> I guess I'm trying to reinvent the wheel
No. You are putting skids on a wheel.
You have the voltage-waste of a resistor with the cost/weight of a choke.
In an ideal world, there's probably a better way to do it.
But this being a Real World, anything goes.
> a wirewound resistor IS a choke.,.. with resistance
A truly terrible "choke". 10W 1K is probably 10 MILLI-Henries, 1/1,000th of the inductance needed to put a big hit on power ripple.
For most audio purposes, you may pretend a wire-wound has "no inductance." (This assertion must be checked when using low-ohm like 8-ohm resistors as loads for amplifiers being tested above 20KHz.... but even then, the "error" is minor.)
> Any choke has a DC resistance
Yes, and in that ideal world you could special-order a choke with higher resistance than "necessary". Or you could DIY: take the winding off, count the turns and gauge, compute a smaller gauge to give the desired higher resistance, and use the same number of turns. Should be a dime cheaper: less copper. Heat would be higher and you should check that. Obviously in a practical world it is easier to take the "too good" standard choke as-is then add standard resistor to hit your goal.
> older amps (tweed Deluxe, etc) used a resistor, around 10k usually, INSTEAD of a choke. This lowered the B+ voltage and had a part in the tone of the amp.
AND that resistor (with the filter capacitor) cut ripple buzz.
Rectifier, first cap, that through OT to 6V6 plates, Say we have 300V DC with 10V ripple.
Screen voltage should be cleaner, and may be lower. 5K and 16uFd will reduce ripple frequency by about 60:1, to 1/6th of a Volt. Pretty good filtering! It will also, for reasonable screen and preamp current, drop about 50V, to 250V DC, at idle. At FULL ROAR the screens suck harder and it may drop 100V, to 200V.
This is fine for "polite amps" which overload gracefully. But Rock has a place for amps which overload brash, harsh. To get this we want high and non-saggy screen supply.
OK, switch to 500 ohms resistor. Sag is only 5V-10V, negligible, it will be loud and harsh. But filtering with 16uFd cap is only 6:1, 1.7V ripple on screens (and usually driver). That may buzz.
Raising the 16uFd cap to 160uFd would get the ripple back down. 160uFd 450V was an impossibly large size in the classic era, and still a large cost.
We want ~~500 ohms DC drop but ~~5K AC drop. A 7H choke will do that.
Putting together a 7H choke and a 5K resistor gives 5.5K DC impedance and 10K AC impedance (ignoring a phase-correction). Ripple reduction is slightly better than a resistor alone. Cost/weight is much higher.
A good choke also stores energy. But a choke with a large resistor, you can't get the stored energy out with musical speed. Like a town water-tower, with a windshield-washer hose outlet.
I'm just saying. I _do_ think you should try the experiment: you probably have the parts, and you have the ear.
If we were really curious, you'd wire a switch to bypass either choke or resistor, have a friend secretly switch it while you played, learn if you really can tell a difference in a blind test. I suspect, despite all my blather, that there is some difference with/without the choke, but you can't reliably say which is which. If so, then for large-production amps, you would just omit the choke (profit is hard to make). In boutique production with savvy buyers, the choke may be a sales-point, worth the cost even if the sonics are ambiguous. (I am sure you can tell when a 5K resistor is in there whenever you play LOUD. This could be a valuable voice-switch.)
Topic: choke or B+ resistor... are both possible? (Read 17830 times)