Adjusting 1V to 2V input sensitivity

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Adjusting 1V to 2V input sensitivity

Postby spacey » Sat Jan 26, 2013 3:24 pm

I've just adjusted my 25A pros from 1V to 2V input sensitivity and thought I'd share the experience; It’s a doddle to do. The pot is already turned max clockwise.. All that’s needed is a turn to max anti-clockwise, which is about 3/4 of a turn. They remain fully balanced at both extremes so nothing to worry about. The hole to adjust is the one on the right when you're behind the speaker. The left hole is for bass boost, which I've left at factory setting. Seems to make for a fuller sound with more drive. I'm happy with the outcome. Tools needed are a little torch and a small 5mm-ish flat blade screwdriver; only takes a few seconds to do!

In the terms of gain control on my DAC the INVICTA, Its gone from -45db to about -25db for normal listening levels.

Hope that helps :)

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Re: Adjusting 1V to 2V input sensitivity

Postby MattSPL » Sat Jan 26, 2013 10:35 pm

Good stuff spacey, it's a nice little tweak :)
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Re: Adjusting 1V to 2V input sensitivity

Postby spacey » Sun Jan 27, 2013 1:31 am

Update: after a few hours use and now into the night where i can really understand levels a li'll more to a reference. I'd say the gain difference isn't as large as i first gathered, it's still considerable and worthwhile though :)
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Re: Adjusting 1V to 2V input sensitivity

Postby Brad Lunde » Tue Jan 29, 2013 4:42 pm

I have to say here in the spirit of correctness, there is absolutely no difference between 1V or 2V. Its simply a level difference-which is why good ole' "Fletcher Munson " effects can trick us all into thinking its different, better, has more bass, has more top end, less bass, less top end, etc. I know when I do do demos, a lot of care has to be taken for a very small difference in level will often be heard as more bass in the louder one. The reason the adjustment is there is that some consoles/preamps may have lower or higher output levels and you want to adjust the speakers relative to "where" on the knob rotation or fader level Full Output is found. So in rare occasions you have to adjust it upon installation and never again.

ATC's recommendation is to leave the controls alone, there is far more damage one can do by playing around with them. 99% of devices operate a 1V= full output, the factory setting.

I have had to repair many demo speakers in LA due to people fiddling with them and pushing to hard with a screwdriver and inadvertently cracking the pot. With a metal screwdriver, its hard to "feel" how hard you pressing, and this why you should use a small plastic trimmer tool (small all plastic screwdriver). A bit too hard too often and the whole speaker goes intermittent and requires service of the amp packs to replace the PC board trimmer. The freight and hassle cost hundreds, the part a few pounds.

Brad
Last edited by Brad Lunde on Wed Jan 30, 2013 6:22 am, edited 1 time in total.
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Re: Adjusting 1V to 2V input sensitivity

Postby spacey » Tue Jan 29, 2013 7:38 pm

Agreed Brad, however adjusting the voltage does help when you're using digital dithered volume attenuation. It helps reduce the amount required which in turn means when using below the 32bit threshold there's less of the LSBs disregarded.

In terms of the actual physical process, i used one of those tiny 2 finger screwdrivers, the ones where you have to put a finger on the end, which you'd use in model making or watch and glasses repairs. Not a hand held screwdriver, which would be way too numb feeling :)

I have this set http://www.ebay.co.uk/itm/Facom-HB-1B-P ... 23278e8316
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Re: Adjusting 1V to 2V input sensitivity

Postby Brad Lunde » Wed Jan 30, 2013 5:28 pm

spacey wrote:Agreed Brad, however adjusting the voltage does help when you're using digital dithered volume attenuation. It helps reduce the amount required which in turn means when using below the 32bit threshold there's less of the LSBs disregarded.

In terms of the actual physical process, i used one of those tiny 2 finger screwdrivers, the ones where you have to put a finger on the end, which you'd use in model making or watch and glasses repairs. Not a hand held screwdriver, which would be way too numb feeling :)

I have this set http://www.ebay.co.uk/itm/Facom-HB-1B-P ... 23278e8316


Spacey
Yes those screwdrivers offer far more feel, well done!

On gain, it is true that with digital gear, it is better nearer the top of the range of the gain control. For analogue however, that is not necessarily true. Very low source/preamp settings (say 8 o'clock) on a continuously variable pot (gain control) could result in more noise; very high settings (say 4 o'clock) could result in less headroom. Many high gain analog preamps are set up for 1V for full output to occur in the ideal place on the dial for that device, usually somewhere between 9 and 3. So lower amplifier input sensitivity may or may not improve the situation in all systems. Each system is unique depending on the gear and gain staging combinations in the system to know for sure. This is an ideal example of why you go to a dealer for advice!
Brad

My only point was on your first post, you appear to advise everyone to lower sensitivity, which I would not always recommend as it does not always benefit everyone, and many folks have messed up their speakers fiddling with this sensitivity control over and over.
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Re: Adjusting 1V to 2V input sensitivity

Postby spacey » Wed Jan 30, 2013 7:53 pm

Thats true, Brad. For analog active preamps it may well be totally fine at 1V as the factory setting is. I've come across quite a few active ATC owners with (Naim and...) other active preamps, most say anything above 9 o'clock becomes too loud?? Surely this 6dbu reduction helps and would allow the volume pots, which as optimal at around '11 - 2' on the dial, to perform to their optimum and most balanced.

I'd not recommend people to play with these lightly or even over and over again; set it once to either 1V or 2V then leave it well alone :)
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Re: Adjusting 1V to 2V input sensitivity

Postby Brad Lunde » Thu Jan 31, 2013 6:52 am

spacey wrote:Thats true, Brad. For analog active preamps it may well be totally fine at 1V as the factory setting is. I've come across quite a few active ATC owners with (Naim and...) other active preamps, most say anything above 9 o'clock becomes too loud?? Surely this 6dbu reduction helps and would allow the volume pots, which as optimal at around '11 - 2' on the dial, to perform to their optimum and most balanced.

I'd not recommend people to play with these lightly or even over and over again; set it once to either 1V or 2V then leave it well alone :)

Agreed!
Brad
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Re: Adjusting 1V to 2V input sensitivity

Postby darrenyeats » Tue Jul 15, 2014 11:51 am

I'm thinking it’s actually 1V/4V (since that's what ATC quoted for the new 20A Pros on Facebook, and all the manuals say ”+/-" 6db ...)

Anyhow, I agree you should set to minimum or maximum and not in between, to maintain L/R level matching.

A precision screwdriver set helps ... the screws are sometimes a little offset in the hole so you need something thin enough so there's leeway as the screwdriver passes through the hole yet with a big enough blade to get proper purchase on the plastic screw head without gouging it. Don't apply too much force.

If your system is too loud it's likely the ideal place to attenuate, late in the playback chain - ATC confirmed to me that input impedance is unaffected.
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Re: Adjusting 1V to 2V input sensitivity

Postby darrenyeats » Mon Jan 26, 2015 1:16 am

darrenyeats wrote:I'm thinking it’s actually 1V/4V (since that's what ATC quoted for the new 20A Pros on Facebook, and all the manuals say ”+/-" 6db ...)

FWIW, this has been clarified on the website to be "0dB to -6dB/1V – 2V" ... so I thought wrong.

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Re: Adjusting 1V to 2V input sensitivity

Postby MattSPL » Mon Jan 26, 2015 9:08 pm

Thanks for the info Darren, I found this adjustment very useful in my system and I do the same with my current speakers.
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