File Size: Kb Number of Views: After downloading, the file may take a moment to open in the browser. Fender – Bassman 5f6a -Schematic Thumbnail. The Bassman 5F6-A preamp contains two voltage amplifiers, one for the bright inputs and one for the Fender Bassman 5F6-A schematic of first two stages. 5F6A Amp Kit Item Code: 5f6a_c_kt We provide a layout and a schematic (on the Technical Details tab), but we do not include step by step assembly.

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High gain amps often use a hot or cool biased triode bypassed at. Click here for an explanation of complexity ratings.

You simply replace the master volume pot with a resistor on a switch. Unfortunately, this means you can’t get the full experience. The Fender 5F6A schematic shows v as the bias voltage for tubes which would yield a significantly cooler bias. Chart is from the Duncan Tone Stack Calculator. Many Fender tweed and blackface amps used a 25uF bypass cap on the first preamp stage. Amp fuses suggested by R. Increasing the V1A load resistor from k to k will increase the channel’s gain and make distortion in the V2A preamp more likely.

My 5E3P Proluxe fixed bias 6L6 power transformer is rated scyematic volts but actually puts out under idle load and an input wall voltage of Photo by Mark Herrick. Many of the mods on this page apply to the Bassman Reissue.

Fender Bassman 5F6-A Circuit Analysis

These two resistors will drop the heater voltage by 0. A higher resistor value will dim the LED. We would like for you to read the following information so you are aware of some of the issues involved with building an amp kit. From right to left, they implement a first-stage preamp, a second-stage voltage amplifier and DC-coupled cathode follower, a long-tailed-pair phase inverter, a fixed-bias push-pull power amp, and a high-voltage DC power supply.


We do not recommend anyone attempting to build any of our kits that are rated at 3 scjematic higher in complexity unless you have the assistance of a qualified amp builder or electronics technician. This circuit is designed for use only schematkc bridge rectifiers no power transformer center tap.

If you would like to cut even more highs than the pF cap, you can go all the way up to a. Fender also added a 4. This will make the sockets compatible with EL34 power tubes. Use a 1MA pot with a push-pull DPDT switch and wire one leg of the master volume through the switch so when the master volume knob is down the circuit is completely disconnected.

Prowess Amplifiers – Fender – Schematics – Bassman 5f6a – Schematic

This, along with a headphone jack, is a common mod request. Standard 5F6A or 5E5 Pro style round tubey warmth and compression. These are some minor upgrade’s or tweaks I suggest for a 5F6A build. The grid leak resistors have been clipped or removed.

I find myself using this switch to instantly find a known, 5f6aa tone. When I need more headroom I’ll flip the feedback switch to the JTM45 position but this pairs well with the preamp gain boost switch which adds more preamp gain. AC from the power transformer: If you still want to build one of our kits, but are a little uncertain, please enlist the aid of a qualified tech.

Turn on the Power Switch then wait around 15 seconds for the tube heaters to come up to temp and for the pop resistor to charge the filter caps enough to prevent a current inrush which is what causes the pop.

This simple mod will give you the choice of normal tube rectification with it’s inherent voltage sag or give you solid state rectification with its higher, stiffer voltage.


List of Mods

Many modern amps use a tiny. No power tube cathode resistor bypass capacitor was installed.

Remove the two wires that run from the top of the grid leak resistors to the power tube grids or stopper resistors. Your amp 5fa also run hotter and consume more electricity. The lead channel voice mod gives 5v6a and B their own cathode resistor so the lead scbematic can be biased cooler with a 2.

If you are going to push the amp hard with EL34’s on a regular basis I recommend upgrading the screen resistors to ohms and 5 watts. Socket mounted V2A Load Resistor. The extra feedback makes the cleans cleaner and tightens up the boundary between clean and overdrive which can make it easier to control overdrive with finger technique. This “Lead” Channel mod will blow away your Marshall buddies.

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Here is a photo of the inside of an original 5F6-A chassis, courtesy of our friends at Technical University Berlin. The equation to determine the amount of resistance in ohms to drop a voltage is:. The uF micro Farad value of the coupling cap controls the preamp’s low end frequency cutoff. A KL dual-gang master volume pot is added at top left. It also supplies a near constant current flow shared between the two cathodes–as current increases through the upper cathode the current decreases through the lower and vice versa.

To make the 5F6A’s bias adjustable you simply replace the bias circuit’s 56k resistor connected to 15k resistor and ground with a minik linear pot or trim pot and 27k resistor. You simply connect both 6.

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