Fender FR-12 preamp mod : The Hissterectomy

WallyG3 said:
I received my V2s a few weeks ago. Gigged with one a week ago in my FR-12, and it was great. Sound wise, I didn't notice any difference (yay), and it was really nice that the knobs stayed in place while moving the amp around.

Today, I changed out the ICs on the original preamp. I wanted to wait until I had some time with the V2 in case I screwed it up :). I used sockets and 3 OPA4227s.

I (admittedly unscientifically) checked the noise/hiss levels this morning with a phone app, placing my phone in the middle of the speaker, 1 inch away. Here are the readings I got:
Amp off: 20.8db
Original FR12: 28.6db
FR12 with 3x OPA4227: 23.3db
V2: 22.6db.

Take it with a grain of salt, as I do not have good instrumentation, but the measurements show what my ears heard. The original Fender is annoying, changing the ICs helps, and the V2 is the best option, barely any perceptible noise.
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The hiss level on my FR-10s is much higher than that, in the low-to-mid 30s.
 
Hey all, just swapped in my V2 Gold and I think I'm having a strange issue.. On par for me and electronics 🤡

I made a quick vid to demonstrate. Basically, no hiss, and the musicality/tone is awesome. But I'm getting a weird ground hum. It's louder than the original stock preamp hiss was (with F-Corps Lysander copy half-fix).

  • I followed the instructions to a tee
  • I double checked all connections and ports prior to closing it back up
  • I tried two power sources - 1 power conditioner and 1 straight into a wall outlet - no different
  • It isn't my guitars, as it persists when nothing is plugged in
  • I tried different XLR/Balanced cables - no difference
  • The sound persists without anything plugged into the input

Any ideas what might be going on? @WKSmith
Might need to turn the volume up a bit to hear what's happening.

Cheers!

 
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bigswifty said:
Hey all, just swapped in my V2 Gold and I think I'm having a strange issue.. On par for me and electronics 🤡

I made a quick vid to demonstrate. Basically, no hiss, and the musicality/tone is awesome. But I'm getting a weird ground hum. It's louder than the original stock preamp hiss was (with F-Corps Lysander copy half-fix).

  • I followed the instructions to a tee
  • I double checked all connections and ports prior to closing it back up
  • I tried two power sources - 1 power conditioner and 1 straight into a wall outlet - no different
  • It isn't my guitars, as it persists when nothing is plugged in
  • I tried different XLR/Balanced cables - no difference
  • The sound persists without anything plugged into the input

Any ideas what might be going on? @WKSmith
Might need to turn the volume up a bit to hear what's happening.

Cheers!

Click to expand...

Yep that is not right.
I had only one other customer with this issue.

I will send you a replacement out in the next couple of days with a return label for that one.

The pads for the pot mounting tabs can ground to the surrounding ground plane.. if I pour solder to that too heavy or run the iron too hot for to long and they swell... It is an issue with the isolation tolerances around those pads from the PCB house.

I will make it right. 🙂

In most preamps you would want the pot body to be grounded. The FR has a separate floating ground from the 0V supply ground. If they touch anywhere it will make a loud ground loop hum.

There is always a small ground loop hum if you use a 1/4 input jack. That is a stock input board design issue baked into every FR.

This is not that though from the sound of it, if you are using a XLR balanced input (Important!) .

I will get another one right out. And cover shipping both ways. 🙂

Liam
 
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WKSmith said:
Yep that is not right.
I had only one other customer with this issue.

I will send you a replacement out in the next couple of days with a return label for that one.

The pads for the pot mounting tabs can ground to the surrounding ground plane.. if I pour solder to that too heavy or run the iron too hot for to long and they swell... It is an issue with the isolation tolerances around those pads from the PCB house.

I will make it right. 🙂

In most preamps you would want the pot body to be grounded. The FR has a separate floating ground from the 0V supply ground. If they touch anywhere it will make a loud ground loop hum.

There is always a small ground loop hum if you use a 1/4 input jack. That is a stock input board design issue baked into every FR.

This is not that though from the sound of it, if you are using a XLR balanced input (Important!) .

I will get another one right out. And cover shipping both ways. 🙂

Liam
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Thanks Liam, I appreciate that!

I knew something wasn't right given every other review saying it's dead silent.
So by the sounds of it (I don't speak electrical engineer..), there's nothing I can do on this end to fix it?

I am using an XLR balanced input. But either way, it makes the same noise regardless of having one plugged in or not.

Thank you good sir.
 
No Sir, thank you! Many folks would be flipping out over this.

