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02-10-2026, 04:50 PM
Hi foreverstrung
Your amp has an ultralinear output stage if it is 70W. Many players did not like the sound of that, but the problem was not really the UL connection; rather, it is that in combination with Fender's low-value feedback loop.
Fender copied hifi circuits, as did every other early amp builder, and the goal was simply to have a portable PA for the instrument. All those inputs were meant to accommodate more than one player using the same amp. Times changed; player requirements changed; the amps stayed the same... for a while. The hifi motif imposes many restrictions and can make the sound a bit dull. Thankfully the preamps have free-running gain stages and in this amp there is reverb to liven things up.
As TUTs mention, and I have repeated in other places including here, the low-value loop is not a good choice for a musical instrument amp. Fender used 820R for series and 100R for shunt in most of its amps. Increasing the values by ten opens up the sound while retaining the same gain. That's the fist mod I would do.
Other things are pretty standard reliability improvements: Change the screen-stops to 1k-5W wire-wounds or metal-oxide as long as they are flame-proof; change the 1k5 grid-stops to metal-film for better reliability; add 1R-1W metal-oxide cathode current-sense resistors for safe idle monitoring - add meter pin-tip jacks to make this easy.
The FPM kit on our site updates the used and unused channels into a Fender clean plus any distortion you desire. Use ERK or a relay for channel switching.
If you intend to try any power tube swaps, make sure their heater current does not exceed 900mA, like the stock 6L6s. Many other types have heavier heaters and you might want to add an auxiliary PT just to power the output tubes. If you do this, you will have to hang the grid-stop off pin-5, then mount the 1R-1W between pin-1 and pin-8, grounding pin-1. This allows EL-34 and 6CA7 to work and gives a handy support for the current-sense resistors.
As with most amps, grounding is atrocious and should be rewired according to the Galactic Ground Method in TUT3. As a low-gain amp, these Fenders just had to be quieter than Fender's single-coil guitars. For modern players and if any mods are undertaken, noise needs to be reduced.
Have fun
Your amp has an ultralinear output stage if it is 70W. Many players did not like the sound of that, but the problem was not really the UL connection; rather, it is that in combination with Fender's low-value feedback loop.
Fender copied hifi circuits, as did every other early amp builder, and the goal was simply to have a portable PA for the instrument. All those inputs were meant to accommodate more than one player using the same amp. Times changed; player requirements changed; the amps stayed the same... for a while. The hifi motif imposes many restrictions and can make the sound a bit dull. Thankfully the preamps have free-running gain stages and in this amp there is reverb to liven things up.
As TUTs mention, and I have repeated in other places including here, the low-value loop is not a good choice for a musical instrument amp. Fender used 820R for series and 100R for shunt in most of its amps. Increasing the values by ten opens up the sound while retaining the same gain. That's the fist mod I would do.
Other things are pretty standard reliability improvements: Change the screen-stops to 1k-5W wire-wounds or metal-oxide as long as they are flame-proof; change the 1k5 grid-stops to metal-film for better reliability; add 1R-1W metal-oxide cathode current-sense resistors for safe idle monitoring - add meter pin-tip jacks to make this easy.
The FPM kit on our site updates the used and unused channels into a Fender clean plus any distortion you desire. Use ERK or a relay for channel switching.
If you intend to try any power tube swaps, make sure their heater current does not exceed 900mA, like the stock 6L6s. Many other types have heavier heaters and you might want to add an auxiliary PT just to power the output tubes. If you do this, you will have to hang the grid-stop off pin-5, then mount the 1R-1W between pin-1 and pin-8, grounding pin-1. This allows EL-34 and 6CA7 to work and gives a handy support for the current-sense resistors.
As with most amps, grounding is atrocious and should be rewired according to the Galactic Ground Method in TUT3. As a low-gain amp, these Fenders just had to be quieter than Fender's single-coil guitars. For modern players and if any mods are undertaken, noise needs to be reduced.
Have fun
