How can to connect a NTP 177-710 Peakmeter to NTP 179-400 Compressor/Limiter?

[opacheco]

Hi,

Someone have an idea in order to connect a NTP 177-710 Peakmeter to a NTP 179-400 Compressor/Limiter (or Siemens U273 Compressor/Limiter)?....I would like to get them work together but well calibrated too!!

Any idea??

Thanks

 

[opacheco]

Any Idea??.....

Opacheco

 

[gyraf]

Hi Opacheco,

It is unclear what you are trying to achieve - the 177-710 and NTP 179-400 are separate modules, not intended for working together...

Jakob E.

 

[opacheco]

Hi Opacheco,

It is unclear what you are trying to achieve - the 177-710 and NTP 179-400 are separate modules, not intended for working together...

Jakob E.

Jakob thanks for your response and I am so sorry for my bad english!!....I am tring to use the NTP177-710(level meter) in order to measure the gain reduction(and input/output levels too if this is possible) in the NTP179-400 like a compressor with VU meter in one only units do.

Maybe this be clear now!
Opacheco.

 

[gyraf]

The 179-400 limiter card outputs 1mA/20dB GR at pins 26-27, and there is no simple way to interface this to an audio-reading peak meter like the 177-710.

NTP GR Readouts were analogue moving-coil meters.

The easiest would be to use a 1mA full-scale analogue panel meter - this would/should give a nice linear readout of 1dB per 50uA, that is 20dB GR for full-scale

There also is an output for a led to show limiting action, pins 14-15

Jakob E.

 

[opacheco]

The 179-400 limiter card outputs 1mA/20dB GR at pins 26-27, and there is no simple way to interface this to an audio-reading peak meter like the 177-710.

NTP GR Readouts were analogue moving-coil meters.

The easiest would be to use a 1mA full-scale analogue panel meter - this would/should give a nice linear readout of 1dB per 50uA, that is 20dB GR for full-scale

There also is an output for a led to show limiting action, pins 14-15

Jakob E.

Jakob, thanks for your explanations and suggestions!....But how about if I use Opamp amplifiers between this units instance direct conection?......

I have a pair of Siemens U273 too and Do you belive could I use this NTP177-710(level meter) with these Siemens U273 instance the NTP179-400?

Thanks again!
Opacheco.

 

[gyraf]

The 177-710 is only an audio-reading meter, for AC input - can't be used for GR readout in any simple way, unless you rebuild it internally (which won't be simple)

Jakob E.

 

[opacheco]

The 177-710 is only an audio-reading meter, for AC input - can't be used for GR readout in any simple way, unless you rebuild it internally (which won't be simple)

Jakob E.

That is a shame!.....Had this unit a GR meter in that days?? How these guys did measurement the gain reduction with this unit (U273/NTP179-400)??.

Thanks a lot Jakob

Opacheco.

 

[audiomixer]

Well anyway the first thing after buffering that happens in an analog meter would be rectification of the AC audio waveform... no?

It might be easier to build a simple linear bargraph with a LM3914/15/16
I never know which one does what as per the datasheet and display the GR signal as per the earlier post.

- Michael

 

[SkunkFunk]

Hi,

know I'm bumping an a year old thread, but I have found a solution your problem, that I would like to share if you still have the meter or someone else is interested. Significant modifications are not necessary, but an extra opamp and a few resistors and caps are.

My goal was to use an 177-710 as both a GR meter and PPM, depending on a meter selector switch bank. I've solved this by adding a separate input for GR signals, that is added through an already existing virtual ground summation point that comes after the input processing cirtuitry such as integration, log-amp etc. This makes it possible to just have a differential amp as the new input.  The result of an input GR voltage will then give a proportional value shown at the display. I have also added a large bias current when in GR mode, that raises the display level to 0dB when the GR is zero. When GR increases, the display level decreases.

However, the fall-back time is as far as i have found not a property of the input circuitry, but the logic output circuitry. This prohibits bypassing it in a simple manner. It seems that the meter level is stored in a counter, that decreases one step every time the level in a RC circuit reaches a certain level. Since I  want the meter to decrease very fast (this is what happens during the attack cycle in my setup), I have changed this capacitor to a thousandth of its original value without any problems.

I have added a relay that switches this capacitor back to original and removes the GR input current, when it is supposed to measure PPM. This can be controlled from my switch bank. Note that the audio input signal is not removed when in GR mode, but a termination resistor in the switch bank ensures that the audio signal is still zero when in GR mode.

So far I have not gotten my relay yet, but the rest of the circuitry works as intended.

I've attached a small illustration of the extra pcb I've added. All new features are fit on the small protoboard seen in the corner. The GR input is connected in wrong polarity in the schematic. A TL071 is used as OP and even though the circuit operates near the boundry of its common-mode input range, it seems to work. The GR signal to be used is 4V through 4k for 20dB of gain reduction, intended to use with a 1mA/20dB meter. For a compressor with different vaules, you may need to change some resistors.