fet boy

Help Support GroupDIY:

usekgb

Well-known member
Joined
Mar 26, 2006
Messages
454
Location
Salt Lake City, UT USA
I would like to add an impedance balanced output to this pre as referenced here:
http://www.jensen-transformers.com/an/an003.pdf
Can I simply wire another 10uF cap from pin 3 to ground, or would I need to add another resistor as well.  I am unsure of the existing output impedance of the circuit, and what value, if any, resistor to add.  This is for a very compact portable build, and I just don't have room for an output transformer.  Thanks for the help!
 

3nity

Well-known member
Joined
Dec 30, 2005
Messages
3,584
Location
MTL, CANADA
Actually the fet boy its impedance balanced.
the hamptone needs an op transformer.
Do you have a look at fet boy schem?
 

Hamstertronix

New member
Joined
Dec 9, 2008
Messages
1
Hey there, I built 4 fet boys a few years ago, and now 1 channel is intermittent.  Does anyone have a working link to the schematic and layout diagrams?

I love these pres. Been otherwise my workhorse go to pre's.
 

PeteC

Well-known member
Joined
Jul 1, 2011
Messages
240
resurrecting this......

now that my 2 Calrec EQs are well under way I am interested in doing a couple of FETboys - but the project links are no longer operating on this thread.  I've googled a lot too.

anyone have the info for me to build using self etch pcbs ?

Cheers
Pete
 

rock soderstrom

⚽️⚽️⚽️⚽️⚽️
Joined
Oct 14, 2009
Messages
1,471
Location
Berlin
Hi Pete,

here is a lot of information.

https://web.archive.org/web/20110501011353/http://www.diyfactory.com:80/projects/fetboy/fetboy.htm

https://web.archive.org/web/20060819043420/http://www.diyfactory.com/projects/fetboy/hamptone_fet_scan.jpg

8)
 

pstcho

Well-known member
Joined
Dec 20, 2008
Messages
168
Location
Greece
Hello guys, i finally build this preamp but i see the transistors are getting super hot

Heating could be solution or i made a mistake somewhere

I found several forums talking about it but no real explanation
 

3nity

Well-known member
Joined
Dec 30, 2005
Messages
3,584
Location
MTL, CANADA
Transistors on mine were really hot as well. If I remember correctly calibration should limit the heat.
 

pstcho

Well-known member
Joined
Dec 20, 2008
Messages
168
Location
Greece
I calibrated as described and indeed it works fine, just scared they won't last much maybe nowadays we can find other transistors holding better this curent ?

The ztx and 2n5457 are running very hot
 

pstcho

Well-known member
Joined
Dec 20, 2008
Messages
168
Location
Greece
Lots of gain in this preamp, it's crazy

Also it feels like it sounds brighter than all the other preamps i own, anybody else noticed that ?
 
Top