But this will also lower my entire preamp voltages of course, unless I compensate some other dropping resistors downstream after V3. I am considering lowering it again to get it closer to the 330V. ![]() When my DSL was stock, I had 450V on the plate of of my V3 cathode follower! I knocked it down to this 370V by increasing a dropping resistor value in the power supply B+ rail. The 6DJ8-based cathode follower presents an output impedance of about 100 ohms. Solving its high output impedance is easy enough, as we can simply add a cathode follower. 10uF 40 Hz bass guitar frequency 398 Ohms. MC Phono PreampTube-Based After a month of thinking about tube-based moving-coil pre-preamps, I began to wonder if this trip was really necessary. 12AX7 cathode follower output impedance 625 Ohms. One chapter toward the back discusses a transformerless headphone amplifier built around a White cathode follower tube. 6N6P might work, but needs more plate current. You could also change the tube to one with lower mu (amplification factor). The load of the tone stack on the preceding common cathode stage will reduce the gain though, and its higher output. But tonal preference is an individual thing and some may prefer the amp without it. It’s a rather ponderous tome for a guy like me who barely passed Algebra but it’s loaded with lots of great design ideas. It includes a voltage divider after the plate of the first tube, before the grid of the cathode follower. The dc coupled cathode follower will affect the tone and may be seen to be part of the amps character. I know that the max on the difference for a 12AX7 is 180V. Anybody that needs several uF coupling cap from a 12AX7 cathode follower, is probably driving to low of an impedance at the next stage. The book is by Merlin Blencowe, known on the internet as The Valve Wizard ( ). My phase inverter plates are at about 262VDC.īut my cathode follower is 373VDC/224VDC. My power valves are running at 481VDC plate and 474VDC screens. I have seen my Service go as high 125VAC, so 122VAC is a blessing around here. That could also work, if the 12AU7 plate current is properly set (different cathode resistor) and its power dissipation is not too high. ![]() My house Service is giving me about 122VAC, and we have some appliances going at the moment. I lowered the B+ in my preamp last year, but now I am thinking I should have went a bit lower. Is anyone else having any problems with valve life in their DSL cathode follower slot V3? I am figuring these amps are hard on valves in this slot due to the high B+ voltages these amps have. ![]() I just swapped out another valve in my DSL100 V3 slot.
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