Adding line input Transformers to Neve 82 series

[cariocaman85]

Dear all,

I'm lucky to mix trough a well maintained Neve 8232 and I like the sound of it but I was wondering if I could lean toward an optional more "organic" sound with a small option:
I'm thinking of adding switchable transformers (Carnhill VTB2281 600:600 bridging tranny) in front of the line inputs of the console (which has transformerless line inputs).
I would driving them from the outputs of an Antelope Goliath HD and switch them on at will so they could be inserted in front of the line input.

What do you think of this idea? I know it will not get this console in the ballpark of the 80 series, but I'm just looking to give it a "beefier" sound option. Would it work in your opinion?

All the best,

 

[cariocaman85]

Or maybe VTB 2280 for a gapped one ?

 

[ruffrecords]

The VTB2281 is an output transformer so it is not what Neve would have traditionally use don a line input.The 31267 was the standard line in transformer but they were wired 10K:600 but they can be wired 10K:2K4. Wj]what you really need is a 10K:10K input transformer.

Cheers

Ian

 

[cariocaman85]

Thanks a lot Ian!

So the VTB 9071 10k;10k would be better for this application?

Could you please explain why a 10k:10k would be better suited than a 600:600? The ratio is the same but the load is different?

Thanks!
Best,

Rémi

 

[ruffrecords]

Basically yes, the ratio is the same but the load is different.

Neve line inputs were/are 10K line bridging. This means the input impedance looking into the input is 10K. Such a bridging input presents a minimal load to most outputs which means if you want you can safely drive several bridging inputs form a single output.

In the days before Neve, many audio circuits were 600 ohm out and in. A line input would present a 600 ohm load to a source and the sources were also designed to have a driving impedance of 600 ohms so you could only connect one output to one input (and you lost 6dB of level when you did it). Onece 10K bridging inputs started to be used, the need for 600 ohm outputs declined with the result that many of today's interfaces will not drive a 600 ohm load

Today you sometimes find some vintage devices with 600 ohm input (e.g Pultec EQP1A) but some devices maybe unable to drive them satisfactorily so if you want a line input to bee safely driven by any device, 600 ohms is not your best choice.

Cheers

Ian

 

[cariocaman85]

I'm getting confused... here it is said that Marinair LI 31267 is 600:600 in 1:1 configuration ... but it is also said that the replacement part is VTB9046 which is 2.4k:2.4k in 1:1 configuration...

I think I missed something...

 

[cariocaman85]

Basically yes, the ratio is the same but the load is different.

Neve line inputs were/are 10K line bridging. This means the input impedance looking into the input is 10K. Such a bridging input presents a minimal load to most outputs which means if you want you can safely drive several bridging inputs form a single output.

In the days before Neve, many audio circuits were 600 ohm out and in. A line input would present a 600 ohm load to a source and the sources were also designed to have a driving impedance of 600 ohms so you could only connect one output to one input (and you lost 6dB of level when you did it). Onece 10K bridging inputs started to be used, the need for 600 ohm outputs declined with the result that many of today's interfaces will not drive a 600 ohm load

Today you sometimes find some vintage devices with 600 ohm input (e.g Pultec EQP1A) but some devices maybe unable to drive them satisfactorily so if you want a line input to bee safely driven by any device, 600 ohms is not your best choice.

Cheers

Ian

Thanks a lot Ian for this explanation.

If I understand well, driving 600 load or not depends on my DA, not on the Neve?
I would be safe with 10k, but not sure with 600? Plus there might be a 6dB loss?

 

[ruffrecords]

I'm getting confused... here it is said that Marinair LI 31267 is 600:600 in 1:1 configuration ... but it is also said that the replacement part is VTB9046 which is 2.4k:2.4k in 1:1 configuration...

I think I missed something...

The first link is completely wrong. I don't know where is gets the 600:600 from but that is quite wrong for a 31267. The 10468 which is the traditional Neve mic input transformer can be wired 1K2:1K2 but not 600:600. The VTB9046 can be wired 2K4:2K4 (as can the 31267) and this will do the job just as well as a 10K:10K input transformer.

Somewhere I have the original drawing from when I was at Neve which shows the 31267 wiring options. If I can find it I will scan it and post it here.

Cheers

ian

 

[cariocaman85]

Thanks for sharing your knowledge Ian!

