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

[zmgwg]

what if signal is low, thin, distorted and wave in DAW looks very asymetrical?

 

[culteousness1]

Finally I found time to finish my SILVERLINE D-ASY26:

Some testing still needs to be done, but so far no smoke or weirdness.

Thanks to Kubi, Volker and Jens. Thanks to Frank at NRG for the panel.

Best,
Carsten

 

[[silent:arts]]

Finally I found time to finish my SILVERLINE D-ASY26:

WOW - was für eine Schönheit
8) 8) 8) 8)

 

[nielsk]

So I had one die (51x version),  the rearmost C16 was dead short, taking out R1... pretty strange, it was a very high quality 35V cap. I take it that both C16s are just more power filtering?
The only thing I can figure is a faulty component.
It draws .08A on the +24 leg, is that correct?

 

[100WChris]

Hi!
has anybody some mouser-numbers for the switches?
kind regards
Chris

 

[Hank Dussen]

Hi!
has anybody some mouser-numbers for the switches?
kind regards
Chris

I bought them at Farnell:
http://be.farnell.com/jsp/search/productdetail.jsp?SKU=9473319
http://be.farnell.com/jsp/search/productdetail.jsp?SKU=9473297

 

[culteousness1]

Hi!
has anybody some mouser-numbers for the switches?
kind regards
Chris

Mine came from Reichelt:

http://www.reichelt.de/Kippschalter/MS-500AVT/3/index.html?;ACTION=3;LA=446;ARTICLE=13151;GROUPID=3275;artnr=MS+500AVT;SID=13T8iwn38AAAIAAErQgEk28acc4ce2f87d111d86a9b9ff3a7a41b
http://www.reichelt.de/Kippschalter/MS-500FVT/3/index.html?;ACTION=3;LA=446;ARTICLE=13161;GROUPID=3275;artnr=MS+500FVT;SID=13T8iwn38AAAIAAErQgEk28acc4ce2f87d111d86a9b9ff3a7a41b

Best,
Carsten

 

[100WChris]

Thanky for the links. i live in germany, so reichelt is perfect 
Chris

 

[okgb]

I'll go through the thread & check but only recently having gotten the psu together for my 51x rack
I finally got to try the Jensamp kit I bought from silent arts , but

............no sound
just a slow periodic  motorboating / clicking kind of noise at lowest gain setting , quiet in the middle ranges
and a similar noise at higher gain . 

don't mount the TO39 transistors flat on the PCB. the metall can would do a short on the double sided PCB.
the same is true with the Haufe ST8456 transformer. the metall can is exactly over the PCB pads for the LL1538 option.
Either put a peace of (non conductive) tape over the Lundahl pads, or just leave 1/2 mm of air between the PCB and the Haufe transformer.

o.k. it looks close but only one pins meters to the case  [ the one with no pad going to it on the bottom ] ???

I know the xisters are mounted well , I'll check the transformer    pcb is ver 3

Besides the obvious connections , and I guess I have to rig up a 51x extender to check signal
Any expert opinions or idea's where to start , what it maybe ?

 

[culteousness1]

............no sound
just a slow periodic  motorboating / clicking kind of noise at lowest gain setting , quiet in the middle ranges
and a similar noise at higher gain . 

I am having something similar in one of my 51x Jensamps. Only couldn't fix it properly.
I can stop the motorboating by touching the upper side of the case of C2 and C7.

Maybe this is the same with your preamp.

Best,
Carsten

 

[okgb]

Edit

  O.k. plea for help answered,  advice solved problems through , checking my work , the board and
values  [ Problem was I hadn't decided on whether to install  trimmer or  R6 gain resister and forgot
to use either one , so I install the trimmer set at the 1/2 value point preamp now works ]
  after reading the threads , saw I had the grayhill stop pin in the wrong spot , changed as posted
and fine working preamp now .  I don't mind stupid problems if they are simple , the complication here
was that I built it and many months went by before I had a chance to check it  , moral of the story
double and read the thread , thanks

 

[[silent:arts]]

Greg, hard to tell remotely with no measuring.
Check all component values first.

Is the problem with the same with MIC / HiZ inputs?

 

[okgb]

the main germ transister seems to test o.k.  [ Hfe of 37 ? ]
It is somewhat apart so I was trying to take out the input transformer to add a spacer
but not enough luck or skill with that [ I move to outlaw plate through holes where NOT needed , ha ! ]
the transformer doesn't seem to have any shorts , but I guess checking the d.i. input may confirm that ,

O.k. that's Mr Dumas to you , was focused on the input xfmr that when I moved on the silent arts basic and correct advice
- checking the board & parts values - I see I neither installed the trimmer or a resister , Oops..........

 

[okgb]

O.k. installed 1k trimmer preset to 1/2 value [ 520 Ohms ]  and Viola,  Sound !
quick check has a nice softness and the imp switch on a 58 yields noticeable results
[ slightly brighter or  soft / slightly murky ]  gtr into the d.i. also sounds better than the average d.i.
not quite as rubbery and again with a softer or muted high end that is palatable for a d.i.
BUT
must have switch stop in the wrong position or gain resisters wrong as As I seem to get the 2nd half of
the gain in the first set of stops , 

It turns out that the stop pin was in the wrong position. It gave me the twelve point rotation I needed, but not the correct gain staging; hence no sound after 7 on the dial. In case anyone was wondering or having problems, the pin goes in top dead center. Box is dead silent, has a much more appropriate starting point in volume and the clean to sweet distortion is much more gradual.

Yes thanks my problem as well , I had placed mine exactly opposite on the bottom [ wrong ] All is well now ,
I maybe sad I didn't buy two ! thanks for all the posts      Hey ! in the tradition of spinal tap's Marshall's this pre goes to 11  ? [ dots on the face even though  there are 12 positions on the switch ]

 

[[silent:arts]]

No chance to mix up the gain resistors continues ...
Will be the Grayhill stop pin  8)

 

[nolivdacom]

Hello,
I finally had the time to test my two Jensamp already build by Volker!

I've got a problem with DI inputs on both preamps...
I have just read this entire thread and see that someone else have the same problem:

   

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 ;-)

I tried with acoustic and electric guitar and I have the same problem describe above.
The DI inputs are not usable like this... :-\
Did you find anything about this problem?

Thanks for this thread and all your advices!

 

[3nity]

you mean [silent:arts] built this for you??
if so i dont think theres an issue!!

I used mine with active basses, Godin electrics and keys and never noticed something like that.

Good luck.

 

[nolivdacom]

you mean [silent:arts] built this for you??

I mean, I bought preamps that Volker had already build!  ;D
Something must be wrong with mine.. DI inputs are not usable like this!

We will find what's wrong, for sure!  ;D

 

[dmp]

I only tried the DI on mine once, but I noticed the same problem.

 

[[silent:arts]]

Bad timing, I need to pack and will be away for a week ...

No, I did not build the Jensamps nolivdacom bought.
They have been returned from a customer who wanted to "upgrade" to OV560 instead.
But I tested them (incl. 24h burn in test) - perfectly.

However, there seams to be a problem others have too, we need more User experience / input here.
(the HiZ was tested too, but for sure with sine waves etc, NOT with transient signals).

Looking at the schematic: there is nearly nothing in the HiZ circuit which isn't in the Microphone input circuit.
C14 and R18 ...

Since it is in BOTH channels I doubt there is a faulty component.

I still think it is too much level.
Take the lowest on the Jensamp, and try it with reduced (source) level in the HiZ input.
(Lets say - 0dBu or lower on the output)
Still the same?