Old Bitch Hiss

Jer

Jer

New member
My OB has just a few hours on it and it's hissing (sounds like someone saying "ssshhh").

Sound is present without any inputs, just plugged into cab. I've tried other heads with the cab so I know it's not the cab.

Hiss gets louder as volume is raised. Can I just take this back to George to look at or do I need to follow a particular process?
 
did it do this from the beginning? have you changed any settings? what toggle ( the left one ) you using? far right increases the gain stage and makes it super noisey. I have tried tubes and the such and nothing changed it. on stage it was pretty bad so i put a decimator pro g in the front and thru the loop and it is very quiet now. the loop seems to generate the most noise. i love the pro g
 
Wow you nailed it right out of the gate! :)

I feel stupid I didn't try the loop but I have a Metro 12k and the loop is very quiet so I didn't even think it could be a factor.

Thanks for the help Pbfoot!
 
Jer,

i learned the hardway. the amp showed up at noon friday and i used it onstage that night, i had to turn it down between songs it was so bad. i checked with a few people and since it is high gain with a high noisefloor it generates alot of whitenoise. mark day told me to use the decimator, my rig is now quiter onstage than the singers triple rec. the tubes do make a difference, the tad 9th gen are really noisey, i put some tung sol in and it really quited the amp down but i lost all of the gain and grind. that amp is really tube dependant
 
I'm sorry to hear you had to find out the hard way but I sure appreciate the all the good info. Good thing ISP is 30 min from here lol!
 
The amp should be easy to work on as George builds them. If you are handy try lowering the input grid stop resistor going to the first stage grid down to 15k. See if it oscillates with a 15k ohm resistor. If no, that should quiet it right down. Probably has a 68k now. My early Aldrich had no grid stop resistor and has zero hiss. A little bit of low hum but no hiss. Hiss covers hum so I added a 15k to mine. I would rather hear a tiny bit of hiss than hum as that sounds normal to me. Super quiet amp. Like ridiculously quiet for a high gain head. Hiss is not the sound of gain as some people may think.
 
If I get a new amp with that kind of hiss, I become the Old Bitch...... :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL:

There's really no reason for the amp to make noise with nothing plugged in with gain/volume at respectable gig levels and any clipping/bright switches turned off. Having to cover up the problem with a noise gate is a temporary fix.

Those TAD pre's are actually pretty good tubes. The first place I would be suspect is the input ground. Also, another common thing is the bias being set too hot relative to the quality/type of EL34 in the amp.
 
The amp has gobs of gain. With that much gain comes hiss. The amp has more gain then anything I can think of. Loop does not add hiss if you are using it right. Changing the input resistor only works if you plug straight in. The minute you put a pedal in front or buffer the hiss will come back.
 
RACKSYSTEMS":1ul5d0z5 said:
The amp has gobs of gain. With that much gain comes hiss. The amp has more gain then anything I can think of. Loop does not add hiss if you are using it right. Changing the input resistor only works if you plug straight in. The minute you put a pedal in front or buffer the hiss will come back.
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This is why I find the lowest noise floor pedals possible. Is the hiss you are referring to coming back from pedal noise Dave? I have a Caroline Icarus boost that adds just about zero hiss, not that one would need a boost with this amp. :LOL: :LOL: It is an option for him though, no? It does work very well at least in the amps I tried it in. The tone is better also with a lower value. Is the stock value 68k Dave? Am I correct or no? Swapping this resistor really should not void warranty as its so simple to do if one solders at all. An easy fix unless my findings do not work with this amp. I would think it's universal amp 101 for dummys as I am a big dummy compared to you Sir. :rock:
 
What I am saying is yes changing the resistor in the input does lower hiss but only if the guitar in plugged straight in. If you say have a boss pedal or any other pedal that is active (buffer etc.) it cancels the effect of the lower resistor. So not really the best idea. 68k is standard in the amp as per Mark Cameron. I stay with Marks design always unless something has to be delt with. Not looking to add my 2 cents to the Cameron products unless I have no choice.
 
RACKSYSTEMS":3tsu70zk said:
What I am saying is yes changing the resistor in the input does lower hiss but only if the guitar in plugged straight in. If you say have a boss pedal or any other pedal that is active (buffer etc.) it cancels the effect of the lower resistor. So not really the best idea. 68k is standard in the amp as per Mark Cameron. I stay with Marks design always unless something has to be delt with. Not looking to add my 2 cents to the Cameron products unless I have no choice.
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Thanks Dave. I would like to understand this. An amp has very low hiss with a 15k input grid resistor right up against the tube socket pin and I use a pedal with this configuration, I will add a certain amount of noise to my tube's grid from the pedal. Are you saying that the sum of the noise with a 15k input resistor and a pedal will not be much lower than the sum of a 68K and the same pedal? :confused: My findings were much different.
 
Using the loop right? Try having it active with nothing plugged in and the gain switch to the right, it howls and screams. In reality the amp has a ton of gain with the stock tubes, other tubes will make it much more silent but take all the flavor out of the amp. The amp has a lot of very cool flavor with the right tubes. You just have to control it. I use a 10 band mxr at 18 v thru the loop for a solo boost and a suhr iso out to axe fx for wet so I am not running a bunch of stuff thru the front or loop. ( no pedals in front). Btw the atomica I had was exactly the same
 
Dont feel bad,I had a $6000 two rock custom sig reverb that hissed like a stuck pig.I never could fix it, i called amp guru s called 2 rock no one could believe that (the best amp on the planet) could ever have something wrong.I got so frustrated i sent it back.No mo 2rock fo me. Maybe it would have helped for me to read some of the good advice on this thread.
 
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