So you would advice for a VTB9046 2k4:2k4
or a VTB9071 10k:10k?

What would be the change in sound in your opinion?

 

[ruffrecords]

Thanks a lot Ian for this explanation.

If I understand well, driving 600 load or not depends on my DA, not on the Neve?

Correct

I would be safe with 10k, but not sure with 600? Plus there might be a 6dB loss?

Correct but the 6dB loss is unlikely with anything other than a few vintage devices.

Cheers

Ian

 

[ruffrecords]

Neve transformer winding drawing attached.

Cheers

Ian

 

[cariocaman85]

Thanks a lot!!!

So the vtb9046 would be the closer to the "original" even if no transformer was originally intended to be on the line input of 82 series.

 

[ruffrecords]

Thanks a lot!!!

So the vtb9046 would be the closer to the "original" even if no transformer was originally intended to be on the line input of 82 series.

Yes.

Cheers

Ian

 

[Matt Syson]

A transformer has no 'impedance' of it's own but all are optimised to best suit the requirements of it's original user/specifier. So to feed signal into a long piece of cable (significant capacitance between hot and cold legs and ground) lower resistance windings are more typical. Of course all transformers have some loss due to winding resistance and the 'power' required to magnetise the core of an 'output' transformer will lose a bit more power than one with a smaller core and possibly thinner windings but tighter coupling. There are always multiple compromises to be made so trying to second guess how any particular transformer will perform is very difficult as it depends on the characteristics of the sending amplifier, the cables before and after the transformer, and the characteristics of the input stage. Passive EQ circuits like the Pultec EQP1A as mentioned by Ian do not work correctly unless they are FED from a 600 Ohm output. They are 'close enough' when fed from less than 600 Ohms but the boost and cut are not strictly correct. If fed from a TL071/072 from an insert send for example the loading will cause increased distortion from the TL0 amplifier. The many internet threads waxing lyrical about 'wonderful transformers' usually fail to define the circumstances where they are being used, to specific 'pieces of gear.

 

[cariocaman85]

Thanks a lot!
I will order a couple of VTB9046 and try them!

I will feed them from Antelope Converters, 56Ohm outputs.

 

[nielsk]

Matt,
What about strapping a 10k resistor across the 600 ohm input of a Pultec EQ?
This works great on limiters (as used by Gates) to make them Bridging In, does it negatively affect the EQ operation?
Might work for line inputs as well...

 

[Matt Syson]

Just putting a 10K resistor in parallel with the input of (for example) Pultec EQ or accurate clone serves no purpose except additional loading of the amplifier DRIVING the EQ. 'Strapping a 10K across the input of a gates limiter' why would anyone do that? Unless it is an attempt to fudge some other aspect it is pointless. The trend to emulate things done in the past, with gear that is now decades old and expecting performance based on false memories is getting a bit bizarre.
Vintage (neve/API/whatever) in fact anything with capacitors in it essentially can NEVER be exactly what it was 40 years ago. Capacitor manufacturing techniques and chemicals have changed and any 'New Old Stock' will have degraded even if never powered up.
'Bridging inputs' is an undefined term. When 600 Ohm outputs were the norm, it was common to think of 10K as a 'bridging' input impedance bexcause you could have up to 10 of them in parallel (1K Ohms total)and each 10K load would cause around 0.5dB drop in signal level but 10 in parallel would not embarrass the current drive capability of the sending amplifier, even though the level drop would be approaching 6dB. The output impedance, and the output current drive capability are separate parameters and one does not imply the other.
Matt S

 

[nielsk]

Actually, I oversimplified. If you look at the Gates Dual Limiter
https://groupdiy.com/threads/gates.44868/#post-770977
you will see that is uses a 10k resistor in series on each leg for a "bridging" input, with a 600 ohm load resistor, this is on a 600 ohm input tap.
AS to "false memories" this is a 100% restored unit in daily use, that everyone (and we are talking engineers that have used EVERYTHING) agrees is about the best sounding limiter ever made.
There have been no loading problems typical of other 600 ohm input pieces with the input configured this way.
My question is how this input configuration would affect a passive EQ circuit, since they are so likely to load (= sound terrible) dependent on input source Z

 

[john12ax7]

Anyone happen to have schematics for the Neve 82 series?

 

[nielsk]

You might try the folks at 81 dot com, the volumes of schematics on this one are huge...
It may help to narrow it down to a specific part of the console