EQN build thread

[jrowell]

Nope.

That would be the filter switch.

Reread the posts, I have described the points in there. You will have to use the layout on the first page of this thread, as your designators will be covered with components.

Deep in an amp, so will post plot and pic tomm


James

 

[jrowell]

You got the non switch end right. The 12K end is correct.

James

 

[jrowell]

The correct link is labeled in green.

James

 

[canidoit]

Thanks James for fixing up the diagram!

I am very much considering doing this fix, but I just need some assurance before taking up some down time. Hopefully someone with more electronic experience than me and a regular here can confirm your fix and findings.

 

[jrowell]

No problem. I might be able to get a plot up today.

I would like some confirmation as well, if it is every card out there.

Perhaps someone with some raw cards could see if those two points are connected on theirs,

If we think it though we can probably check from the top of the card, without having to take things apart.

A simple resistance test will show it. Those two points need to be connected.

I have serviced hundreds of N*v-e modules over the last 15 years. I know what they are supposed to sound like, in all modes of operation, and condition. The first audio test of these lasted 2 seconds, because I knew something was wrong. I make a point of listening before testing.

1.8dB down below 500Hz as a shelf is highly audible. Setup a comparison test, as I have previously outlined, and you will hear it, if it is there. Trust your ears.

I located a missing connection that exactly coordinated with the symptom.

When I installed the connection, the symptom went away, and the performance returned to correct N*v-e specification, in all modes. That would suggest a correct methodology and result.

Unless this has been caught in a board rev, or I got two bad boards (very unlikely) it is safe to say they all do it.

Switching bands off cleans up the sound. It is just good practice. So I always start out that way. That is why I noticed it immediately.

That is why N*v-e's don't use center detent pots. Center is never center on detents, so use a normal pot, and switch the EQ band off if you are not using it.

James

 

[whomper]

Hey,

Starting my build and am in the process of sourcing parts. Anyone have a source for the 4m7 minis?

Could only locate 4m75 mini on Mouser, will they work just as well?

 

[jrowell]

Whomper,

Could you measure your cards on resistance between the LF pot wiper end of R10, and the LF switch end of C29?

Tell us what you get?

The 4M75 will work fine.

Any value from 4M7 to 10M will work there.

I like 4M7.

I will get you a part number for the 4M7 (likely cheaper)

Check those points for me.

Thanks,

James

 

[peter purpose]

RS 136-115P

 

[whomper]

Whomper,

Could you measure your cards on resistance between the LF pot wiper end of R10, and the LF switch end of C29?

Tell us what you get?

James,

Will be happy to, but my board is only 15% populated. Which components do you require on board for that test? Am looking to get a Mouser order in a matter of two weeks or so.

Thanks James and Peter for the part number.

 

[jrowell]

Any amount of components will do...

Checking the PN now,

James

 

[jrowell]

Mouser 660-CFS1/4CT52R475J for the mini 4M7.

These work well too, and we were getting the pots from there, so...

James

 

[whomper]

Any amount of components will do...

Well, checked resistance between the two spots (R10 and C29) and it reads nothing. Perhaps since there is little components in that path at the moment. Not sure if it means anything...

EDIT: just to be clear, no continuity.

 

[dmp]

jrowell, Thanks for sharing your findings on this!
This is why DIY is great.
The explanation makes sense looking at the schematics. I wouldn't hesitate to make this mod if the test points of R10 and C29 do not show continuity.
Here are the schems for anyone curious to see what he's talking about.
The left side shows the 1081 schematic with the BA205 LF module. The pot wiper is connecting to 'L' and the off positions of the switch. On the right is the BA205 schematic, showing the 'L' connection going to both the 12k (R10) and 10N (C29). Making this connection is the jrowell fix.

Now, why didn't I see this when I swept all the frequency bands in RMAA when I built my pair? Thanks again.

 

[jrowell]

Thanks so much, it is no problem.

Yes those points should be joined.

The board layout stock feeds the wiper to the 12K and the offs to the 10N.

This creates two point 'L' s on the schem.

They need to be joined. As do the one end of the 10N and the 12K.

DMP, unless you swept the LF band on off, it wouldn't show.

It should have shown on the other band sweeps, if you returned the LF to off.

James

 

[Beeswax]

Chaps - I've finished and calibrated accurately but experiencing a persistant wheezing, buzzing noise in the lunchbox.  Still present with the amp boards out.  Thoughts?

 

[peter purpose]

If in the last slot next to the power supply, try moving it.
If it persists I have no idea.

 

[dandeurloo]

I have noticed the low end roll off form the beginning.  I always thought I did something wrong that I could not track down.  I am gonna try James mod.  It seems very simple to do a nice 20 min fix!  I will report back. 

 

[haima]

Chaps - I've finished and calibrated accurately but experiencing a persistant wheezing, buzzing noise in the lunchbox.  Still present with the amp boards out.  Thoughts?

Perhaps some kind of missing ground connection? Maybe double check your transformer wiring? wiring to the pots? etc

Have you tried the EQN with all the other modules in the lunchbox removed? Maybe you've exceeded the current supply of the lunchbox?

 

[dandeurloo]

The mod fixed!  Thanks James great catch. 

 

[qmp audio]

The mod fixed!  Thanks James great catch.

I'm almost complete w/ my first pair of these ( just need to do wiring ).  I did also test continuity between (R10 and C29) and was null before i started the build.  So, just to be clear,  the mod is simply one wire between those two points?