Fender Custom Shop  57' Lower Power Twin Mods

Vastly improves the tone! 


Fender has been putting out a number of Tweed models through their Custom shop.  They are fairly expensive and boast quality components and hand-wiring.  They are some of the best amps Fender puts out.  


One of these is the 57' Low Power Twin. It's got Mecury Magnetics Transformers and Weber or Eminience Designed Alnico speakers but sounds murky when over-driven and harsher and duller clean in comparison to vintage amps and my custom builds. The punch and clarity just seem to be missing.    Carl's Custom Amps can easily improve the tone so that it will out perform most vintage examples.  I will give you an overview of the changes we make and hope to have your amp in the shop for improvement! 


The mods necessary to make it sound it's best fall into three categories: component upgrades, tubes changes, pre-amp mods,  power section mods.


Components:


Most of the components in the 57' Twin are very nice but few need changing:


1.  Fender used Illinois electrolytic caps.  These are the large grey caps within. They are of very low quality and cause a lack of clarity and punch with amp turned up. We replace these with German made F&T caps and US made Sprauge Atom caps.

2. Some models used tiny red  polyprop coupling caps throughout (some have Fender's very nice Red paper Caps).  The polys sound hi-fi so we replace these with Malory 150s or Fender paper and oil for a rounder warmer tone in all positions except the phase inverter  circuit where they add to clarity.

Tube Changes:


Fender used 12AX7s throughout the pre-amp in the reissue which makes it sound harsh.  The original Fender's came with 12AY7s and 12AX7s.  We replace the first gain with 12AY7s.  It make the amp smoother feeling and gives more headroom. 


Pre-amp Changes:  

Fender added a cap in the tone stack that dumps treble. This was not in the original so we take it out and retain more sparkle.

 

Power Section Changes:


These are the most important changes.  The original Low Power Twin had a few flaws in the power section that knowledgeable techs and boutique builders generally correct.  Fender made some of these changes themselves with the Tweed Bassman and High Power Twin in the 50's  but repeated them in 57' Low Power . By correcting the filter caps supply, choke position, and adding screen resistors the amp will become "alive" sounding:  open and clear when clean and throaty and muscular when overdriven! These mods will also prevent the amp from eating power tubes which in it's stock form is an issue.  

Lastly Fender increased the plate voltage in the amp to 480 VDC.  The original amps ran closer to 420VDC.  This is big increase and makes the amp sound harsher and more like a Blackface Fender.  We reduce the voltage to vintage levels. 

Adding a Master:

For many players adding a Master volume can be very useful. In these I can install one that is bypassed when turned all the way up.  The master is pretty effective in these amps and good overdrive can be had from it.  I usually install then where the Standby switch is and replace the power switch with an combined On/Standby/Off switch.  

 

 

The mods begin at $245 plus return shipping.  All you need to do is send in you amp's chassis and tubes.  No need to send in the speaker cab.  We will test all the tubes and recommend replacing any bad or weak ones.  If you want Fender Red Caps and Mojotone Vitamin Ts  instead of Malory caps added to an older models with polyprop caps it will be a $75 extra.  

Use the contact form and we'll get the mod process started! 

Fully Modded 57' Tweed Twin with Fender Red Caps and Mojotone VTs. 

Fully Modded 57' Tweed Twin with Fender Red Caps and Mojotone VTs.