V475 translation + summing network

[phenomental]

I want to jump in and started also building a summing amp with a 475-2A.
I'd like to know if there are really big sound differences between the 475 versions?

And if so how about this:

I'd like to use some air gap switches (Neumann relais card RK12) for jumpering the on board lpf. So I could switch between modern and vintage freq characteristics. :wink:
Does it make sense anyway regarding the sound difference?
Would I get losses due the cabling of approx. 1 m length?

Which one is the lpf board anyway? I am not THAT good in reading schematics...

Big thanks in advance!

 

[phenomental]

Hi Volker (silentarts) !

Thanks a lot for the resistor list for Rg.
How did you manage to get exact those values?
I am thinking of using trim pots in the approx. range - good or bad idea?

Is the wiring cable quality/length sensitive to signal quality? My understanding is that Rg is just an electronic signal lead - not an audio signal lead. Am I right or wrong?

Patrick

 

[phenomental]

Hi - finally I got mine up and running. Anyone wants to have a look? www.phenomental.com/diy/diy.html

I just ordered a dual layer plate which will look really sexy. It'll come next week - I'll post new photos then.

I got a 475-2A which needs different resistor values for Rg e.g. V +6dB = 15 KOhm.

Can anyone help me with the formula from Neumann?

Here it is:

V (dB)=20log (Rg(KOhm) +2 / 2Re(kOhm) * 1.25


:roll:

 

[phenomental]

Great - thanks!

 

[laitue5]

phenomental!
What?s this:

?
:shock:
Is it something you wanna talk with us?

:green:

 

[phenomental]

Yeah, why not? :grin:

I was not sure about posting it here since it is not all *real* DIY. I used mostly common components form the 80's radio era in germany; and you guys brought me to the idea since I had no idea about 475s before I read your articel and I was seriously thinking about buying a new summing device since I just sold my desk.

So the first statement: it sound stunning! I am really happy with the sound reg. it's resolution and roomy depth. Breathtaking!
The problem is that we have to convert after the analog chain to digital which is - even if it is done by one of the best converters available - still a breakdown in spaciness and depth and overall presence of even the not so loud signals.
A LOT get's lost when returning to digital.... when some has experience with some better A/D converters than Rosetta: please feel free to tell me.... :wink:

OK- back to the device:

What you see on the photo is a 32-in-2 summing device consisting of a Neumann 475, Neumann Power Supply ( though I had to build an 27,5 V AC converter on my own, well THAT is DIY! )
two Telefunken splitters and two relais cards plus another relais card with dampening resistors.

So what is this good for?

Well, I was thinking of having some more opportunities despite just summing 32 channels.
What I liked mostly about my previous console before selling was the easy soloing and muting it offered.
Therefor I used 4 switches for muting 4x 8-groups which still gives me flexibility for listening e.g. drums, effects, vocals, instrument groups soloed.
Since the last 8-group of channels was thought to be for FX I run them through a dampening relay section which damps them down -15 dB by default. When adjusting the reverb sound I want to hear it loud therefore it is switchable for two stereo returns.
Two Mono switches allow channels 1-4 to be mono. Enough for BD/SN/BASS/Vocals. Solved by laying a parallel signal lead before the 5k1 resistors on the summing chain.
Then there is a insert path for the stereo sum which allows to bypass inserted compressors/signal processors.

Well, that's it... :wink:

The funky stuff was the wiring and soldering on the relais cards since the legs are very close together.

Couldn't be happier - just wann go for a *real* SSL summing comp now. (it never stops, but I guess you know)

P.S. the dampenig card with the carbon potentiometers was crap. I soldered some 1% tolerance resistors directly on the multi-switch.

(BTW: the summing resistors are 0.1 % . I think I can hear it... )

 

[laitue5]

Thanks :thumb:

 

[hejsan]

Hi. I have a 475-2 now, so I have two questions now.

phenomental: Where did you get those multi-pin connectors? What are they called? are they available gold plated?

Someone: What effect would it have if all my line outputs are single ended (read unbalanced)? All bad? Would I need different resistors? Would it work at all?

Thanks,
hejsan

 

[phenomental]

Hi hejsan,

in Germany you can get them from conrad or schuricht.

http://www.distrelec.com:80/ishopWebFront/catalog/product.do?id=01&node=aeacabacacaa&series=2

They belong to the DIN 41 617 norm.

I think you can connect unsymmetrical lines to the summing amp.
I'd connect the ground of each line to the phase reversed in.
Resistors should be the same.

Patrick

 

[hejsan]

Thank you phenomental!

 

[Moby]

My v475 summing box is almost finished :green:
BTW, I don't know how to terminate the output transformers, so the unit can be well matched with 10k equipment. I was thinking about 330+330 ohm :roll: Any suggestion :?:

 

[[silent:arts]]

You don't need to terminate the output, it will work well with 10K

 

[Moby]

Thanks. BTW I'm asking because I used to see transformer output devices asking for proper termination. Especially when transformer is "light" with Henry's It's not too hard to measure response and do some listening , but will like to know what Neumann say about.
What's the situation in Neumann console summed with V475?

 

[[silent:arts]]

I measured my V475 summing box with 600R and 100K - no problems.
Neumann said it have to be OVER 300 Ohm.
with the Neumann consoles I know there is no problem with driving a Pro Tools or Digas AWS.[/quote]

 

[Moby]

Thanks, good to know you're experience. :wink:

 

[digichild]

[quote author="[silent:arts]"]
while I have the 475-2B I decided to have gain switched (-6, -4, -3, -2, -1, 0, +1, +2, +3, +4, +6 dB).
still waiting for the case [/quote]

hi volker,
i am using a 475-2c in my summing box...which sounds pretty nice sofar...
i want to add the possibility for a simple gain control - can i use a pot of 15k for Rg?

 

[digichild]

hmm, also seems hard to find good pots like alps in 15k...any other ideas?
i dont want to put a switch...i like more the idea to have a pot...maybe put a resistor of 3 k or 5k in serie?

 

[[silent:arts]]

I don't think a pot will work very well.
IIRC the V475-2C needs 4 RGs, 2 per Channel.
the tracking between the deks of the pot would need to be VERY close, not the 10-20% you have on normal pots. the law is another issue ...
take a rotary switch and match the resistors, much more easier :grin:

 

[digichild]

right-it need 2 rg...thanks for your help

 

[Moby]

[quote author="[silent:arts]"]I measured my V475 summing box with 600R and 100K - no problems.
Neumann said it have to be OVER 300 Ohm.
with the Neumann consoles I know there is no problem with driving a Pro Tools or Digas AWS.[/quote][/quote]
I did some listening test of my summing box and found that there is some sound changes when load impedance is 600 or 10k :roll: For me, the best solution is when i terminate the output of the Neumann with the 600 ohm :wink: