Nuemann V475 Summing - Again! - Need guidance

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whiskeynipple0088

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Joined
Jul 28, 2013
Messages
32
Location
Maryland - USA
Hi All and thanks!
yup Im late as hell to this party!

Sorta a newbee but have repaired many electronics (tv, refrigerator, dryer, mixer, A/D converter etc....    I can solder)
I can repair alot of electronics but and just starting to understand what each componant does (thanks Ethan Winner for his Hardware Tutor).

Please forgive me, I know this topic exists and I saw alot of disscussion, but alot (and I mean a lot,...  all Prodigy Pro) links are dead.

Ive seen the work by Vintage maker, Volker, Crostov, Studio B and Holger......    I want in. (man what I wouldnt give for a diagram or schematic of some of those extra controls like centering or gain - meters... oh my. or the pcb Holger has at the dsub connection)
I have been educating myself on the subject and I know someone has done something nearly (Holger, Studio B) identical to what I want to do.
After reading too many threads I think I have confused myself. It seemed much more clear reading NYD, Fred Forssel and Ethan Winner info....... (yeah I know ,... why dont you just do that then!)
Also looking for where things go in the signal chain.
I will only be  using 4 stereo outputs from my daw for now - so I need to be able to change the gain (I think) when I add more and more outputs from my daw.

what I would like to build: Summing amp.
16 (or just 8...) Stereo inputs (all with center switch or not since I have 4 mono)
4 Mono (centered) inputs
2 Send /Return (not sure if that should be before or after the amp)
1 (do I need?.... I would like) Gain
can I get multiple outputs directly from the amp? (if not Ill use a re-amp in another box)

the other box Id like to build: dont know the proper name for it BOX (this would go after the summing amp - believe I will need a re-amp for this)
3 inputs - selectable by switch
2 (stereo) meters
3 Monitor outputs - selectable by switch
2 Headphone outputs - with gain knob
2 Record outputs
1 talkback mic - direct to headphone only, with gain knob


the second box is not priority at this moment

I ordered Model: 10657 V475-2

If you know a link to a good 'heres step by step what I did' link, please pass it on.

thanks again and great work out there guys
chris
 
I think the first thing you need to do is get your thoughts in order because some aspects of what you describe sound more like a mixer than a summing box plus the 475 is a virtual earth mixing amp so its not quite the same as a classic passive summer. So some questions:


1. Send and return. What is this for? Is it meant to operate on the overall mix or on a per input basis?

2. Gain control - is this an overall master or a per channel gain control

3. What does a 'centre' switch do to a stereo channel?

4. How do you intend to use it? Is it basically going to be fed with 8 stereo stems?

Cheers

Ian
 
yeah a bit confused me too :)))
send return - do you mean channel insert section??? that's where you insert external hardware?

center switch - mono switch?

the other box as i suppose it's gonna be monitor controller, something similar to Mackie Big know, or central station.
 
firstly thanks for taking the time to reply guys.

yes I admit I am not the most forum savy when it comes to explaining myself - I often spend too much time re-writing my posts - prolly making them worse.....

ruffrecords said:
I think the first thing you need to do is get your thoughts in order because some aspects of what you describe sound more like a mixer than a summing box plus the 475 is a virtual earth mixing amp so its not quite the same as a classic passive summer. So some questions:


1. Send and return. What is this for? Is it meant to operate on the overall mix or on a per input basis?

2. Gain control - is this an overall master or a per channel gain control

3. What does a 'centre' switch do to a stereo channel?

4. How do you intend to use it? Is it basically going to be fed with 8 stereo stems?

Cheers

Ian
Olegarich said:
yeah a bit confused me too :)))
send return - do you mean channel insert section??? that's where you insert external hardware?

center switch - mono switch?

the other box as i suppose it's gonna be monitor controller, something similar to Mackie Big know, or central station.

ruffrecords & Olegarich,
1. send return - yes overall mix -for stereo compression, stereo eq etc...
2. Gain for stereo out (or should I say)'resistor selector'? (Im a bit confused on this part......  see below)
3. centre - this would give me the ability to make any channel dead centre (mono) - Im not a pro I may be wishing too much - so maybe it makes more sense to just have 4 monos?
4. At first just 4 stereo stems then 8 and ultimately 12 or 16.
5. 'the other box' - yes Olegarich similar to central station (but better cleaner and more taylored for my use,  ...not a priority right now - just want to plan for it as needed)


