Yeah, very happy with the sound. An high quality tube preamp but I don`t know what to do with the noise.... do you have an idea???
It is an high frequency noise who come and go !
It is an high frequency noise who come and go !
Since it is intermittent, it's probably not a design defect.
Some possibilities:
1. An intermittent connection or bad solder joint, very likely a ground.
2. External interference.
If you hear something from the pre-amp with volume off, then an oscillating power supply circuit or bad transformer could be the cause.
Does the noise coming from the speaker change with volume setting?
Swap inputs and then outputs from the pre-amp in which case does the noise move to the other channel?
Some possibilities:
1. An intermittent connection or bad solder joint, very likely a ground.
2. External interference.
If you hear something from the pre-amp with volume off, then an oscillating power supply circuit or bad transformer could be the cause.
Does the noise coming from the speaker change with volume setting?
Swap inputs and then outputs from the pre-amp in which case does the noise move to the other channel?
Yes, I hear something from the preamp with volume OFF.
Today, I look inside the preamp and I put the power On without amplifier or speakers, and I hear the same noise that is coming out the speakers but I cannot locate where it came from... There a way to find a noisy component inside electronic chassis???
Also, I took some mesure, the voltage coming out the bridge is 430Vdc, and I have 360V after the first regulator, maybe the secondary of my transformer is to high ?
Can i made other test?
An other thing, the ground from the wall of my appartment is bad, maybe missing. I have 60Vac between the neutral and the ground pin...is that my noise problem?
Thank
Today, I look inside the preamp and I put the power On without amplifier or speakers, and I hear the same noise that is coming out the speakers but I cannot locate where it came from... There a way to find a noisy component inside electronic chassis???
Also, I took some mesure, the voltage coming out the bridge is 430Vdc, and I have 360V after the first regulator, maybe the secondary of my transformer is to high ?
Can i made other test?
An other thing, the ground from the wall of my appartment is bad, maybe missing. I have 60Vac between the neutral and the ground pin...is that my noise problem?
Thank
Please clarify "I put the power On without amplifier or speakers".arold19 said:
Normally parts contributing to noise will require a lot of amplification, so a bad part in the power amp seems quite unlikely. Both channels? Short amplifier input to RCA jack ground one channels at a time.
60VAC neutral to ground is too high, try to find the cause of this. Leave voltmeter on HiFi power jack with receptacle empty. Go around unplugging things in the house, see if anything reduces this voltage.
I mean, The only thing I pluged was the 120V from the wall. The preamp was on my kitchen table... and the noise is still there.
The noise seam stronger in on channel but still present on the other one.
For the ground, yesterday, I check in the panel and all cable is well ground...I will check today the plug...
I think the problem is the transformer... but I'm not realy shure.... Do you know where I can get ¨potted¨ transformer for tube power supply? Hammond has but around 260$.
The noise seam stronger in on channel but still present on the other one.
For the ground, yesterday, I check in the panel and all cable is well ground...I will check today the plug...
I think the problem is the transformer... but I'm not realy shure.... Do you know where I can get ¨potted¨ transformer for tube power supply? Hammond has but around 260$.
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![372jxp_b[1].jpg](/community/data/attachments/115/115165-72db0ab8c62ed40c184f2f0e22446c69.jpg?hash=ctsKuMYu1A)
Transformers are perfectly capable of making a mechanical "hum" due to loose coils or laminations. I do not know of a way that a transformer can fail that produces an electrical signal in the speakers.
In most equipment there is a simple network that connects the incoming neutral power lead to chassis ground. The neutral lead is normally within a volt or two of ground or zero volts. In an earlier post you mentioned 60V on the neutral lead, if this is true, it is a likely candidate for your problem. In this case, an extension cord for the power amp and an alternate AC outlet could provide a quick test for power line problems
In general assume a simple answer for problems. Although this might turn out not to be true, often the simplest answer is the correct one. You seem pre-disposed to presume a complex, less likely answer for a given problem.
If your power amplifier is a vacuum tube type, a common failure connects filament AC voltage to the internal control elements in a tube causing a hum or buzzing sound..
Power down the amp, disconnect the amplifier inputs. Remove the output tubes, power back up and see if he noise is affected. If it is gone, re-install output tubes but remove driver tubes, repeat test. Work your way to the input stage one stage at a time to see if a bad tube is your problem. If removing the output tubes does not affect the noise, skip the rest of the tube testing.
In most equipment there is a simple network that connects the incoming neutral power lead to chassis ground. The neutral lead is normally within a volt or two of ground or zero volts. In an earlier post you mentioned 60V on the neutral lead, if this is true, it is a likely candidate for your problem. In this case, an extension cord for the power amp and an alternate AC outlet could provide a quick test for power line problems
In general assume a simple answer for problems. Although this might turn out not to be true, often the simplest answer is the correct one. You seem pre-disposed to presume a complex, less likely answer for a given problem.
If your power amplifier is a vacuum tube type, a common failure connects filament AC voltage to the internal control elements in a tube causing a hum or buzzing sound..
