Recent content by QuantumDot

I tested the two channels with different powertubes today and I didn't see any red plates during the 20 minutes of play time. If the amp was indeed biased too hot for these tubes, I would have probably seen red plates by then and not just blue/red glow Fortunately this wasn't the case. As far...

I received the "gray" tubes today, which draw a little bit less idle current than the blue tubes, and I noticed something strange. I powered on the 2:90 without any preamp signal just to see if the tubes are working and, during the warm-up phase in standby mode, the tubes looked normal to me...

I'm no amp tech either, but if the plate voltage stays the same, no matter the power tube you put in, you could most definitely calculate the definitive plate voltage. If you have the plate voltage, it's easy to get the idle plate current a tube must have to work correctly with a bias setting...

Has anybody here measured the plate voltages of their Mesa 2:90 with any Mesa 400 series tube with a specific color code?

Do you guys know what the standard Mesa bias setting is for the 2:90 poweramp? Is there such a thing or is every 2:90 set differently when it comes to the bias resistor? Since Mesa is using color codes ranging from Red (lowest idle plate current rating around 20mA) to White (highest idle plate...

As far as I know, Mesa uses color codes to match tubes. Any tubes with the same color code are interchangeable. My question is this: If your Mesa tube amp has a set of four 6L6GC color code white tubes in it, could you replace that set with any other color without changing the bias resistor...

I need replacement tubes for my Mesa 2:90 and the current power tubes are the Mesa Boogie STR 420 6L6GC with the color code GR BLU. I thought about buying the new Tube Amp Doctor 6L6GCM-STR REDBASE power tubes but TAD is having problems coming up with plate current values that match the STR...

Here's a new set of pictures that I received just now: https://imgur.com/a/qfq22A9 Still don't know what to think of the power tubes. From the side, they look prisitine, but the tube tops with the brown rings and dark spots really make me question the quality of these tubes.

I'm considering buying a Mesa 2:90 power amp, but I'm not sure if I'd need to pay for a matched set of 8 x 6L6GC power tubes... Here's an imgur album that shows the current state of these tubes: https://imgur.com/a/U5I8j8G As you can see, these tubes have strange brown rings or black spots on...