otherwise unbalanced gain stage-to-power stage situation. It could be from bad or wrong type of cabling, cheap worn out parts on the circuit board or a loose solder joint. In short, itâ€™s a PITA that involves a process of elimination, unless you have a real pro in the room who can tell you in an instant that he knows what is causing that particular sound.

Donny Hinson · Post by **Donny Hinson** » 27 Jul 2020 2:13 pm

"Hiss" can be caused by a bad tube, or a bad IC. If the circuit has discrete solid state components, it can also be a bad (leaky) transistor. It can also be exacerbated by poor circuit design, so it's important to know if the hiss has been there all along, or it's something new. As far as "noise", that's a pretty vague term, so you'll have to be more specific as to what kind of noise it is you're hearing.

Brandon Mills · Post by **Brandon Mills** » 31 Jul 2020 11:43 pm

Usually itâ€™s caused by dirty power

Bob Hoffnar · Post by **Bob Hoffnar** » 1 Aug 2020 7:11 am

Hiss is present on some level even with the most high end tube pre amps you can buy. Iâ€™m not sure of the technical causes but it seems to be an essential part of all great sounding tube amps. Some have more and some have less. There seems to be a balance between hiss and sonic richness that is dialed in by the builder. Solid state and digital amps donâ€™t have the same issue but they sound like solid state and digital amps...

Donny Hinson · Post by **Donny Hinson** » 1 Aug 2020 9:20 am

Bob Hoffnar wrote:Hiss is present on some level even with the most high end tube pre amps you can buy. Iâ€™m not sure of the technical causes but it seems to be an essential part of all great sounding tube amps.

The hiss you usually hear in a tube amp is actually the sound of electrons hitting the plates of the tubes! It's exacerbated by high gains, high voltages, and emphasis on high frequencies. But, some of the better tube gear can be almost dead-quiet. The negative feedback circuit used in many amps helps to reduce hiss and gain. Take the feedback resistor out of a Twin Reverb, and you'll get hiss galore, along with treble like you've never heard.

Godfrey Arthur · Post by **Godfrey Arthur** » 2 Aug 2020 1:46 am

Is it a modern preamp or something decades old and the hiss always there and you just noticed it from using digital quiet devices?

I have a Korg A3 great sounding patches from back in the 80's but by today's standards, the hiss on the output is unbearable and can't be masked rendering it useless for modern recording and some live gig work.