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

[shabtek]

I just ordered a panel from fpe for this--you can get the coordinates for the holes out from the fpd software.

edit:if you open download the fpd software and poke around in the file you will find :
(here are the coordinates for the holes
Type Position [mm] Description
X Y 

Frame 0.00 0.00 Height: 5.2500 " /
Width: 1.5000 "
Drill hole 19.05 129.39 Diameter: 3.20 mm
(with countersink) $1.11
Drill hole 19.05 3.96 Diameter: 3.20 mm
(with countersink) $1.11
Drill hole 15.22 27.30 Diameter: 11.20 mm $0.41
Drill hole 15.07 56.52 Diameter: 6.50 mm $0.29
Drill hole 15.07 43.84 Diameter: 6.50 mm $0.29
Drill hole 15.07 69.22 Diameter: 6.50 mm $0.29
Drill hole 15.07 81.96 Diameter: 6.50 mm $0.29
Drill hole 32.07 43.84 Diameter: 6.20 mm $0.28
Drill hole 32.07 81.96 Diameter: 6.20 mm $0.28
Drill hole 18.07 103.50 Diameter: 6.50 mm $0.29

 

[3nity]

Wheres my caliper?

 

[benlindell]

Hey guys.

I spent my afternoon building my pair of these, gonna take them into the studio tomorrow and see how they sound, I'm looking forward to it. Thanks silent:arts for making these boards and kits, they are incredibly well engineered, everything fit perfectly and was easy to put together.

More pics : http://blog.benlindell.com/?p=344

 

[benlindell]

So one works perfectly and one just makes a crackling noise on some gain steps and no signal on others. The LEDs are working but nothing else. I have a spare edge connector on it's way so I can test it on the bench. I built them one after the other so I must have done something silly on this one. It couldn't be the used Lundahl right?

 

[3nity]

Didnt Volker said he tested them?? im pretty sure they are.
You got no sound at all??if you hear a noise its because the Lundahl works!

 

[benlindell]

So it turns out that I had one pin of the output transformer unsoldered, after fixing that and checking the rest of the board for stupid mistakes I brought it back to the studio to try in the rack again, now the clicking noise is much louder I had a 51X card edge on the way do I can test outside the rack but does anyone have any ideas what could cause this?

 

[3nity]

compare side to side against the working one!
Thanks

 

[3nity]

So did you found the culprit?
Killer fp by the way!
Thanks.

 

[benlindell]

So did you found the culprit?
Killer fp by the way!
Thanks.

the FP is the one volker is including in the kit, it is pretty sweet.

as far as the culprit, it's getting better but the symptom is getting weirder.
from pos 8 up it's all fine. below pos 8 sometimes it's fine then sometimes it starts making pulsing noises and also loud switching pops.

I verified all the caps and resistors. double check the diodes and transistors. I reflowed every point and it got a little better now sometimes it doesn't make noise in the lower positions but if I go slow between the positions the noise starts, that's weird right? do I have a defective switch?

 

[Winetree]

What position does the pin go in on the Grayhill switch?

 

[mikeyB]

So did you found the culprit?
Killer fp by the way!
Thanks.

the FP is the one volker is including in the kit, it is pretty sweet.

as far as the culprit, it's getting better but the symptom is getting weirder.
from pos 8 up it's all fine. below pos 8 sometimes it's fine then sometimes it starts making pulsing noises and also loud switching pops.

I verified all the caps and resistors. double check the diodes and transistors. I reflowed every point and it got a little better now sometimes it doesn't make noise in the lower positions but if I go slow between the positions the noise starts, that's weird right? do I have a defective switch?

Did you check the electrolytics polarity against the good unit - i`ve had one electrolytic reversed on a preamp and it presented weird stuff as you report. I`ve even had one or two caps  a good while ago labelled with the wrong polarity!! - this was a brand name as well (or a very indistinguishable fake!!!!).
ps Fantastic looking piece of kit - but a chromed nut jack would totally sex it up!!

 

[benlindell]

What position does the pin go in on the Grayhill switch?

12.

 

[Winetree]

Frist unit First power up loud pops and pulses. No Sound.
Changed polarity on C7. Works
problems now.
1. loud pops when switching to positions 3 and 4 only. Others positions quiet.
2. Plug bass into D.I. jack, sounds good until I hit the string a little harder
    then there's a loud distortion squeal with a large volume spike. Does this at all gain settings.
    Does not do this with a mic pluged into the XLR.
I read that these don't have a lot of headroom, but in both problems it still sounds like a DC problem
Second unit reversed C7 first power up. mic plugged in all good, quiet clicks but all gain stages work.
D.I. bass, starts loud pops on 3rd click, 4th click start to get overload squeal, 5th click loud rythmic pulses.
Go back to mic, 3rd click starts loud squeal. Shut power off.
When building these, I measured and checked every part 3 times
I've rechecked everything 10 times for hours. There must be some bad parts. Where do I even start?

 

[TimS]

starts loud pops on 3rd click, 4th click start to get overload squeal, 5th click loud rythmic pulses.

Don't they call that "dubstep"? ;D

 

[[silent:arts]]

1. loud pops when switching to positions 3 and 4 only. Others positions quiet.

MUST be something around the switch, check the solder joints of the gain setting resistors / compensation caps

2. Plug bass into D.I. jack, sounds good until I hit the string a little harder
    then there's a loud distortion squeal with a large volume spike. Does this at all gain settings.
    Does not do this with a mic pluged into the XLR.

Active Bass? too much level. The Jensamp doesn't like to be overdriven, and it does not only distort, too much input level makes it alive.
Mr. Kubi said this is a feature he builds in all of his projects ;-)

 

[culteousness1]

Thanks to Kubi, Volker and Jens!

Unfortunately these guys are for a friend of mine  :'(

Building was a breeze. Great kit, Volker!

Cheers,
Carsten

 

[[silent:arts]]

Thanks to Kubi, Volker and Jens!

... and Frank for the Frontpanels and Cemal for the L-Brackets ;D
and my daughter for counting caps etc ;D
it is teamwork :-*

nice work, and nice photo 8)

 

[culteousness1]

Thanks to Kubi, Volker and Jens!

... and Frank for the Frontpanels and Cemal for the L-Brackets ;D
and my daughter for counting caps etc ;D
it is teamwork :-*

Yes, you are right. You all did a great job!
As said before, everything fit from the beginning.

 

[[silent:arts]]

Geht runter wie Öl, danke!

Nice to hear you are happy!
Sometimes we need days like today

 

[Winetree]

After many, many hours of looking over and checking values and resoldering, I gave it a retest.
It it passes audio with the following problems,
loud pops between 3 and 4 and 5 of gain, distortion on DI Bass when played to hard.
(Passive pick-ups on an orginal '68 Fender P-Bass). Being plugged  into middle slot of an empty 51x rack, I started touching the transistors too see if they were running hot, Yes. When i touched the last small transistor ASY2619
I got a the same distortion clipping noise out of the speakers every time I touched it. And scratching the transistor was like scratching a pick-up on a guitar, monophonic. Is this right? I think these are BAD Transistors. I'm having the same trouble with both units. It's what been causing these problems all along.  Help!  I've got two boat anchors.