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PAC LC-1 Passive Volume Control Review

Rate this product:

  • 1. Poor (headless panther)

    Votes: 2 1.8%
  • 2. Not terrible (postman panther)

    Votes: 24 21.1%
  • 3. Fine (happy panther

    Votes: 75 65.8%
  • 4. Great (golfing panther)

    Votes: 13 11.4%

  • Total voters
    114

amirm

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This is the review and detailed measurements of the PAC LC-1 passive attenuator. It was kindly purchased new by a member and costs just $9.50 including shipping from Amazon.
PAC LC-1 Remote Amplifier Level Controller Review.jpg


I must say for such a cheap device, the RCA cables feely nice and supple. And volume control itself is smooth. Inside there is a tiny PCB where all the cross connections are made. From documentation it seems that it is for car stereos but obviously you can also use it for home audio as long as all you want is attenuation.

PAC LC-1 Measurements
I used the LC-1 between my Audio Precision APx555 unbalanced input and output across two 6 foot sections of cabling. Here is the dashboard:

PAC LC-1 Remote Amplifier Level Controller Measurements.png


So at this volume level, performance is completely transparent. Let's see how good channel separation is:
PAC LC-1 Remote Amplifier Level Controller Measurements Crosstalk.png


So there is a distinct hit but it is still more than good enough for most things.

The issue with passive volume controls is that it messes with the impedance of the device you are connecting to. This in turn causes a frequency response error as you can see below:

PAC LC-1 Remote Amplifier Level Controller Measurements Frequency Response.png


The level of attenuation may be worse in your device. As is, it is not too bad at roughly 1 dB at 20 kHz.

What I didn't like is the taper that they selected. Most of the range is useless as you only get meaningful attenuation once you are below 12:00 o'clock. That accentuates the channel differential in the pot used:
PAC LC-1 Remote Amplifier Level Controller Measurements Level Match.png


Of course your example may be worse or better than this. Company rates the unit at ± 8 dB. Not sure how you get +8 dB from a passive control. Assuming they only mean -8 dB, then they are meeting spec.

Conclusions
A passive volume control is going to be bring its native problems so there is no getting around that. In that context, for less than $10, you are getting what looks like a high quality little box and cabling. Yes, the box is plastic but still, I like the total package and am going to recommend the PAC LC-1.
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As always, questions, comments, recommendations, etc. are welcome.

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This product looks like its intended for car audio, as I've seen products like this get used for attenuating output usually for the subwoofer amplifier. I figure for those use cases its perfectly adequate. But in a home audio situation you might want something a bit better.
 
I've seen someone in the PC mods thread on Reddit use something like this to build a passive volume controller inside his wooden desk. Looked really cool. Good to know these are decent enough. Thanks for the review!
 
I use one of these to control subwoofer level -- without getting on my knees, reaching around to adjust the pot on the back of the sub, and getting back to my listening spot to check if I got it right. Seeing as that's essentially a very low frequency mono application, this gadget is just dandy for the job -- small, absurdly cheap, and very handy.
 
I must say for such a cheap device, the RCA cables feely nice and supple. And volume control itself is smooth.

Yep, looks like the same folks that make the stock HD600-series of cables for Sennheiser judging by the Y-Splitter and the general merging of the two channel sleeves. This to me is my ideal cable (no shirt tugging microphonics, Y splitter perfectly sized and positioned, soft and supple and pliable as you say.. Thank GOODNESS no one sees this sort of cable as anything special to charge more for it. I liked this so much I got the stock cable terminated in 4-pin and got rid of a silly and stiff paracord sleeved one that cost like 5x more or so.
 
I bought this specimen to manually adjust the volume of a sub, with a very bad result, hiss and noise noticeable when changing the volume, I replaced an expensive but definitely much better nobsound passive controller that works perfectly and has a nice big knob and a good feedback
51dA0gTsKKL._AC_SL1000_.jpg
 
Hi Amir and thank you for carrying out my request. If you have this device still laying around, would a dashboard SINAD measurement at -6dB possible? Considering @jasonhanjk claim.
 
