The Amp Garage

I currently have it going to the OD relay NO2 per the board plans - but nothing connecting to that cap on the board. I think I’m going to try a jumper from OD relay NO2 to that cap.... Going to try the simplest way first and jump relay to board. That's it. The Eyelet board plan relay connections sa...

Just OD; and with everything maxed out and PAB on. Worst (or best) case for starting an oscillation. Try chopsticking and see if you can make anything change. How would I drive the power amp with 102? Preamp out from 102 plugged into power amp in on BM? Would I use regular cables or speaker cables?...

The OD section volume acts more like a master and the Drive like a pre-amp volume; but even cranked all the way up - still weak. If I dime the master, OD volume, and drive (and pre-amp volume) then switch on PAB - I get a high-pitched whistle (oscillation?). The strange preamp behavior could be an ...

No slight intended, I just thought it made an interesting plot.

Speedypancake wrote: ↑Sat May 18, 2024 9:39 am Can you help me turn it into a simple overdrive circuit to replace the Guyatone pedal??

Guyatone tube pedal? There are a couple of versions: https://juggbox.blog.jp/archives/15803877.html

When the voltage drop across the MOSFET is larger, the voltage on the tube plate is smaller. When the voltage on the tube plate is smaller, the tube draws less current. So when the drain-to-source voltage increases, the drain-to-source current decreases. Let's graph that: MOSFET Dissipation 1.JPG T...

Well, it looks great, anyway! Your lack of OD may be some wiring error in the relay switching, and it seems strange that you have to set the volume and master very high to get decent volume. DC voltages look good except for the FET, which needs a bias adjustment. BTW, the "top" and "bottom" of the F...

Seemed like I had a better balance between the channels too but that required maxing out the volume and keeping overdrive around 50%. Was a low dB test though and may not be reflective of normal playing levels. More fun later tonight after work.... I ran a simulation including source impedance for ...

Great! looking forward to seeing photos and maybe a sound clip.

Good to hear you figured it out. Note in the Bluesmaster layout the switches shown are slide types, but the lug connections are shown as they would be for toggle switches.

So I have a question. Using this board and this transformer The AC bias tap should be 60VAC, transformer puts out 45vac. Is this enough voltage or do I need to do something different to get 60 volts? Just have to reduce the 3k9 resistor to something smaller, maybe 470 ohms or so. Correction, 47 to ...

Dragon1 wrote: ↑Thu May 16, 2024 9:19 pm So I have a question. Using this board and this transformer The AC bias tap should be 60VAC, transformer puts out 45vac. Is this enough voltage or do I need to do something different to get 60 volts?

Just have to reduce the 3k9 resistor to something smaller, maybe 470 ohms or so.

Raoul Duke wrote: ↑Thu May 16, 2024 8:02 pm Not hearing any weird noise from the PI or OT, so I guess V3b plate wire is ok where it is for now?

Do you mean the OT primary connections/NFB?

It's the same as placing two same-value resistors in series to reduce voltage instead of one at the same total resistance. In the case of two resistors, half of the voltage is dropped in each one, current is the same, so half the power (V*I) is dissipated in each.

Thinking about this more and running some numbers here is what I've come up with. Voltage dividers are linear (though a pot may have a different taper) meaning if you think of the divider as attenuating a certain percentage of signal voltage, it does not matter if that input is 10V or 50V, the rati...