H_A_M_P_T_O_N_E jfet amp modules

[chrissugar]

I saw that there is some interest in this so here are some pictures with the ones I made. The idea was to build these as some general purpose amp modules for DI, mic pre, makeup gain for compressors or summing buss amp.

If you are interested in this PCB design I can post the file.

chrissugar

 

[rafafredd]

You are a machine!!!

 

[Greg]

Nice !!!

 

[Bauman]

I had PM'd you dude :grin:

 

[tk@halmi]

Very nice! You are a busy man. I especially like the heatsink solution.

 

[daArry]

Nice, similar to my layout - heatsink too :wink: I'm also using those same chunky wimas :thumb:....

 

[tony dB]

:shock:

and i thought i saw sometimes things a bit out of proportion :green:
Why do you need al those channels for?

MASSIVE! aï :thumb:

tdB

 

[neilium]

those are pretty cute. Nice work.

 

[rafafredd]

what is that beaultifull electrolytic cap? Panasonic FC?

 

[clintrubber]

Cool, over 40 units, at whatwassit dB a piece, ehhh..., you definitely got some amplification going on over there. :thumb:

 

[fallout]

Looks great! Can you post the artwork?

-Jay

 

[adrianh]

Great heatsink solution!
Artwork?????

Your layout and this layout looks very close?
See daArry posts:
http://www.groupdiy.com/index.php?topic=1097&start=15&sid=64a96f3188619c4d06f7465ebf6ee4c5

 

[haima]

i guess that's one way to get 10 bazilllion dB of gain...!!??!

well, i like this hamptone jfet amp as much as the next guy... but i can't imagine needing 60 of em!

they look great though chris

 

[tubejay]

Yeah, what are you going to do with all of those?!?!? :?: :?:

 

[chrissugar]

Before I answer all the questions here are the pictures for the solder and components side:

and you can download [right click and SAVE TARGET AS] from here the high resolution BMP to make the PCB:
http://www.geocities.com/chrissugar7/CMS-LAB-JFET-AMP-SOLDER.bmp

Sorry Fabio but I have no gerber files, I made the project with a freeware software, then captured it with a freeware printscreen capturing software. I know, it is a bit hardcore but all my small boards are made this way. :grin:

I have to say that I was surprised that DaArry's board is 80 percent like mine. My idea was to make it more like a plugin amp module like the 990 type opamps but in a diferent footprint.
Why do I need all these modules? Good question. I played with this circuit for long enough time and explored it and I can say that I was even more impressed by this than my 10 channels of N_E_V_E preamps or the A_P_I types because it is so simple, it sounds great and is very versatile. From a very clean classA to a coloured distortion box it can do everything. I tried it with Lundahl1636, 1538 and OEP and it can sound beautifull.
A module like this has aproximately 26 to 29 dB gain depending on the fets and resistor values you use.
So why I need all these modules? I have over 120 ouputs from my synthesizers/samplers, many from the harddisk recorder and also many from the digital fx boxes. But that is not the complete answer. I try to design my new toys in dual topology like the Millenias designed by Fred. For example tube and jfet amp modules, or bipolar amp and jfet amp modules. Enough variations. Just think about compressors, limiters, equalisers and you will find that 60 is not too much. :grin:
By the way you could ask why have I built 40 Millenia type opamps, and all those NTP, QuadEight and melcor and the answer would be the same.
:grin:

chrissugar

 

[chrissugar]

I remember people were concerned about problems with temperature variation. I put the soldering iron on the top of the heatsink up to the point when I cant keep my finger in the other end of the heatsink and watched the scope and the dB meter on the computer and the largest gain variation was 0.05dB. I think you don't have to worry because you will never use it in such extreme situation.
I didn't use the 15k value because my fets were biased optimally at a diferent value. I had to select the fets from hundreds to find 60 that will bias correctly with the same resistor value. I used only the fets that gave an output DC value between 11.90 and 12.10 volts.

chrissugar

 

[Bear]

Where would I come by that heat sink? And can i get it in quantities smaller than 50? :grin:

Bear

 

[owel]

[quote author="Bear"]Where would I come by that heat sink? And can i get it in quantities smaller than 50? :grin:

Bear[/quote]

digikey has them. I'm using the same heatsink like that in my Neve PSU.

 

[al_p]

hey Chris

the link for the hi-res version doesn't seem to be working.

 

[rafafredd]

copy and past the adress to your web browser. geocities does not link directly.