Tube Amp Archive

Hi all, I have a question on the chassis size of a 1973 Pro Reverb. More specifically, about the rear panel dimensions/holes. Someone drilled additional holes into my Pro Reverb's rear black aluminum panel (before I acquired it, actually!). I'm wondering if a BF/early SF Super Reverb rear black alum...

Hi all, Working on my AC15 clone, have a question on the 100-ohm screen resistors. Referencing the available schematics, I didn't see that these were anything other than 1/2 watt types. I used 1/2 watt here. Looking at some other builds online, I see that peeps are using 3 watt resistors here... I h...

The 47K and R31 form a voltage divider to reduce the signal fed through C19 to the next grid. I don't know why someone needed to reduce the signal. My AC-15 only has a 150K in that spot. Hi Steve, I noticed in the same amp that pin 6 of the EF86 has a 100k plate resistor instead of 220k. I asked ab...

So, this 47k in the JMI AC15 is a mistake and has no real benefit "benefit" is a subjective judgement. But this resistor does have a FUNCTION, which is to reduce the output amplitude of that stage. So, if you wanted to increase available gain on your amp, you could replace that 47K resistor with a ...

Hi all, Second question on this AC15 clone. For the EF86 wiring, I see they used a 100k plate resistor instead of 220k as per the schem. Does using the 100k plate resistor in the EF86 Vox AC15 circuit result in less gain? If so, did this builder chose to do this to combat the typical microphony of E...

The AC30 has such a split load arrangement there, so perhaps the builder got mixed up https://el34world.com/charts/Schematics/files/Vox/Vox_ac301960.pdf Ah, that has GOT to be it. They were building both AC30 clones as well as AC15 clones. So, this 47k in the JMI AC15 is a mistake and has no real b...

xtian wrote: ↑Sat Dec 26, 2020 3:32 am You're saying there's a 47K resistor in your amp that's not shown on the schematic? OK, as you say, one end is connected to V5 pin1...where is the other end connected?

Pin 1 to one end of the 47k, other end of the 47k to junction of C19 and R31.

Hi all,

I have access to an AC15 clone (JMI Amplification, 2007) that has a 47k plate resistor on pin 1 of V5. What's the purpose of this resistor? It's not on the original schematic.

Thanks,
Chris