Volume controls
Join Our Community Subscribe to Paul's PostsOf all the things we take for granted in our lives, volume controls would have to be high on the list. Whether by remote or the turn of a knob, the volume up and down is perhaps the most familiar control in the repertoire.
Familiarity doesn’t mean unimportant. Despite the fact that every preamp, integrated, receiver, television, and most DACs have them, volume controls should not be taken lightly. Their impact on sound quality cannot be overstated. In fact, I cannot think of anything more important to sound quality within a preamplifier than the volume control.
While we have taken our years of experience with these important functions and eliminated the traditional means of implementing them in our two preamps, the Stellar Gain Cell DAC and the BHK Signature, most other companies still cling to the standard potentiometer or fancier versions of the same.
Ever wonder how these controls work and why they make such a difference? I have put together a simple video in which I take apart a pot and show you what’s inside. Here it is.
There’s no magic inside, as you’ll see. But what can be said are two things: volume controls are like the brakes of a car, not the gas pedal, and their importance to sound quality cannot be overstated.
Have fun.
Traditional control volume, regardless of which brand they are, are subject to wear (sometimes premature) depending on the material, and usually lack the required precision that produce imbalances between channels.
All of them have limited lives counting these in the number of cycles, information given by the manufacturer itself. Generally they are a headache for the user, for the noise they produce themselves, which can be eliminated momentarily with Deoxit when they allow access, otherwise the best solution is to replace them.
I have no experience with PSA audio gain cell, which can be a significant advance in this area, but apart from this I think that the most reliable and accurate is the TVC although its price and sometimes its size make it unusable as after -market solution for fans or even for designers.
I had to look up TVCs and read about them, and stumbled onto a website called Tortuga Audio where they claim LDRs (light dependent resistors) are superior to TVCs. As a layperson in this area, I am clueless as to how these all work, I just want to hit the + sign a few times on my app and have things get louder or the – to get quieter! For this I am grateful to all the designers that make it all come together!
I had a Tortuga balanced preamp with the LDR volume control technology and it was amazingly quiet and effective as a passive preamp in my system. Until the BHK Signature, it was the best attenuator/preamp I ever heard in my system. It had an adjustable output impedance for fine tuning its match with the power amps, which allowed the character of the sound to be tweaked. I liked that feature a lot. But the balance of the adjustable volume between L and R channels was unstable in my unit. I was constantly having to readjust the channel volume balance. LDRs, like tubes, are somewhat unpredictable and are not 100% reliable. When I purchased the PS Audio DS DAC, I no longer needed the Tortuga.
Imbalance from poor tracking dual volume controls is only a problem if your only spatial clue is “Panorama control”. Unfortunately, this is 99% of commercial recordings. Fortunately for me, I never have to listen to any such.
My DSF conversion software has a balance control from L100 to R100. I am never affected by imbalance on my near coincident pair recordings, except when it is so far out that it reduces the dynamic range because one channel is peaking over 3dB hotter than the other. In this case, I level them without regard to the fake stereo content of inter-channel level differences. The phase differences and echo patterns are vastly more stereo information than balance, which is under 8 bits for an entire multi-minute track running at 5.6 Mb/sec.
The dual channel imbalance problem I had with the Tortuga was: the actual volume (not fake perceived volume) of one channel would fluctuate, regardless of the musical content. It had nothing to do with stereo imaging or “panorama control.” It was a problem with the LDR circuitry for that particular channel. I mentioned it as an example of how LDRs as volume controllers are not necessarily reliable.
Paul – re: your story in the video – I nearly âdropped the transmissionâ on my system the other day noodling with the Bridge II update and the mConnect app. Often app volume controls are separate from the other parts of the chain (like the physical gear), so youâd usually run them wide open for best sound. Turns out the little slider in the app was contolling the DSJ volume directly/remotely, and at the moment (since Redcloud) Iâm running the DAC directly to the amp.
So you know where this is going…with one quarter-inch swipe of the finger, I went from 50 to 100 on the DAC volume control. Exhilarating acceleration! 50-100 in a tenth of a second! I was pressed back in my seat, wildly grabbing for the âsteering wheelâ. Thought for a second there I had blown the tweeters in Stevenâs former Harbys (sorry Steven). But they survived, thank god.
My App Driverâs License is suspeneded.
BB canât believe you gave up your Quads (and that beautiful midrange) for a pair of British boxes just to get a couple extra dbâs. When you have some available time go visit your local Magnepan dealer and ask to listen to the 3.7iâs through a high performance amplifier.
Wit or witout those JL Sub’s, the 3.7i will deliver the best of both worlds.
Well, I still have them at this point, and itâs more than a few dB. Iâll give the Maggies a listen some time, theyâre certainly well liked – but I donât know that Iâm really a linesource-ish guy. Borrowed some 20.1âs once, recently heard the Carver ALS (not at a show), the big Scaena system shown with the PS gear at this yearâs Axpona, MR1, etc. I donât get the â9 foot tall saxophoneâ thing. Makes sense for orchestral scale. More of a point source imaging person. But Iâve changed before : )
When I had my Nobis Proteus preamp, I had them replace the cheap pot with a DACT volume control. Brian, who had designed the preamp, said it was the best volume control he had ever tested. I believe he was referring to the two channels matching at all levels. The only problem was it’s steps were two wide, so finding the perfect level was hard at the low end.
My CJ CT-5 has much smaller steps, and was my first preamp that came with a remote. I run everything, including the HDTV through the preamp.