Power down the amp, disconnect the amplifier inputs. Remove the output tubes, power back up and see if he noise is affected. If it is gone, re-install output tubes but remove driver tubes, repeat test. Work your way to the input stage one stage at a time to see if a bad tube is your problem. If removing the output tubes does not affect the noise, skip the rest of the tube testing.
Hi hermanv,
You might get away doing this one channel at a time, but not in a mono bock without a variac to reduce the AC voltage to control the B+.
Hi arold19,
These are simple things you can do at little cost. The rubber bit should be a touch wider than the space it's going in.
-Chris
Bad advice! Never do this with tube power amps. Your B+ will be unloaded for the most part and possibly rise to above the ratings of your filter caps. You can almost guarantee that mechanical transformer noise will change with a changing load current. You are directly changing the flux in the core.
You might get away doing this one channel at a time, but not in a mono bock without a variac to reduce the AC voltage to control the B+.
Hi arold19,
I'd suspect a completely open ground there. Any small leakage ground currents would then travel through your equipment to find a path to ground. The ground may not be connected at your socket or the electrician may depend on the screws to the box (illegal here). You must have a ground wire that connects to your outlet. Of course, this can be very intermittent.
It's too soon to say that, probably not actually.
Try to put a bit of rubber between the transformer bottom and the chassis. Then install the transformer again. This will damp your chassis under the transformer. Also, make sure that there is bare metal contact between the transformer housing and your chassis to bleed any leakage away.
These are simple things you can do at little cost. The rubber bit should be a touch wider than the space it's going in.
-Chris
The ground wire in the plug box was only on the box, not in the plug... So I correct that, I have only a couple mV between the neutral and the ground now. But I still have noise sometime.
When I touch the transformer, it doesn't change anything! The sound is not a "bzzzz" but more like a "eeeeee" it is hard to explain.
I already listen that tube gear ore osciling, what that mean?
Maybe my next experience is to get the transformer out of the chassis to see where the sound is coming out!
Do you have any other idea?
When I touch the transformer, it doesn't change anything! The sound is not a "bzzzz" but more like a "eeeeee" it is hard to explain.
I already listen that tube gear ore osciling, what that mean?
Maybe my next experience is to get the transformer out of the chassis to see where the sound is coming out!
Do you have any other idea?
Hi arold19,
That's great! Now you are protected. You need to fix your other outlets I think. This is very much for you and your family's protection.
Can you take a picture of your preamp please? Top and bottom views.
-Chris
That's great! Now you are protected. You need to fix your other outlets I think. This is very much for you and your family's protection.
Electronic equipment can oscillate if it isn't laid out properly. Some tubes can be very noisy or sensitive to vibration. They need to be changed if they are like this. Lightly tap the top of each tube with your fingernail and let us know what you find. This is a time honored troubleshooting technique. Tap lightly.
Can you take a picture of your preamp please? Top and bottom views.
-Chris
Here is the inside.
The lower section is the power supply. The box on the bottom is a line filter. The 2 big capacitor on the bottom left is the output of the bridge, about 430Vdc. There a transistor near the front panel with a small heat sink, this one regulated the voltage to 363Vdc. After that, there a black cable who separate for each channel, and there 2 other regulator to drop the voltage to 330Vdc. This 2 heat sink are locate at the right of the picture. From there, there 2 pink cable are going to the tubes. There also the regulate power supply for the heater of the tube a little bit higher in the pic. So, the amplification section is on the top. There a relay for preheat near the attenuator.
As you can see, the component are reverse on the board....
I hope this gonna help me.
Don't forget, it is not a humm or ground noise!!!!
The lower section is the power supply. The box on the bottom is a line filter. The 2 big capacitor on the bottom left is the output of the bridge, about 430Vdc. There a transistor near the front panel with a small heat sink, this one regulated the voltage to 363Vdc. After that, there a black cable who separate for each channel, and there 2 other regulator to drop the voltage to 330Vdc. This 2 heat sink are locate at the right of the picture. From there, there 2 pink cable are going to the tubes. There also the regulate power supply for the heater of the tube a little bit higher in the pic. So, the amplification section is on the top. There a relay for preheat near the attenuator.
As you can see, the component are reverse on the board....
I hope this gonna help me.
Don't forget, it is not a humm or ground noise!!!!
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Chris:anatech said:
It is an incredibly poor design principle to design equipment where B+ exceeds capacitor ratings when the load is removed. It is quite possible for an ordinary (and common) tube failure to unload the power supply. Having the capacitors then explode has never happened to anyone I know. I have never heard of this happening. Many tube amps operate unloaded while the output tube filaments heat up. I think your warning is overstated.
Arnold said the noise came from the speakers, a noisy transformer is hardly likely to make a signal heard over the speakers.
I only check this forum occasionally, since you seem quicker to respond, I am quite happy to let you guide the trouble shooting process, good luck.
Hi hermanv,
Since you had given this advice, I found it necessary to point this out to you so that you could consider this effect. No doubt you do accept that the B+ will rise. If the design uses an LC filter, your voltage rise could easily be 1.414 times the loaded state. Anyway, please consider these possibilities in the future.
Therefore we know something isn't right. However, you were correct in assuming a ground problem. The safety ground was intermittently open at the outlet.
