Hi, since I have the same VTL amps and need to lower the power from 300W/chanel down to about 75W/chanel for second system, can I just pull out the power tubes and leave couple power tubes to match 75w/chanel? does it hurt to the amps or ruin any things? Thanks all.
VTL hum on both channels
I have a VTL 75/75 which I purchased recently. Both channels have a slight 60Hz hum. I tried the cheater plug, isolating the amp from the rest of my system, and using a RCA shorting plug to see if it was coming from somewhere else but it seems the amp is noisy.
I even connected a Sola power conditioner for a try.
I was able to download a schematic from the internet for a 50/50 which is similar to the 75/75 and got out my scope. I could see a 60Hz signal on the output at the speaker terminals. Checked all the power caps and had hardly any ripple. The only place where I saw the same looking signal was on the bias power supply. The DC voltage is around –50 volts with around 1 volt of ripple. Being new to tubes I do not know if this could be a cause of the problem. The capacitor in the circuit is 47uF at 100 VDC. I was thinking of increasing the value to see if the hum went away.
Any help would be appreciated.
I even connected a Sola power conditioner for a try.
I was able to download a schematic from the internet for a 50/50 which is similar to the 75/75 and got out my scope. I could see a 60Hz signal on the output at the speaker terminals. Checked all the power caps and had hardly any ripple. The only place where I saw the same looking signal was on the bias power supply. The DC voltage is around –50 volts with around 1 volt of ripple. Being new to tubes I do not know if this could be a cause of the problem. The capacitor in the circuit is 47uF at 100 VDC. I was thinking of increasing the value to see if the hum went away.
Any help would be appreciated.