Advantages/Disadvantages using a choke in 5F2A circuit?

[funkgang49]

What would be the Advantages/Disadvantages to using a Power Supply Choke in an 5F2A (Tweed Princeton) SE circuit?

[Firestorm]

5F2 has the choke; 5F2A omits it as a cost saving. Advantages: SE amps hum and the choke will help quiet that. Disadvantages: cost; and lower B+.

[njolly]

What would be the Advantages/Disadvantages to using a Power Supply Choke in an 5F2A (Tweed Princeton) SE circuit?

The only disadvantage is added cost. The choke is a big help to tame the hum as Firestorm mentioned. I added an additional filter stage (with choke) to mine and it's dead quiet.

[renshen1957]

What would be the Advantages/Disadvantages to using a Power Supply Choke in an 5F2A (Tweed Princeton) SE circuit?

The only disadvantage is added cost. The choke is a big help to tame the hum as Firestorm mentioned. I added an additional filter stage (with choke) to mine and it's dead quiet.

Hi,

Plus one on your comment. The E series tweed Champs had the Choke, but the F series did not, Fender never let Tone get in the way of Economy.

Best regards,

Steve

[funkgang49]

Thanks for the info.
Follow up Q: Will adding a choke, as well as reducing hum, also impart other changes to the overall tone of the circuit? to bass response? to overdrive/saturation characteristics?

[Structo]

I don't think so.

It will just smooth the ripple more.

May drop screen voltages just a bit but not much.

[Roe]

adding a choke usually gives a slightly smoother sound that is a little less ragged (and w/o ghosting). s

[dave g]

Another disadvantage: even after investing in a choke, it will still sound like a 5F2A

Why not build a 5E3 instead? Or better yet, an AC15 or half power Rocket?

[Firestorm]

Are thinking of putting choke up front (5F2) or between the plate and screen?

[tubeswell]

If its a 5F2A, then the choke can be one of these,

http://triodeelectronics.com/22707.html

and its doesn't cost that much really

Furthermore, it won't drop the B+ by more than about 2V, and it doesn't weigh much.

So there's no real disadvantage to using a choke in a 5F2A, and only advantages

[Firestorm]

Good info. But here is the dilemma: 5E1 and 5F2 run the screens hotter than the plate. Lower plate hum but the signal swing messes with the B+ downstream. This is why early Gibsons had a resistive voltage stabilizer. Put the choke between plate and screen and this doesn't happen, but the choke does nothing to quiet B+ hum in the output.

[tubeswell]

Using a CLC filter from the plate to screen node won't do anything for ripple hum reduction in a SE amp. You need to run a 'whole-of-supply' CLC filter using the choke. You can use a 1k-10k screen dropper in the power rail if you're concerned about screen current peaks. Or you could use a 470R Rg2 to eat up surplus screen current if the screen is within a few volts of the plate. It won't affect the tone in any noticeable way.

As for possible concerns about departing from the mojo of the original design, Fender's initial 5E1 and 5F1 designs weren't electrically perfect, nor were they intended to be - they were just low-cost, entry-level amps for beginners. The design-evolution of his SE line of amps into the 5F2A etc and later champ amps developed the concept of 'proper' operation 'more properly' once the mojo of the original had captured public imagination. That's my take on it anyhow. YMMV

[Leo_Gnardo]

Are thinking of putting choke up front (5F2) or between the plate and screen?

Good point. I've made a couple of recording SF Champs dead quiet by "pre-filtering" with a 22 uF and choke. No reason why not a tweed Princeton (which for most purposes is a Champ in a bigger box.)

[funkgang49]

Are thinking of putting choke up front (5F2) or between the plate and screen?

I would be using the choke to filter hum in the power supply. I am currently using 3-electrolytics: 30/22/10uf with 2K dropping resistor between the 30uf & 22uf then to Power tube Anode. The chassis I used for this build was what I had lying around and quite diminutive in size (lunchbox style) and limited me to just 3 electrolytics and no Choke.
This SE build is a foundation/test bed for working out: tonal/power tube substitution/clean headroom/overdrive characteristics. I have a larger chassis on hand that I am currently prepping for paint and then component layout and intend on running 4-electrolytics: 30/22/10/10uf but was also considering using a Choke as well.

adding a choke usually gives a slightly smoother sound that is a little less ragged (and w/o ghosting). s

The OD is a little "ragged" sounding and would definately benefit from some smoothing! Thanks everyone for the input.

[funkgang49]

If its a 5F2A, then the choke can be one of these,

http://triodeelectronics.com/22707.html

and its doesn't cost that much really

Furthermore, it won't drop the B+ by more than about 2V, and it doesn't weigh much.

So there's no real disadvantage to using a choke in a 5F2A, and only advantages

This build is not a true 5F2A. I used that circuit as a starting point.
The Preamp is more closely resembling a 5E3. It's a Single-input with 2 Volumes and a shared Tone control. V1 is a 6SL7. Volume 1 controls V1a, Volume 2 V1b. Both signals are then sent thru shared Tone control then on to V2b Driver Stage ala 5F2A (12AX7).
The Power stage differs from 5F2A as well. I am using a 5AR4/GZ34 Rectifier and anything from 5881/6L6 to EL34/KT77 type Power tubes.
The PT and OT are MM's and are appropriately spec'd to handle up to KT88.
Power tube Cathode Resistor is 500 ohm 10w and Screen Grid R is 1.5K ohm 5w. OT is 3K Primary impedance @ 8 ohm. OT has taps for 4/8/16 ohms and I've installed impedance selector switch.

Voltage at Power tube Anode with Svet 6L6 is 380V, JJ KT77 is similar at 385V.

Would the Choke listed in the link be appropriate for my circuit requirements?