Fender FR-12 preamp mod : The Hissterectomy

Deadpool_25 said:
I've run them WDW. Originally they were out of phase and they sounded pretty cool that way tbh. After @WKSmith told me about the phase issue with the FR-12 I flipped the phase on that output. Still a great and monstrous tone.

They actually work just fine together. Both get plenty loud so no issues there. The low end of the FR is "better" (subjective) to me so I think it helps bolster the EV's relatively lesser low end.

My preferences in order for stereo would be:

1. 2x FR-XX
2. 1x FR, 1x PXM
3. 2x PXM

When mixing them you'd probably want to flip the phase on the FR.
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thanks! much appreciated. thinking I'll use the FR for backline and one of my pxm's as monitors for gigs. use both pxm's as home cuz....why the heck not!
 
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WKSmith said:
Edit 3/20/24:

The 1200+ following posts hacking the FR series preamps turned into a plug and play replacement preamp for the FR-10/12 that solves the hiss problem.. and has several other major design improvements... named the Archangel V2.

If you are just getting here and trying to get on the waitlist, click on my forum name and send me a PM with your email address (important!)

Here are some bookmarks to help navigate this 66 page thread.

The V2 online owners manual.
V2 Features
V2 Boards
V2 Clip Light
V2 Pricing and IC upgrade options, and more waitlist details
V2 Review #1 and Review #2 from my awesome beta testers
V2 Crossover tuning and charts
V2 EQ spice Modeling vs stock eq graphs.
V2 balanced differential input tuning vs stock with Graphs
Gutshots of the original Stock FR preamp and F-corp's "factory hiss fix" secret IC Swap
V2 vs FR-10 vs FR-12 freq Charts
FR dis-assembly instructions from another forum member
Instructions to Bypass the stock EQ with one piece of wire.
V2 tuning vs stock tuning comparison graph with all eq knobs centered, cut knobs on 0
V2 Flat(ish) eq Settings
The Hiss that started all of this.



And Here is where this rabbit hole started:

I hacked the 1st 2 amp stages chasing the hiss. The hiss is still apparent and is probably in the eq. More on that later. I have a much cleaner eq design for this thing.

The FR12 has a true balanced differential front end and can can almost take +4dB line levels. The first 2 stages are using a nasty 4558 (tube screamer) op amp. The first stage is the differential input and averager. Into the volume pot then into the second amp half for gain. The stock gain is set at 1+ 10k/ 1.5k so 1+ 6.66 for 7.66X gain.
Which is too high for even rail-to-rail op amps, and way too high for the 4558.

Edit: gain is still too high, even with first stage signal losses of -12dB from bad design in the stock preamp.

I replaced the poly caps with metal film box caps, replaced 10k feedback resistor with a metal one, Swapped out the 1.5k gain resistor for a 10k trimmer, swapped the electro cap for a metal film 1uf, and socketed a Burr Brown OPA2134.

The hiss is only moderately better. The tone though ..is very nice. It was nice before, now it sounds a lot more refined in the top end , much faster slew rate for the bottom. It's a very musical sounding op amp.

First pic is stock, 2nd pic is modded,
View attachment 128211View attachment 128212View attachment 128213
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Why spend so much precious time, and maybe money, on a FR product while there are tons of "working" products all over the place?
 
lauke-lux said:
Why spend so much precious time, and maybe money, on a FR product while there are tons of "working" products all over the place?
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Because even without a fix, it's 95% perfect and better than most everything else in the market. It sounds like a guitar amp. Really really good
2. With a fix, it's still cost competitive, even less expensive than many other options.
C. The EQ feature and function I now consider a requirement. Can't go back.
IV. For me, having the Fender amp (or any amp) form factor on stage is far better than a PA speaker or analogue.
 
lauke-lux said:
Why spend so much precious time, and maybe money, on a FR product while there are tons of "working" products all over the place?
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Because I can.

And now I have an awesome FR solution for cheap. Three of them in my studio and hundreds headed out into the world. And I shared it with the community. I didn't just fix mine, I invested a great deal of $$$ and time to make it available as a plug and play solution for everyone. And the FR-xx precisely hits the backline amp mojo that is missing with plastic "FRFR" solutions costing a lot more.

If I wanted to drop 5k + in a pair of Meyers, I would do exactly that.

I am a retired electronics engineer and respected designer of boutique preamps. If I want to thumb my nose at F-corp with a cheap solution... it is entirely my will and skill vs. corporate greed. If you are on board.. welcome to the revolution.

If you are not.. you do you boo.
I love you anyway ❤️ I hope you find amazing tone at the end of your journey !
 
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WKSmith said:
Because I can.

And now I have an awesome FR solution for cheap. Three of them in my studio and hundreds headed out into the world. And I shared it with the community. I didn't just fix mine, I invested a great deal of $$$ and time to make it available as a plug and play solution for everyone. And the FR-xx precisely hits the backline amp mojo that is missing with plastic "FRFR" solutions costing a lot more.

If I wanted to drop 5k + in a pair of Meyers, I would do exactly that.

I am a retired electronics engineer and respected designer of boutique preamps. If I want to thumb my nose at F-corp with a cheap solution... it is entirely my will and skill vs. corporate greed. If you are on board.. welcome to the revolution.

If you are not.. you do you boo.
I love you anyway ❤️ I hope you find amazing tone at the end of your journey !
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Not to mention that you had 3 great beta testers one of which was Satriani! All things happen for a reason. No soup for you lauke-lux! ;) Which by the way, did you finally meet with him or is that later in the week? Think he is in my city, Springfield, on the 26th of this month, so four days away!
 
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