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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Amplifying low frequencies requires more energy than mid and highs so removing some bass from the guitar signal keeps the amp from wasting its power to amplify those unneeded low freqs giving you more headroom with louder, cleaner mids and highs. Because it bypasses only 2. I put the NFB switch next to the speaker jacks for short wire runs. Saggy or firm rectification at the flip of a switch.

It is a 50 Watt guitar amplifier driving 4 – 10″ woofers being driven at 2 ohms. Instead of connecting the center terminal to ground as shown, connecting it to a cathode biased amp’s cathode resistor will elevate the center tap and reduce hum. The low voltage, high current AC guitar signal flows through the speaker ‘s voice coil and creates a magnetic field that interacts with the speaker’s magnet to push and pull the speaker cone which creates the air pressure waves our ears perceive as the sweet sound of electric guitar.

If this NFB loop tightens up the tone too much try a larger value resistor like a 44M. It looks like you are visiting our site on a browser that is really old.


Also consider offsetting the amp’s carry handle one or two inches toward the heavy end transformer end of the chassis would be left in picture below to balance the amp during hand carry. Almost all modern amps have power tube grid stopper sdhematic. The equation to determine power in watts is: For my 5F6A build I used the exact component values shown in the original Fender schematic and layout diagram–even the crazy small pF bright channel bright cap.

Lowering tail resistance also alters the Sfhematic phase inverter balance. At about you get the normal 5F6A mid voicing. If your speakers are too shrill this simple, subtle cap can help. They require some thought, experience, and the correct tools. Its cathode resistor is shared with V1A Normal channel preamp and has ohms of resistance which is equivalent to ohms for a non-shared cathode resistor.

You simply replace the master volume pot with schemtic resistor on wchematic switch. Fender’s 3-knob tone stack architecture is perhaps the most copied electronic circuit in music electronics.

Notes on the tweed Bassman schematic.

I ordered my head cab with about one extra inch in height to fit the taller KT88 tubes. The new resistor will function as the V2A preamp’s grid stopper and help control the heavy schematjc caused by the cascade mod.

All the load resistors and V2B cathode resistor run hot and would benefit from an upgrade to 1 watt resistors. See my Amplifier Power Transformer Calculations spreadsheet to automate these calculations.

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Ground switch is deleted3-Prong power cord, balanced 6. If you do not think you have the time, ability, nor tools to do this, maybe this isn’t for you right now.


If you use metal Switchcraft style jacks that ground themselves use a star washer against the inside of the chassis to ensure a good Line Out jack ground. The downsides are I get no speaker breakup and the amp is crazy heavy but the 5F6A sounds fantastic through the hemp coned E Cooler running resistors generate less hiss.

Click here for a hi res pdf. Put two wraps each around the turret for support leave the wire 5f6q on for the wraps and solder each resistor to a wire end. If you end up needing a cooler bias than the circuit provides you can reduce the k resistor try k or k for more room on the cool side of the adjustment range.

Click the image to see the PDF. With the Mid control set at 1 you get lots of headroom, Twin-Reverb like clean. Cathode Follower The cathode follower is DC coupled to the driving stage.

List of Mods

The extra feedback also changes the overdrive tone and is the main reason many rockers prefer the JTM45 over the 5F6A. If your power transformer did not come with a 6. I placed my Raw mini-switch between the Middle and Bass pots. Even at maximum volume the overdrive behavior of the 5F6A stays controlled with no blocking distortion evident.