I am in the process of calibrating a pair of Neve 32254E Limiter/Compressors
and using tones I appear to have them where I want them. However,
there is one calibration on them that I don't know what to do with.
It is labelled "Set +8". I understand that broadcast often uses +8
as a standard as opposed to +4 dBU. However, these are variable
pots so it isn't as if I can "click" them in and out of a higher
operating range. Anyone know what these do?

The other calibrations are "PPM in", "PPM out", "set gain", and "set
threshold", BTW. But these all make sense to me. However, I do
seem to remember that the "PPM" designation is related to +8
broadcast standard.

Related question---I had a rack made for these. While it is pretty
nicely made, they appear to have ignored my request for a larger
power supply. These modules need 250 mA. People like Fletcher and
Geoff Tanner have stated that you need 6 to 10 times that capacity
to operate them optimally meaning I need something in the range of
3 to 5 amps (at 24VDC, not that it matters). The power supply they
installed is only rated at 1.2 amps. I am thinking about ordering
a beefier power supply and putting it in myself. But in the meantime
can I not just avoid saturation/clipping (unless that's
what I want!) by just staying off the makeup gain and compensating
for it on my mixer?

BTW, they sound really good, except for being kind of noisy.

Thanks,

Rob R.

"Rob Reedijk" wrote in message
...
I am in the process of calibrating a pair of Neve 32254E
Limiter/Compressors
and using tones I appear to have them where I want them. However,
there is one calibration on them that I don't know what to do with.
It is labelled "Set +8". I understand that broadcast often uses +8
as a standard as opposed to +4 dBU. However, these are variable
pots so it isn't as if I can "click" them in and out of a higher
operating range. Anyone know what these do?

The other calibrations are "PPM in", "PPM out", "set gain", and "set
threshold", BTW. But these all make sense to me. However, I do
seem to remember that the "PPM" designation is related to +8
broadcast standard.

Related question---I had a rack made for these. While it is pretty
nicely made, they appear to have ignored my request for a larger
power supply. These modules need 250 mA. People like Fletcher and
Geoff Tanner have stated that you need 6 to 10 times that capacity
to operate them optimally meaning I need something in the range of
3 to 5 amps (at 24VDC, not that it matters). The power supply they
installed is only rated at 1.2 amps. I am thinking about ordering
a beefier power supply and putting it in myself. But in the meantime
can I not just avoid saturation/clipping (unless that's
what I want!) by just staying off the makeup gain and compensating
for it on my mixer?

BTW, they sound really good, except for being kind of noisy.

Thanks,

Rob
In the UK and wherever else they are used, PPM scales go from 1 to 7 in
increments of 4dB, where "ppm1" is just about -12 or -14dB below 0 ref ("ppm
4"), and peak level (+8dB above 0 ref) is equal to "ppm 6" - all read at
steady tone state. The dynamic range between electrical Zero (no signal) and
1 is often immaterial.
After adjusting Set Gain and Threshold (BTW, this could be an L/C function)
where 0.775V rms gives peak 4, inject a new level of 1.95V rms, adjust Set
+8 to give peak 6. You may have to juggle between Set Gain and Set +8 to get
a happy compromise.
Because of a law network within PPM amps, certain sections switch in only
when a progressively higher level is detected. If you have 2 PPMs side by
side, ensure that when fed in dual mono mode, your line-up makes the attack
and the decay are visually synchronous.
Don't worry about the available PSU current, the devices are only basically
2 processors, 2 line output drivers and a 1mA meter driver or two per
channel.
Good stuff, Neve! Tried to get the manual from AMS Neve?
http://www.ams-neve.com/cont.htm
Jim

Rob R.

Rob
My error, now I have re-read your intro, I see you don't have an integral
PPM, but the facility for it.
But have you got the panel-mounted Stereo Separate/Link Switch fitted
between these two modules?
Essential to "link" them to maintain the average centre image, not pulling
too much to one side when influenced and controlled by left or right
programme dynamics.

Jim

In article writes:

I am in the process of calibrating a pair of Neve 32254E Limiter/Compressors
and using tones I appear to have them where I want them. However,
there is one calibration on them that I don't know what to do with.
It is labelled "Set +8". I understand that broadcast often uses +8
as a standard as opposed to +4 dBU. However, these are variable
pots so it isn't as if I can "click" them in and out of a higher
operating range. Anyone know what these do?

I suspect that they're for meter calibration. Is there a switch to
select between +4 and +8 dBu nominal operating level? If so, switch it
to +8, put in a tone at +8 dBu, switch the meter to read input, and
adjust the pot so the meter reads 0.

The other calibrations are "PPM in", "PPM out", "set gain", and "set
threshold", BTW. But these all make sense to me. However, I do
seem to remember that the "PPM" designation is related to +8
broadcast standard.

