Pumpkin preamp - More Boring Making Thread

[lykkedk]

Evening all...

Today i tried to cut some unused gnd (black wire's) connection, and this way i got rid of the visible hum, seen on my CRO!
Humm stil happens though, now it just can't be seen anymore

I attached a picture of my initial setup.

Middle just below blue output cap's you can see the cutout black gnd.

It's very hard to explain how i attach everything on picture's.

But i will try anyway:

The 2 orange wire on right picture is pwr-gnd goes to 'star' gnd.

Going from right to left on picture, red wire is +out which goes to +out(rca for now) Yellow goes to -out (attached on gnd rca connection at end of cable) RCA connectors gnd goes to 'star' gnd.

Left picture the input connection's are located. yellow = -in , black=sgnd , red=+in
All 3 goes to 4deck attennuator.

On input rca, the gnd goes to 'star' gnd.
Yellow is attached to gnd too, at my testsetup.

Don't think my description could be usefull though...

Jesper.

[lykkedk]

I attach a picture of my shielded cable... would like to know what is best to use.

I mean should i use the shield as gnd, or just the black one as i do now.
Any other hint, for my next rewiring would be nice

Jesper.

[Variac]

Ok, basic question. Do people mostly use shielded wire for internal hookups? say for the wire that goes internally from a phono jack to the circuit board? OR just a pair, twisted ?

[Holger Barske]

OR just a pair, twisted ?

I use to do it that way. I usually have less hum problems with it.

[jupiterjune]

Ok, basic question. Do people mostly use shielded wire for internal hookups? say for the wire that goes internally from a phono jack to the circuit board? OR just a pair, twisted ?

This could be a whole thread by itself.

For internal wiring, I just use wire, not even a twisted pair.

What does the twisting together do, really? I noticed with shielded microphone (balanced) cable (the kind PE sells for making XLR interconnects) that if I feed a signal in one wire, I can easily read the signal in the wire running parallel to it, but with a slight phase difference.... even when the parallel wire was connected to ground through a 600 ohm resistor.

To me, this says there is a lot of capacitive coupling between the two wires, and I haven't been able to convince myself of any reason why this would be good.

JJ

[carpenter]

Originally posted by jupiterjune


To me, this says there is a lot of capacitive coupling between the two wires, and I haven't been able to convince myself of any reason why this would be good.

JJ

Common mode rejection?

[lykkedk]

lykkkkk

are you hiding in some danske igloo doing some things for family augmenting , or you hiding decreasing gain or...........

Your'e right master ZenMod... family buissnes, work and such thing's is due to my silence.. last few day's.

Problem with gian't noise, hum is nearly solved by now, last funny thing with sensitivity with my 20x gain / no chassis / leachamp, i agree with you, is the comparing to use a pre with a mm/mc input. The reason why some noise/sensitivity appear's when closing -in to gnd, must be that the gain raises som xxx factor while doing this. Right now i must find time to make rest of chassis / inputselector and try all this. (maybee before christmas???) donno.

Going from big big big problem's with this setup/leachamp down to allmost nothing, is that i used the grounding schm. you drawed earlier in thread.

I am hoping that i can try it out some more next few day's.

Jesper.

[Zen Mod]

Originally posted by lykkedk


Your'e right master ZenMod... family buissnes, work and such thing's is due to my silence.. last few day's.

Problem with gian't noise, hum is nearly solved by now, last funny thing with sensitivity with my 20x gain / no chassis / leachamp, i agree with you, is the comparing to use a pre with a mm/mc input. The reason why some noise/sensitivity appear's when closing -in to gnd, must be that the gain raises som xxx factor while doing this. Right now i must find time to make rest of chassis / inputselector and try all this. (maybee before christmas???) donno.

Going from big big big problem's with this setup/leachamp down to allmost nothing, is that i used the grounding schm. you drawed earlier in thread.

I am hoping that i can try it out some more next few day's.

Jesper.

did you finally hear with Leach?

with gain of ,say, 5 ........

[lykkedk]

did you finally hear with Leach?

YesYes... no problem... but with gain 20~25 ... only slight hum... only volume at max!!! 1/4

Jesper.

[Zen Mod]

Originally posted by jkchoi


Still the log box tell me that I have to write post more in order to email direct to him.

So, I had to describe my need to him, before long he will be received email.

whatever road you choose , it will take you to the Rome ........

you can always reach choky at >choky@neobee.net<

copy and paste that between the >< brackets