after 2-3 minutes of work the sound of high frequency starts whistling...... I don't know what to do? ? ? ? help who understands thanks Sergey Moskva
...the mistake can eat? ?
there is a bad lamp of D3A? ? . the lamp itself whistles? ? ?
or all lamps good? ?
...////////////////////////////////////////////////////////////////////////trans" lundahll 1660" alt S 4:4.5
...the mistake can eat? ?
there is a bad lamp of D3A? ? . the lamp itself whistles? ? ?
or all lamps good? ?
...////////////////////////////////////////////////////////////////////////trans" lundahll 1660" alt S 4:4.5
Attachments
Last edited:
Hi!
The D3A is a high transconductance tube it can easily oscillate. Do you have the grid stopper as close to the grid pin as possible?
Try grounding the grid of the 45 if it then still whistles it is caused by the output tube. If not it is in the driver. Then look further there.
Is it present in both channels?
Best regards
Thomas
The D3A is a high transconductance tube it can easily oscillate. Do you have the grid stopper as close to the grid pin as possible?
Try grounding the grid of the 45 if it then still whistles it is caused by the output tube. If not it is in the driver. Then look further there.
Is it present in both channels?
Best regards
Thomas
I can't see but I think that you haven't soldered your grid ressistors directly to the grid?
If not, than turn of your amp, empty caps, solder 7k ressistor directly to the socket pin as colose as possible. Same with the 680ohm ressistor on the 45 grid...
Test it then, if you can hear whistling again then:
Use a wooden or plastic stick. Pick every wire with it, when you hear diferent sound that is the problem. If you pick everything and it still whistles... God help you.
Sorry for my bad english...
If not, than turn of your amp, empty caps, solder 7k ressistor directly to the socket pin as colose as possible. Same with the 680ohm ressistor on the 45 grid...
Test it then, if you can hear whistling again then:
Use a wooden or plastic stick. Pick every wire with it, when you hear diferent sound that is the problem. If you pick everything and it still whistles... God help you.
Sorry for my bad english...
Hi!
It seems that the grid stop resistor is placed far way from the tube sockets between the terminal strips. There it is not doing anything to prevent oscillation. It needs to be right at the grid pin with almost no lead length
Thomas
It seems that the grid stop resistor is placed far way from the tube sockets between the terminal strips. There it is not doing anything to prevent oscillation. It needs to be right at the grid pin with almost no lead length
Thomas
Hi!
Our posts crossed. Not really needed to use 7k. A few hundred ohms should work. The 45 does not need a grid stopper.
Thomas
Our posts crossed. Not really needed to use 7k. A few hundred ohms should work. The 45 does not need a grid stopper.
Thomas
Hi, Vinylsavor
I'm just refering to his schematic... I don't want to interfear into his schematic...
And yes, transformers are not aligned at 90 degrees, it could bring you some unwanted feedback from output to input (not whistle source), or vice versa...
I'm just refering to his schematic... I don't want to interfear into his schematic...
And yes, transformers are not aligned at 90 degrees, it could bring you some unwanted feedback from output to input (not whistle source), or vice versa...
These C-Core transformers have extremely low stray magnetic field. There shouldn't be any problems with the alignment.
The problem is, as others have already mentioned, the wiring.
I will show you a picture of a wired tube socket:
(Source:The Great Cardmatic Tube Testers)
After looking at it, look at your amplifier again 🙂
Riken-ohms, Ruby/Elna/Panasonic caps, Lundahl trafos, Alps pots, Gold bling-bling stuff - doesn't help anything, when your wiring is bad.
The D3A is a very high gm tube and will oscillate very easily.
Thus:
-Keep the wiring as short as possible
-Keep anode and grid wires seperate and not parallel
-Solder the grid resistor directly to the socket
-When you want to be on the safe side, use ferrite beads
Apart from that, nice amplifier 😎
The problem is, as others have already mentioned, the wiring.
I will show you a picture of a wired tube socket:
(Source:The Great Cardmatic Tube Testers)
After looking at it, look at your amplifier again 🙂
Riken-ohms, Ruby/Elna/Panasonic caps, Lundahl trafos, Alps pots, Gold bling-bling stuff - doesn't help anything, when your wiring is bad.
The D3A is a very high gm tube and will oscillate very easily.
Thus:
-Keep the wiring as short as possible
-Keep anode and grid wires seperate and not parallel
-Solder the grid resistor directly to the socket
-When you want to be on the safe side, use ferrite beads
Apart from that, nice amplifier 😎
Last edited:
carbon resistor at the grid
I built a Tubelab SE last year. It uses 5842 and 45 tubes. I had to put a carbon film (Takman REX) right at the 5842 grid pin to prevent oscillation.
I built a Tubelab SE last year. It uses 5842 and 45 tubes. I had to put a carbon film (Takman REX) right at the 5842 grid pin to prevent oscillation.
- Status
- Not open for further replies.