neumann v475 pimping ...

[digichild]

[quote author="[silent:arts]"]ok, can't find an "A" version.

but staring at the PCB and schematics, I'm sure you can convert any V475-2 to the V475-2A (and now I'm sure they used the same PCB)

but anyway, the gain control is overrated :green:
(don't use mine very often)[/quote]

and how would you put in a gain control?
like-6db and -12 db and 0db?

using 12, 13 and 18, 19 for rg like on the v475-a?

 

[[silent:arts]]

for the A version ?
use Rg

as for the B & C version (more decks needed)

or an attenuator at the output
and and and :green:

btw, this is a "Dickreiter" (schoolbook) schematic, haven't seen it from Neumann yet

 

[digichild]

no for version 475-2, without an A...


:?: :?: :?:

the schematic is from kubi`s webside...

 

[[silent:arts]]

all the V475-2 I have seen have been the same like the A version.
they may have added the letters for the B or C version.
can you mail or post a picture ?

 

[digichild]

ok, i posted a picture now...

 

[mitsos]

Hi Volker,

I'm finally getting around to working on a V475-2B I got from a forum member. I wonder though, because my card looks a bit different from the schematic. For example, the input trafos are Haufe 90526 instead of 90456 like on the schemo. I know nothing about Haufe trafos, so I hope it's no big deal. The other obvious difference is that there are no 470uF electrolytics on the MO-11, like on the schemo and your pics. This is the strange one, because I see one (yes only one) empty pad smack in the middle of the little boards.

Also, can you tell me which side the pin count starts at?

thanks!

 

[[silent:arts]]

Hi mitsos,

nothing strange, what you have is one of the later ones.
the MO-13 is a little bit different too.

 

[mitsos]

OK, I figured out the pins.  I bought this as a "complete" but non-working unit.  There is obviously a problem with the resistor network. The guy I got it from had it working on protoboard then made a PCB and it never worked right. So I will re-do this as soon as I can get a boatload of 5K1 resistors.

But I do have some questions as I am not sure about these units.  The schematic has 2 balanced inputs... Pins 8A and 8C are input 1 and Pins 26A and 26C are input 2.  So as a simple example, if you were summing 2 balanced channels, you'd take the input from pin two of each XLR, run it through the 5K1 resistor and split each into Pins 8A and 26A?  And then both Pin 3s would go through the resistor to 8C and 26C? I wonder if I explained that right... Ch1 pin 2 would go to 8A and 26A, Ch2 pin 2 also. Ch1 Pin3 would go to 8C and 26C as would Ch2 pin 3. With the 5K1 resistors in series. Is this correct? I want to make sure I understand what this card does before I start trying to fix this.

Next question is on wiring and pan. Signal is coming in unbalanced from Pin 2 (pin 3 tied to pin 1) to a pot, and then a DP3T switch for L-C-R pan.  Working on a wiring diagram or a picture to show you how it was done here.  The panning never worked from what I understand.  Will get that pic up soon.  Anyway, a bit confused by this old german stuff, and would appreciate the help. Thanks!

 

[mitsos]

OK, here is the wiring diagram. The pot is to reduce level, and the switch to do L-C-R.... There is something wrong with the resistor pcb. The basic idea is what is in the diagram, times 8 channels. They all come together to the same mic cable and go to the same pins on the summing card. Then one left output XLR is connected to 12A (pin 2) and 12C (pin 3) and right output is connected to 22a ((pin2) and 22C (pin3).  Should these be left floating or should their pin1s be connected to 10C and 24C respectively?



The blue thing is the back of the 3 position switch.

V475-2B Schematic:
http://tinyurl.com/V4752BschematicKUBI

Does anything stick out as wrong right off the bat? Thanks in advance!

 

[digichild]

all the V475-2 I have seen have been the same like the A version.
they may have added the letters for the B or C version.
can you mail or post a picture ?

ok, here is the picture, sofar the amp runs very good, but no pad yet for damping...i need to put the pad!
my frontpanel hast already a hole and letters for it
hmm, picture is small, here is a good picture:

http://dl.getdropbox.com/u/163999/V475-2.pdf

 

[digichild]

???
bump

 

[[silent:arts]]

put something like this at the output:
http://www.groupdiy.com/index.php?topic=2229.msg27326#msg27326

 

[digichild]

i know, i should have investigated better before i ordered my frontpanel  :

situation is like this:
i have a 4x toggle switch with 3 positions http://www.reichelt.de/?;ACTION=3;LA=2;GROUP=C21;GROUPID=3275;ARTICLE=13173;START=0;SORT=preis;OFFSET=1000;SID=26r572d6wQARoAADHMmI8f47de85df420cc236d23e1d7c1d03da2
i have 3 position on my frontpanel 0db, -6db, -12db

oh, and one more thing:
my poweramp is a hi-fi, so i have output unsymetrical...maybe this makes it easier
for the toggle switch i want to use

i also need directions in calculating the resistors, please 

 

[clintrubber]

Does anyone know if these separate 'sections' in the output transformers (as indicated by 'a'&'b' and/or 'c'&'d' in the pics above)
are just separate coils for the lowpass filter that for convenience happen to be put in the output-transformers
or
are they magnetically coupled to the output-windings ? (and constituting a feedback loop then 'over' the output-amplifier).

Thanks,

  Peter

 

[clintrubber]

Does anyone know if these separate 'sections' in the output transformers (as indicated by 'a'&'b' and/or 'c'&'d' in the pics above)
are just separate coils for the lowpass filter that for convenience happen to be put in the output-transformers
or
are they magnetically coupled to the output-windings ? (and constituting a feedback loop then 'over' the output-amplifier).

Let's bump...

... but assuming the usual high level of German attention to detail and drawing it like they did
I assume these coils are NOT magnetically coupled to the windings of the actual output-TX.

But please correct if needed.

Bye,

  Peter

 

[[silent:arts]]

Peter, let me know how I can measure this and I will do

 

[clintrubber]

Peter, let me know how I can measure this and I will do

Hi & thanks for the offer 

Assuming you all have removed/skipped the LPF, the coil under discussion can have two completely floating connections now (depending on how you did it; let's assume you completely disconnected the coil).

'The Test' can be easy then: run the amp-without-LPF with a test-signal
and check if there's anything of that signal appearing at that floating winding. Not unlikely there will
appear a tiny bit, but based on the level of it we might be able to conclude if that's some leakage, feedthru or anything OR an intended signal.

I expect it'll be the former (so no intended magnetic coupling), otherwise the schematics would have been drawn in another way. But one never knows, so if you've got those spare minutes then yes please.


It's out of a bit more than curiosity since an alike discrete buffer amp is also found in the various broadcast distribution amps and over there there's no such eventual across the amp feedback by means of an added TX-winding.

Thanks !

  Peter

 

[mitsos]

Hey does either of you guys have any idea on my question on the wiring above? I still haven't succeeded in etching my resistor board but I keep on trying..  I'm not too good at it yet  :

thanks guys!

 

[helterbelter]

Hi guys,

Volker, a question....
The feedback rotary switch you used... Is it a "shorting" type ?

I can imagine that when a break-before-make is used, the audio will be full gain while switching ?

I got mine up and running a while ago, but the rotary switch sucks, and I need a replacement, don't know which one I should buy.

Would this one be a good option ? http://cgi.ebay.nl/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=290291135249

thanks in advance,

Paul

 

[[silent:arts]]

... The feedback rotary switch you used... Is it a "shorting" type ? ...

yes

the switch in your link is "unterbrechendes Schaltverhalten", which means non-shorting (BBM)