Stephen wrote:
Curious to know what value resistor you’re using on the 6L6’s cathode. I’ve built a series of 6V6 based Champs recently and have found that the 470Ω value is way too small. A 470Ω resistor results in a plate dissipation of about 18 watts to 19 watts when it should only be 12W to 14W depending on the tube used. I’ve found that using a 600Ω resistor instead works much better.
Hi Stephen,
Sorry it so long to respond. I'm learning and needed to do a little research. I've built the Tweed Royal and I just took voltage readings and wanted to run that by you. So I've built the amp based on the directions. I had a little extra noise so I followed Morgan's alternate grounding scheme (and adding additional shielding) otherwise it was built to spec. With the amp in Champ mode (SS) and both the tone and cut knobs off and volumes at 0, I see a plate voltage of 310VDC using JJ6V6-S tube(s). Based on Rob Robinette's calculator Cathode Bias (I'm pretty sure the Champ is cathode biased.) This amp is using 470 ohm 5 watt resistor.
85% Cool = 38.4 DC milliamps 95% Average =42.9 100 % Max Safe Dissipation =45.2
I'm seeing 42.3 milliamps which falls in the average range or close enough. This shows a plate dissipation of 14 watts.
Are you measuring the actual plate dissipation in your Champ builds or using a calculator? Let me know if I'm calculating things correctly. If I'm doing this wrong let me know what I need to do to get the correct info.
I just got a text that my Champ cabinet is on the way so I'll be building the Champlifier starting tonight. Once I get this up and running I can give you more of an apples to apples comparison. I plan on trying it with both the JJ6V6-S tubes and the JJ6L6GC tubes and I can let you know how things are measuring and sounding.
Thank you!