Express done...need help calming the hisss

[billyz]

Billyz, interesting that the wattage value is being quoted here. The reason i take note isnyou have suggested tomuse the dale RN series for plates and their wattage rating is 1/2 watt i think. I suppose that's a mil spec resistor though ao one could double or triple that though. Anyway, maybe i will go for the parallel first stage on the DBM and let ya know. I have some dale RN and PRP 1watt to use for this build.

The Dale rn65 has a lower noise rating to begin with. Even though it is rated .50w I am pretty sure compared to a commercial type it would rate higher. The Dale is a much higher quality resistor. The PRP's are good too, Go for 1W and parallel them, I think you are getting into the law of diminishing returns though. I originally used two because I did not have the 50K value. But now I do it for the lower noise too.

[amplifiednation]

Ok, I moved the gain stage and paralleled the first two triodes. I added the resistors. I tried to keep it as neat as possible and it worked out pretty well for me.

I almost lost the shielded cable on V2's grid, but decided to keep it to try to hear the difference with less variables. Plus, that is a long grid run all the way to the volume control.

Still have hiss.

There is that hiss even with the volume all the way off. Maybe thats just normal...I mean there isn't one spot on the volume control that isn't loud. I still need to try some more tubes too.

I did notice an increase in sensitivity, it is picking up everything in the room. It's like a huge condensor mic. I'm nervous the Express can hear my thoughts! The tone is out of control though. Even if my hiss isn't gone I feel good about the mod, I think it added some good tone to the amp. This amp is really riding on the edge, there is no doubt about that.

After I took these pictures i raised up the grid and plate wires on V2a to clear the heater wire better.

I was thinking about adding a grid stopper on V1 of 10 or 15k. Am I going to lose the feel?

[billyz]

Ok, I moved the gain stage and paralleled the first two triodes. I added the resistors. I tried to keep it as neat as possible and it worked out pretty well for me.

I almost lost the shielded cable on V2's grid, but decided to keep it to try to hear the difference with less variables. Plus, that is a long grid run all the way to the volume control.

Still have hiss.

There is that hiss even with the volume all the way off. Maybe thats just normal...I mean there isn't one spot on the volume control that isn't loud. I still need to try some more tubes too.

I did notice an increase in sensitivity, it is picking up everything in the room. It's like a huge condensor mic. I'm nervous the Express can hear my thoughts! The tone is out of control though. Even if my hiss isn't gone I feel good about the mod, I think it added some additional tone to the amp.

After I took these pictures i raised up the grid and plate wires on V2a to clear the heater wire better.

I was thinking about trid a grid stopper on V1 of 10 or 15k. Am I going to lose the feel?

I use a 10k grid stopper on V1 with no apparent downside. It did reduce RF pickup though. I used to hear some Cell phone noises before installing the 10k grid input resistor.

Every amp I have done this too has greatly reduced hiss though.
I think you must be getting the hiss from a later stage.

Well, at least you like the tone. BTW, I don't even use shielded input wire.

[selloutrr]

have you tried lifting your signal wires from touching your heater wires?

you may also have a lower noise floor if you did a tight wrap on the heater wires and elevated them as to not touch other signal cables.

generally speaking with the TW's being the exception the loose wrap is problematic to noise. I guess it comes down to how spot on you want to be.

Double triple check your grounding and tighten all bolts and screws.

Meter the OHM load from your grounds to chassis make sure nothing it above the average or over 0.01.

Did you test your electrolytics before you installed them? no leaks or out of spec parts?

shortest runs possible..

tubes...

[surfsup]

Is that all carbon film in there? If so that will create more hiss than MF. I've got a bit of hiss on my x10 after 8.5 on the vol and was planning to swap out the plates and thbe two 470ks for better MF than the xicon CFs i have now.

[amplifiednation]

Yeah I chopsticked a few wires but didn't have a lot of time. The amp seems much more touchy than before. Even plugging my guitar in made it squeal a little. I think there is a lot going on in there, a ton of amplification, and the pi tube started oscillating too, when I touched it, it stopped. Need some dampers

It really needs that plate mounted tight on the bottom and to go into a cabinet, probably one with shielding. I will check the grounds and really need to try more tubes.

Where else could the hiss be coming from? Just the sheer power of the amp? I will throw a stopper on the first grid. It is not unbearable I just want it to be quieter. Its so cool how sensitive the amp is

[davesi]

Taylor, o-rings helped me a little, but I'm still playing with my Express build. If you add the stopper on V1, you might try pointing it up a little off the pin and routing your sheilded wire above the board for more heater seperation. I had a lot of your symptons and went with a 15K V1 stopper. It didn't seem to lose much.

[amplifiednation]

Could it be problematic if I grounded my sheilded cable to the shunt rather than the sleeve of the input? I may have I can't remember

[amplifiednation]

Taylor, o-rings helped me a little, but I'm still playing with my Express build. If you add the stopper on V1, you might try pointing it up a little off the pin and routing your sheilded wire above the board for more heater seperation. I had a lot of your symptons and went with a 15K V1 stopper. It didn't seem to lose much.

