Tube Amp Archive

Thanks Helmholtz. Does anyone have recommendations for power resistors for a dummy load? Parts Express sells wirewound braking resistors as 'non inductive' load resistors. I believe that the Weber Tru-Load uses this style of resistor. The aluminum enclosure, i suspect, has the benefit of acting as a...

Thanks for that suggestion Helmholtz.

I will be working on my AC30 (35Watts max power, I believe). I might eventually begin working on amps up to 100watts.

Would you be able to provide a rough diagram of what you are suggesting, please?

Thank you both.

Would my 3" 8ohm .5 watt speaker prefer line level? Should I use a different value for R2, or will that suffice? Thank you

Thank you Martin. Is the purpose of R2 to protect the scope in case of shorting?

A side question. I noticed in your Rev2 that J1 and J2 are connected to the same position on R1. Wouldn't J1 need to be connected to another point on the resistor, other than the 8 to achieve 4ohm? Also, what impact does R2 and RV1 have on the impedance presented to the load inputs? Sorry for all th...

Thanks Martin. Looking at your schematic, would a 1/4watt resistor suffice for R2 and what wattage would you recommend for RV1? Also, can you explain the monitor select switch, please? Is that determining what impedance is expected to be connected to the line out (or speaker in my case). Or is it su...

I am planning to build a variable impedance (4,8,16R) dummy load with voltage and scope ports for testing amplifiers. I was wondering if anyone has any tips for safely integrating a small speaker for monitoring the audio. I'd. Also like to be able to add a pot to adjust the volume of this speaker an...