Things Im really am having trouble rapping my head around is the input resistor network:
6. From what Ive read the more inputs I have changes the ohms when it reaches the amp. (correct?)
7. So if I build it to take 16 stereo (32 mono) but only plug in 4 I will need to make up the gain loss (or have a switch to switch between different resistors depending on inputs used?
8. I understand this amp can handle 100 ohm load (50 each side). Is the idea to obtain 100ohm load when the summing network reaches the amp?
9. Some people use 2k, others 5k or 10k in their network - I think this is realated to #8 above?

again thanks - I hope this makes more sense now
chris

 
whiskeynipple0088 said:
ruffrecords & Olegarich,
1. send return - yes overall mix -for stereo compression, stereo eq etc...
2. Gain for stereo out (or should I say)'resistor selector'? (Im a bit confused on this part......  see below)
3. centre - this would give me the ability to make any channel dead centre (mono) - Im not a pro I may be wishing too much - so maybe it makes more sense to just have 4 monos?
4. At first just 4 stereo stems then 8 and ultimately 12 or 16.
5. 'the other box' - yes Olegarich similar to central station (but better cleaner and more taylored for my use,  ...not a priority right now - just want to plan for it as needed)


Things Im really am having trouble rapping my head around is the input resistor network:
6. From what Ive read the more inputs I have changes the ohms when it reaches the amp. (correct?)
7. So if I build it to take 16 stereo (32 mono) but only plug in 4 I will need to make up the gain loss (or have a switch to switch between different resistors depending on inputs used?
8. I understand this amp can handle 100 ohm load (50 each side). Is the idea to obtain 100ohm load when the summing network reaches the amp?
9. Some people use 2k, others 5k or 10k in their network - I think this is realated to #8 above?

again thanks - I hope this makes more sense now
chris

For the passive summing network you can use 5k1 resistors for L and R signals.
After some tests if I want to have the same level of the MONO signal (dead centre) I'll use the same resistors value (5k1).

So, you have to use a 2x 5k1 resistor network for L or R (stereo) signals and 4x 5k1 for mono.
If you want you can use a selector.

I think v475 can handle up to 100 inputs (with 5k1 resistors network).

The value of the resistors for a passive summing network for v475 is 5k1 for sure (check the datasheet).

Neumann V475-2 hasn't Rg, so you can't regulate the gain of the board (you have only a trim for each channel so you can set the total fixed gain for the card).
I usually set them high (+2-3dB) and use a passive attenuator to set the total gain of the summing mixer.

A.
 
thanks Aleguitarpro
so if I understand correct:
all inputs for L or R get 1x 5k1 on + (positive) and 1x 5k1 on - (negative). The sum connects directly to the v475 (no shunt resistor?)
inputs for mono get 1x 5k1 on + and - , connect to the end of the L sum and 1x 5k1 on + and - connect to the end of the R sum. So Im just feeding the signal to both sides with resistors respectively (+ and - x2 connections = 4 resistors).

can you elaborate more on this:
"Neumann V475-2 hasn't Rg, so you can't regulate the gain of the board (you have only a trim for each channel so you can set the total fixed gain for the card).
I usually set them high (+2-3dB) and use a passive attenuator to set the total gain of the summing mixer."

So the trim is used to make up the gain loss in the summing network?
Why do some use a 'shunt' resistor at the end of the sum?

I think I want a fixed output level - equal to what comes in. Is there a reason Im not seeing for wanting to attenuate?
I thought thats why I would need a switch to select the correct shunt resistor depending on the number of inputs.

BTW: my motu is 600ohm at the outputs

also does anyone know of the data sheet in english?

again thanks
chris


 
[silent:arts] said:
Don't mix up passive and active summing.

Passive summing needs a shunt resistor.
The V475 is an active summing device.
ok that makes sense now - thanks for clarifying
btw, great work!
I was planning on using your PSU PCB - is it in stock anywhere or do I just etch my own?
thanks again
 
So ive order boards from Ian - and received my V475-2 from Schmitronics.

A few things I could use help with are:
POSPSU - BOM? - looks like this has been used in both the V475 builds and GSSL - which use different voltages. And it provides only a single voltage (from what i understand). Is there a BOM for various voltage requirements (as GSSL is my next build) (i only found something by tobi P). I would like to order a few boards for future builds.

Case - frontpanels.de does great work but Im in the states - anyone have experience with anyone on this side of the pond? or lower cost alternatives.

V475 - removing the broadcast HPF's - I have gone through the 'pimping V475' thread. I have the schematic. My V475 has no labels on the board so locating the correct resistors and holes is concerning me. Am I missing a thread thats out there? (I attached some pics of my V475-2). From what It seems Im left to trace the signal path to said resistors etc.

