Yes where the gain is off balance L R. I may just do what you said with dual volumes and use the DAC volume for overall gain. For headphones uneven balance is very noticeable, no room reflections, not like two speakers coupled into a giant mixed pool of air, vs earcups coupled directly into your ear canal.
I am in desparite need of some help. I would be very appreciative of anyone who can help me solve a problem with hum.
First, some background. I built the following headphone amp and it works perfectly, no hum.
Nobsound 6N5P+6N11 Vacuum Tube Headphone Amplifier Board DIY KIT Single end Class A Amp|Amplifier| - AliExpress
Next I got more ambitious and built the following headphone amp:
A Single-Ended OTL Amplifier for Dynamic Headphones. – HeadWize Memorial
This headphone is almost identical to the first. The amp part I built is exactly as in the Headwize link. The power supply for the filament is identical to the one from aliexpress. The high voltage power supply is a custom based on a bridge rectifier, followed by 47uf cap, followed by 50 ohm voltage dropping resistor, followed by 330uf cap, followed by 50 ohm voltage dropping resistor followed by 47uf cap. I have separate transformers for both filament and high voltage. The negative of both transformers is connected to circuit ground. The high voltage supply is on a separate board. The filament supply is on the same board, but on the other side of the board. the filament transformer is about 2 inches from the 6AS7.
The problem is that the Headwize amp has a severe hum. The hum is the same no matter what the volume is set to. The hum starts about 30 seconds after power on. If i turn the power off, the music continues to play for a few seconds without any hum. Also, I tried using 4 D batteries for the filament supply and the hum went away.
I have tried everything I can think of to solve this problem with no success, so as I said in the beginning I would greatly appreciate any help I can get. I used high end parts in the Headwize amp, hoping to have a better sound than the aliexpress one.
First, some background. I built the following headphone amp and it works perfectly, no hum.
Nobsound 6N5P+6N11 Vacuum Tube Headphone Amplifier Board DIY KIT Single end Class A Amp|Amplifier| - AliExpress
Next I got more ambitious and built the following headphone amp:
A Single-Ended OTL Amplifier for Dynamic Headphones. – HeadWize Memorial
This headphone is almost identical to the first. The amp part I built is exactly as in the Headwize link. The power supply for the filament is identical to the one from aliexpress. The high voltage power supply is a custom based on a bridge rectifier, followed by 47uf cap, followed by 50 ohm voltage dropping resistor, followed by 330uf cap, followed by 50 ohm voltage dropping resistor followed by 47uf cap. I have separate transformers for both filament and high voltage. The negative of both transformers is connected to circuit ground. The high voltage supply is on a separate board. The filament supply is on the same board, but on the other side of the board. the filament transformer is about 2 inches from the 6AS7.
The problem is that the Headwize amp has a severe hum. The hum is the same no matter what the volume is set to. The hum starts about 30 seconds after power on. If i turn the power off, the music continues to play for a few seconds without any hum. Also, I tried using 4 D batteries for the filament supply and the hum went away.
I have tried everything I can think of to solve this problem with no success, so as I said in the beginning I would greatly appreciate any help I can get. I used high end parts in the Headwize amp, hoping to have a better sound than the aliexpress one.
Just a novice reading up to start my first amp project. Your DC filament supply is in theory not causing of hum.
Is your filament power ground directly connected to a common ground point?
"The negative of both transformers is connected to circuit ground." do you mean this:
"the primary connects to the two AC leads and the secondary to the bridge AC input, the negative of the bridge output is the circuit ground"
Is your filament power ground directly connected to a common ground point?
"The negative of both transformers is connected to circuit ground." do you mean this:
"the primary connects to the two AC leads and the secondary to the bridge AC input, the negative of the bridge output is the circuit ground"
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