The amp is ready!!
Now it's my first 5 min. I listen to it!!!
BUT hummmmmmmm.
I use a bus bar from the input RCA to output tranny.Not FDB,yet.
And ground them at the chassis between them.I didn't use any cap or resistor.Will this solve the problem???
PSU and all caps are grounded separetaly and they go to chassis with the main ground and CT of filaments at another place.
What to do?
Now it's my first 5 min. I listen to it!!!
BUT hummmmmmmm.
I use a bus bar from the input RCA to output tranny.Not FDB,yet.
And ground them at the chassis between them.I didn't use any cap or resistor.Will this solve the problem???
PSU and all caps are grounded separetaly and they go to chassis with the main ground and CT of filaments at another place.
What to do?
resident said:The amp is ready!!
Now it's my first 5 min. I listen to it!!!
BUT hummmmmmmm.
I use a bus bar from the input RCA to output tranny.Not FDB,yet.
And ground them at the chassis between them.I didn't use any cap or resistor.Will this solve the problem???
PSU and all caps are grounded separetaly and they go to chassis with the main ground and CT of filaments at another place.
What to do?
What kind of hum is it? I mean, is it a clean, 'round' sounding 50Hz? In that case you probably pick it up as said above from the transformer or wiring.
Does it sound with a rattling, 'sharp' character? In that case, it probably is supply current resulting from incorrect grounding scheme.
Jan Didden
I LIKE THIS FORUM!
Thank you guys for your help.
@ 845
@janneman
@Dick
My inputs are at the front of the chassis (near the input tube) and the PSU at the back.
Do you believe it will be better to use a thick wire from the front of the chassis to back and ground it over there with the other grounds?
I saw that many use a cap or resistor to ground the circuit earth.
Maybe this will solve my problem.What do you say?
An other problem that I have is that my tubes are getting too blue.Is this normal with 6L6s at 430V and Ia 65mA?
Thank you guys for your help.
@ 845
I don't think it's over here the problem 'cause the power in relation with OPTs are at 90 degrees.The power tranny is vertical and the OPTs are horizontal.
@janneman
I'm not very experienced on hummm sounding.I think it's clean 50Hz.It's like "vvvvvvvvvvvv"!
@Dick
How to do this right now?
My inputs are at the front of the chassis (near the input tube) and the PSU at the back.
Do you believe it will be better to use a thick wire from the front of the chassis to back and ground it over there with the other grounds?
I saw that many use a cap or resistor to ground the circuit earth.
Maybe this will solve my problem.What do you say?
An other problem that I have is that my tubes are getting too blue.Is this normal with 6L6s at 430V and Ia 65mA?
6L6 is beam tetrode,blue glow in beam tetrode this usual phenomenon.
You can reed about blue glow here :
http://www.jacmusic.com/html/articles/blueglow/blueglow.htm
First of all, is it a hum or a buzzzz? Is it coming from any of the transformers? Does it increase or decrease with the position of the volume knob? Have you definitely got something plugged into the input...
I would run a star type earthing system. Use a single point on the chassis for earthing. Run one earth wire from the input jacks and volume control, one wire from the preamp tube cathodes resistors, one wire from the power tube cathodes resistors, one wire from all power supply earths, and one from the output transformer ground.
This kills earth hum in 99% of all my amps...
I would run a star type earthing system. Use a single point on the chassis for earthing. Run one earth wire from the input jacks and volume control, one wire from the preamp tube cathodes resistors, one wire from the power tube cathodes resistors, one wire from all power supply earths, and one from the output transformer ground.
This kills earth hum in 99% of all my amps...
Hi Shifty
It’s a hum (I think so).It’s the same sound that power transformer produces.
If I get close my ear to power transformer I here the same sound I have to my speakers.
Hope the fault is not by the positioning of transformers. They’re at 90 degrees as I said.
I also don’t use chokes.
With grounded inputs the hum is the same to both channels.
With open inputs, one channel hums louder.
If I connect a preamp to it and the volume of preamp it’s at zero I have more hum than I have with grounded inputs. And it’s audible at low levels but, the same at both channels. And it doesn't increase with different volume levels.
Things got better when I change the wire that connects the input tube with the phase splitter with a shield wire. So, I believe my problem is on wiring. I think I’ll try star earth. What do you say to try something like this in the attached foto.
Now I use a bus bar from the RCA inputs and follow the signal until the OPT. And I grounded them between the RCA at the chassis.
The supply starts from the first caps of the PSU and continues with a twisted wire until the last cap near the input tube. This ground is taken from the first cap of PSU and goes to chassis with the main earth and CT of filament windings.
Please help me guys ‘cause I love the sound of this 6L6GC UL amp. And I haven’t use feedback, yet. Also, not any matching of the signals at the outputs of the phase splitter. I haven’t tested different bias at the 6L6. Now I’m at 65mA and Va at 420V.
It’s a hum (I think so).It’s the same sound that power transformer produces.
If I get close my ear to power transformer I here the same sound I have to my speakers.