That may have something to do with it. I guess you really need answer
from someone who knows that limiter or at least has the documentation.
But there doesn't necessarily have to be a relation. Some studios just
operated at +8 dBu nominal, and you always want to read 0 VU at
nominal level, whatever your choice for that happens to be.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Rob Reedijk wrote:
I am in the process of calibrating a pair of Neve 32254E Limiter/Compressors
and using tones I appear to have them where I want them. However,
there is one calibration on them that I don't know what to do with.
It is labelled "Set +8". I understand that broadcast often uses +8
as a standard as opposed to +4 dBU. However, these are variable
pots so it isn't as if I can "click" them in and out of a higher
operating range. Anyone know what these do?

Geoff Tanner sent me an email and I can now tell you that "set +8" is
a calibration for the limiter. Basically, crank a very high level tone
into the unit, set the limiter to +8, and adjust this setting until the
output reads +8.

I will post my steps for calibrating 2254Es in the next day, once I have
confirmed proper operation.

Rob R.

I have finished calibrating my 32254Es and thought it might be
helpful if I posted my procedure for anyone in the future
trying to do this. I am going to first post it here, to give those
of you who are more experienced an opportunity to offer corrections
and then I will repost a final version.

On the back of the units are 5 calibration settings.

Assumptions:

2254Es and 32254Es are identical

32254Es and 2254Es have PPM meters. I set a reference based on
0.775V RMS as measured by a digital multimeter on a 1 KHz tone
to represent PPM 4 or 0 (zero) on the PPM meters, measured across pin 2
and pin 3 (hot and cold on a balanced system).
I realise that there are other reference levels that will work.
I tried a few others, but this one seems to work best for me.

There must be some sort of a soft knee to the compression. In
choosing a way to ÒSet ThresholdÓ I decided to set the compressor
so that the front panel threshold was set significantly lower
than the input tone so that I could set the ÒSet ThresholdÓ
to cause the amount of gain reduction reflected by the ratio
setting. I chose 3:1 ratio only because it is the middle choice.
I decided not to set the threshold to reflect where gain reduction
began since there seems to be a soft knee and so it is difficult
to find out where that knee actually is.


Step one: Set gain
If you have a stereo pair, disengage the link switch.
Set Gain Make Up to 0, set threshold(front) to highest setting clockwise.
Once you have, on a mixer or any other tone generating device, set a
tone at a level 0.775V RMS by hanging a digital multimeter across
pins 2 and 3 (hot and cold), connect it to the input of one of the
2254Es. Now hang the multimeter across pin 2 and 3 of the output
of the unit. Take the unit out of bypass mode, but without either the
compressor or limiter being engaged. Adjust Òset gainÓ so that the
unit outputs the same voltage (0.775V or close to it) whether or
not the bypass switch is engaged. The set gain setting only affects
it when it is out of bypass mode.

Step two: PPM In and PPM out
Set the meter so that it reads the input level and adjust ÒPPM InÓ so that
the meter shows 0. Switch the meter to read the output. Adjust ÒPPM OutÓ
so that it also reads 0. The voltmeter should continue to read 0.775 V.

Repeat the first two steps for the other compressor if you have a pair.

Step three: Set Threshold
Split the output of the tone source and feed both units. Adjust the level
of the tone so that with the meters showing input, you have +8 level.
Set a ratio of 3:1 on both units. Set front panel Thresholds to -10.
Switch meters to gain reduction. Adjust ÒSet ThresholdsÓ for 12 dB
of gain reduction.

Step four: Set +8
Switch out the compressors, switch in the limiters to fast. Set meters to
read output. Set Limit Level to +8. Crank the level of the tones you
are feeding the unit, to +20 or so. Do not read this with the meters set
to input as you don't want to damage them. It doesn't matter how high,
as long as you are significantly over the limiter threshold. You can
probably use your multimeter to measure a level of at least 5V coming
off the tone generator. Adjust ÒSet +8Ó so that you read +8 on the
meter.

Step five: Test your work
Lower the tone back to a level where the input meter shows normal levels.
Switch out the limiters and switch in the compressors. Do NOT yet
link the compressors. Try different levels of tones hitting the
compressors. Set both units to the same ratios, thresholds and
make up gain settings. Watch the meters on output and make sure
they are behaving similarly to each other. They probably won't be
exact. Trying different input levels with the ratios and threshold
in different positions should give you reasonably correct amounts of
gain reduction. I didn't do this, but you could hook up the outputs
to an oscilloscope to check how well the two sides match.

Now, link them. The link in these compressors works very nicely.

Once again, if any of you more savvy and experienced engineers have
any comments on this, please feel free to post them. It is my
intention to help others like myself: people who are operating
older analog gear but don't have a lot of that very useful technical
background to maintain them.

I want to thank Jim Gregory and Geoff Tanner for their help.

Rob R.