Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mrjomo on October 15, 2025, 08:29:23 pm
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Greetings,
Curious the reverb driver in a Fender Blues Junior is half of a TLO 72 chip. Z-in of the tank is nominally 800 Ω. In my pro audio experience, I wouldn’t design to drive that load with that chip. Anything less than 2-3kΩ load seems wrong without serious current help. Using old skool cheepie chips, i would think a 5532 would be a better choice. It sucks a fair bit more current but there’s only ONE of ‘em… Modern chips bring all sorts of better options. TLO 72 was old when this amp came out. Did Fender have an inventory to use up?
Hmm… of course the ’72 seems like a reasonable rvb recovery chip...
Of course, i might be accused of polishing a turd by even thinking about this.
Thoughts?
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Later revs used the 4560.
TL072 output impedance is 125Ω. An 800Ω tank doesn't seem unreasonable, especially with the huge signal attenuation at the input.