Taming noise in Liverpool build

[bandade]

What kind of tricks/mods have yall been doing to decrease noise in the liverpool/express? I am refering to the hiss that you get by turning up the volume knob. I have a Lar Mar PPIMV along with the normal volume and both add a fair amount of hiss to the sound; a bit more than my Dumble build.

I am using shielded cable on the input and PPIMV which has helped slightly. I have also tried it on the NFB lead with no improvement and the pre-amp volume with no real change. My preamp tubes have shields, EL84's have wire retainers and I shielded my head cabinet with standard aluminum tape. The aluminum tape doesn't seam to make a difference; would an aluminum bottom plate be beneficial or be the same as the tape? I have also moved the amp all around my house to see if one place is better than another; it is pretty obvious where the AC runs throught he walls.

I have also tried many different tubes in all position with no change. The hiss isn't totally unacceptable but I would like to reduce it as much as possible.

Thanks

[steviea55]

There are some previous threads on this. Can you post some pic's of the layout? What tube do you have in the PI socket? What type of wire did you use? Sorry to answer with so many questions.

[bandade]

[quote="steviea55"]There are some previous threads on this. Can you post some pic's of the layout? What tube do you have in the PI socket? What type of wire did you use? Sorry to answer with so many questions.[/quote]

I have tried various 12ax7's in the PI: EH, JJ, Sovtek LPS, Sovetk WA....no collection of NOS tubes at this time unfortunately.


For wire I used 20 gage stranded PVC for everything except for heaters which are 18 gage. I used a couple pieces of 22 guage on the eq pots and RG174 on the input.

I will snap some gut shots when I get home from work.

[jaysg]

The normal setting is 500pF hi cap in and the pots around 1 to 1:30, if you used the nominal pots. Don't go any higher on the volume. Try lower gain 12a_7 tubes in V1 as a test. If the hiss does not decrease, then there's something truly wrong.

[Allynmey]

One watt carbon films instead of 1/2 watt does lower noise a little.

[dave g]

I put the socket for V1 right next to the input jack. Helps immensely.

[jjman]

There should be essentially no hiss with the MV maxed and the volume at zero. And vise versa. Same for hum.

[bandade]

I'm starting to think that the hiss is mainly caused by the AC running through my walls. I have the amp in a room that is around 10' x 10' and it has probably 6 outlets. Depending on where I am playing the guitar, the hiss is louder and when the volume on the guitar is turned down, there is significantly less. I also tried the amp in a buddys basement and there was far less noise. It just seams that the amp is more sensitive to picking up ac through the guitar than others.

i dimed the volume and rolled off the master and there was no noise and then I dimed the master and rolled off the Volume and there was just a slight amount of noise.

I moved around wires and grounds and got no change so I really think this is the environment and not the amp; guess I just need a bigger room.

[bandade]

I forgot to add that I ended up using a Sovtek WA in V1. Suprising to me but it seems a bit quieter than the others and didn't deteriorate tone. Someday soon, i will try some NOS tubes.

[keewee]

I like the rca 7025 nos for v1 in gainy amps less hiss and nice tone too. fwiw

[solderstain]

I just took a good read through this for the first time, and am a little confused by what the OP is dealing with. Maybe he can clear up my confusion?

Initially the question is about hiss... and later you talk about interference your guitar picks up and the phenomenon reducing when the amp is plugged in at another house.

To me, the problem of noise reducing at another location is indicative of 'hum' or 'buzz'. 'Hiss' is something else entirely. And their causes and remedies are different.

I can relate on the 'noise on the AC line' problem - I deal with it every day in the older house I live in. I even went so far as to add IEC power connectors with built-in EMI filters to a couple of my own builds to help reduce that somewhat. Like the OP, I routinely take every single one of my personal builds over to a buddy's house who lives in a newer part of town and play the amps there (he never objects... ) just to satisfy myself that what I'm hearing at my place isn't a boo-boo in my build.

'Hiss', on the other hand, is stuff that's caused by components. Allyn made a good point about large carbon film resistors. I simply will NOT use carbon comps anywhere in the signal path, and to be honest, anywhere at all. NOISE NOISE NOISE... in the form of hiss.

Tubes can cause hiss just because of what they're doing - massively multiplying the amplitude of the original signal. In my recent Express build, I went through a BUNCHA tubes for the first gain stage of my Express (I located the second and third gain stages on V2), searching for the best signal-to-noise ration coming out of Stage 1. Tubes can make a TREMENDOUS difference in the amount of 'hiss'.

So, Mr. bandade, it sounds like changing tubes helped your problem? Or are you still dealing with interference from AC line stuff? Is it 60 hz (or 120 Hz) noise that you're hearing?

[Gaz]

There should be essentially no hiss with the MV maxed and the volume at zero. And vise versa. Same for hum.

I've never heard that one before. There will always be some hiss unless you've got some secret technique you're hiding!

[Tone Lover]

Ive found that elevating your heaters is helpfull in finding quiet new production tubes . But as one of the other gentlman said that rca 7025 that has been tested for noise is a good way to go.
One of the sellers on here tests the crap out of em cant think of his name at the moment, there a little expensive but you have to figure he probably trash cans a few so his costs are more. Bill

[bandade]

[quote="solderstain"]I just took a good read through this for the first time, and am a little confused by what the OP is dealing with. Maybe he can clear up my confusion? :lol:

Initially the question is about hiss... and later you talk about interference your guitar picks up and the phenomenon reducing when the amp is plugged in at another house.

To me, the problem of noise reducing at another location is indicative of 'hum' or 'buzz'. 'Hiss' is something else entirely. And their causes and remedies are different.

I can relate on the 'noise on the AC line' problem - I deal with it every day in the older house I live in. I even went so far as to add IEC power connectors with built-in EMI filters to a couple of my own builds to help reduce that somewhat. Like the OP, I routinely take every single one of my personal builds over to a buddy's house who lives in a newer part of town and play the amps there (he never objects... :lol: ) just to satisfy myself that what I'm hearing at my place isn't a boo-boo in my build. :oops:

'Hiss', on the other hand, is stuff that's caused by components. Allyn made a good point about large carbon film resistors. I simply will NOT use carbon comps anywhere in the signal path, and to be honest, anywhere at all. NOISE NOISE NOISE... in the form of hiss.

Tubes can cause hiss just because of what they're doing - massively multiplying the amplitude of the original signal. In my recent Express build, I went through a BUNCHA tubes for the first gain stage of my Express (I located the second and third gain stages on V2), searching for the best signal-to-noise ration coming out of Stage 1. Tubes can make a TREMENDOUS difference in the amount of 'hiss'.

So, Mr. bandade, it sounds like changing tubes helped your problem? Or are you still dealing with interference from AC line stuff? Is it 60 hz (or 120 Hz) noise that you're hearing?[/quote]


Thanks for the continued responses guys, What I ended up with was a hiss which was mostly caused by the AC running through my walls, Walking to different areas with the guitar plugged in yields different leveles of hum, at its best, the hum is inaudible. I have the amp in a 12' x 10' room so there is no complete escape of the AC in the walls. When I crank up the MV, there is a a linear progression of hiss as the knob is turned as I would expect but even at what I would consider stage volume, the hiss is acceptable. I will try a 7025 in the next next few weeks but for now, things are good. In a larger room there is no noticeable AC hum.

[Tone Lover]

Another thing to try shield the cavity in your guitar better with some of that copper tape worked wonders in my epiphone sg.
Bill