31267 optimal wiring in the solid state Pultec

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Purusha

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Jan 14, 2006
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Hi,

I have a few Marinair 31267 wired as 6db step down in my Nevetec but I can't
restore enough gain with Fabios Neve output driver stage vs true bypass so I need to
find a solution for this gain loss.

Does anyone have a wiring info for 31267 wiring (1:1)?
 
look at JML http://www.jlmaudio.com/Neve%20transformer%20info.htm

or this thread http://www.groupdiy.com/index.php?topic=7126&highlight=31267
 
31267info.jpg


Can someone please confirm if I got it right?

10K/600Ohms -13db:

pin 2 = XLR hot
pin 5 = XLR cold
pin 6 = XLR gnd
pin 3 & 4 tied
pin 7 & 8 tied = to EQ input
pin 9 & 10 tied = to EQ gnd
1.5nF cap across pins 7&8 + 9&10


10K/2K4 -6db:

pin 2 = XLR hot
pin 5 = XLR cold
pin 6 = XLR gnd
pin 3 & 4 tied
pin 7 = to EQ input
pin 10 = to EQ gnd
pin 8 & 9 tied
1.5nF cap across pins 7 and 10 ???
 
Any 31276 experts here?

I would like to know if wiring it 1:1 would be too much colouring in a bad way for the hot mixes passing through.

What is the difference in those two -6db step down wiring options?
 
Yes, but it wouldn't make any sense.

Tell ya what, I'll explain it if you if you promise to book an Electronics 101 class next quarter at the local free college.

I was looking at your account, and you only have 9 "newbie" questions left before your membership expires.
:razz:
 
[quote author="CJ"]
I was looking at your account, and you only have 9 "newbie" questions left before your membership expires.
:razz:[/quote]

LOL :green:

Perusha,...google and the METAs are your friend.
 
[quote author="Purusha"]
Can someone please confirm if I got it right?
[/quote]

Correct - not sure about the capacitance value for the Zoebel, but you should be able to find that out, or test yourself with a sig. gen. and a 'scope.

I would like to know if wiring it 1:1 would be too much colouring in a bad way for the hot mixes passing through.

Why? Because of the level at the input or because of impedance mismatch? Are you using the 31267 to make a 600 Ohm input look like 10K?

What is the difference in those two -6db step down wiring options?

This is something Id like to know more about myself - your ratio is the same, but I gather your copper resistance will halve on primary and secondary, but your capacitances and inductances will change as well? And as for leakage? I'll need to read up on that....
 
Why? Because of the level at the input or because of impedance mismatch? Are you using the 31267 to convert a line output to 600 Ohms?

Hi Roddy, I am concerned more about the sound than anything else. But I know it's all connected
in a way. First I wanted to use the LL5402 for the input but I found out that it takes away the bass
cause the impedance was wrong for the solid state circuit. I am still very much in the dark about
the impedance thing. What I need is to raise the input level into the passive Pultec section but I don't
know if I can go wrong with raising it to 1:1. I need this EQ for the mix buss where signal can be
very hot and I don't want to have too much colouring happening.

I can always do the listening tests but some knowledge in advance won't hurt anyone.
 
As far as I remember, the Pultec is designed for matching impedances (like old-fashioned equipment).

You'll need to check this yourself, but I seem to remember it is set to have a 600 Ohm input impedance which should be connected to a 600 Ohms source.

So, your 31267 will make the 600 Ohm input look like a 10K (or whatever you choose) input if you look into the transformer. This will keep your main mix output happy.

If you use a 1:1, then you risk loading down your main mix output which could result in bass loss and other problems.

People here have already discussed the Pultec eq circuit - my memory is not great and I can't remember it that well. I think Jakob stated the minimum input impedance it would give at a particular setting which is important. Also the maximum level loss. I would think you would be ok with that setup though - the BA283 should give you enough make-up gain.

Roddy
 
31267info.jpg


OK, it seems I have only two options. -13db and -6 wiring they all see the 600Ohms in the 31267 out.
I tried the -13db and I couldn't make up for the lost gain even when B283 was adjusted to give the maximum gain.
I guess I'll have to try the -6db with 2K4/600 setup.

Thanks Roddy, you really are a gentleman :wink:
 
I'd maybe check how much gain you are getting with the BA283.

Read the old posts here about the Pultec circuit.
 

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