Access-312 Build Thread

[buildafriend]

Hm.. the problem is the most persistant in the amp nearest the toroid. Ill try it and see what happens. How can I shield it? I've never shielded a toroid before.

 

[sr1200]

dunno if you can shield it,  I had this issue with my 4 ch unit w/ ps inthe same case.  I had to point the part of the torroid where the wires come out to the back right corner (the torroid was IN the back right corner) for the buzz to go away on the 4th channel.

 

[buildafriend]

dunno if you can shield it,  I had this issue with my 4 ch unit w/ ps inthe same case.  I had to point the part of the torroid where the wires come out to the back right corner (the torroid was IN the back right corner) for the buzz to go away on the 4th channel.

ugh man, i know i pointed mine that way already. its fairly far away too.. there has to be a way to shield it.. I'll try shielding it first. Thanks man.

 

[3nity]

theres a guy who used to sell shieldings for toroidals..
dont remember who it was...
Hope you solve it.

 

[3nity]

http://www.don-audio.com/trafo-shield

 

[sr1200]

i know this is kind of dangerous, but with the unit powered on and hooked up to some kind of monitoring device (ie a cheap pair of headphones)turn her on and move the torroid until you hear the buzz go away.  Had to do that with mine, there was a direction i had to turn it for it to go away. 

good find 3nity, i might have to pick some of that stuff up

 

[buildafriend]

http://www.don-audio.com/trafo-shield

That looks like it should do the trick 

 

[buildafriend]

dunno if you can shield it,  I had this issue with my 4 ch unit w/ ps inthe same case.  I had to point the part of the torroid where the wires come out to the back right corner (the torroid was IN the back right corner) for the buzz to go away on the 4th channel.

My issue is a screaming oscillation past a certain amount of gain. Its not a buzz..

 

[sr1200]

Check your grounding for everything.

 

[buildafriend]

okay.. but im guessing its the toroid because its screaming easier and more as the channels get closer.

 

[LesPaul]

Another newbie question...

Can't get my head around the grounding issue. Do I connect all the input XLR pin 1 together to star ground? And the output XLR pin 1 to ground on one of the terminal blocks on the PCB?
This is my first build...

Thanks

 

[tfletchii]

Another newbie question...

Can't get my head around the grounding issue. Do I connect all the input XLR pin 1 together to star ground? And the output XLR pin 1 to ground on one of the terminal blocks on the PCB?
This is my first build...

Thanks

you run all the xlr input and outputs to the star ground.

 

[LesPaul]

Thanks

Here's a pic of the finished unit. These things has an enourmous amount of gain! The only bad thing is that one of the pots needs to be replaced...

Thanks to 3nity who made this possible! Have to start my second one soon

 

[LesPaul]

Another one...

 

[3nity]

@ lespaul.
WOw what a nice front panel design.
FOr grounding i suggest running 1 gnd from each board to star ground too.
Thanks

 

[LesPaul]

Thanks for the kind words. It's actually made with regular laser printer paper, and good old ironing. Costs about nothing I'll post a thread about this when I get the time.

My unit is really quiet, can't see it could get more quiet... Is there any other advantages with grounding from each board?

 

[buildafriend]

Dude, nice. You don't get any oscillations? I have my arranged nearly the same with nothing shielding the toroid. Maybe your shielded op xfrmrs are saving you... At least they look shielded.. Beautiful build congrats!

 

[LesPaul]

From my initial testing I got no oscillations, but I'll have a second test in a big studio on friday (since I have major problems with grounding in my own studio) so we'll see then.

3nity: grounding from each PCB added

Already started my second 4-channel. Just need to save some money to spend in Jeff's store...

 

[buildafriend]

 

[LesPaul]

Have you tried to measure the resistance in the pot? It should change when you turn it. One of my pots had unlimited amount of gain when turned CW or CCW. I changed it with a new one, and everything worked!