I'm not trying to start an argument here but tone controls have got a lot of bad press for a long time. I don’t believe they are the devil reincarnate.
I use tone controls for two reasons;
Somebody who loves bass mastered some of my favourite recordings. Either that or the monitors were lacking in bottom end. Try Arron Neville’s “Warm Your Heart,” there are others. This is particularly a problem for me because my system is flat to 25Hz and if the recording isn’t you know’ll it.
Secondly, the loudness curve is generally accepted, (ISO standard 226). If I’m playing music below its natural level a bit of extra boom and zing never hurts. In fact it sounds more natural.
Having said that I switch in the controls less than 5% of the time, only when the need dictates.
The tone controls that I use are shunt controls and are easily disconnected, (via a switch) from the preamp. They can not degrade the sound when disconnected.
the APT preamp had nice tone controls
My current homebrew preamp doesn't have tone controls. However, my previous one did. I found them useful, but because it was a homebrew, there were some things I did to eliminate some of the negative issues surrounding their use.
I think most commercial products have too much range for their controls. I've seen some that advertise +/- 20dB! I think the limit should be +/6dB.
The turnover frequencies need to be chosen very carefully and the circuit topology needs to be one that minimizes interaction, doesn't introduce excessive noise, distortion, etc. I modeled my tone controls after the APT preamp from the 80's. The design was patented, but simple to analyze and change if one so desired. Worked quite well. Actually, the entire APT preamp was a nice design that was executed well for its day. I would be curious to see how well a modern execution of the design would perform. Quality of opamps and attention to design of power supply and grounding details have gotten much better since the APT was available. Doug Self's preamp designs use what I consider to be an improved form of the feedback volume control. This worked very well in my homebrew preamp also.
However, I think DSP tech is poised to rapidly take this analog domain function over to the digital domain, especially with the emphasis on surround sound these days.
So, it's a moot point :-)
I think that tone controls cannot degrade quality, if and *only if* properly designed, and *correctly* adapted to the others stages.
Very good results can be reached with Baxandall design, in old fashionned style : 12AU7 tubes, oil-paper condensers, and other good components, with cathode-follower stage at both inputs and outputs : 3 tubes for complete stereo unit. Cathode heaters must be powered with stablized dc current. The entire appliance must be shielded, and properly grounded.
In my opinion, it's more difficult (but not impossible) to reach as good results with transistorized designs, although slight changes in sound coherence, fluidity, are unavoidable.
Futhermore, I do agree with you : +/- 6 db at 100 and 10000 Hz are reasonnable values. But sometimes, buyers think that more efficiency is more quality...
I totally agree with Walker....
Sometimes tone controls are necesseary.
I too have a lot of records and CDs with a tonal imbalance, which at times one wishes to correct. Sometimes it is rather astonishing that modern technology can be handled so ignorantly, particularly with a lot of the relaunches of e.g. classicial jazz, and other recordings, that are sent to market these days.
In addition, I also work with a community radio station, and frequently have to listen through recordings done under marginally conditions, in addition to the technological "abuse" that follows with rather untrained "reporters".
Somewhere along the line, this "no control" mania occurred. I can understand that, given some of the old fashioned and rather poorly constructed controls, but it is really only a matter of a high quality bypass switch.
Some 10 years ago, or so, I remember John Linsley Hood had some very interesting designs published, that combined with the best of modern op amps should do an excellent job. These designs had switchable freq's and were of the shelving type. But. -I would still go for the bypass switch......
[Edited by AuroraB on 12-03-2001 at 02:50 PM]
Parametric equalizers give you more control than standard tone controls and they can more accurately correct some problems. Unfortunately they often remove more detail than simple tone controls. As always you don't get something for nothing.
I use both but tend to use the parametric for PA use and tone controls at home. At home I always try to fix response problems at the source, but when the problem is in the recording what else can you do.
It's interesting that many fanatics (and I consider myself fairly fanatical) will use active equalisation and crossovers but refuse to consider tone controls.
Of course the best sound quality comes when you don't have to use either.
