... Would a choke be beneficial? If so, what value should I get. Still leaning on building it like Big Daddy's 6L6 Champ which shows a choke. ...
Why does the schematic show a choke at all?
Most guitar amps use a single filter cap after the rectifier, which is then also attached to the output tube plates via the output transformer. Then again, most guitar amps are push-pull, and push-pull operation cancels much of the hum at that 1st filter cap node.
You don't have that in single-ended, and what a lot of folks here have found is that when they use a speaker with full reproduction down to a guitar's low E (80 Hz), they also get full reproduction of B+ hum (120Hz). We've found the solution is adding an extra stage of filtering before the original 1st filter cap; either C to ground and series R, or C to ground and series choke. But the B+ current of the entire amp gets pulled through that series-R or -L, and if you make the R big enough to get the same filtering effect as a choke the B+ voltage drops significantly.
So you use a choke to maintain the B+ voltage while still providing good filtering; the caps are only half the equation.
How big? Start with the current rating first. You were contemplating 6L6 earlier, don't know if you decided to go that route. PRR was talking as much as 70-90mA for the output tube plate, another 5-10mA seems reasonable for the screen, couple-mA for the preamp. Your choke might be rated as low as 70mA up to 100mA depending on your envisioned output tube. A 6V6 @ 350v B+ might only need ~35mA plus 5-10 for screens plus preamp, so 50mA rating is plenty adequate.
The current rating will dictate the available choke Henry-ratings, size and cost. 3-4H is probably a reasonable lower limit, especially since your caps are likely to be bigger than 8uF. You can go bigger to the extent space and budget allows.
From what I see on the attached 5Y3 datasheet if you use a choke, that comes before a cap.
DPM's posted schematic doesn't do what the data sheet does. The schematic shows a cap-to-ground right after the rectifier, so this is a "cap-input" arrangement. The data sheet info for cap-input would apply.
Also the B+ seems higher? 500 vs 350 with a choke?
If that cap-to-ground at the rectifier and before the choke were not there, then this would be a choke-input filter. Different results occur when you rectify a.c. and apply it to a choke-input power supply. Assuming zero voltage drop across the rectifier, a cap-input supply attempts to rectify to V
RMS * 1.414, meaning the cap charges to the peak of the incoming rectified a.c. voltage. In a choke-input supply, that formula changes to V
RMS * 0.9. That's because the choke is attempting to reduce the voltage/current variation coming out of the rectifier before it even gets to the cap.
That why you see a higher starting a.c. supply voltage going into the rectifier on the choke-input example, to achieve roughly the same output d.c. voltage.
Topic: 5F2A Hybrid (Read 10705 times)