Fader Log Scale for Engraving

[21bower]

I'm looking to get some fader face plates / fascia's made for an MTA series 980 that i've just acquired, It is without faders also so I'll probably end up getting some Alps K Series Log 100mm faders.

One thing I can't seem to find is a consistent dB (?) scale for the print, the original desk plates go up to +5 (see picture), but I've seen other plates range between 0 and +10...

The Alps documentation is no help, P&G have a %scale which is useful, but i'm struggling to find anything conclusive.

Hoping someone can shed some light as I'm scratching my head slightly here!

 

[Rob Flinn]

I had to make some fader plates for a Tweed console I was restoring for someone. In this case P&G faders were being used & there was a template that I used on their website to get the graduations correct.

 

[Newmarket]

Be aware that manufacturers' audio tapers can be more loggish than log and may vary. This in order to give finer resolution around '0dB' position. And after -40dB it's all pretty coarse.

 

[abbey road d enfer]

One thing I can't seem to find is a consistent dB (?) scale for the print, the original desk plates go up to +5 (see picture), but I've seen other plates range between 0 and +10...

It depends very much on how much extra gain the designer has put there.
Many mixers have 10dB extra gain on channels but only zero on masters.
If you don't have a technical manual, you need to make measurements. Usually, one must measure the pre-fader level (often the same than the insert send) and the direct output, if it exists, or the level on the bus resistors.
The fader must then be adusted for equal levels, and that will be the "0" mark. For the rest of the markings, you need to measure.
OTOH, one should mix with his ears, not his eyes.

 

[21bower]

Wow, thank you all, first time posting on this forum so thrilled with the replies so far!

I'm thinking the only way forward is to get 'hands on' and measure (as Abbey road mentioned above), as long as I have the '0' mark covered then everything else can be referential and doesn't have to be 'bang on'.

Onwards and Upwards!

 

[JohnRoberts]

+1 to what Abbey said... I used to manage a mixer engineering group and we had to measure actual fader laws when designing in new faders. Of course the post fader make-up gain matters. +10dB is typical but some manufacturers have experimented with variants on that.

JR

 

[FIX]

Audio faders are not really LOG, they are linear, with "slugs" that alter the scale as you move the fader. So it's best to measure the fader, mark a piece of paper, then use that for your scale. Alsothe load that is on the fader is important, correctly, the load should be 10X the fader resistance. Some are equal, it does stretch the taper, but can also make them different between faders if loaded too much. The attached pic is a P&G element from a Neve console, it is stereo, which they typically made all of the elements stereo, and then used the best track. You can see a smear on the upper slug, that makes that element useless.

The two outside tracks are the wiper contacts, the next two are the wiper, and the little black lines going towards the center are the slug resistors that attach to a ground bus (silver traces in the center). The white scrapes are from a pin that catches off some of the resist, so the two elements match. at the bottom, you can see a diagonal slice, that is called a "HOP-OFF" which is as the fader is pulled down, the wiper actually fades off the signal trace and sits firmly at ground, or it "hops off". This improves turn off or cut off. Older faders had these, typically 600 ohm, 1K and 5K. Their was enough current running through the element that you wouldn't get good cut off. These faders had 4 wires, TOP, WIPER, LOW and HOP-OFF.The hop-off would go directly to the next stage's ground.

 

[JohnRoberts]

Most modestly priced faders are simpler than that inside but attempt an audio taper that is more log than linear (some use multiple resistive element screen overlays.

The 4 wire (Kelvin) wiring connection can be used with 3 terminal faders also, to improved fader kill. It is just about using a ground sense lead that doesn't get corrupted by the faders audio current.

JR

 

[FIX]

Most modestly priced faders are simpler than that inside but attempt an audio taper that is more log than linear (some use multiple resistive element screen overlays.

The 4 wire (Kelvin) wiring connection can be used with 3 terminal faders also, to improved fader kill. It is just about using a ground sense lead that doesn't get corrupted by the faders audio current.

JR

Truth. P&G faders used a slug about every CM. Cheaper ones spread them out. Rotary pots, most are multi-layer screened, and are not really log. Good ones use 3-4, I have seem some that have 1...

 

[boji]

I'm thinking the only way forward is to get 'hands on' and measure

+1 Same task a few months ago!
Differences tended to occur near the ends of their tracks. I did the hands-on, recursive thing to average them out.

Edit: Used an NTI MR1 and Minilyzer on direct outs.

 

[FIX]

The old API oscillator output had a Clarostat pot with one taper screened overlay, the +4 setting was dead on the junction, and you could never get it right...