#1
Hey UG,
So yesterday I bought an old tube amp,
It's an London City(made in the early 70's, some sort of marshall clone)
It's sound is really awesome, but it produces a (loud) hiss when not playing, this is a lot more quieter when connected to a grounded socket, but it's still good hear able.
The are new tubes in there but they haven't been tuned, can it be that this his is produced because of that? (It hasn't been producing this hiss before the retubing)

What are your thoughts of it?
Thanks, Farether
A hero of war, Yeah that's what I'll be

(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)
#2
are you using single coils? is it grounded properly? is the reverb tank doing?


what amp is it?
Quote by gregs1020
Brett has been saving for a splawn for 4 years
countries have been toppled in the time it's taking, revolutions won got a black pres

yawn


Quote by bubb_tubbs
When he finally gets one it'll probably be televised like the Berlin Wall coming down.
The end of an era
#3
It's with bot SC and humbuckers, it's also making that noise without a guitar attached, I don't know about the grounding, but I do know that it didn't make that hiss before they put new tubes in it.

EDIT: It's a London City DEA100 MK4 (100W)
and there are 4 mullard EL34 power tubes in it.
A hero of war, Yeah that's what I'll be

(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)
#4
try this, go to the back of the amp and get a pencil, with the eraser tap all the preamp tubes with the amp on of noise comes out then it's a preamp tube and you just need to put a new one in cause it went microphonic
Quote by gregs1020
Brett has been saving for a splawn for 4 years
countries have been toppled in the time it's taking, revolutions won got a black pres

yawn


Quote by bubb_tubbs
When he finally gets one it'll probably be televised like the Berlin Wall coming down.
The end of an era
#5
ok I'll try that, thanks for the help
A hero of war, Yeah that's what I'll be

(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)
#6
no problem
Quote by gregs1020
Brett has been saving for a splawn for 4 years
countries have been toppled in the time it's taking, revolutions won got a black pres

yawn


Quote by bubb_tubbs
When he finally gets one it'll probably be televised like the Berlin Wall coming down.
The end of an era
#7
also what I forgot to mention is that it only occurs when it put it from standby to on. as long as I have it on standby nothing happens.

EDIT: I also just discovered that when I put the middle and the treble to '0' the hiss is gone, could it be just some bad pots, since they're probably over 35 years old?
A hero of war, Yeah that's what I'll be

(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)
Last edited by Farether at Dec 11, 2008,
#8
yeah that doesn't mean anything stanby is like a mute switch
Quote by gregs1020
Brett has been saving for a splawn for 4 years
countries have been toppled in the time it's taking, revolutions won got a black pres

yawn


Quote by bubb_tubbs
When he finally gets one it'll probably be televised like the Berlin Wall coming down.
The end of an era
#9
you might have 60's cycle hum... if your outlet isn't grounded or even if the cord that you plug from the amp into the socket is ****ty...

You could always invest in a used ISP decimator for 100 bucks or so... my friend has one and they are amazing...
My gear:
PRS SE custom
~!~--Peavey XXX super 40 EFX --~!~
Peavey VK 112

===WGS Vet30
===JJ power tubes

---Pedals:
-ISP Decimator
-Digitech Bad Monkey
-Crybaby wah
-Korg Pitchblack
-Danelectro FnC EQ
#10
I checked the pre-amp tubes, there all fine. but when I turn the middle, treble and the presence(just a little bit) knob all the way down too '0' the hiss disappears, so I'm guessing it's somewhere in that circuit. I would like to take it to an tube amp tech, but I don't know where to find one where I live.
A hero of war, Yeah that's what I'll be

(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)..........(.)(.)
#11
Sorry to bring this up, but I get this on my amp a lot. It's a Sound City, and the hum and hiss is very characteristic indeed of these amps. Mine is a 1973 all valve EL34 powered machine, made by Dallas Arbiter. One common mod to these amps is to replace the preamp circuit with a Hiwatt circuit (the two amps are very similar)

EDIT: Same happens with me with the treble and presence. Turn them down, just get old valve hum. Turn them up, you get a lot more hiss.
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Last edited by Calum_Barrow at Dec 24, 2008,