Hi everyone
I just built a small minimalistic ecc82/83 ecc99 combo, but it hums and hisses a lot! Tried a lot of things like elevating the heaters and tried to switch up the preamp heaters.
I have checked all the ground cables, but I still think there is something with the grounding that is of.. if I plug in certain pedals the hum almost goes away!
Anyone have any idea?
Cheers
Gustav
I just built a small minimalistic ecc82/83 ecc99 combo, but it hums and hisses a lot! Tried a lot of things like elevating the heaters and tried to switch up the preamp heaters.
I have checked all the ground cables, but I still think there is something with the grounding that is of.. if I plug in certain pedals the hum almost goes away!
Anyone have any idea?
Cheers
Gustav
Is the hum 100Hz or 50Hz? 50Hz is from shielding or radiation hum or "ground" hum. 100Hz hum comes from power supply ripple.
Your small amp is single ended. Push-pull amps have power supply ripple cancellation, but single ended amps do not. The B+ supply has to be totally clean to eliminate B+ ripple hum. Most small amaps like a Fender Champ draw the power tube B+ direct from th first reservoir filter cap. That will always hum.
Agree, please post a schemtic.
Your small amp is single ended. Push-pull amps have power supply ripple cancellation, but single ended amps do not. The B+ supply has to be totally clean to eliminate B+ ripple hum. Most small amaps like a Fender Champ draw the power tube B+ direct from th first reservoir filter cap. That will always hum.
Agree, please post a schemtic.
I will have to draw up a quick schematic then!
I built it with some parts I already had, one of which was a single ended output transformer! So I decided to make a ecc99 SRPP power stage in hope of some hum cancelling? Instead of parallel single end.
I was always expecting some hum! But what makes me think there is some grounding issue is that when I plug in certain pedal infront the noise level dies down to expectable levels!
Anyway I come back when I have listened to the hum a bit more and drawn up a schematic
I built it with some parts I already had, one of which was a single ended output transformer! So I decided to make a ecc99 SRPP power stage in hope of some hum cancelling? Instead of parallel single end.
I was always expecting some hum! But what makes me think there is some grounding issue is that when I plug in certain pedal infront the noise level dies down to expectable levels!
Anyway I come back when I have listened to the hum a bit more and drawn up a schematic
> when I plug in certain pedal infront the noise level dies down
That's why I say "clipleads". It sounds like a missing ground connection. You don't see it because you are too close. We can't see it because we are too far. Schematics are never accurate (the map is not the land). Random temporary connections of "grounds" may reveal the problem.
Which of your boxes have proper 3-pin wall-power plugs?
BTW a SRPP has nearly no "hum cancelling" against power supply hum. But your infront pedal says that may not be the problem anyway.
That's why I say "clipleads". It sounds like a missing ground connection. You don't see it because you are too close. We can't see it because we are too far. Schematics are never accurate (the map is not the land). Random temporary connections of "grounds" may reveal the problem.
Which of your boxes have proper 3-pin wall-power plugs?
BTW a SRPP has nearly no "hum cancelling" against power supply hum. But your infront pedal says that may not be the problem anyway.
I think you are rigtht! Don’t have clipleads, but Something similar to test.. I think I found a leading cause! The input jack from the guitar is giving lots of noise, its a cheap jack and not very good I’m afraid.
It is still better with some drive pedals infront! But now it is ok to play with the ecc82 as driver tubes! The ecc83 still makes too much noise with its higher gain!
I will get that schematic up! Just need to make one that is a bit easier to see!
It is still better with some drive pedals infront! But now it is ok to play with the ecc82 as driver tubes! The ecc83 still makes too much noise with its higher gain!
I will get that schematic up! Just need to make one that is a bit easier to see!
That, and..... is that really the low-low-level guitar signal laying right on the wall-voltage AC sockets?
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Point taken! The absence of a metal chassis was the biggest problem!
I used some aluminum foil-tape to make a kind of losely connected Faraday cage and connected it to ground!
Before that I already tried to move the B+ till after the first smoothing stage, losing some voltage for some smoothing! (My schematic is missing a 4.7k between the filter caps)
And the input wires is not that close to the daisy chained 220v outlet
Now it is playing very nicely! Thanks
I used some aluminum foil-tape to make a kind of losely connected Faraday cage and connected it to ground!
Before that I already tried to move the B+ till after the first smoothing stage, losing some voltage for some smoothing! (My schematic is missing a 4.7k between the filter caps)
And the input wires is not that close to the daisy chained 220v outlet
Now it is playing very nicely! Thanks
Hi, the hum will be created first by missing a metal chassis and case. Further the near of the power transformer and the mains cables to the amplifying circuit. Next, I recommend DC heating because heater to cathode assembly always provides little bit of hum. Early AC heater designs already had a de-hum potentiometer to balance hum out. Also the high tension filtering needs to be checked with a scope whether it works suffiecently. Maybe a second R-C filter may be necessary. Hiss may come from the first stage because there seems to be no volume/gain potentiometer in the circuit.
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