[SteveRB]

i need help...

ok this is what happened so far...   after small ground "hum" problem, i got my cornet2 working perfectly. the unit is spectacular. feeling that DIY project was pretty much done; i began making a couple of pairs of interconnects for it. i was using 3 strands of braided silver wire (home grown audio) with a cool pair of locking ends. i screwed them on/off the cornet a couple times which losened the femail rca's (upgraded pair from AES).

so...

i took apart the chassis (Lansing, aluminum) and cranked the nuts down real tight. after that the unit devloped a noticeable "buzzzzz". i've rewired the rca's numerous times (using single strand 22gauge silver wire).  buzzzz is still there.  

placement of the unit effects volume of buzzzz slightly but does not get rid of it. (any way it's in the same spot as it was for the first week while it was working fine). the only thing different was that i thightened the nuts.

i need help, i feel like i'm going in circles. it's real frustrating .

as a side note -- i noticed a nickel sized burn mark on the side of the glass of the 12au7. i can't say whether that was there before... is this related

[hagtech]

Astronaut,

Here's an important tip I need to add to the manual:  The Lansing chassis are anodized, which acts as an insulator.  This should be scraped off under the screw heads (countersink drill, anyone?) and under the fahnstock clips to hold the sides in place.  I noticed sometimes you don't get an electrical connection to all of the chassis pieces.  They MUST be connected to the Earth ground on the back panel for quiet operation.

Easy way to check is by touching the chassis with your hand.  If the buzz or hum changes, this is the problem.

Also, make sure the insulated washers properly hold the AES jacks in place.

jh

[SteveRB]

i have scraped away the finnish and have a good connection between all the chassis pieces. the buzz doesn't change when i touch the unit or pick it up. it does change when i move it closer to different ends of my ingrated amp.

 i have used the insolating washers on both sides of the chassis; am i to make sure the rca shell does not to touch the chassis at all and is grounded only to the board or can the shell ground to the back panel?

could i have damaged the rca jacks themselves?

could this not be the problem and i should look somewhere else?

thanks for the patients.  i am new to this level of diy.

[hagtech]

Best if the RCA shells do not connect to the chassis.  You get a big loop then.  I have the reference goudn for input set near the inputs by the mono switch.  This return is then piped to the rear connectors without touching anything else.

It's doubtful you damaged the connectors.

How loud is the buzz?  Just above noise floor, or way high.  Is it really a buzz or more of a hum?

If it changes with orientation, as you imply, then perhaps the interference is from the power supply of the integrated amp.  Try moving the box away, turned at various angles.  Often the best solution is a little distance.

jh

[SteveRB]

the problem seems to be with the input connectors. lastnight me and a friend got the unit running almost silent. i had to leave the input rca jacks a little loose in the chassis and get them to sit just right. but it still wasn't as quiet as it was a week ago.

i realize that placement can be a big issue but i wanted to get it working right, in the same spot it was in last week.

the lame thing is tomarrow i've got to move to vancouver. the preamp is now packed. i'm thinking when i get to vancouver i may order some new connectors (center pin is rotates free in the shell of the ones i'm using)  and bore out the mounting holes. my friend seems to think the rca's may need to be replaced. is it worth insolating the connectors from the side of the holes in the chassis if the vinyl washers aren't enough?

(ps. i will check back wed morning. after that i may not be able to respond until my internet gets hooked back up.)

[Wayne1]

If you are using these connectors, then it is VERY inportant that any metal of the jack does not touch the chassis. As Jim says, it will create a ground loop.

Something like the Cardas females

might be better. They do not have a separate ground strap and the insulators completely isolate the jack from the chassis. I used those on the two Cornets I built.

Another choice, but more expensive, is the WBT NextGen RCA connector


The body is totally non conducting and they sound very good.

I hope this helps a bit

[SteveRB]

Wayne1,

do you recomend the short/long, thin/thick  cardas mounts (a bit more my price range)

thanks for the post.

[Wayne1]

It depends on what chassis you are using.

The Lansing would take the short body/thin nut.

The IAG chassis needs the long body/thin nut.

[SteveRB]

thanks,
i'll let you know how they work out.