In your quest for tone have you found that tone that you desire only to wind up with power supply hum coming out of the speaker?
Been there done that right? Trying to track down that particular tube or tubes that is contributing to the noise can take a few hours. If the tubes are cold it may not be apparent, but once they are at their optimum temp the noise seems to appear.
If you already have a collection of preamp tubes, perhaps you have some that are not all that great but are very quiet in terms of buzz or rectifier hum. I have quite a few of the old Mesa Chinese tubes. I was in the habit to replace all tubes at the same time. They still sound great but most of all, without a guitar signal, all channels are whisper quiet (within reason). I have used them to find the noisy tube. As part of a tube roll, if I get the hum, all preamp tubes will come out and the old Chinese tubes go it (with the exception of the PI tube unless the noise is still there with the known to be quite tubes are installed. Keep the tubes removed in the same order you had them in the amp. If all is quiet with the test tubes, replace each tube one at a time, power up and check each channel for the noise.
I have a few Tung Sol and EH tubes that were causing me grief. Noise was generated in the driver circuits of my Mark V which are also shared with the reverb send and return drivers. Sometimes you can id the noisy tube if it only occurs per a given channel. However, sometimes it is not so easy. Clean channels and or mild gain circuits will operate at a different voltage than the high gain channel. What sounds good and quiet on the clean channel may not perform well in the high gain mode on a given shared tube.
Case in point: Mark V. Voltage rails that supply some of the shared tubes operate at different voltages depending on which channel you are using. Ch1, operates V3 at 376V, CH2 operates the same tube at 378V and CH3 operates at 410V. Not all tubes have adjustable bias supplies but a few in the amp do. With this amp, V1 and V3 are common to all 3 channels.
Been there done that right? Trying to track down that particular tube or tubes that is contributing to the noise can take a few hours. If the tubes are cold it may not be apparent, but once they are at their optimum temp the noise seems to appear.
If you already have a collection of preamp tubes, perhaps you have some that are not all that great but are very quiet in terms of buzz or rectifier hum. I have quite a few of the old Mesa Chinese tubes. I was in the habit to replace all tubes at the same time. They still sound great but most of all, without a guitar signal, all channels are whisper quiet (within reason). I have used them to find the noisy tube. As part of a tube roll, if I get the hum, all preamp tubes will come out and the old Chinese tubes go it (with the exception of the PI tube unless the noise is still there with the known to be quite tubes are installed. Keep the tubes removed in the same order you had them in the amp. If all is quiet with the test tubes, replace each tube one at a time, power up and check each channel for the noise.
I have a few Tung Sol and EH tubes that were causing me grief. Noise was generated in the driver circuits of my Mark V which are also shared with the reverb send and return drivers. Sometimes you can id the noisy tube if it only occurs per a given channel. However, sometimes it is not so easy. Clean channels and or mild gain circuits will operate at a different voltage than the high gain channel. What sounds good and quiet on the clean channel may not perform well in the high gain mode on a given shared tube.
Case in point: Mark V. Voltage rails that supply some of the shared tubes operate at different voltages depending on which channel you are using. Ch1, operates V3 at 376V, CH2 operates the same tube at 378V and CH3 operates at 410V. Not all tubes have adjustable bias supplies but a few in the amp do. With this amp, V1 and V3 are common to all 3 channels.
