Any experience with a Neumann VAB-84?

[dmills]

It was a dynamically variable S component HPF which appears to have been designed as an alternative to an elliptical EQ right at the end of the original Vinyl era.
Never actually seen one, much less heard the thing, but I did find a short form datasheet.

Anyone know if it was actually any good, because with modern parts it would be very, very easy to implement?

Neumann-VAB.pdf

[gold]

I’ve seen and heard them but never used them on a regular basis. The general consensus among people who have experience with them is that they are not worth the trouble. The sliding crossover point was more audible than a simple EE. The way the crossover was done is very interesting though. Wayne Kirkwood did a deep dive into it. His EE is the result of the research.

[dmills]

I figured that the dynamically changing phase shift would likely be rather audible, it is usually the trap with that kind of thing, what I was wondering is if there was some secret sauce that made it a non problem, but it sounds like it probably did what you would expect.

Waynes second order EE with the allpass to compensate the group delay?

Thanks for the info.

Regards, Dan.

[gold]

Waynes second order EE with the allpass to compensate the group delay?

That’s the one. It was inspired by the way the VAB does the crossover.

[andybee]

better not 100% audible, than a jumping needle as far as I know, the VAB-84 was mostly used with DMM lathes, but I have also seen in a SP-79 desk for a VMS-80...
as far I undestand the VAB84 is a EEQ with variable crossover frequency?
somebody has done a bunch of clones, but never finished.... neumann used a very early version of a VCA, as far as I remember, they called it VCA101.
ah, I found it:
https://www.lathetrolls.com/viewtopic.php?t=4032

[dmills]

Ah DMM, that makes some sense.
Yea it basically amounts to a program responsive EE, trouble is the phase shift thru the thing must inevitably vary as the filter corner is moved up and down the band, which is likely audible.

Today, if you were prepared to tolerate a DIGITAL version you could I think use a linear phase filter rather then a minimum phase one and thereby sidestep the issue, might need to write some matlab and see how it does.

Designing a variable linear phase filter that can be tuned on the fly might be an interesting party trick however, time to hit the literature.

[flozki]

the VAB84 was the first thing i threw out of the SP79 desk.
i did mor than 10 years of DMM cutting.
it was unacceptable. and another reason why dmm sounded so bad in the 80ies.
but yes it had a neumann logo on it so it must be good.

use a good phasefree mix. or use a fixed crossover. or if variable go for a modern plug in solution.
i guess there is a lot of stuff like that out.

[dmills]

Oh every company doing anything meaningful as new product has a pup or two, you don't win them all.

Got to admit something that is so obviously flawed in concept making it out of Neumann is not what you would expect but 80s was peak vinyl 'loudness wars' and maybe they felt they had to in order to make DMM compete? This was also the era of the various attempts to compensate the playback geometry distortions, and as far as I can tell ALL of those boxes sounded worse then not using them.

Hell maybe a major player asked for it, we get that sometimes, one of the whales requiring a particular feature, and we do it against our better judgement because they hang an order for a few hundred units on it, I would not be surprised if this originated with one of the labels and Neumann rolled with the request.

[gold]

This was also the era of the various attempts to compensate the playback geometry distortions, and as far as I can tell ALL of those boxes sounded worse then not using them.

It goes back further than that. There are microswitches on the VMS66 for the Neumann system. Another flawed concept as it relied on ‘standard playback geometry’ which doesn’t exist. If there was distortion on playback the system would hiccup. So no loud records where it would actually be useful.

[dmills]

CBS had something as well didn't they as in house 'secret sauce'? As I recall it sucked like all the other similar attempts.

IIRC there were a LOT of JAES papers discussing compensating playback tracing distortion in the 60s - 80s sort of time period, many of them collected in the (excellent) AES disk cutting anthologies.

[gold]

CBS had something as well didn't they as in house 'secret sauce'? As I recall it sucked like all the other similar attempts.

I bought the lot of DisComputers from Sony. I was never able to get them going. There was a box that did the low frequency crossover. I didn’t have schematics for it. IiRC is was more complex than a simple EE but my memory is fuzzy on that.

[gold]

Some of that CBS low frequency crossover box is coming back to me. It was in a card cage frame with VU meters. The inputs and outputs were transformer balanced with Melcor 1731 opamps. I think it was an EE with two crossover points. The reason I didn’t use them is that I was using a Neumann SP66 tape machine console at the time. It had an EE. This was no improvement. I think I had two of them. I may have sold them with the DisComputers or saved the In/Out cards and trashed the rest.