5:50 clean channel hissing.

There is a constant static noise or hissing from the clean channel of my 5:50 express head. I have to believe that this is more than "normal". I typically have the master fairly high and the gain low, in order to keep the tone clean. I already swapped out all the tubes and the hiss didn't get any better. Oddly, the crunch, blues, and burn channels have much less static noise than the clean. But, it's the clean channel that I want to use. Any suggestions or similar issues?

My 5:50 hisses a bit. It's not a problem playing live. I don't know if it would be a problem recording.
It's louder than my other amps (a '66 Vibrolux Reverb and a 5E3 clone) though I never really notice it unless I'm alone. No one in my band has ever noticed it either.

Believe it or not..... if you re-tube with all JJs your noise woes will go away. I had an F30 that was noisy as well (and the DCs are said to be noisy too with stock tubes). I re-tubed with a full set of JJs and BINGO. No more noise. The clean channel was quieter and cleaner, and the distortion channel was quieter, crunchier, and tighter. My DC-3 came with all JJs so I was set from the start. HIGHLY recommend the JJs for the DC, F, and Express series amps.

I already have JJs in there. Again, the hiss is ONLY in the clean channel. Even with no guitar attached to the input. When I switch to crunch, blues, or burn, it goes away. My only real question: Is this "common" with the Express amps or does mine need servicing?

hector said:

I already have JJs in there. Again, the hiss is ONLY in the clean channel. Even with no guitar attached to the input. When I switch to crunch, blues, or burn, it goes away. My only real question: Is this "common" with the Express amps or does mine need servicing?

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Ah - gotcha. Only in the clean channel... hmmm. I'm surprised the JJs didn't take care of the hiss to be honest. Maybe someone else will chime in that will be able to help. Good luck.

did you try diffent preamp tubes? It sounds like that could be it. Find out which preamp tube handles the clean channel.

Try turning your Master, mids, & bass way down and setting your volume mainly with the Gain & Treble controls.....then ease up the Master till you get what you want. On my 5:25, on the clean channel, the gain and treble act strangely like master volume controls. If I crank my Master on clean, HIISSSSS. I imagine the both amps have the same gain structure.

I've found on mine, that setting the general volume level with the Gain and EQ controls FIRST, greatly helps reduce the noise on all the channels. I've learned how to get mine pretty dang quiet. The controls are very robust....tiny changes make large differences in the tone and background noise levels.

Worth a try. Good luck. This amp gave me fits for a while till I learned how it behaved.

I'm not sure I buy the "retube and it'll be silent" thing. I'm sure better tubes could help, but I think the main "problem" is the strange gain relationship among the controls.

One man's thoughts.

I talked to Mesa tech support today. This issue has nothing to do with the tubes. Apparently, some hiss on the clean channel is inherent to the design of the amp. I'm used to maxing out the master with master vol. amps in order to get max clean headroom, but no so on this amp. Like the last responder said, it's best not to crank up the master. I found that if I keep it at 12 o'clock max and keep gain around 10 or 11 o'clock, I can get a good compromise of volume, clean headroom, and minimal hiss. I also like the contour (on clean), but keep it under 11 o'clock. The hiss is still there, and it's more than on my other amps (mostly Fenders), but I can deal with it now. I only really notice it when I'm not playing, and doubt it will be an issue when playing live. I do like the tone of the amp.

I put in a couple of Tung Sol preamp tubes and left the tube covers off on all the preamp tubes. This seems to have tamed a lot of the noise to the point where I rarely notice it now.

hector said:

I talked to Mesa tech support today. This issue has nothing to do with the tubes. Apparently, some hiss on the clean channel is inherent to the design of the amp. I'm used to maxing out the master with master vol. amps in order to get max clean headroom, but no so on this amp. Like the last responder said, it's best not to crank up the master. I found that if I keep it at 12 o'clock max and keep gain around 10 or 11 o'clock, I can get a good compromise of volume, clean headroom, and minimal hiss. I also like the contour (on clean), but keep it under 11 o'clock. The hiss is still there, and it's more than on my other amps (mostly Fenders), but I can deal with it now. I only really notice it when I'm not playing, and doubt it will be an issue when playing live. I do like the tone of the amp.

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Even so the hiss on the clean channel should not be anywhere near the burn channel. My 5:50 certainly is not. It's about 10% of it no matter how you dial it up. I'd take it to Mesa for repair.
Then if you want a totally silent rig get an MXR Smartgate or an ISP Decimator pedal. Both are excellent noise gates that don't effect tone. I also did a tube swap and that reduced the amp hiss by 60-70%.

I'm the proud new owner of an Express 5:50 1x12 and I, too, find the hiss on the clean channel to be more than normal and somewhat annoying. Compared to five other amps, there is way more hiss on the Express' clean channel. The clean channel has the most hiss of any of the "channels" (the three other modes). I would love to know what circuit tweak(s) would take care of this.

I'll try the setting recommendations above but will probably also trace out the circuit to better understand what is going on.

My buddy's Lonestar Special is the same way. The clean channel has much more hiss than the second channel. So much so that he sent it back to Mesa to have it checked out. It is there now. It will be interesting to see what Mesa has to say about his amp and how it may relate to the Express.

