Choke versus cement resistor: Why use one over the other?

[Decko]

Hi All,

Why would one use a choke over a large cement resistor? What are the design and tonal considerations?

Decko

[eniam rognab]

to better filter mains hum

resistors will limit current and drop voltage but not react with frequency changes

the choke is a series inductor which acts as a low pass filter presenting high impedence to unwanted frequencies. basically a RLC filter is better than a RC filter

design? resistors are small and cheap, chokes are large and costly

tonality i will let others chime in on

neal

[Leo_Gnardo]

Hi All,

Why would one use a choke over a large cement resistor? What are the design and tonal considerations?

Decko

Depending on value of the L or R, more current is generally available with the choke when it's asked for in large signal conditions. If the R is chosen to mimic the filtering quality of a choke (say 1000 ohms or more), more likely the amp will "compress". If the R is chosen to mimic the DC resistance of a choke (say 300 ohms or less), less compression but more hum to hear or else filter with larger filter caps.

Has less to do strictly with tone, rather the "feel" of the amp when playing loud, ie near, at, or beyond the clean power rating.

Good amps have been made with either. If you're on a tight budget the R is the choice.

[Blackburn]

For me, it works out to tube rectified amps usually getting a choke and SS rectified amps not. I tend not to use a choke with a tube rect if it's going to be a designated clean amp. Tube rects can sag pretty bad and with some higher gain circuits that can be undesirable. SS rects are just about perfect and can sag a little if you want them to.

[Decko]

Thanks for your responses...

How do you size your RLC or RC?

I am building a Naylor SD60 with re-purposed parts.

4 12AX7 tubes at the preamp and pi.

2 EL-34's on the power section

My power transformer gives me 330 VAC.

OT is a Heyboer HTS-5122 50 watt, 3400 ohm primary.

I havea Hammond 159P inductor, 10H at 125ma.

Will this work for my application?

Regards,
Decko

[Blackburn]

Thanks for your responses...

How do you size your RLC or RC?

I am building a Naylor SD60 with re-purposed parts.

4 12AX7 tubes at the preamp and pi.

2 EL-34's on the power section

My power transformer gives me 330 VAC.

OT is a Heyboer HTS-5122 50 watt, 3400 ohm primary.

I havea Hammond 159P inductor, 10H at 125ma.

Will this work for my application?

Regards,
Decko

I don't think you'll have any trouble with that choke in there.

[LeftyStrat]

tonality i will let others chime in on

Yeah, that's the tough part. I swear it makes a difference in some amps, but I don't have an understanding of why. It's also hard to AB, there are other things that change when switching between a resistor and a choke.

I do know I prefer Marshall circuits with a choke. Again, that 'feel' thing.

So yeah, what Neal said, weight and expense are certainly things to consider.

If you're a big manufacturer, resistors sound fantastic.

If you're building, it's worth the expense to experiment. A major advantage of building amps is you can build what you can't buy.

[Decko]

Thanks All,

I will experiment with both!

again, thanks for the input!

Regards,
Decko

[Cantplay]

The only time I've added a choke to power supply was SS rectified SET.

An idea I got after seeing that some MM upgrade trafo sets included an added choke.

I noticed a gain in resolution. Better string to string definition on clean chords, and even overdriven an ability to hear deeper.

John

[LeftyStrat]

The only time I've added a choke to power supply was SS rectified SET.

An idea I got after seeing that some MM upgrade trafo sets included an added choke.

I noticed a gain in resolution. Better string to string definition on clean chords, and even overdriven an ability to hear deeper.

John

Similar experience here. I find more complexity with a choke. Could it be that a resistor has a linear response, and a choke is frequency dependent and non linear?

A resistor is "flat" compared to the more lively choke.

[eniam rognab]

Thanks for your responses...

How do you size your RLC or RC?

C is dependent on the load

R meets voltage needs and couples different power stages

[Cantplay]

I tried to find a choke with the same DCR as the resistor it replaced.

John

[Leo_Gnardo]

If you're a big manufacturer, resistors sound fantastic.

Roger THAT! ka-CHING... (musicians - they'll never know)

That's the sound!

[Miket]

How does one determine the appropriate value of a choke for a given circuit?
I have come across a few and would like to use them in future builds, but not sure how to work out which to use.

[eniam rognab]

How does one determine the appropriate value of a choke for a given circuit?
I have come across a few and would like to use them in future builds, but not sure how to work out which to use.

hi mike

found this online

"Chokes have ratings of voltage, DC current ( measured in milliamps), resistance (measured in ohms) and inductance (measured in Henries). A typical choke for a 50 watt guitar amp is rated for about 500 volts and 50 milliamps. The resistance measures in the 250 ohm range and inductance between 10 – 20 Henries. The inductance of the choke coupled with the capacitance of the filter capacitors determine the bass response of the amplifier. A larger inductance value choke will have a better bass response than a smaller value choke"

hope that helps!