April 27, 2015 at 7:58 am #5081
Somewhere along the way of my 2Stroke build, I drifted over to the Maggie schematic, then back again to the Hunter design. As a result (I think), I am running a single 6V6 that seems very hot: 342v at the plate, 40ma of current through the cathode, and 13.6 watts dissipated. This seems like a recipe for short tube life. Given that I wired the power tube circuit according to Weber’s design rather than Dave Hunter’s, should I stay away from the single 6V6 configuration? In other words, does the Weber design, with its different grid circuits, rule out the use of the lower power 6V6?
The grids seemed to be wired differently in the two schematics, but since I have not mastered the theory or math, I can’t sort out exactly what the different grid configurations would actually mean for a power tube in there. The Two Stroke has a 1.5k control grid resistor that is no found in the Maggie. On the other hand, the Maggie has 1k 2W resistor on the screen grid that is not found in the Two Stroke. Any help would be appreciated. Schematics attached.
[attachment=130]twostrokeschematic.jpg[/attachment]April 29, 2015 at 9:25 pm #6074
What’s the plate voltage on the power tube?April 30, 2015 at 8:36 am #6075
I used the Compu Bias and got 342v on the plate. While that voltage doesn’t seem like the craziest number I have seen for a 6V6, I am wondering if the 13.6 watts of static dissipation with that 342v number are going to kill tubes faster than I can afford!April 30, 2015 at 8:57 am #6076
I got about 32 mA, so 40 is high, but not that high, how does it sound?May 2, 2015 at 8:30 am #6077
Thanks for the response. It does sound pretty good. Very responsive to attack, edgy if not crunchy right away. To be honest, it is so loud that I probably haven’t turned it past 8. That was one of the biggest surprises of the whole build–how loud it was, even at 3. Maybe I’m just used to dinky practice amps.
If 40 doesn’t sound crazy and 13.6 watts of static dissipation doesn’t sound like a tube-killer, then perhaps I’m fussing over nothing. Just wondered what people found in terms of tube life when pushing a 6V6 in this particular circuit.May 2, 2015 at 8:34 pm #6078
I have not used a 6V6 that much, after trying a number of different tubes, I pretty much stick with a good 6L6. The Two Stroke has surprising volume, I added a 1/2 power switch to mine so I could dime it and still have reasonable stage volume (using it as a monitor and mic-ing it into a house system).June 2, 2015 at 4:19 am #6079
Remember that both of these designs are based closely on a Fender Tweed Champ (5E1/5F1)circuit. Fender never put a Grid Stopper resistor on the power tube of the Tweed Champ but Dave Hunter added one (which is a good idea). You can find more info here: http://www.valvewizard.co.uk/gridstopper.html
The cathode bias values are the same on both amps and the power sections should preform that same. Which is to say, you get that same sweet, sing-y compression from both amps which is a hallmark of single-ended, cathode-biased circuits.September 25, 2015 at 1:37 pm #7870
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