NTP 179-120 - possible to build?

[Whoops]

Hello,
I've been a long time fan of this compressor since I heard it for the first time in Masterdisk in NY.
Unfortunately it's very rare to find them nowadays in the used market, and when theres one available the prices are quite high.

I was thinking if it would be possible to DIY?

For people that dont know this compressor here is some info:

"Danish made NTP 179-120 mid-70's vintage compressors/limiters, fully racked and in excellent working condition.  These have been the “secret weapons” of numerous mastering engineers (such as Bob Ludwig, who has often praised them in interviews) since they were introduced, and are legendary for their ultra-smooth and classic sounding compression.  They are currently found in the racks of a number of high end mastering studios, including Gateway, Masterdisk, SAE, Trutone, Tocano, and numerous studios in Europe (where they are well known for their excellence) as well.  Besides mastering these compressors can also work excellently for tracking and mixing. "

here are some schematics:

http://groupdiy.com/index.php?action=dlattach;topic=46971.0;attach=17998


Does anyone wants to join me in analyzing the possibilities of doing a DIY build of this compressor?

Whats your interest in a compressor like this?

thanks

 

[gyraf]

The unobtanium part here is the "179-1218 A4" selected and xtal-oven-mounted FET used for signal control (attenuation). With the drying out of unobtainium mines, this part was probably the reason for NTP to move into VCA-based designs for their later compressors.

Not saying it can't be done, just that it's no easy task. A lot of the charisma of the NTP units comes from the obsessive/compulsive parts selection.

Jakob E.

 

[RuudNL]

Is there a schematic diagram available with component values?

 

[gyraf]

Uploaded full manual, but with lower resolution schematics (as these are already here)
http://groupdiy.com/index.php?topic=46971.msg766143#msg766143

Jakob E.

 

[RuudNL]

Great Jakob! I think I would dare to give it a try!...

 

[gyraf]

In my 179-120 folder I have had this pic for a while - attached

A googling finds a page from old days: http://www.romanblack.com/xoven.htm

Jakob E.

 

[analogguru]

In my 179-120 folder I have had this pic for a while - attached

A googling finds a page from old days: http://www.romanblack.com/xoven.htm

Jakob E.

This could be done easier with a PTC ..... like this:

The "oven" is used to stabilize the FET - for what reason ever, (maybe only for the purpose of technical overkill).

The FET is a Si 216N which can be replaced by a BC264B.

So.... voila... it can be done...

And yes - very important - you may not forget to use tantalum-caps in the audio-path to obtain the perfect tone of the "mastering-gurus".

But for what all of this effort - only to have FET-Compressor No. 2347 in the collection ?

 

[gyraf]

Naa, the PTC actual temp will to some degree depend on applied voltage and external temp. The transistor setup is kinda self-normalizing if I understand it correctly.

Jakob E.

 

[analogguru]

Naa, the PTC actual temp will to some degree depend on applied voltage and external temp. The transistor setup is kinda self-normalizing if I understand it correctly.

Jakob E.

Since ages there exist special designed PTC-discs which are soldered directly on to the quartz and hold the quartz at a constant temperature at a nominal voltage of 12V for an ambient temperature range from -40 degrees C to +70 degrees C.

http://www.qsl.net/ok2ugs/gb_137141/down_converter_1691_gb.htm

http://iopscience.iop.org/article/10.1088/0022-3735/15/7/008/pdf;jsessionid=EF9725635D2DB9479EBF3DBBB8E035C3.c1

You can buy these parts (Siemens P330/2492-A60) for example at the link below for € 1,53/pcs:
http://www.giga-tech.de/pageID_10548044.html
P 330......60°C.....1, 53€

So......  but if you don´t trust this solution you can always (mis-)use a good old uA723 like this (which can even be simplified):

http://remco.org/index.php/2008/12/31/thermostat-for-system-clock/

http://people.zeelandnet.nl/axxes/tco/tco2.htm

 

[Whoops]

Naa, the PTC actual temp will to some degree depend on applied voltage and external temp. The transistor setup is kinda self-normalizing if I understand it correctly.

Jakob E.

Since ages there exist special designed PTC-discs which are soldered directly on to the quartz and hold the quartz at a constant temperature at a nominal voltage of 12V for an ambient temperature range from -40 degrees C to +70 degrees C.

http://www.qsl.net/ok2ugs/gb_137141/down_converter_1691_gb.htm

http://iopscience.iop.org/article/10.1088/0022-3735/15/7/008/pdf;jsessionid=EF9725635D2DB9479EBF3DBBB8E035C3.c1

You can buy these parts (Siemens P330/2492-A60) for example at the link below for € 1,53/pcs:
http://www.giga-tech.de/pageID_10548044.html
P 330......60°C.....1, 53€

So......  but if you don´t trust this solution you can always (mis-)use a good old uA723 like this (which can even be simplified):

http://remco.org/index.php/2008/12/31/thermostat-for-system-clock/

http://people.zeelandnet.nl/axxes/tco/tco2.htm

Thanks, great ideas
Maybe it would be nice to try it both ways and see the results.

Need to investigate more on this

 

[pvision]

Add a variable temperature control and - voila! - you have something new for the recall sheets - preferred compressor temperature!

Calibrate the front-panel control from Sub-Zero, through Ultra-Cool, Nicely Chilled, Room Temperature, It's Getting Hot in Here right through to Smokin' Hot

I'd buy one!

Nick Froome

 

[RuudNL]

I doubt if it is really necessary to add an 'oven' for the FET...
(I have never seen this in other FET compressors)
Maybe there will be a small drift with temperature, but I suppose it is not enough to justify the temperature stabilization mechanizm.