ntp limiters

[tommia]

they look like 100 microamp, you have to put a resistor in series. Try 39 k

 

[musika]

It's a project I put aside because of other pressing issues, but now need to finish.  Here is my meter rack.  I'm going to add a power supply for the limiters in this.  Thanks for the suggestion, yes they are 100mA.

 

[thomasdf]

Nice box
Do anyone have access to documents explaining the aligning procedure for the NTP 179 400? I know P5 needs to be adjusted to have a 18V supply... but I have no idea how I am supposed to set up the threshold using P4. How did you guys do it?
Thanks!
Btw, pics of my racking soon!

 

[musika]

https://groupdiy.com/index.php?topic=46971.msg790506#msg790506

The graphs in this document show how the limiter should react.  I personally do not have the equipment nor the knowledge to recreate the graphs in this document.

But right above the P5 and P4 specs it states that normally the limiter amplifier will stay correctly adjusted, except when component has failed and has been replaced; then it may be necessary to make certain adjustments.

Have you changed P4 or P5?

 

[thomasdf]

No, but I will recap the units soon, and I don't know who used them before me, or how.. So I'd like to make sure they are aligned properly
From what I understand from the graphs, the threshold must be set so that the limiters kicks in when (at unity gain) the input signal is hotter than the set output signal (logical) but I have no clue how to do that! And I am not even sure I am understanding this properly...?

 

[tommia]

Are you guys using the standard recovery time? If No, what is your favorite setting when it comes to recovery times?

 

[thomasdf]

So I racked my pair of limiters with a regulated 24VDC for the cards power supply, and a regulated 12VDC for the bypass relays and switch lighting.
For some reason, I have to run the input unbalanced to have a full frequency responses, otherwise all the low mid an below is gone I am running them straight on impedance balanced converters (Echo Audiofire 12). Do anybody know if this is somehow related? With pin2 to ground, they sound delightful!

Edit: tried it after a GSSL and transformer gear and it works perfectly... so yeah, forget about impedance balanced stuff...

Also, I tried linking pin 28s together with no success.. so link is not working for me right now (red limit LEDs do not blink together when linked)

Still interested in any tips for calibration?

Tommia, standard recovery times sounds perfect to me, very fast and transparent.

 

[musika]

Thomasdf :

Glad to hear about your progress on this project!

What did you use for the bypass relay?  Do you think it really makes a difference?  Was this a  diy forum kit?

 

[thomasdf]

The bypass relay boards are from DIY tubes, it's just a regular relay bypass, and it works just fine. The problem really comes from my converters balancing the signal with a impedance balacing, instead of regular (active or transformer) balacing.
I was planning on changing converters soon so...
So far I really like the way the NTP works, even tho they are a bit tricky. The gain is def an input gain, and the Lim Level is a sort of threshold pot... My main complain is that there is too much of a gain jump between position 0 and 1.5 but I can live with that
Also, I realised that they eat a little of the extreme low end... maybe a recap will help on that matter.
I need to calibrate them too, as one triggers a bit earlier than the second one.
Oh yes, and figure that link thingie too...
Anybody got their link to work? How?
Thanks

 

[musika]

I found this wiring map of the NTP 179-470 - a dual 179-400 rack which seems to show the control voltage connector for stereo setup.  An interesting connector to the power supply.  Can anyone make some sense of this for the NTP 179-400 stereo setup?  It seems to provide a clue.

 

[thomasdf]

They seem to be both controlled by an external voltage, and not by the PSU. That may be a used for ducking functions, automatic gain control etc.. 1V / 5dB (according to the schematics)

The question is, can the 2 limiter cards provide this voltage control to each other? Maybe something like feeding each limiter pin XX to the other limiter's pin 28 or something like this?
I'll investigate a bit more when possible

 

[tommia]

stereo linking by  pin 28 is a joke, don't try it. I replaced the 20k resistor from the side chain by 2 10k resistors in series. Connect the joining of both resistors to the joining of the other module. Instead of just hardwire them jou could put a pot there so jou could control the amount of stereo linking.

 

[peeping tom]

@strangeandbouncy: Do you change your recovery time settings often? Or do you leave them on one setting?

If you don't change them a lot a dip switch on the back will do the trick as well I guess, although I really like PRR's solution with the rotary switch.

Hi sir,
Is it possible to send me this info via email?

[email protected]

I just bought pair of these limiters and it would be very helpful for me!

Best regards!
Mihail

 

[peeping tom]

> the selection of the recovery times. i'm a bit stumped

According to the data: you need three SPST switches for Attack, three more for Recovery. The switches short pins A, B, C to ground, or go open. Ground is "0" and open is "1". The table in Note 2 tells what you get for each of the 8 possible combinations of 3 switches. All 3 shorted is 4S recovery, C shorted and A, B open is 400mS.

Instead of 3 switches, you get a "hexadecimal switch" or "BCD decimal switch" such as DigiKey 401-1037-5-ND. (Do NOT get "complement".) Connect switch pin "C" to ground, switch pin "1" to limiter "A", switch pin "2" to limiter "B", switch pin "4" to limiter "C". Ignore switch pin "8": what you really want is an Octal switch, but they don't make them any more, you buy a 10 or 16 way switch and ignore the excess.

It would also be possible to do this with a simple 1-pole 8-throw switch. Ground the wiper. Start connecting diodes, band-end to the switch, to the ABC terminals marked "0" in Note 2. Position 0 has no diodes. Pos 1 has one diode to pin A. Position 7 has three diodes, to A B and C.

You could also use open-collector TTL chips to interface to a PC printer port... total overkill for one or two such boxes.

Hi sir,
can you send me this information to my email:
[email protected]

I just bought pair of them and it would be very helpful for me !
Thanks!

Mihail

 

[PRR]

> can you send me this information to my email:

? ? ?

Copy info from forum. Start email to yourself. Paste info. Send.

If you say you are on an internet device which is awkward to copy/paste... well, find a better device, don't ask others to do it for you.