I bought this specimen to manually adjust the volume of a sub, with a very bad result, hiss and noise noticeable when changing the volume, I replaced an expensive but definitely much better nobsound passive controller that works perfectly and has a nice big knob and a good feedback

That would be my concern in that the high resistance of the pot along with it probably not having its housing tied to the shield lead means it will be vulnerable to noise pickup. In cars way back when my solution was to just put the full-range amps up front so that I did not have to have long RCA cable runs in the interior that pick up alternator whine and such. I'm guessing that the noise is probably from these acting a bit like carbon mics when the resistive tracks wear and particles get between the wiper and the track. In my amp I built I used analog controls and even using high-end mil-spec stuff they still get crackly after a while and need cleaning to be quiet again.
 
That would be my concern in that the high resistance of the pot along with it probably not having its housing tied to the shield lead means it will be vulnerable to noise pickup. In cars way back when my solution was to just put the full-range amps up front so that I did not have to have long RCA cable runs in the interior that pick up alternator whine and such. I'm guessing that the noise is probably from these acting a bit like carbon mics when the resistive tracks wear and particles get between the wiper and the track. In my amp I built I used analog controls and even using high-end mil-spec stuff they still get crackly after a while and need cleaning to be quiet again.

An aerosol can of decent contact cleaner costs more than this gadget. Mine has been perfectly functional for years now, so I guess I risked a few $$ and won my bet. I have a lot of gear with the usual carbon pots and none of them are the least bit noisy or otherwise troublesome -- even my 35 year old Yamaha DSP-1's tiny level adjusters still work perfectly.
 
I like you testing stuff like this. Because this is the kind of stuff that can be very useful in certain situations but the price and looks make you question the performance.
 
Hi Amir and thank you for carrying out my request. If you have this device still laying around, would a dashboard SINAD measurement at -6dB possible? Considering @jasonhanjk claim.
I can do that test but how much my analyzer distorts is different than another device,
 
Why wasn't this available during my modding days. Could have easily bought / made power amp kits that didn't have their own volume control.

Voted golfing at first but saw the channel separation isn't perfect, but decent enough so changed to a happy. I don't see how a stereo volume pot can affect channel separation with RCA cabling unless the ground is somehow shared? Then again I don't know how bad a 3.5mm cable affects channel separation so I don't have a baseline to compare with. If a 3.5mm cable does better than this I would go crazy tho.
 
An aerosol can of decent contact cleaner costs more than this gadget. Mine has been perfectly functional for years now, so I guess I risked a few $$ and won my bet. I have a lot of gear with the usual carbon pots and none of them are the least bit noisy or otherwise troublesome -- even my 35 year old Yamaha DSP-1's tiny level adjusters still work perfectly.
Depends on the environment as well. My amp is somewhere where it can get humid, depending on if I'm using the AC or not. Probably an issue with oxidation. The sub with its integral plate amp has the same problems in its analog controls in that it needs TLC periodically or the levels aren't right. Thank god for measurements and target curves, or it would drive me nuts. Since this thing is intended for cars it has much lower specs than what you would normally find in hi-fi gear, esp. since it doesn't look to actually have a log-taper pot. Just some generic linear one (I wonder what its resistance is?). Very much built down to a cost. Doesn't mean it can't work, but since its in a plastic housing with just a bare pot it can introduce noise into the system, and it probably is not good for that many cycles. Not that it would matter much if its a "set and forget". But since its not much more than a meal at a fast-food restaurant, you can't really go wrong. If it doesn't work, chuck it...
 
I used a Fostex PC-1 Volume Controller for a while on my powered speaker setup without it's own volume knob. Was a real life saver.
This one has a better "Quality" of looks for a Desktop usage if others are interested in similar products. I had good use of it for a couple years.

Just a few days ago I removed it as I installed a EX5 to do the work instead of the previous solution I had running.
 
Nice little device. I've thought of putting a passive volume control in a digital volume control desktop system as an "oh shucks!" knob. If something is miss-set in the chain and really high volume appears, I can grab it and not have to fiddle with digital settings.

Yes, I am a little paranoid.

Plus, I can't hear a thing above 10kHz, so that roll off is strictly theoretical.
 
, I replaced an expensive but definitely much better nobsound passive controller that works perfectly and has a nice big knob and a good feedback
So would you say that the Nobsound knob is the knob of knobs?

:facepalm: I really must stop this. It can't be the single malt because it's almost gone.... oh:(
 
Cool little device. Glad to know there's a passing score!
 
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