The Amp Garage

Replacing the bias resistor would prevent this high bias current? I believe the caps to be ok. 2-47uf 100 v in parallel. The tap directly off tranfo should be approx. 50 -60 VAC? My bias current is 80ma + and I have verified the tubes as well. It will not adjust to my desired setting. The amp has be...

I am re-working a Sound City 50+. It seems that the transformer is hard wired to the 105v input tap. I am ok with b+ at 482, but my bias current is way too high. Would it be easiest for me to tap the HV tap with a 220K resistor and re-work the bias circuit or is there an easier way to achieve my goal?

Progress pics. Just about ready to wire in board!

Received new output transformer. I would like to clarify color codes. 4 wires to include-- . black / green - red / blue. The input side of transformer is blue to the plate connection 1 & 6. Red is the other half of input that connects directly to A1. Then the secondary is black ground with green fee...

I have made a few changes to schem. How can I apply feedback to powerstage?

I am trying a simplicity on this project. Hope to get a decent sound with some distortion for a micro amp type layout. Small with a nice punch running thru a 6-8" speaker. Thanks for all the great feedback!

What formula did you use to obtain figure?

Re-drawn voltage doubler. This will cut my amperage in half, but still should have enough power only 2 tubes- 12AX7 and 12AT7. My secondary is 120VAC. With this configuration what will my plate voltage be?

Here is my proposed schematic for a small simple 1 watt design. My understanding of the voltage doubler is as shown. 120VAC X 2.8 = 336VDC. Is there an easier way to achieve the same results? Are the component choices ok?

Here is a transformer option, but need to use voltage doubler to obtain desired voltage. Hammond 262E6 18VA 120V secondary @ 87ma. 1.2A for heaters.

I am ok with the reverb transformer for the output, but I would like to use a smaller transformer other than the Hammond type. I believe I can get by with a 350V rail voltage after rectifier and 1.2 a for the heater. Maybe 15-20VA. I am working on a schematic now. Thanks for all the great info!

I want to build a 1 watt tube amp using a 12AU7 for a power tube and a 12AX7 for the preamp. Does anyone know of any transformers that would work for this application?
Thanks

Problem solved. My footswitch jack was providing ground to 25uf cap. Installed isolating washer to jack. The boost control now works great. The control boosts as it should now!

Here is a pic of my new 18W build using carbon comp resistors. The tone is incredible. I am using an EF86 preamp tube for my amp and I am trying to incorporate a foot switchable boost. I am using a shared cathode on my tube between pin 3 and pin 8. I have a 2.2K for my cathode resisitor and I added ...

I didnt add any compression or anything. Only watever you tube does automatically. The mic was directly out from the center of cone. I was using a mic pre on a vintage Vestax 4 track recorder. I think it sounds ok. I think I need to hit the studio for raw recordings anyway. Thanks