Hope the fault is not by the positioning of transformers. They’re at 90 degrees as I said.
I also don’t use chokes.
With grounded inputs the hum is the same to both channels.
With open inputs, one channel hums louder.
If I connect a preamp to it and the volume of preamp it’s at zero I have more hum than I have with grounded inputs. And it’s audible at low levels but, the same at both channels. And it doesn't increase with different volume levels.
Things got better when I change the wire that connects the input tube with the phase splitter with a shield wire. So, I believe my problem is on wiring. I think I’ll try star earth. What do you say to try something like this in the attached foto.
Now I use a bus bar from the RCA inputs and follow the signal until the OPT. And I grounded them between the RCA at the chassis.
The supply starts from the first caps of the PSU and continues with a twisted wire until the last cap near the input tube. This ground is taken from the first cap of PSU and goes to chassis with the main earth and CT of filament windings.
Please help me guys ‘cause I love the sound of this 6L6GC UL amp. And I haven’t use feedback, yet. Also, not any matching of the signals at the outputs of the phase splitter. I haven’t tested different bias at the 6L6. Now I’m at 65mA and Va at 420V.
Attachments
Hi,
I think u should look at residents picture but earth only at "ONE" point to ur chassis and the second thing is... ur main transformer is he screwed directly to the chassis because u can better use some rubber rings between the transformer and the chassis so they will absorbe the 50Hz from the main trafo so it wount be shaiking ur OTP no more and reduce the hummmm in ur speakers !
Greetz Lukasz
I think u should look at residents picture but earth only at "ONE" point to ur chassis and the second thing is... ur main transformer is he screwed directly to the chassis because u can better use some rubber rings between the transformer and the chassis so they will absorbe the 50Hz from the main trafo so it wount be shaiking ur OTP no more and reduce the hummmm in ur speakers !
Greetz Lukasz
ONLY ONE EARTH and u use two ! U have to remove the main earth from the chassis and connect it with the other earth !
Hi Resident,
You have already received some excellent advice from other members of this forum. Here is something else for you to consider:
Does your 6V filament winding on your mains transformer have a centre-tap to earth, (i.e. three wires, 3.15 - 0 - 3.15 Volts), or are there only two wires from the LT supply (i.e. 0 - 6.3V)? If there is a centre tap winding, ensure it is, in fact, earthed. If there are only two wires, then take two 100-ohm resistors and connect them in series across the 6.3v winding. Then earth the centre point of the two resistors to your single chassis earth.
Please note that this is only to be used for your amplifier tubes and NOT the tube rectifier filaments if you're using a tube rectifier.
-Eric
You have already received some excellent advice from other members of this forum. Here is something else for you to consider:
Does your 6V filament winding on your mains transformer have a centre-tap to earth, (i.e. three wires, 3.15 - 0 - 3.15 Volts), or are there only two wires from the LT supply (i.e. 0 - 6.3V)? If there is a centre tap winding, ensure it is, in fact, earthed. If there are only two wires, then take two 100-ohm resistors and connect them in series across the 6.3v winding. Then earth the centre point of the two resistors to your single chassis earth.
Please note that this is only to be used for your amplifier tubes and NOT the tube rectifier filaments if you're using a tube rectifier.
-Eric
Szyderca said:
SAFETY! Never, ever, remove the mains earth from the chassis! If you have a hum loop because of two earth connections, break the connection between the signal earth and the chassis, NEVER the mains earth. We don't want people missing from the forum because of an electrical accident.
Star earth is ready. I use only one chassis earth point with 100R resistor.
Things become too much better!!
BUT I still have a little.
With grounded inputs you must place your ear very close to speaker to hear it. With open inputs I have more and in one channel is louder. Why?
I’m sure, my hum becomes from power transformer. I’m placing my ear on it and I hear the same thing on my speakers. I put some rubber rings but it remains audible. Do you believe it’s my winders fault or all big EI-core transformers have this noise? ( It’s rated at 560W )
I don’t know if this is normal. So, please tell me, do you have this little hum, too? From listeners place everything is ok. But at late hours it’s audible.
For an experiment I pull out the input tube and phase splitter to see what I’ll hear and hum went dramatically out. You don’t hear anything. It’s sooo little that I love it. This means that my problem is on wiring?
Things become too much better!!
BUT I still have a little.
With grounded inputs you must place your ear very close to speaker to hear it. With open inputs I have more and in one channel is louder. Why?
I’m sure, my hum becomes from power transformer. I’m placing my ear on it and I hear the same thing on my speakers. I put some rubber rings but it remains audible. Do you believe it’s my winders fault or all big EI-core transformers have this noise? ( It’s rated at 560W )
I don’t know if this is normal. So, please tell me, do you have this little hum, too? From listeners place everything is ok. But at late hours it’s audible.
For an experiment I pull out the input tube and phase splitter to see what I’ll hear and hum went dramatically out. You don’t hear anything. It’s sooo little that I love it. This means that my problem is on wiring?
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