Should an Amp be dead quiet?

[playonit]

I ask this because I have never owned a commercially built amp so I have nothing to compare to. All the Amps I have built so far after working out the bugs all have a barely discernible sound coming from them with the guitar unplugged... The sound isn't bothersome and since I don't have a comparison I don't know if this is normal?

[sliberty]

I've never owned an amp that was dead quiet. Wish they were though

[xtian]

All amps exhibit noise. The best ones have just a little white noise or hiss, and you have to lean in to hear it.

Many amps (all of my SE builds, for example) have some level of 60 cycle hum. None of my commercial PP amps hum, but they all hiss a little.

Bad tubes, components and solder joints can contribute to amp noise. Avant garde guitar players probably contribute the most.

[David Root]

Grounding schemes can elevate noise if not done right.

I used to think only a galactic star ground system with a single chassis ground point near the input jack(s), with all jacks isolated from the chassis, was the grail answer, but since I started build D-style amps that has changed. Dumble's grounding system is every bit as quiet. Even the old Fender brass buss style can be quiet if properly done.

I believe SE designs improve in this respect with all-DC heaters.

[husky]

If the gain is off and Master at a reasonable loud level yes they should be dead quiet IMO.

I will say DC heaters are usually a requirement for this unless the amp is not high gain. Ground path is paramount. I don't personally care for star grounding unless there are multiple stars (had it cause problems) and I usually never use the chassis as a ground path unless I'm being lazy and it is a known entity. If I practice what I preach they are pretty dam quiet ignoring white noise from shitloads of gain

[selloutrr]

transformers have some noise regardless of grounding scheme. so no transformer based amplifier is ever 100% silent. You can get pretty close but noise floor is still a reality. as long as you have X amount of signal over the noise floor it's considered a success. that's why they made noise gates

[gingertube]

It is reasonably easy to get the power amp section dead quiet BUT it will be very HiFi'ish in sound as a result - tight power supply rails etc. That is OK for a Dumble Clone or similar where the desired sound is generated in the preamp but will not suit the guys who want power amp compression and sag (TrainWreckers etc.)
.
It is much more difficult to get a high gain preamp to be dead quiet. There is just too much gain which brings tube noise and resistor noise up to quite noticable levels. Having said that we can do a LOT better than most commercial amps. Keep the drive impedance to each preamp tube grid low. This can be achieved in a number of ways but the interstage attenuator will always help because the "drive impedance" is significantly reduced by the lower arm of the attenuator thus shunting "grid noise" to signal ground. Also a reason for opting for lower value gain, volume and tone stack pots. You may end up sacrificing a bit of gain this way but what you do have will produce much less noise.

Also (as he dons his flame proof vest) Carbon Composition resistors are to be avoided - particularly where you have any real current flow - anode loads in parrticular should NOT be Carbon Comp. Grid stoppers can be Carbon Comp with little noise contribution. Most grid stoppers that is - not output tube screen resistors (which are grid stops).

I found these things out early when building a dual channel design with 4 gain stages in the lead channel while changing the design to use 6SL7 octals in place of the 12AX7s.

As stated above correct grounding can help and here I am pretty much an orphan - I ALWAYS use a bussed 0V ground where the connection to the bus follows the schematic - that is Rg1 of the input stage is the first connection with the power supply cap 0V at the extreme other end of the bus, that keeps big return currents away from the sensitive input stages, I then us a single 0V to chassis connection at the same point as the input stage Rg1 connection.

One often overlooked noise source (hum) is the bias supply, it must be squeeky clean. On the tube HiFi Amps I build I always use a cathode follower (or MOSFET Source Follower) to drive (direct couple) the output tube grids and I use a current source load on them rather than a resistor. This puts a large AC impedance between the output tube grids and the negative supply thus isolating any noise on that negative supply. The bias is then applied to the follower grid (or gate). My current HiFi Amp uses push pull Ultralinear 6V6G with this scheme and has the "blackest" (lowest noise) background I've ever heard in any amp, HiFi or Guitar, Solid State or Tube.

Cheers,
Ian

[diagrammatiks]

They can be dead quiet with no input plugged in.

The only noise should be transformer hum.

Every since I've started building i've pretty much found most commercial amps, especially budget ones to be obscenely loud.

[Gaz]

It's always funny when I'm in my quiet workshop at night obsessing about getting every little tiny bit of hum/buzz of an amp, then...

I plug in a guitar will single coils

[Leviman]

Mine buzzes like mad, but when you crank it up the signal to noise ratio is fine. And I like to think that that's how it likes to be run

[Gaz]

I remember some discussion (I think it was here) where someone was suggesting that perhaps the noise in old production amps contributed favorably to their overall tone. No comment, but I do think about it from time to time when I hear a noisy old amp that sounds sweet!

[Reeltarded]

My rig hisses about half as loud as running a tub of water, and it starts squeeling when the guitar volume gets above.. say 4.

Wild horse. Giddy up.

[Structo]

My 100w Dumble ODS clone seems to be pretty quiet.
Especially when in clean mode.

I can have it at a pretty loud bedroom level where you would have to shout over it and when I am muting the strings, I don't hear anything other than just a tiny bit of power transformer mechanical hum.
That is with a humbucker guitar.

When the Overdrive is on, it is a bit noisier although I can turn my body to a certain angle and quiet it down.

And if I am playing where I would stand during a gig it would be pretty quiet.

So yes, the more gain the more noise.

When you stand close to the amplifier, it will be noisier.

When you have the guitar unplugged, that shorts the grid of the first stage to ground, in effect killing/ muting that tube.

A better test is to have your guitar plugged in.

Single coil pickups are going to be noisy no matter what unless they are noise cancelling.

I hear the Express amps have quite a bit of hiss depending on the tube in V1.

[Milkmansound]

I've built a few mojo kits with a distributed star ground and they are usually dead quiet.

The more creative I get on my own, the noisier the amp ends up

That said, I can never get the reverb circuit to be completely quiet - even on the mojo clones. But a '71 Twin just came through my shop and the reverb is dead quiet.

I think the answer is yes, but its not worth obsessing about. Even my noisiest amp, when in use, seems perfectly quiet in between the notes especially when a band is playing