Boss - FA-1 Fet Amplifier  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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Duckman
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Post by Duckman »

Hi, guys!
After my search for options, here's the problem:
reading some reviews about the FA-1, I became interested in build it, so I breadbord it first, but for some reason got less volume than I expected. To make it short, I checked, double and triple checked, change parts, change breadboard and... nothing... still a kind of 1:1 volume. I never got the oportunity to try one of this, but I see reviews that claim it as a louder device. I also read here that some factory schems have "mistakeks" included.

Maybe the problem it's obvious for someone with a little more knowledge than me :oops:
If someone used this schem without a problem, I accept any help.

Tkx!
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Boss_FA-1_FET_Amplifier-1.png
Boss_FA-1_FET_Amplifier.pdf
Boss FA1 Fet Amp
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Duckman
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Post by Duckman »

Nobody?

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Post by Duckman »

Ok, got it.
Maybe somebody got the schems or some gut shots of the Analog Man version to see diferences by my self?
Tkx!
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fa-1-clone.jpg
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roseblood11
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Post by roseblood11 »

Hi,

I think the schematic is correct. And as far as I know, it IS a very loud unit...
The same schematic is published on ustomp: http://ustomp.com/?p=6,
but he uses a different opamp in his layout.
He claims that C2 is a "non-polar 47F cap", but he must have misread the schematic, I´m sure that it says "0.47µF np"...

Did you use the HA1457W opamp?

regards, Immo

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Post by Duckman »

Thanks for your post, Immo!

I noticed that C2 value is a little unclear, so I tried both values, and I don't ear a big difference. Also, I buyed the two HA1457W and the 2SK246GR at Small Bear, trying to keep the original configuration, but no "loudest" at all.
What about R5? Is the only value not printed, just handwritten. Maybe...?
In order to reach some satisfaction, I'll try the 4558/J201 version, just in case... and I tell you when I'm done.
Thanks for your time!!
I found this too:
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fa-1pcba.jpg
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fa-1clone.jpg
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Post by Dimitree »

so I want to confirm that the original schematic is 100% correct and that cap is a 0,47uF, not a 47uF. I have the original pedal at home and compared with the clone I can't tell any difference.

the pedal shown in the attached pic is not mine, it's another version of the FA1 based around another IC, but the rest is identical (except the ceramic caps, different values and different connection with the IC), and you can see C2 0,47uf. I will add some pics of mine too.
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BOSS FA-1 COMPONENTS BOARD.JPG
Last edited by Dimitree on 11 Mar 2011, 20:55, edited 1 time in total.

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Post by Dimitree »

pics of mine:

ps. I confirm 15K for the handwritten resistor
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pic2.jpg
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Dimitree
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Post by Dimitree »

this is the other version
it's easy to spot the differences: different IC, 2 more resistors, different values for the 2 ceramic caps. you can notices that those differences are only to adapt this different IC on the circuit
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fp1.png
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Duckman
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Post by Duckman »

Awesome!! :applause: :applause: :applause:
You're a very kind person :hug:

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Post by iq01221 »

Y just did a improved version, sounds great!!!!
Layout:
http://ustomp.com/files/fa1buildetch.pdf

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Post by Rockhound252 »

Have you got any othe layout¿ In a springboard i think

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Duckman
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Post by Duckman »

:scratch: Springboard? You mean stripboard, right?

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Post by iq01221 »

I've made the ustomp version, with 4,7uF, like the schem says, j201 and TLC2272 SMD dual-opamp. And it's a very loud stomp.
I've tried with 47uF cap too, but it don't affect the out volume anyway...
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It's a great sounding pedal. I hope you can solve it.
Regards!!

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Duckman
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Post by Duckman »

Well done. In one of the photos posted above by Dimitree, you can see clearly a 0.47uF in the original board, but, as I said before, not a big difference in sound.
Mine, I finally gave it to a friend because I do not settle for the sound.

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Post by RnFR »

with all these gutshots, ive decided to turn this into the official FA-1 thread, since we don't have one yet.
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guycapuano
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Post by guycapuano »

Anyone have a vero for this one? I had an original here yesterday and am FLOORED!

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guycapuano
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Post by guycapuano »

bump anyone?

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roseblood11
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Post by roseblood11 »

download the "do it yourself layout creator" and make a vero...

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Post by guycapuano »

roseblood11 wrote:download the "do it yourself layout creator" and make a vero...
I dont know how yet, I'm a noob remember? :hmmm:

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Post by Duckman »

C'mon guycapuano! Give it a chance! The DIYLC program it's not hard at all and you'll be satisfied doing it by yourself :horsey:

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