V-475 - Still sorting Pinouts from threads - if anyone has that info at hand that would be a help. - - inputs 10,11 20,21 - - outputs 6,7 24,25 - - power + 1,2 3,4 - - power - (negative) 8,9,14,15 16,17,22,23. Is that correct?

thanks
chris
 

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OK, starting to get a clearer idea. You send/return is really just an insert point where you can insert outboard gear into the signal chain. I often get confused when people say send/return because, coming from a mixer background, it makes me think of AUX sends and returns which are certainly something completely different.

For your output gain control I guess a stepped attenuator would be the sort of thing you need. I designed one for use on the output of a summing mixer which should do the job. Details here:

http://www.ianbell.ukfsn.org/db25/oneKsteppedATT.pdf

Cheers

Ian
 
ruffrecords said:
OK, starting to get a clearer idea. You send/return is really just an insert point where you can insert outboard gear into the signal chain. I often get confused when people say send/return because, coming from a mixer background, it makes me think of AUX sends and returns which are certainly something completely different.

For your output gain control I guess a stepped attenuator would be the sort of thing you need. I designed one for use on the output of a summing mixer which should do the job. Details here:

http://www.ianbell.ukfsn.org/db25/oneKsteppedATT.pdf

Cheers

Ian

thanks for the reply Ian,
Yeah the idea was insert not aux.  But I think it is more usefull in the long run for me to handle patching with a patch bay as I will need that as my outboard gear grows.

The bigger picture is to have the final stereo summed mix go to a box that will output to several outputs - but this will be handled at a later date

thanks to you and Aleguitarpro - (and receiving my V475) Im getting the picture - turn up the input trim - dial it back with the attenuators.
does it make sense to do 2 mono attenuator or a single stereo?
So your link to the attenuator... - is that the one you designed but is sold by goldpoint?

thanks
 
whiskeynipple0088 said:
does it make sense to do 2 mono attenuator or a single stereo?
So your link to the attenuator... - is that the one you designed but is sold by goldpoint?

thanks

The only reason I can think of to do separate mono stepped attenuators is to make tweaks to the final stereo image but the steps are probably too coarse to do that and the stereo image ought to be correct before it reaches the summer so on balance I would say go stereo.

I have no association with goldpoint. As far as I know they do not have a 1K version of their stepped attenuator. However, you can use their blank switches to build my 1K attenuator. Their designs use expensive 0.1% tolerance resistors in part yo make sure the steps are all exactly the same. My design uses standard low cost 1% resistors. The means the steps are not all exactly the same but most are within one tenth of a dB of each other which I suspect is undetectable.

Cheers

Ian
 
thanks Ian - BTW received your boards today - thanks
been making some progress -

Pinouts: http://german-modules.de-blog.jp/photos/uncategorized/2008/06/06/v4752pinout.jpg

If someone could give these parts a once over, I would appreciate it.

power toggle switch: http://www.mouser.com/Search/ProductDetail.aspx?R=DK284-73virtualkey69100000virtualkey691-DK284-73

Line toggle switch (for mono): - question: should I use 2 or 3 position toggle? - 3 position: http://www.mouser.com/Search/ProductDetail.aspx?R=A201SYCB04virtualkey50660000virtualkey506-A201SYCB04

Dsub 25: http://www.mouser.com/Search/ProductDetail.aspx?R=10090099-S254VLFvirtualkey64910000virtualkey649-10090099-S254VLF


POSPSU: still cant bridge the gap between the PCB and materials based on voltage requirements or how to size the transformer. Im clearly missing something that's right in front of me.

attached is a preliminary half rack case design.
 

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getting closer on the POSPSU

Heres the BOM at mouser for the POSPSU:
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=3e80c72603
(Conrad doesnt ship to the US)
I had to find an alternative for the 'faston connector' & 'heatsink'

Im still not super confident in the transformer & heatsink:
trans:
http://www.mouser.com/Search/ProductDetail.aspx?R=182K12virtualkey54600000virtualkey546-182K12
heatsink:
http://www.mouser.com/Search/ProductDetail.aspx?R=513002B02500Gvirtualkey53210000virtualkey532-513002B25G

could someone please verify these two or advise otherwise

thanks
 
the heat sink is good...

could someone please recommend a transformer for the POSPSU for 24V. I just don't know enough about them. Some have 2 secondary voltages and others have 1 - prices are any were from $20 to $50. I don't know which one to get.

thanks
 
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