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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Many of the mods on this page apply to the Schemaitc Reissue. This will allow you to install a balanced adjustable bias circuit or add a dual pot post phase inverter master volume PPIMV.

Install the Zeners with their stripe cathode toward the rectifier, the other end anode toward the first filter cap. Bump the watt rating of the ohm 1 watt power tube screen resistors mounted schemmatic the power tube sockets to 5 watts. 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.

Fender Bassman 5F6A Amplifier Project – By Edmund Henke on Behance

All voltages are DC unless specified as AC. Class A uses a factor of 2. I ordered my head cab with about one extra inch in height to fit the taller KT88 tubes. My circuit increases the value of the two filter caps to reduce schrmatic and reverses the value of the pot and resistor to increase the bias range to work with more amps and tube types. Scnematic dual gang Schejatic pot one shaft turns both pots, audio or log taper replaces the two k power tube grid leak resistors.

With the cautions out of the way here is a very simple Line Out that does capture the tone and distortion of the entire amp except for the speaker. The first step for this mod is to separate V1’s cathodes so we can use different value bypass capacitors on each channel.


If you do go with Weber I recommend you have Weber break their speakers in for you so they will sound great right out of the box. For typical guitar amplifier applications, unity gain and a zero-ohm output impedance can generally be assumed without a significant loss of accuracy.

Disconnect the bottom of the Normal channel k mixing resistor. One downside to doing this is it will also raise the voltage on the phase inverter and preamp tubes and the V2B cathode follower is already stressed by the stock voltage. Connect the diode’s striped end to scchematic ohm resistor. The pulsing negative DC put out by the diode is filtered by the two 25uF filter caps and 15k resistor. Morgan Jones, Valve Amplifiers4th Edition. Cooler running resistors generate less hiss.

Notes on the tweed Bassman schematic.

The switch ties the power tubes’ screens to the plates which eliminates the screens’ function creating a virtual triode which cuts the tubes’ output power almost in half. The mod connects a preamp’s second or third gain stage plate back to its grid through a 22M to 44M resistor and.

You can bend the resistor’s lead into a small loop to make attaching the wire easier.

But if you build the amp with a bigger 6L6 power tranny then the 6V6 loses a lot of voltage sag so it sounds stiffer and punchier with a noticeably tighter low end sounds more solid state and less tubey. This circuit is designed for use only with power transformers using a center schmeatic and conventional rectifier.

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The 5Y3’s current rating of only milliamps would strangle a 5F6A but the 5R4 will work nicely. High gain amps often use a hot or cool scjematic triode bypassed at. The power transformer must put out enough 6.

The Fender 5F6A schematic shows v as the bias voltage for tubes which would yield a significantly cooler bias. And at 10 you get full tweed – meaning the tone stack is almost completely eliminated from the amp circuit so you get a nice signal boost.

schemafic You can reduce the value of the ohm resistor to brighten the LED if it appears dim. This works in both cathode schemztic amps elevates the heater ground or fixed bias amps grounded cathode. Run a jumper wire from the output of the Normal Channel’s k mixing resistor to V1 pin 7.

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If you are cramped for space for an additional jack you can use your amp’s ‘extra’ speaker jack or even add a small 5f6. These resistors are not required if your power transformer has a 6.

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. If we were worried about running a valve rectifier too close to its maximum Va rms [AC voltage rating], we could place one or more silicon diodes having a much higher peak inverse voltage in series with each anode, as protection elements. Having two diodes in series one solid state and one tube will also greatly increase the rectifier circuit’s peak inverse voltage PIV handling capability and should increase the rectifier tube’s lifespan.

This effect can be overcome in the 5F6A by using a 5Y3 rectifier tube which will still cause voltage sag with 6V6 tubes. There’s no added coupling capacitors to change the amp’s voicing. Achematic your amp is fixed bias and taps its bias voltage from the power transformer’s high voltage secondary you must keep the bias tap BEFORE 5r6a diodes because the high voltage bias circuit must be fed AC voltage.

This mod uses two bias pots so you can set the bias for each power tube. Signal flow schematoc with red arrows. It will quiet or eliminate the Standby Switch ‘pop’ by allowing a small current to flow around the Standby Switch to charge the Filter Capacitors.

Combine this position with the Gain Boost Switch and you have a virtual 5E3. You can replace the 22k resistor with a k reverse audio pot wired as a variable resistor as a line out level volume control.