Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dwp on July 06, 2010, 10:50:21 pm
-
Hey what difference will I hear or see between a 3H Blackface Choke and a 10H Vox/Marshall choke? I gotta ask. the voltage drop on the 3 Henry is like 1, the 10 Henry is 3VDC, +/-. Talking a PP 6L6 build, standard first stage location, 410VDC at the start of the string. (5AR4 Rectifier)
I would like to know the plus/delta on using either.
All input is appreciated as always.
Thanks in advance, dwp
-
You might play with Duncan's PSU to see if there's a significant reduction in ripple with the higher inductance. http://www.duncanamps.com/software.html
While you probably know this already, the current rating of the choke is really important. The choke for a 100 watt Marshall has to be able to handle a lot of current relatively speaking.
Sorry I can't make any informed statements about tonal and/or sensitivity differences.
Cheers,
Chip
-
More and better filteration will get you a better bass response, reducing sag. Good for hard rock and metal machine gunning drop D.
-
More and better filteration will get you a better bass response, reducing sag. Good for hard rock and metal machine gunning drop D.
so more henrys equals more filtration? load isn't an issue between the two, one is a repro AC30 Choke, (10H) other is BF repro, (3H) running pair 6L6's....
-
so more henrys equals more filtration?
Yes, the choke in series is part of a low pass filter. It's a reactive component with a fixed term, it's DC resistance, and a variable one, it's reactance, which varies with frequency.
DC resistance is between a few ohms and up to 400 ohms or so for models commonly found in MI amps, a typical Fender 4H choke shows app. 100R DCR. Low DCR => small DC voltage drop.
Reactance varies with frequency: Xl = 2 * Pi * F * L => higher frequency, higher inductance => better filtering. At 120 Hz, a 4H choke will have a reactance of 2 * 3.14159 * 120 * 4 = 3.016 Kohms => high value, better filtering.
Impedance is the product of resistance and reactance: Z = SQR (DCR^2 + Xl^2), so a 4H 100R choke will show app. 3.02 Kohms at 120 Hz, 6.03 Kohms at 240 Hz, etc.
BTW, a capacitor is also a reactive component with Xl = 1 / (2 * Pi * F * C). Impedance decreases with higher capacitance and higher frequency. It acts the same when connected in parallel.
Another aspect is energy storage: current thru a choke creates a magnetic field, any change in current results in a voltage change across it. A choke regulates voltage, just as a capacitor, by acting as a reservoir. Mo' inductance or mo' capacitance => stiffer supply, less sag.