Fender FR-12 preamp mod : The Hissterectomy

MLocascio said:
I bought a FR-10 and FR-12 from Sweetwater about four weeks ago to compare with what I had. The FR-12 was quiet. The FR-10 had the hiss issue.

I had been occasionally checking stock of the 10 and 12 at Sweetwater and other places over the last few months and the 12 was sold out at times, but the times that I checked, the 10 was always in stock. I suspect Fender has sold more 12's than 10's, and if that is the case, the 10 I received may have been from an older batch that didn't have the fix.
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My FR10s from Sweetwater are dead quiet.
 
My used one came from GC today, and it has the always on (with nothing connected) hiss. Is it noticeable at basement volume? Yes. At gig volume? Not when playing.

Regardless, it shouldn't be there, and I am very much looking forward to turning mine into a V2.

Even my EV PXM-12MP (EDIT) has a low level hiss, without anything connected. Note that it is much quieter than the FR-10.
 
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WKSmith said:
So here is the difference in the way the V2 mounts vs. the stock preamp.

The stock pre mounts facing the front of the amp to studs in the back plane of the chassis.
This exposes it to all kinds of interference (and faces the power amp board). It is especially noisy when sitting right next to a tube amps power transformer side. Dumb. AF. Especially for a single sided board mounted in an open chassis.

View attachment 137344


The V2 is firmly mounted to the backside of the pots. It also has solid polygon ground plane pours on both sides of the board. The exposed side is now facing down and is oriented with its tiny side profile at at a right angle to the power supply board EMF.. and is much smaller so it's offset forward and to the left a good bit. It is quiet as a mouse ..even right next to a huge tube amp power transformer lit up.

View attachment 137343
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Just ordered 2 FR-12's today, not sure how far down the waiting list I am, but I'll take two of those bad boys once you start shipping!!
 
Without reading through 68 pages…

Are the “fixed” FR12s anything like the @WKSmith modded ones or did he make improvements that the “fixed” ones haven’t included?
 
ruso said:
Without reading through 68 pages…

Are the “fixed” FR12s anything like the @WKSmith modded ones or did he make improvements that the “fixed” ones haven’t included?
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The factory "fix" is suspiciously similar the @Lysander hiss fix mod. F-corp only swapped 3 of the 5 ICs though.

The V2 is a complete redesign of the preamp. From input to output with the massively bloated stock eq section completely replaced with an Archangel original EQ design with 8 less op amp channels.
 
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