Advantages/Disadvantages using a choke in 5F2A circuit?

[funkgang49]

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

Just wanted to bump for answer to my last Q.

Thanks all!

[Firestorm]

That choke could be used to filter the screen supply and preamps. It is not sufficiently robust to filter the whole power supply (including output tube anode). EL34, for example, idles around 100mA.

[pdf64]

It's only rated at 40mA.
From my reading of your amp, the choke is intended to filter the whole B+, not just the screen and downstream.
What is the cathode voltage of the power tube, static and heavily overdriven?
That will tell you the B+ current.
Pete

[funkgang49]

Hey Pete,

With KT77 power tube:
Anode voltage is 382v
Cathode voltage is 27v
This is with 500 ohm @ 10watt Cathode resistor & 1.5K ohm @ 5watt Screen Grid resistor.

[pdf64]

So that's 54mA.
What happens to the cathode voltage when you crank the amp?
Pete

[funkgang49]

What happens to the cathode voltage when you crank the amp?

With no input signal (significant other is home) and both Volumes dimed there is no change in Cathode voltage, it stays constant at 27v.

[pdf64]

If you've not got a dummy load then will need to wait until you can overdrive it.

[funkgang49]

K. It'll have to wait til tomorrow then.

[Firestorm]

Single-ended (or any Class A) won't have all that much difference between idle and Max signal. I forgot your anode voltage was that high. That should help limit current if the cathode resistor is sized appropriately.

[pdf64]

My understanding is that the 'class of operation', eg A, AB, B, is only valid up to the point of clipping.
Even a 'clean' guitar tone tends to incorporate a degree of (power amp) clipping and guitar amps tend to be pushed into (and need to be designed to accommodate) heavy clipping.
Up there, even the screen grids can be passing 10s of mA.
And with a SE amp, the duty cycle of the wave, which may be affected by control settings, frequency and the load, may have an effect on the average current.
Pete

[funkgang49]

OK - significant other gone, amp cranked!
I'm getting readings from the baseline 27v to 40v with occasional spikes up to 45v.

[pdf64]

It looks like a 100mA choke may be needed then.
Perhaps a 156M http://www.hammondmfg.com/153.htm
Pete

[funkgang49]

Thanks Pete!

The 156M is 3H/100ma/86ohms and is rated at 400 max voltage.

Idle Power tube Anode voltage is no greater than 385v - would the 400v max. of the 156M be sufficient?

Also

What do the value of the other operating parameters; Henries & DC resistance have on the sound or performance of the amp?

[pdf64]

385V is within the voltage spec of 400V but I am using one (from that series) at 450V, no probs so far.
3H means that it will have an inductive reactance of ~2k3 at 120Hz, so that's a big improvement in filtering.
86ohms means that it will drop ~4V static, 8V cranked on the VB+, so a bit more sag.
Pete

[funkgang49]

So would that mean that as you increase the Henries value the greater the filtering?

As the ohms value increases the greater the voltage drop?