Robben Modden
Moderators: pompeiisneaks, Colossal
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garysanders
- Posts: 30
- Joined: Wed Sep 16, 2009 3:39 am
Robben Modden
Some use a 500R 10W resistor in place of the choke.(Robben Ford,right?)What would a 350R 10W do?
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tubedogsmith
- Posts: 597
- Joined: Mon Jan 17, 2005 11:52 pm
Re: Robben Modden
IMO 350 ohms is better, I use 330 ohms.
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tubedogsmith
- Posts: 597
- Joined: Mon Jan 17, 2005 11:52 pm
Re: Robben Modden
IMO 350 ohms is better, I use 330 ohms.
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garysanders
- Posts: 30
- Joined: Wed Sep 16, 2009 3:39 am
Re: Robben Modden
Cool.Reason I ask is I happen to have one! 
Re: Robben Modden
Robben's amps currently have chokes.......
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Funkalicousgroove
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- Location: Denver, CO
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Re: Robben Modden
The Dumble amps that had no chokes used Peavey Transformers, and the Plates ran 465, Choke is 250R resistor, dropping string then goes 10K, 22K, 2.2K. The only reason these amps had no choke is because the "Donor amp" the trannies came from didn't have a choke.
Owner/Solder Jockey Bludotone Amp Works
Re: Robben Modden
What is the difference between using a choke and a resistor?
Does the resistor have more sag?
What value choke is used and would it be different for a 50 watt amp vs a 100w amp?
Does the resistor have more sag?
What value choke is used and would it be different for a 50 watt amp vs a 100w amp?
Tom
Don't let that smoke out!
Don't let that smoke out!
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Funkalicousgroove
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Re: Robben Modden
THere is a difference in feel, but it hardly warrants the time involved in doing the mod.
Owner/Solder Jockey Bludotone Amp Works
Re: Robben Modden
Taken from
1Richard Kuehnel, Circuit Analysis of a Legendary Tube Amplifier: The Fender Bassman 5F6-A, 2nd ed., (Seattle: Pentode Press, 2005) pp. 159-160.
RC filters are simple and inexpensive. When they need to supply lots of current, however, they create a large DC voltage drop across the resistor. For the same amount of ripple attenuation and the same size capacitor an LC filter creates much less DC voltage drop.
The RC filters in a guitar amplifier perform more than AC ripple filtering. They also decouple preamp stages to prevent feedback that can lead to motorboating. For adequate decoupling, the high-frequency cutoff for each RC filter should be much lower than the low-frequency cutoff for the preamps. If large coupling capacitors connect the preamp stages to provide generous bass response, then better power supply filters are required for the preamp plate supplies to prevent feedback.
A resistor-capacitor filter is simple and inexpensive. When it needs to supply lots of current, however, it creates a large DC voltage drop, requiring a higher input voltage to achieve the same output. In high-power guitar amplifiers the power tube screens, phase inverter, and preamps draw enough current at full power to make a choke-capacitor filter more economical (at least in the early days of the Fender Bassman and the Marshall JTM45).
An LC filter with the same amount of ripple attenuation and the same size capacitor creates much less DC voltage drop than an RC filter. The key difference is that the inductance of the choke reacts to AC signals but presents, ideally, a short circuit to DC. A real-world choke creates only a slight DC voltage drop due to internal winding resistance.
The default values are for the LC filter in a Fender Bassman 5F6-A, which delivers about 11 milliamps to the power tube screens, the phase inverter, and the preamps at idle, and about 27 milliamps at full power. My 10-henry choke measures 107 ohms with a volt-ohm meter, representing winding resistance of about 11 ohms per henry.
Taken from
1Richard Kuehnel, Circuit Analysis of a Legendary Tube Amplifier: The Fender Bassman 5F6-A, 2nd ed., (Seattle: Pentode Press, 2005) pp. 159-160.
Tony VVT
1Richard Kuehnel, Circuit Analysis of a Legendary Tube Amplifier: The Fender Bassman 5F6-A, 2nd ed., (Seattle: Pentode Press, 2005) pp. 159-160.
RC filters are simple and inexpensive. When they need to supply lots of current, however, they create a large DC voltage drop across the resistor. For the same amount of ripple attenuation and the same size capacitor an LC filter creates much less DC voltage drop.
The RC filters in a guitar amplifier perform more than AC ripple filtering. They also decouple preamp stages to prevent feedback that can lead to motorboating. For adequate decoupling, the high-frequency cutoff for each RC filter should be much lower than the low-frequency cutoff for the preamps. If large coupling capacitors connect the preamp stages to provide generous bass response, then better power supply filters are required for the preamp plate supplies to prevent feedback.
A resistor-capacitor filter is simple and inexpensive. When it needs to supply lots of current, however, it creates a large DC voltage drop, requiring a higher input voltage to achieve the same output. In high-power guitar amplifiers the power tube screens, phase inverter, and preamps draw enough current at full power to make a choke-capacitor filter more economical (at least in the early days of the Fender Bassman and the Marshall JTM45).
An LC filter with the same amount of ripple attenuation and the same size capacitor creates much less DC voltage drop than an RC filter. The key difference is that the inductance of the choke reacts to AC signals but presents, ideally, a short circuit to DC. A real-world choke creates only a slight DC voltage drop due to internal winding resistance.
The default values are for the LC filter in a Fender Bassman 5F6-A, which delivers about 11 milliamps to the power tube screens, the phase inverter, and the preamps at idle, and about 27 milliamps at full power. My 10-henry choke measures 107 ohms with a volt-ohm meter, representing winding resistance of about 11 ohms per henry.
Taken from
1Richard Kuehnel, Circuit Analysis of a Legendary Tube Amplifier: The Fender Bassman 5F6-A, 2nd ed., (Seattle: Pentode Press, 2005) pp. 159-160.
Tony VVT