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FDP Forum / Fender Amps: 1985 - Current / 57 Pro- fixed or cathode bias?

Progressive Kit

USA

Jul 4th, 2019 12:17 AM Edit Profile
I read a review of this amp that says that it's a cathode bias but in closer inspection I saw that the website says it's a 5E5-A circuit (which uses a fixed bias). I am trying to get to the bottom of this since Fender does not specifically state it in their literature. Any input? Thanks ahead of time.

Leftee
Contributing Member
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VA

The Escalator
Jul 4th, 2019 01:06 PM Edit Profile
Just a guess, but a pair of 6L6s that are cathode-biased would produce around 26 watts. Generally speaking you can get about 50 Watts out of a pair - fixed bias.

I’m totally guessing based on what I’ve seen. I’m hoping someone with knowledge of the actual amp will chime in.

Peegoo
Contributing Member
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If irritation occurs

discontinue use.
Jul 4th, 2019 01:24 PM Edit Profile
I could find no schematics for the current-production '57 Custom Pro Amp.

It would be nice if they stuck to the original 5E5A circuit.

But until we can get a peek at the schematic or an actual chassis, all bets are off.

cisco
Contributing Member
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Show Low, Arizona

Bottom Sucker
Jul 4th, 2019 04:45 PM Edit Profile
I have this amp so I opened the back for you all to see that this is a fixed bias amp.
Fender 57 Pro-Amp wiring

Leftee
Contributing Member
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VA

The Escalator
Jul 4th, 2019 08:12 PM Edit Profile
Welp! There you have it!

Progressive Kit

USA

Jul 4th, 2019 08:41 PM Edit Profile
thank you!

SoK66

USA

We had the hit but Van got the money
Dec 7th, 2019 07:03 AM Edit Profile
This is essentially the same amp as the '57 Bandmaster. (The original Bandmaster, Pro & Super were all virtually identical, save an 8 ohm OT on the Pro and a few resistor values.)

Fender has yanked all their online diagrams & schematics, but if you google around you can find this one or the earlier 3x10 Bandmaster. With a few exceptions they are (spec-wise) relatively identical to the vintage amps.
(This message was last edited by SoK66 at 08:59 AM, Dec 10th, 2019)

FDP Forum / Fender Amps: 1985 - Current / 57 Pro- fixed or cathode bias?

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