Fender FR-12 preamp mod : The Hissterectomy

notalemming said:
After following this thread, I can only imagine how many shortcuts, cheap parts & bad design decisions are in the Tone Master Pro.
Click to expand...
Yeah, I think about this. Some companies care about producing good quality products. Others make them as cheaply as possible hoping that nobody will notice or complain and pocket the added profit.

The later companies deserve to be boycotted because they're ripping off people who expect to be buying something that is well made. Greed drives their decisions. I'm happy to pay for a well-made product because I don't like buying things twice.
 
Greg Ferguson said:
Yeah, I think about this. Some companies care about producing good quality products. Others make them as cheaply as possible hoping that nobody will notice or complain and pocket the added profit.

The later companies deserve to be boycotted because they're ripping off people who expect to be buying something that is well made. Greed drives their decisions. I'm happy to pay for a well-made product because I don't like buying things twice.
Click to expand...
I agree completely,
but you almost entirely need to buy directly from a builder anymore (like I don't know say ... Fractal 🙂) ..to get that level of product, ingredients, and customer support,

which sadly used to be the standard.

The guitarCtr big box model won't allow that.
 
Greg Ferguson said:
I'm happy to pay for a well-made product because I don't like buying things twice.
Click to expand...

Me too, but in some cases it is simply not possible. Aftermarket electric water pumps for R53 MINI is a good example. The best one you can get is still not entirely trustworthy. Got a year of intermittent use (including almost 6 mos. parked waiting on some cosmetic work) out of the one that came with the Harrop TVS900 supercharger conversion kit, which is supposed to be the highest quality, most reliable one available. At least now I know what the thing sounds like when it's getting ready to die....
 
skolacki said:
All we really need is a parts list and pcb’s plus layout and schematic. I’m going to buy one of these. 1 because aside from the hiss everyone says it’s sounds great. 2 because they just look sexy, like a nice combo amp. So if you @WKSmith finalize a design and get some boards, I would be more than happy to make it worth your while.
Click to expand...
Me too, I can help fund this adventure.
 
marsonic said:
I think he meant the other way around, that the lack of delay is part of the cab feel.

IMHO, it's probably not.

It's possible that's the one proverbial straw that pushes the total latency over what you can tolerate, but...I think people wouldn't run wireless, let alone wireless to a modeler and then a digital mixer and then wireless to in-ears if it was that big of a problem.
Click to expand...
For those attached close to their amp forever and then wading into digital.…for me understand, it is an issue…I‘m kinda of an audiophile and want the most direct solution, which the Fender helps. Regardless of my lack of hissue(hiss issue)…(I think I did it again :) ) , a simple amp design easily modded is an invitation to modding it up to audiophile specs, and it is a privilege that @WKSmith has waded into this water. Thanks @WKSmith …
 
200man said:
For those attached close to their amp forever and then wading into digital.…for me understand, it is an issue…I‘m kinda of an audiophile and want the most direct solution, which the Fender helps. Regardless of my lack of hissue(hiss issue)…(I think I did it again :) ) , a simple amp design easily modded is an invitation to modding it up to audiophile specs, and it is a privilege that @WKSmith has waded into this water. Thanks @WKSmith …
Click to expand...

I always thought the latency was going to be an issue, but even sending the fractal through my computer isn't really a problem. Though, the computer isn't exactly a slouch...I think I run a 64-sample buffer at 48k by default.

"Audiophile" is almost a dirty word to me. For whatever reason, it makes me think of magical acoustic hockey pucks and $500 USB cables that ignore the spec and only don't cause problems because they're so short.
 
Hi everybody, sorry for repeatedly asking questions over time in this thread, but I'm currently preparing a Mouser order and would like to ask about two things:
1. If I wouldn't want to use a 10k trimmer for R2 but install a fixed (CMF55 Dale) resistor, what would be your recommended value to use?
Original value is 1.5k if I read that correctly?
I believe @WKSmith would recommend to use a somewhat higher value here? Would it be better to be closer to 10k or stay relatively lower, something below 5k?

2. And is there a consensus regarding the useage of the OPA4227PA through-hole IC vs the OPA1604AIDR SMD IC + adapter that @Lysander used? Mouser has both of them in stock so if both would work equally well, I would also like not having to solder the SMD ICs to adapters first... ;-)

Thanks a lot folks, FR-12 incoming this week... :)
 
quasimono said:
2. And is there a consensus regarding the useage of the OPA4227PA through-hole IC vs the OPA1604AIDR SMD IC + adapter that Lysander used? Mouser has both of them in stock so if both would work equally well, I would also like not having to solder the SMD ICs to adapters first... ;-)
Click to expand...

I'm still waiting for feedback from people trying the DIP version of OPA4227, but i see no reason why it shouldn't work. It's spec- and pin-compatible with the TL084, and the noise floor is very very low at 3 nV/√Hz. The preamp for the FR-10/12 is not exactly a precision design, and pretty much any opamp that handles the board's voltages will fit in just fine.

OPA1604 is a marginally better (and cheaper) audio-oriented part, but it's a shame it's not available in through-hole packaging 😢
 
Thanks @Lysander!