-Chris
Possibly, but this is extremely common practice with original classic equipment. Every older service technician knows that you can not run an amplifier without it's output tubes.
Since you had given this advice, I found it necessary to point this out to you so that you could consider this effect. No doubt you do accept that the B+ will rise. If the design uses an LC filter, your voltage rise could easily be 1.414 times the loaded state. Anyway, please consider these possibilities in the future.
If the power amp is off, this is only possible if the preamp power transformer is magnetically coupled to the output transformers on the amplifier chassis.
Therefore we know something isn't right. However, you were correct in assuming a ground problem. The safety ground was intermittently open at the outlet.
-Chris
Hi arold19,
From what I can see, you may be getting coupling between your circuit input and output. Lead dress is very important with high impedance circuits.
Where you have input wires that must cross an output wire, make sure they cross at a 90° angle. Put as much vertical space as you can between them. Keep all audio leads away from you heater supply wires or traces.
Remember that the outside plate on your signal capacitors work as antennas, radiating or receiving signals. You may need to put a metal shield around some of these capacitors. Try routing your signal wires first. All inputs together and outputs routed away from these. Remember, consider each capacitor as a big, flat wire. You may need to use shielded wire in there (for audio) as a last resort.
-Chris
From what I can see, you may be getting coupling between your circuit input and output. Lead dress is very important with high impedance circuits.
Where you have input wires that must cross an output wire, make sure they cross at a 90° angle. Put as much vertical space as you can between them. Keep all audio leads away from you heater supply wires or traces.
Remember that the outside plate on your signal capacitors work as antennas, radiating or receiving signals. You may need to put a metal shield around some of these capacitors. Try routing your signal wires first. All inputs together and outputs routed away from these. Remember, consider each capacitor as a big, flat wire. You may need to use shielded wire in there (for audio) as a last resort.
-Chris
I don't think I express myself very good, sorry for my english... but: "when my preamp is on the kitchen table, without any other audio equipment link on it, only the 120V power cable, the high frequency noise is present." The sound is coming out of the chassis. I don't think this can be cause by the input wire????
But if you think that the input wire can be the problem, I will work on it, but for myself, I understand that an interference at the input of an amplifier will affect the output...
But I have noise at the output because there an audible sound inside the metal box...
I begin to be discouraged, thank you for your help, I hope we gonna fixt the problem togetter...
But if you think that the input wire can be the problem, I will work on it, but for myself, I understand that an interference at the input of an amplifier will affect the output...
But I have noise at the output because there an audible sound inside the metal box...
I begin to be discouraged, thank you for your help, I hope we gonna fixt the problem togetter...
Hi arold19,
Capacitors can make audible sounds, normally higher in frequency as you are experiencing.
You can put a hollow paper tube to your ear and move it around your chassis. In this way you can find out where the noise is coming from. If you hear it from a capacitor, carefully press on it to see if the noise is less.
The cause would be oscillation, due to possible coupling between input and output (most likely). Using an oscilloscope would be another way to trace this noise down.
-Chris
Capacitors can make audible sounds, normally higher in frequency as you are experiencing.
You can put a hollow paper tube to your ear and move it around your chassis. In this way you can find out where the noise is coming from. If you hear it from a capacitor, carefully press on it to see if the noise is less.
The cause would be oscillation, due to possible coupling between input and output (most likely). Using an oscilloscope would be another way to trace this noise down.
-Chris
Anatech, I tried to hit the top of one tube with my nail and it work, the sound dissapear, and I tried a couple of time.... what that mean??
Thank
Thank
Hi arold19,
Watch you don't get any on the glass, or say goodbye to the numbers on the tube.
-Chris
Bad connections with the tube pins to the socket most likely. Time to clean your tube pins, then clean off the cleaner.
Watch you don't get any on the glass, or say goodbye to the numbers on the tube.
-Chris
Hi Shoog, Could you give me some details on your preamp? email me directly: raybronk@gmail.com Thanks. Does this also include the power supply?
Ray Bronk
Ray Bronk
Hi there,
My current preamp is a version of the FVP5 built using ECF80's. It uses one of the pentodes as the CCS on the bottom of the output totem, and the other pentode is up at the top, triode strapped, as the Constant Voltage element. The two triode are used as the front end voltage amplifier and the CF in the middle of the totem.
It is working well and has been for about 8mths now. Unfortunately I never wrote out a schematic and looking at some of the scibbled rough notes they don't quite make sense in terms of the components I actually ended up using. I would have to open up the beast and component trace whats in there which I haven't really got time to do at the moment.
Shoog
My current preamp is a version of the FVP5 built using ECF80's. It uses one of the pentodes as the CCS on the bottom of the output totem, and the other pentode is up at the top, triode strapped, as the Constant Voltage element. The two triode are used as the front end voltage amplifier and the CF in the middle of the totem.
It is working well and has been for about 8mths now. Unfortunately I never wrote out a schematic and looking at some of the scibbled rough notes they don't quite make sense in terms of the components I actually ended up using. I would have to open up the beast and component trace whats in there which I haven't really got time to do at the moment.
Shoog
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