Speaker hiss with Mark V:25

[SouthamptonPdls]

Had this amp about 2 weeks, and it's been awesome so far. It's my first foray into Mesa amps and I'm blown away by the versatility. The issue I'm having - and maybe it's not an issue - is a noticeable speaker hiss. It's not that bad, and it doesn't appear to increase in volume when increasing the master. In fact as I turn up the amp the hiss is less apparent as it's masked by the sound of the guitar. The sound doesn't go away even if the master is all the way off, guitar unplugged, etc.

The weird thing is that when I use the headphone output, there is no hiss whatsoever. I don't know if this is just a part of normal operation; I don't think this was happening before, but it's very possible I just started noticing it.

Does this sound normal, or should I try to do something about this? Does anyone else have a small hiss during operation?

Thanks!

 

[Monstercastle]

Welcome! All tube amps have a little hiss, so it's most likely normal.

 

[SouthamptonPdls]

Welcome! All tube amps have a little hiss, so it's most likely normal.

Thanks! I know hiss is normal, but with all my other tube amps this goes away when the matter is turned to zero. Is this normal based on the v:25 layout? It's much less noticeable in 10 w mode and not there at all through headphones.

 

[Monstercastle]

Can't say for sure without hearing it. It's possible you have a bad tube or something making your amp louder than others. My V25 has a little hiss but nothing I'm remotely concerned about, and it's far more quiet than any of my other amps have been. I swapped all my preamp tubes for the SPAX7's (both my V25 and by big V) and am very happy with the tone and silence of both amps.

 

[bandit2013]

The hiss is generated by the preamp and power tubes. I get the same thing with the Mark V and a few of my other Mesa amps depending on where the gain is set (no signal and volume at zero). At zero input signal, there will be some white noise passing through the amp as each tube is operating at a bias point (preamp tubes included). All of the tubes will be pulling current (AKA quiescent current) such that noise generated by transformers, rectifiers, resistors and capacitors will be heard through the speaker. Some preamp and or power tubes may have more or less noise at the same operating conditions. This is all common and if it gets louder or worse in character (popping noises) it may be a preamp tube somewhere in the gain stages, also this would include the EL84 power tubes. In some cases it may be related to electron flow and noise generated by the heater element of the tube. If you switch the channel voice switch or switch to other channel, the noise will change in tone and volume based on the preamp characteristic between the two channels. Also note that solid state amps also exhibit a level of white noise or hiss unless it has a noise gate before the power amp section. In other words, all amps are prone to have the noise.

 

[SouthamptonPdls]

Thanks, this is really helpful! I had a good play this morning at a decent volume and the noise was not an issue. Thanks for both your replies.