Dual rectifier tubes?

[dayn]

I have a PP 6AQ5 amp that runs dual rectifier tubes, both 6x4. I love it, and have always been curios why there are two rectifiers. In this amp it looks like each 6x4 rectifier is fed by a different side of the PT, then the outputs are bridged.



There is also a parallel single-ended 5F2a type amp called the Angela Super Single-Ended that I want to build, that uses two 5y3's along with two 6v6's in parallel. In this amp the 2nd 5y3 is wired to the same pins as the first.



Generally speaking, what is the purpose of having two rectifiers tubes - to lower the B+ voltage? Other benefits? Different ways to wire them together like above, and why?

Ultimately, I'm wondering if adding a second 5y3 to a vintage 5e3 type amp that already has an extra octal socket in the right place is a helpful way to lower the voltage that is now too high because of modern 123v at my outlet, in lieu of or in addition to other methods of lowering the B+ like zener diode, or resistors (currently uses an adjustable 10w 500r resistor).

[FUCHSAUDIO]

You are basically making the rectifier more efficient and handle more current. A single (larger) bottle would do the same thing basically.
I suppose you could pull one for more sag, but I would worry about drawing too much through the one tube might be asking too much.

[sluckey]

Dual rectifiers is not about lower B+ voltage. It's about being able to provide more current. The 6X4 in your first circuit can only handle 70mA, so it's a bit too lightweight to handle P/P 6AQ5s. Using parallel 6X4s doubles the current capacity.

Same principle for Angela's circuit. However, the 5Y3 can handle 125mA which is fine for many P/P 6V6 circuits. Maybe the SE parallel 6V6s need a bit more current, or maybe dual rectifier is just part of the "Super Cool" factor. The downside is finding a PT that can supply 5V @ 4A. IMO a 5AR4 would be a better choice but would lose a bit of the "Super Cool" factor.

[dayn]

You are basically making the rectifier more efficient and handle more current. A single (larger) bottle would do the same thing basically.
I suppose you could pull one for more sag, but I would worry about drawing too much through the one tube might be asking too much.

Dual rectifiers is not about lower B+ voltage. It's about being able to provide more current. The 6X4 in your first circuit can only handle 70mA, so it's a bit too lightweight to handle P/P 6AQ5s. Using parallel 6X4s doubles the current capacity.

Same principle for Angela's circuit. However, the 5Y3 can handle 125mA which is fine for many P/P 6V6 circuits. Maybe the SE parallel 6V6s need a bit more current, or maybe dual rectifier is just part of the "Super Cool" factor. The downside is finding a PT that can supply 5V @ 4A. IMO a 5AR4 would be a better choice but would lose a bit of the "Super Cool" factor.

I see, not about B+, just more current. Tell me more about the PT having enough amps for a second 5y3? Cool factor is important!

And I'm wondering about the different way of wiring implementation - the two examples above seem to be wired differently in relation to the PT and each other. Maybe it is electrically equivalent?

[sluckey]

Tell me more about the PT having enough amps for a second 5y3

Not much to say. One 5Y3 needs 5V@2A. Plenty of PT choices available. Two 5Y3s need 5V@4A. Fewer choices and they are likely to be BIG and HEAVY.

the two examples above seem to be wired differently in relation to the PT and each other. Maybe it is electrically equivalent?

Correct

[dayn]

Tell me more about the PT having enough amps for a second 5y3

Not much to say. One 5Y3 needs 5V@2A. Plenty of PT choices available. Two 5Y3s need 5V@4A. Fewer choices and they are likely to be BIG and HEAVY.

the two examples above seem to be wired differently in relation to the PT and each other. Maybe it is electrically equivalent?

Correct

Thanks, I appreciate the insight!

[FUCHSAUDIO]

The wiring difference is just that in one amp the two plates of ONE rectifier tube are in parallel. On the other drawing one plate from each tube is in parallel with the other tube.
Technically the "same circuit" just split differently between the two tube plates.

[R.G.]

It's worth noting that subbing in silicon diodes in series with a resistor to fake the voltage drop of the tubes would be able to provide even more current than the tubes, as well as lowering the loading on the power transformer by not using any 5Vac heater winding current at all.