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

[[silent:arts]]

I fixed the other channels problems

8) 8) 8)

 

[Gus]

Why the double set of output devices?  Why not two modern transistor instead of four?  Does not look like it would change the sound.

 

[Sansodor]

Hi guys, I'm almost finished with my first module. Everything is done except for two things. I'm wondering if I should wait and get a trimpot for R6? Could someone please translate Kubis post to english? Also, I'm wondering about the orientation of the relays. How is the polarity marked? There's a line but I'm not sure how to read it.

Best regards,
Sami

 

[[silent:arts]]

I'm wondering if I should wait and get a trimpot for R6?

you can start with the resistor and put in a trimpot later (if needed).
no de-soldering equipment needed, they use different pads - you can just snip the resistor out and solder the trimpot in.

I'm wondering about the orientation of the relays. How is the polarity marked? There's a line but I'm not sure how to read it.

watching the PCB with the gold fingers to the right side, components facing to you, the line on the relays is the "upper" position.

 

[Sansodor]

Your advice is greatly appreciated, I'll finish the module tomorrow and get on with testing. Thanks again!

 

[3nity]

I have a happy working Jensamp here.
I was expecting the transistors to get hot but barely warm!
Hot output though!
Thanks to Kubi and Volker.

Thanks.

 

[mylesgm]

So should the bc140 transistors get hot or not?  mine are quite hot even with heatsinks though the module works correctly.

 

[[silent:arts]]

hot BC140 are ok

 

[Hank Dussen]

I'm thinking of adding an extra output-pad (-10 or 20 dB or so) to drive the preamp some more.
Or is this a stupid idea?

 

[[silent:arts]]

why not - THD is very different between gain stages
try it out!

 

[shabtek]

does someone have a drawing or measurements for laying out a 51X front panel for the jensamp?
I am most concerned about getting the hole for the grayhill correct.

 

[[silent:arts]]

Jensamp-51X Front panel designer file

 

[culteousness1]

Volker,

would you mind sharing your D-ASY26 file with us racking people?
Would be much appreciated!

Cheers,
Carsten

 

[[silent:arts]]

would you mind sharing your D-ASY26 file with us racking people?

sure: D-ASY26-clean.fpd

note: I deleted the Kubarth Kensamp part since Darius asked for it, and I deleted the mounting holes since every case will need them different. mine was not par-metal etc.

now you have all other holes, be creative with your own design 8)

 

[Blackout]

Hello, i'm finishing up the final wiring on a 2ch rack build, and was unsure of two aspects of what I should do. The final contact, far right on the card connector is labeled as -24v per 51x pinout, and from what I can see in the pics posted by [silent arts], that point is wired from the "fixed" point on the FP48PSU board. I am also using this power supply, so that should help make this a bit easier. This also leads me to my other question. There are only two contacts for the transformer secondaries, not the usual four that I often see. I have the wires all going to these two points with black and yellow on either side and red then orange in the center (left to right). Is this right? As to the other question, I would greatly appreciate any help. I included a pic just in case anyone wanted a visual of what is going on. Thanks you and sorry to bother you guys with my problem.
                                                                                                                                                              -----Blackout

 

[nashkato]

well , i guess you reversed polarities of some parts and the relays as on the +24vmod pdf .
so the usual -24V of a 51X rack becomes a +24V . that´s why you cannot use those modded pcbs in a GDIY 51X rack anymore.
i don´t know your PS , but i would guess you got +24/48V and a third fixed voltage ? (which would need to be populated to get +24V to be of any use here)

edith : nice wiring btw

edith2 : as to your PS question : depends on what Transformer you´re using . i assume the PCB wants a 2Pole AC voltage and your PT delievers for instance 2x24V AC . if that is the case then you want the secondaries to be  connected parallel. i don´t know the color code of your specific PT

 

[[silent:arts]]

everything nashkato wrote is true

 

[culteousness1]

Hi Volker,

I just came across these guys:

http://de.farnell.com/fischer-elektronik/skk-56/heatsink/dp/1892348

Are these the ones you got from Buerklin?

Cheers,
Carsten

 

[[silent:arts]]

Looks cool

 

[Blackout]

well , i guess you reversed polarities of some parts and the relays as on the +24vmod pdf .
so the usual -24V of a 51X rack becomes a +24V . that´s why you cannot use those modded pcbs in a GDIY 51X rack anymore.
i don´t know your PS , but i would guess you got +24/48V and a third fixed voltage ? (which would need to be populated to get +24V to be of any use here)

edith : nice wiring btw

edith2 : as to your PS question : depends on what Transformer you´re using . i assume the PCB wants a 2Pole AC voltage and your PT delievers for instance 2x24V AC . if that is the case then you want the secondaries to be  connected parallel. i don´t know the color code of your specific PT

Yes, I did the +24v mod per the pdf. You are also correct on the third rail being a fixed voltage. I put a +24v regulator in there. The transformer is indeed 2x24v AC with the two middle wires (CT) being orange and red, while the outer are black and yellow. You are three for three so far, not bad. You should gamble. Do I really have it wired in parallel with the order I have and only having two through holes to work with? (Blk & Ylw on the outside and the center tap wires, org & red in the middle). I was really hoping to hear from [silent arts] on this point because it is your board and looking at your build it appears you did exactly this. Just want to be sure on this because of the importance of wiring the power correctly. Thanks so much for you're time.  Just curious, what did you have in mind for the on board relays and fixed voltage when designing this?

PS - Thanks for the compliment on the wiring!
Adios.