I was just going to answer my own question about the ICs after reading up on the datasheets of both ICs:
OPA4227: https://www.ti.com/lit/ds/symlink/opa4227.pdf
OPA1604: https://www.ti.com/lit/ds/symlink/opa1604.pdf

The latter one is explicitly described having "superior sound quality" with the "SoundPlus™" moniker and has the revered Burr-Brown Audio flair, whereas the (older?) OPA4227 seems to be a more generic, albeit also very good piece of equipment?

Anyways, I believe I will go the extra mile and buy the "better" (and cheaper too!) part along with adapters to obtain my OCD DIY ease-of-mind... ;-)
 
quasimono said:
The latter one is explicitly described having "superior sound quality" with the "SoundPlus™" moniker and has the revered Burr-Brown Audio flair, whereas the (older?) OPA4227 seems to be a more generic, albeit also very good piece of equipment?
Click to expand...

Don't sweat too much about the difference, specially for a mod in the EQ section :D I'm willing to bet both parts will sound exactly the same. OPA4227 is an excellent opamp for audio applications.

A much better use for a Burr-Brown would be replacing the opamp in the differential input stage (RC4558) - don't expect a night-and-day difference though. I think switching the RC4558s for OPA1656 marginally improved tone and response on my FR-12, but i could very well be deluding myself. @WKSmith used a OPA2134 on his, which is a very similar IC also available in DIP packaging.
 
Last edited:
quasimono said:
Hi everybody, sorry for repeatedly asking questions over time in this thread, but I'm currently preparing a Mouser order and would like to ask about two things:
1. If I wouldn't want to use a 10k trimmer for R2 but install a fixed (CMF55 Dale) resistor, what would be your recommended value to use?
Original value is 1.5k if I read that correctly?
I believe @WKSmith would recommend to use a somewhat higher value here? Would it be better to be closer to 10k or stay relatively lower, something below 5k?

2. And is there a consensus regarding the useage of the OPA4227PA through-hole IC vs the OPA1604AIDR SMD IC + adapter that @Lysander used? Mouser has both of them in stock so if both would work equally well, I would also like not having to solder the SMD ICs to adapters first... ;-)

Thanks a lot folks, FR-12 incoming this week... :)
Click to expand...
If you are using @Lysander 's op amp recommendations .. it is not too important to change the gain values of R13 / R2 . Those ICs play rail to rail .
 
OPA1604

$5.58 (buying a lot of 10) at Mouser Thailand + $16.62 shipping to Bangkok
$0.52 (buying a lot of 10) at AliExpress + $0.11 shiping to Bangkok

Is thee such a thing as a lower quality OPA1604?
 
Thank you guys a lot! 👍
I got lucky and found two OPA2134s in my stash box, so I will use these to replace both RC4558s.
Any recommendation regarding the value of R2 in this case?
Apart from that I just ordered the OPA1604 with adapters from Mouser to replace the three TL084s.
Will report back, once everything has arrived and I got to test stock vs. modded amp.
Cheers you good people!
 
WKSmith said:
No, but there are lot of fakes!
Click to expand...
But they are supposed to work. They have thousands of sales without negative votes.

Maybe it is like the Arduino boards. The cost from ALiExpress is 10 times cheaper than from the official manufacturer, and they work exactly the same. I've been using many since long time ago without issues. The only difference is that they do not come in a nice box.

Anyway, I first will try to find it in a local store
 
Last edited:
quasimono said:
Thank you guys a lot! 👍
I got lucky and found two OPA2134s in my stash box, so I will use these to replace both RC4558s.
Any recommendation regarding the value of R2 in this case?
Apart from that I just ordered the OPA1604 with adapters from Mouser to replace the three TL084s.
Will report back, once everything has arrived and I got to test stock vs. modded amp.
Cheers you good people!
Click to expand...

Instead of giving you the answer, I will show you the math behind your questions.

You need to know a couple of things to solve the equations.

1) the supply voltage (It's 36v)
2) the op amps input voltage rating From the datasheet. ( it's 30v for the 4558, and +/- .7v of the supply voltage 34.6v for the opa2134)
3) the input level you are putting into the amp.
Balanced +4dB is 4.77v

To keep this circuit gain close to the original design, you will want to max the gain to put the input at the max rated input voltage of the op amp.

The formula for gain in this non-inverting amp stage is 1 + R13/R2 .

So if you want make a 4.77v input into 34.6v ,
You need 34.6 / 4.77 = or 7.25 X gain. So we are looking for 1+ 6.25.

You can use different values for R2 or R13
I would use 1K for R2 and 6.2k for R13 for the OPA2134.
 
Piing said:
$0.52 (buying a lot of 10) at AliExpress + $0.11 shiping to Bangkok
Click to expand...

DON'T buy ICs from AliExpress, specially when suspiciously cheap: 9 out of 10 times, you'll get re-labeled fakes. They might work, but you're not getting the part you're paying for.

LCSC is a trustworthy distributor based in Asia, but you'll find their prices to be in line with Mouser, Digi-Key and the likes. Shipping might be cheaper, thou.
 
You must log in or register to reply here.
Back
Top Bottom