Will try the grid stopper today

[billyz]

If you still hear the hiss with the volume control down it is after that. Check your presence control, is it way up? If the bright is engaged and the treble up along with the presence, that is going to be noisey.

I use all carbon comp , no shielded wire and mostly I cannot tell the amp is even on if nothing is plugged in. I am not saying it is dead silent but not extra hissy. Hope you figure it out. Pull V2 , is it still there ? pull the PI ? That should help you localize it.

I like a 12at7 for the pi, might help with the hiss.

[amplifiednation]

Amp with no guitar plugged in:

It hisses quietly with the volume all the way down.

The presence control is sounds scratchy when turned.

If I pull any of the preamp tubes (starting with the PI) the hiss stops completely, and there is no sound at all through the speakers.

Now I'm getting some pretty crazy buzz with the bright switch in it's middle position. That wasn't happening before. I wonder if I moved a wire or two when I rewired the amp this morning. No buzz in the other positions.

I threw a 12AT7 in the PI and the hiss is noticeably less, but still there.

No grid resistor yet. It's pretty crazy I can hear noise through the amp when adjusting any of the controls or touching any part of the chassis by the pre amp.

Should I try running the input grid over the board? Should the amp be this sensitive to outside noise?

[amplifiednation]

Is that all carbon film in there? If so that will create more hiss than MF. I've got a bit of hiss on my x10 after 8.5 on the vol and was planning to swap out the plates and thbe two 470ks for better MF than the xicon CFs i have now.

yeah it's all CF.

[billyz]

Amp with no guitar plugged in:

It hisses quietly with the volume all the way down.

The presence control is sounds scratchy when turned.

If I pull any of the preamp tubes (starting with the PI) the hiss stops completely, and there is no sound at all through the speakers.

Now I'm getting some pretty crazy buzz with the bright switch in it's middle position. That wasn't happening before. I wonder if I moved a wire or two when I rewired the amp this morning. No buzz in the other positions.

I threw a 12AT7 in the PI and the hiss is noticeably less, but still there.

No grid resistor yet. It's pretty crazy I can hear noise through the amp when adjusting any of the controls or touching any part of the chassis by the pre amp.

Should I try running the input grid over the board? Should the amp be this sensitive to outside noise?

Well, it might be subjective . I am 57 and do have some hearing loss as most of us do. But I think I hear pretty well still. There will be some hiss. I hope I did not mislead you into thinking there would be none. Sometimes we start to fixate on something, like a dripping faucet and it drives us crazy. Stand back 4-5 feet , play your guitar for 20 mins , when you stop does the hiss stand out ?
Start pulling tubes from the V1 first and when it stops it is before that stage, or that stage.

[martin manning]

Amp with no guitar plugged in:

It hisses quietly with the volume all the way down.

The presence control is sounds scratchy when turned.

If I pull any of the preamp tubes (starting with the PI) the hiss stops completely, and there is no sound at all through the speakers.

Now I'm getting some pretty crazy buzz with the bright switch in it's middle position. That wasn't happening before. I wonder if I moved a wire or two when I rewired the amp this morning. No buzz in the other positions.

I threw a 12AT7 in the PI and the hiss is noticeably less, but still there.

No grid resistor yet. It's pretty crazy I can hear noise through the amp when adjusting any of the controls or touching any part of the chassis by the pre amp.

Should I try running the input grid over the board? Should the amp be this sensitive to outside noise?

The hiss is comming from V1. Could be noisy plate resistor(s), but does it change with different tubes in that slot? Re the other noises, maybe check your preamp grounds?

[amplifiednation]

Amp with no guitar plugged in:

It hisses quietly with the volume all the way down.

The presence control is sounds scratchy when turned.

If I pull any of the preamp tubes (starting with the PI) the hiss stops completely, and there is no sound at all through the speakers.

Now I'm getting some pretty crazy buzz with the bright switch in it's middle position. That wasn't happening before. I wonder if I moved a wire or two when I rewired the amp this morning. No buzz in the other positions.

I threw a 12AT7 in the PI and the hiss is noticeably less, but still there.

No grid resistor yet. It's pretty crazy I can hear noise through the amp when adjusting any of the controls or touching any part of the chassis by the pre amp.

Should I try running the input grid over the board? Should the amp be this sensitive to outside noise?

The hiss is comming from V1. Could be noisy plate resistor(s), but does it change with different tubes in that slot? Re the other noises, maybe check your preamp grounds?

There are a lot of changes with different tubes. I had a couple that caused hum, some squeal, the Express is like a tube tester!! I have an old Bugle Boy that had the least noise from my limited selection.

I just chopsticked around in there. I couldn't find much that made any difference other than when I poke one of the power tube grids there is some serious buzz when it hit's the chassis. No problem anywhere else though.

The amp sounds really good, its definately stable. I did find a bad joint at the volume control. I am going to correct that now. I'm not sure what it will do though. Maybe get rid of all my hiss!