Being a closet Luddite, I much prefer physical remotes to apps. When I had to replace my first 7″ tablet, I got a Best Buy 8″. I didn’t even bother to load the free JRiver app. If I use JRiver or Tidal, I walk over to the dedicated music player laptop and program anywhere from 2-8 hours of music.
For everything else, I always have my box of remotes within reach.
I suppose someday I will have to use a tablet to control a music player, other than the Raspberry in the bedroom, but I am not looking forward to it.
Getting up from the listening chair to physically adjust the volume control, flip LPs and change CDs periodically is healthy behavior.
Since we can’t (or don’t wish to) always listen at “concert volume” we are also changing the perceived frequency balance when we attenuate the “volume”. The old “loudness” button on Stereo receivers really wasn’t up to the job, even the “variable loudness” controls seldom produced satisfactory results. In any case, any loudness compensation is by very nature a compromise since any “curves” that exist are based on averages, and what humans perceive varies fairly widely, just based on physical differences in our ears. Typical tone controls are not much help, either.
Plus, everyone’s room and speakers are different and any electronics would need to be smart enough to deal with different speaker efficiencies, along with humans non-linear hearing at different volumes, which is probably why any of the above mentioned “solutions” seldom worked well.
I’m curious as to how people deal with this. Do we set up our listening rooms scientifically and then always listen at concert volume, or as close as we can? Or, setting things up for serious listening and have an alternative setting (or settings) for casual listening at lower levels or using your audio system as part of an A/V setup? Or do we set things up by using our ears at the volume levels we are comfortable with and just enjoy what we hear? Or maybe some combination of both approaches and reach a compromise we can agree with?
Loudness compensation is a non-linear function of absolute level, and varies perceptually depending on your recent loudness history. This means that 99% of the time you are listening to dynamic frequency response distortion from relative levels. The closest you can get is level matching the loudness of the original music performance – if indeed there was an actual musical performance instead of days to months of noodling in a studio.
I find the most musical loudness compensation is volume controls on a DSP active crossover. I set my crossovers as close as practical to the knees in the loudness curve at 400Hz and 4KHz, use 2nd order Bessel slopes, ignore impedance interaction since each driver sees a direct voltage source and never use subtractive overlap (which causes a host of problems). Listening below reality level, bump up woofer and tweeter to taste.
Note you also can’t use drivers with bumps in the raw curves or cone breakup in the passband plus at least an octave guard band.
A impressively set up system. I’d be interested which active DSP crossover you employed.
I use Bessel 2nd at 40Hz, 400Hz, 4.7 kHz – but still passive exept the sub.
Passive crossovers shift the volume control to the driver level, where there are several diverse interactions between attenuation and frequency response, much worse than preamp level volume controls. Just thinking about loudness compensation in a passive crossover gives me a headache!
It is theoretically possible to use Tungsten filaments to implement an automatic loudness compensator, but it could only be optimized for one type of orchestration.
I use Behringer DCX2496, not an audiophile component or even a very reliable one, but it has the control functions I need at a low cost. Since I use up to six channels of crossover input at a time, cost is more of a factor.
I listen between 40 and 90 dB without need for loudness compensation so far. For higher levels I have to retune a bit but this happens once or twice a year.
I would rather not digitize the analogue signal of my DAC again, so I have been looking around for something like a DAC with a built in DSP, xover, and six channel output, and of more quality than the Behringer for a reasonable price .
One DAC/xover I was tempted to buy was the ADI 2 PRO by RME, a nice machine for 1500$ but it has only four outputs. I guess one could do this also with a computer and multi channel output. But who wants to run three separate DACs?
There is maybe a misunderstanding about the volume control. I control volume mainly
in my computer, 24 bit into the DAC. From there into two amps, sub and main, with pots.
??? Now I’m confused. 40dBA-90dBA is exactly where you need loudness compensation.
Also, computer is the worst place to do volume control because it throws away bit resolution and amplifies quantization noise in proportion to the volume reduction. If you are running a 24 bit file through a system with maximum output of 100dB, then playing at 40dB is attenuating 60dB and throwing away 10 bits for an effective resolution of 14 bits. If you are playing a 16 bit WAV, you are down to 6 bits, less than a ’70s video game.
RME gets high marks for reliability and stability of drivers, but pro gear is not exactly audiophile. The MiniDSP line comes recommended by a friend whose ears I trust:
https://www.minidsp.com/products/minidsp-in-a-box/minidsp-4×10-hd
I built my own volume control. It consists of metal film resistors combined in parallel series and shunt combinations, switched by the world’s cleanest relays. Because there are only seven DPDT relays, the transfer function is highly non-linear and non-monotonic. It has great resolution at mid-gain setting where most of us listen, with the steps growing larger at the extreme ends of the scale.
The relays are mag-latching, vacuum sealed and have a proprietary surface composition and treatment. I know they are superior because Hewlett Packard uses them to switch inputs on their HP34401A digital multi-meter. It has stability and resolution to nanovolts and picoamps, all going through a set of relay contacts.
Standard Gold-to-Gold contacts have a minimum switching current of 10 microamps, below which they have noise problems because the contact does not maintain over time. Silver is better than Gold because AgO is conductive, but even Mercury wetted contacts can’t compete with this ultra-low noise (including thermal drift) relay for audio.
Over the ten years I worked with this relay, it was never available in the US. I had to purchase it through a Japanese parent company.
I know a whole class of preamp problems that sound worse that potentiometers: CAPACITORS.
Coupling caps, bypass caps, power supply caps, and the capacitance inherent in wiring and circuit boards, Aluminum caps, ceramic caps, polyester caps, FR4 epoxy distorts more than pots.
Unless of course the impedance mis-match of poorly implemented volume controls has greater fr variation than your speakers and room…