Tube Amp Archive

You're right, I got it backwards.

I had to triple check myself

Okay,

They ARE in series - for half the capacitance. So if the tube is fine with 50uF, then I'm thinking that Ronman is correct and the tube is bad...? It's a brand new JJ, which I know doesn't really mean anything (and could be part of the problem in some peoples book).

The filter might be the culprit... When I researched it, the datasheet I found said 40uF was typical operating value and didn't list a maximum. Now, upon digging a little harder, I see that it looks like 40uF is the max. My filter is a stacked pair of 100uF caps for 50uF (in case anyone's wondering,...

Hello, I have a scratch built bass amp based on the ampeg B15N circuit with some modifications - the major ones are: I only have one input channel, and I'm using a 5U4GB power tube instead of the 5AR4. My chassis was scavenged from a wurlitzer organ amp, and I'm using it's PT which was meant for a 5...

Booyah! Well, I don't know exactly what rework I did that made the difference, but the amp is now quiet and passes a signal all the way through. I got pretty frustrated and ended up taking apart and redoing several complete circuits. My question now has to do with fine tuning some of the voltages (m...

Well, I've made a little progress in that I got something to change... Some background: For grounding, I have two star grounds, one for the power supply filter caps and the output tubes, and one for the input stage and phase inverter tube, then they both tie to the chassis at one point. My output tr...

On my filament supply I used a 47 ohm resistor from each leg to ground, thinking that it was approximately the same as each leg of a 100 ohm pot - should I add more resistance? I'm convinced that it's a wiring/grounding issue. Today I lifted the input wire from the phase inverter and the waveform at...

Thanks for the reply's! I do need to look at lead dress, and I'll recheck my component values, but I think when I said hum, I used the wrong word. This is MASSIVE. It's buzzing so badly with the PI tube in the circuit that I can actually hear it in the components. I have a Sencore tube checker that ...

Hello! My first time posting here. I've built myself a bass amp based on the Ampeg B15N (Rev C. for whatever that's worth). I just built one input channel with one jack instead of the 2x2 inputs that the originals had, and for various reasons, I'm using a 5U4GB instead of a 5AR4 . I've built one oth...