Replacing Neumann card with Lawo (Summing Mixer)

[kike]

Hi guys

I need to replace a Neumann v475-2A card with LAWO DV975-4 on my existing summing  mixer

but i have 5.11kOkm resistors on the summing network  in there and lawo requires 6.81kOhm.

Do I need to replace these resistors or can I leave the 5.11kOhm?
What will happen if i leave 5.11kOhm?

I have found this info on removing Filter on the Lawo card:

HPF Adjustments for the LAWO DV975-3.

C18, C19, C22, C23 are the highpass filters, increase the values for more low end.
C11, C12, C14, C15, C16, C17 are parts of the lowpass filters, remove them and insert 10nF per channel for C11 and C12 to avoid oscillations. Replace L1 and L2 with a wire bridge.
That should give you around 50kHz at the upper end of the bandwidth

as for recapping...it's only those two dark red caps that need to be replaced...



Can someone tell me the values i need for C18, C19, C22, C23?

Thanks

 

[My3gger]

Why do you want to replace Neumann? Forum has at least some information about Lawo values.

 

[[silent:arts]]

You can leave the 5K11 but won't have unity gain.

 

[kike]

Can I put 1.7kOhm at the output of resistor network? (Between the resistor network and the lawo card)

Would that work?

I have searched the forum but didn't found information about these cap (C18, C19, C22, C23) values just to increase them.

Left    Right
C18  -  C19    0,68u
C22  -  C23    0,68u

I have attach schematic

 

[[silent:arts]]

Can I put 1.7kOhm at the output of resistor network? (Between the resistor network and the lawo card)

Don't know if that works. Try it. You have the fine trim too if unity gain is important to you.

Why do you want to change the filters?

 

[kike]

neumman has a rolloff at around 50hz and i don't want that.

I have found on the vintagemaker.net illustration of frequency response and appears that lawo don't have that.

But I have to pimp lawo to do that, I think?!

Sorry, wrong file above

 

[[silent:arts]]

neumman has a rolloff at around 50hz and i don't want that.

Did you hear this with your card? Did you measure it?
Or is it some internet rumors?
A healthy V475 is flat down to 40 Hz and is -10dB at 10 Hz without any modification.

The LAWO is flat down to 40 Hz too except the DV975/6 is -2dB at 40 Hz.

 

[kike]

Hmm

So, your advice is that I don't have to change anything?

I have red that v475-2A has a rolloff and that 2-C and 2-B don't.

That is why I wanted to change it.

I cant find 2-C or 2-B so i decided to go for lawo.

And didn't measure it, noob, what to say

 

[[silent:arts]]

Try it unchanged first. Of course replace all electrolytics, they are old.
If you are missing any low end you can still mess with the filters.
But first make sure everything works fine with the stock values.

 

[kike]

Oh, it works.
I am using it for about a year or so.
But didn't change the caps. I will do that.

Thanks for the help.

One more question, when I shut it down, it starts popping sounds until all the current run out from the power supply.

Is there a simple way to fix that?

 

[andow]

I also was overthinking this frequency response thing way too much. In the end I just left it as is and it sounds wonderful...