You could verify this with a multi-meter set to continuity, checking between the right pad of the 2 mute pads (next to the XOVER jumper) and any metal of the eq pots. But it is not necessary to verify the issue. It will show which pot is grounded though

. ..But the board is not repairable when solder wicks into the ground plane. I have increased the isolation for the next PCB order, to stay far away from the ground plane.

I have slowed way down on the pot installation, and I have turned down the temp. I verify every V2 with a meter for ground isolation and then test every single one by installing it into an FR and burning it in with a guitar and FM9.

I will immediately send you a replacement, just send that one back after you get it replaced.

Edit: just throw it away. Maybe keep the Burr Brown ICs though , or make wall art out of it.
I pulled your order and saw that it is international shipping + customs (even though we are neighbors)

My apologies for having to install it twice. And many thanks for showing much grace.

😎
 
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How does everyone have their output set when using the FR-12? Seems a bit low to me, even with the FR-12 volume all the way up. Not loud enough for the stage with a band.
 
Ledvedder said:
How does everyone have their output set when using the FR-12? Seems a bit low to me, even with the FR-12 volume all the way up. Not loud enough for the stage with a band.
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I don't need to run my FR-10s high at all to obtain near-gig volume in the basement, similar to the Blueamps Cubo (which are dead-silent). The Elis 8s need to be cranked to obtain full volume, high SPL.
 
pima1234 said:
I don't need to run my FR-10s high at all to obtain near-gig volume in the basement, similar to the Blueamps Cubo (which are dead-silent). The Elis 8s need to be cranked to obtain full volume, high SPL.
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How do you have the output set on you Fractal unit?
 
FM3 into the FR10 with V2, output1 level around 1-2 o’clock. I can get very loud without diming the FR-10. For at home 80-85db output1 is between 12 and 1 o’clock.
 
Ledvedder said:
How does everyone have their output set when using the FR-12? Seems a bit low to me, even with the FR-12 volume all the way up. Not loud enough for the stage with a band.
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In the "setup" menu on your FM3, I think under "outputs" there is a choice to make between -10 Dbm (low output for consumer electronics) or +4 Dbu which is louder for pro equipment.
 
Ken Os said:
In the "setup" menu on your FM3, I think under "outputs" there is a choice to make between -10 Dbm (low output for consumer electronics) or +4 Dbu which is louder for pro equipment.
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First, you need to set Output 2 Type from Unity Gain to Line Level.

Then you can set the Output 2 Level to -10 or +4.

Edit:

Note that @Ledvedder mentioned using Output 2 in another thread
 
So I'm still looking for a second-hand one in Spain, but so far, I haven't found one with an attractive price.
I've seen some in a store, but I don't know which version it is.
Is there a way to know if it is or not the model with Fender's arrangement?, serial number or something like that.
 
They have published a range of serial numbers that will be covered under warranty. My two Fr-12s are outside that range and those still have the original hissy unmodified stock preamp.

The only certain way to know is to open them up.
 
Or listen to it.

But it's a pretty slim chance you're going to get a fixed second-hand one. They're too new into the marketplace. If sometime is selling theirs this quickly, it's not a stretch to suspect it's probably because of the hiss.
 
No, my idea is to buy it with the hiss if I find it second hand.
I have already signed up on the waiting list.
But of course, if I buy it new, I would like it to come with the fix to see how it works.
 
I picked up my FR-12 with the V2 Gold installed from my tech yesterday and spent some time during the last 24 hours dialing in my FM9 with it.

No hiss. Dead silent from five feet away. I didn't put my ear up to the speaker because I usually don't play that way.

It sounds great. Plenty of volume, more bass than I'll ever use, and headroom to spare.

I didn't do an A/B comparison with the original preamp but while the original sounded good, the V2 seems to have more clarity. I'll need to spend more time with it and more time dialing in the FM9 after a firmware upgrade.

I know I'm not hearing the FM9 at its best because I'm still using firmware 1.0. I hadn't upgraded the firmware because I have a killer Jazz preset dialed in and that's what's most important to me so there was really no need but since I need to dial in my presets all over for the FR12 (all were originally done using a pair of Presonus Eris 4.5s) I might as well upgrade the firmware at the same time.

Once I do the firmware upgrade I'll be better able to hear what the V2 can do but even with the ancient firmware it sounds really good.

My tech commented on the quality of the build and he is usually very sparse with his praise. Coming from him that says a lot.

Kudos to Liam for putting together such a well thought out and built replacement preamp. He made a very good product exceptional.
 
I just saw that Fender spain has new stock. But there is no information.
I'm going to ask them via email to see what they say and I'll tell you.
 
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