Thanks,
John

Good luck to all hissing mesa owners.
I went crazy with , I think 5 mesa 5:50 from Guitar Center, I drove them crazy too.
But what if you play a jazz duo, and its quiet, hissssss, damned.
I went with a lonestar instaed, but had similar problems. The final one doesnt have the ring or hiss,
but died in tone after 12 hours. I live close to petaluma, so I am lucky, got there , they put in a new preamp tube, and the combo worked for 4 month. Currently in repair , since the footswitch does its job , and than stops
working,than its ok again. Boy, I had to buy me a back up amp, F 30, nice and loud.
Back to the ringing sound, I saw some advises to check the tube holders, check all screws and so on.
good luck, and no, mesa boogie, its not OK that sometimes you hear a little ringring. That does not work in a studio situation when you mic the amp

Could one of you fine gentlemen who have been able to solve the hiss issue via control settings please disclose settings which work?

Thank you,
John

If you've got the Master HIGH and the Gain LOW on the clean channel, you're set up for huge hiss. Should be just the opposite. I never go over 9:00 on the Master for the clean channel. Gain way up. It's sorta counterintuitive. (Well, Clean, Blues, or Burn actually.....I can go noon to 1:00 oclock on Crunch with little noise if the Treble control isn't set high. But I really have no need for that.)

Set the volume first with the Gain & then EQ (especially Treble) before fine tuning with the Master, keeping the Master as low as possible. And...if you crank the Gain AND the EQ, you'll get hiss. As the Gain goes up, the EQ should generally come down. I've found the sweet spot for my Master is always at 10:00 or below, usually far below. And there, the background hiss is minimal, in fact, much less than a Marshall DSL50 that I've played against at the same levels. If you've got to have more volume that that, mike it, or get an amp that's meant to be played at earthshaking levels.

Another thing, the Gain/EQ relationships are very robust. Small changes in either direction make big differences in tone and background noise. You have to do a LOT of experimenting with the various relationships.

I also get less background hiss and more headroom running into external cabs.

Of course, my experience is with a 5:25, but I'm betting the gain structure is the same for both.

klangart said:

Good luck to all hissing mesa owners.
I went crazy with , I think 5 mesa 5:50 from Guitar Center, I drove them crazy too.
But what if you play a jazz duo, and its quiet, hissssss, damned.
I went with a lonestar instaed, but had similar problems. The final one doesnt have the ring or hiss,
but died in tone after 12 hours. I live close to petaluma, so I am lucky, got there , they put in a new preamp tube, and the combo worked for 4 month. Currently in repair , since the footswitch does its job , and than stops
working,than its ok again. Boy, I had to buy me a back up amp, F 30, nice and loud.
Back to the ringing sound, I saw some advises to check the tube holders, check all screws and so on.
good luck, and no, mesa boogie, its not OK that sometimes you hear a little ringring. That does not work in a studio situation when you mic the amp

Click to expand...

Geez Klangart - you've made a meal out of this IMHO.
You could have solved this amp hiss problem very quickly and been running totally silent by

1) making sure the amp was running as designed;
2) changing tubes to those recommended by www.dougstubes.com;

and if still needed

3) sticking either an MXR Smart Gate or ISP Decimater pedal in the loop.

that's what i've done and the amp is 100% silent.

I talked to Mesa today and was simply told the hiss is part of the design and it's not going away. He said they tried to reduce it but doing so degraded the tone.

I tried some known good, low noise tubes in it and it didn't help. Which exact tubes does Doug's recommend?

Thanks,
John

After tracing the circuit I identified the design "feature" which causes the noise to be so bad on the clean channel. They cut the guitar level by 60% before the first stage which means preamp noise is about 2.5 times more than it needs to be! Testing a very simple mod proved extremely successful and the noise was cut way down without "special" tubes or control settings.

"Tone?" you ask. To me it sounded every bit as good on the clean channel. Actually a little better but that could be because I can now hear details that the hiss was covering up. The mod brings the input stage of the clean channel in-line with most other amps, including those deemed to be clean tone monsters.

- John

What's the mod?

as others have indicated: try reducing the master volume a bit and turning up the input gain a bit. the input may be too low and as the post gain section tries to amplify it, inherent circuit noise is also amplified...

ty

ty,
The problem is that the signal reduction occurs before the first stage and the gain control is after the first stage and the tone stack. No matter what you do with the knobs, the noise level is at least about 2.5 times higher than "necessary" out of the first stage. A 60% reduction in input level means you must amplify by an additional 2.5 times to achieve the same output level. You can't get away from that.

Some knob settings may help reduce the impact of that fact, but don't change it. In theory, one wants to run the gain setting as high as possible to increase the signal level going to the next stages. For a given input signal level, the signal to noise ratio is the same from the first stage no matter where the gain knob is set. Therefore, you want to minimize the amplification needed from the next two stages so that their noise impact is minimized.

Don,
I want to experiment a bit before I spell it out but it's basically taking the 1.5M Ohm resistor between the input and the grid of V2A out of the circuit when the clean mode is active. If you look at the schematic of the Caliber 50, you'll see that they use a 1.5M and 1M resistor to form a voltage divider at the input. That same scheme is used on the Express.

- John