JENSAMP-51X (Germanium Mic-Pre by Darius Kubarth)

[mitsos]

Not sure if this helps with the switching pop, but they do make Form D relays which are make-before-break.  Never used them and have no idea of the footprints available, but here is one:

http://www.mouser.com/ProductDetail/Panasonic-Electric-Works/TXD2-2M-24V/?qs=sGAEpiMZZMs3UE%252bXNiFaVLEqkBmKhltPwBja9wlghNE%3d

 

[nashkato]

ok
finished up my pair of rev.2 today.
some (crappy phone) pics (gotta get my camera back) sorry



ps:

yeah , that's my '73 marshall 1987 head

its a shame that the frontpanel corners are always bent .
my ´69 superbass looks even worse , yours is in great shape

 

[[silent:arts]]

wow, you are fast
clean and nice, congratulations!

how do you like it?

 

[nashkato]

thanks

hadn´t had a chance to listen to it carefully , just hung up a AKG c535 for checking .
i will give it a shootout the next few days and report back.

anyways , a nice and uncomplicated project to work on with great documentation . thanks for that.

 

[3nity]

Im almost done with mine just 3-4 things missing..
Relays...im thinking of using 48V relays..anyone has experience with using 48V at the same time powering relays??
Grayhill its on its way!
Im still looking for an input transformer to use...i want something else than Haufe or Lundhall...
Thanks.

 

[edanderson]

the haufe ST8456 is a really good transformer, especially for the money; you're not going to do "better" than that.  what are you trying to achieve with a different transformer?  there's probably a cinemag that would work, but it won't be cheaper and you'll have to figure out how to mount it.  same goes for the 10468 types from carnhill or hairball, which will definitely be more expensive.

ed

[edit] PS- great project guys, glad to see a kit version

 

[3nity]

Yeah you're completely right!
I think im gonna stick with that.
Thanks.

 

[jsteiger]

My postal carrier brought me a nice little package from Germany today!  ;D Thanks Volker! 

Can't wait to start but I need to fulfill my 51x rack obligations first. 

 

[nashkato]

i got some sowter 4706 mic input transformers laying around.
this is what i got on info about them.

"For a small microphone input transformer with split primary to give ratio
1:6 when connected in series and 1:2 when connected in parallel, for 200-300
ohms and 50-75 ohms mics respectively. Frequency response +/-1dB  30Hz -
20kHz."

you think this would work in a jensamp ?

 

[braeden]

Very nice! very clean builds in this thread. I am assuming that all you would need to mount these PCB's into a rack enclosure is a power supply with sufficient voltage + a toroidal transformer?

 

[[silent:arts]]

"For a small microphone input transformer with split primary to give ratio
1:6 when connected in series and 1:2 when connected in parallel, for 200-300
ohms and 50-75 ohms mics respectively. Frequency response +/-1dB  30Hz -
20kHz."

you think this would work in a jensamp ?

try it. should work.

Very nice! very clean builds in this thread. I am assuming that all you would need to mount these PCB's into a rack enclosure is a power supply with sufficient voltage + a toroidal transformer?

mainly they are done to work in a GDIY511 Rack.
for a non 511 conform solution you are right, and have some photos how it could be done.

 

[Hank Dussen]

I partially stuffed the board and now I notice that the BOM calls for 1/2 watt resistors. Which seems unusual for an non-tube project.
Is here a reason for 1/2 watt resistors?

 

[[silent:arts]]

I partially stuffed the board and now I notice that the BOM calls for 1/2 watt resistors. Which seems unusual for an non-tube project.
Is here a reason for 1/2 watt resistors?

I builded the first prototype with 1/4W resistors (without burning one).
since 1/2W have the same form-factor (0207) I go the save line
the resistors in the kit are indeed 1/2W

 

[mylesgm]

Built my pair and they're working in my 51x rack.  Easiest build, very well laid out pcb and easy to follow overlay and schematic.  Brilliant work!

Quick question though, the BC140 have the heatsinks but they still get quite hot.  too hot to leave a finger on them for more than 10 seconds.  I've checked the 51x voltage supply and its a steady 24v.  How hot should they get and how long will they last if they are getting that hot?

 

[baadc0de]

Hi guys,




Rack, preamps and PSU done in two afternoons. I have only tested with DI for now (no mics at home lol) and the right one has to be debugged a bit, it passes a low passed signal and the gain switch doesn't change gain. The left one works perfectly.

I'd describe the sound (at max gain) as saturated, full and immediate. I love it, best DI'd sound I have heard to date and it makes all the guitar / bass amp simulator plugins sound much better. Especially clean and crunch tones. Mad props to jensenmann, kubarth and silent:arts for making this possible. I first thought to get two germanium preamps for fun, so I would have something different, but now I'm contemplating to get more

 

[mylesgm]

yeah I tracked a hohner bass for an album though the jensamp DI and its a killer vibe esp. feeding into my lundahl mnats 1176.  Do your BC140s get hot?

 

[baadc0de]

yeah I tracked a hohner bass for an album though the jensamp DI and its a killer vibe esp. feeding into my lundahl mnats 1176.  Do your BC140s get hot?

Yeah, they do. But I read their specs today and it seems Tj is 175°C!

 

[mylesgm]

woah... Dont think there'll be a problem then as long as they dont cause other things to overheat.

 

[baadc0de]

I fixed the other channels problems. Surprise, surprise, it was a solder bridge. A tiny little bastard, but there it was. I really need to up my soldering skills / replace the old cheapo iron I have. It seems all the troubleshooting I'm doing lately is solder bridges, cold solder joints and so on... pffff!

 

[3nity]

I got mine almost finished.
i got 1 resistor, 3 small caps and im done.

Im using 48V relays so i will need a 24V/48V psu.

Hope it will work.

Thanks.