Actually a good parametric eq can be gentler on the sound than traditional (graphic) tone controls. One of the big advantages to a fully parametric eq is that you set the 'Q' (bandwidth) as well as the center frequency, which means that you can tailor the systems frequency response to deal precisely with problems. The best professional sound reinforment systems use parametric eq's (typically DSP based) to get the best sound out of their FOH speaker systems. The problem is that properly setting up a parametric eq takes more experiance (and test gear) than the usual 31 band graphic eq and it is visually less obvious what is being adjusted.
P.S. Ashley makes a 7 band parametric eq that is absolutely killer. Best value in an analog parametric I have ever seen.
We all need tone controls
Every one should have the ability to make the most out of their system and fine-tune it to their environment and ears. My upcoming preamp project will have tone controls.
If you believe that the recording engineer adjusted the sound to be perfect when using his monitor speakers then of course you do not need tone controls. However if the tone control (equalization) settings at the time of recording were not perfect for your system then you may just need to do some re-equalization. Hence you would need tone controls.
There are significant amounts of equalization used when recording studios record. It is part of life. Along with equalizers there are lots of compressors, noise gates, reverbs and other equipment that modifies the properties of signal. Mostly all audiophile purists deem this equipment bad to use in the home environment but seldom appear to take into consideration their use in recording studios. The fact of the matter is of course is that much of this equipment is required to give us decent recordings when using most modern recording techniques.
Tone controls are thus a tool that can be used at times to improve sound quality at home just like it can in recording studios.
I've always been amused by this position that opamps/tone controls/multiple gain states/whatever are bad...so let's throw some more in.
The logic escapes me.
If you've got a dirty window, the solution is not to smear <i>more</i> dirt on it. If it's the best view you're going to get of the outdoors, at least don't mess it up any more than it already is.
In the case of tone controls, people <i>assume</i> that they know what the tonal balance should be. With only rare exceptions, they weren't in on the recording sessions, and haven't a clue. Now, I'm not saying that all recording engineers are competent--many clearly aren't--but I've never been convinced that tone controls are the answer, at least in a high-end system. The phase shift alone is enough to put me off, not to mention all the other gunk you've got to put in the signal path. I'll leave it for the low and mid-fi systems out there.
(There...you knew someone would finally show up to give a counterpoint...)
Grey, your comment implying that using tone controls "assumes" you know what the correct tonal balance should be, should also apply to not using tone controls. Since none of us were in at the recording session, none of us know what the sound should be. Is it correct to presume that our speaker/room combo sounds so like the one in the studio that we have no need of any form of correction?. This seems unlikely to me. Furthermore, not all recordings sound pleasant when played at home. The question one is faced with is whether to doctor the playback to be pleasant to ones ear and hence enjoy the music, or reject the music because of some notion of what it should sound like that is sacrosanct. With studio recordings there is no reference of "closest approach to the original sound", since the "original" was that heard through the studio monitors after sometimes extensive processing. Obviously if the tone controls even in their flat position butcher the sound then they should not be used. But if after the controls are adjusted, the result is more enjoyable, isn't this a good thing? Even Mark Levinson designed a very high end preamp (under the Cello label) with extensive tone controls, with the philosophy that they could improve playback quality. Even the best speakers are tone controls in reality!!
I would agree that the goal of designing a system is neutrality so that it works with the widest range of recordings, but then I see no harm of individual adjustement away from this to compensate for non-neutral recordings. The argument then becomes one of what is an appropriate form of adjustement that will be capable of "correcting" such recordings.
OK-- let's get the heat up...;-)
Most newer recordings are processed to a degree that I seriously doubt that even the sound engineer is able to recall the setting on the desk without his cue sheet or the CPU recall function on modern desks. It is all about "creating the sound stage". Fair enough- but this should also give us the clue that a lot of the modern recordings are unusable as "reference recordings" for determining fidelity,- who of us knows how it was all intended to be ???
For a great number of years, it's been quite astonishing to witness the heat generated over minimalistic reproduction of recordings that have been passed though bucketloads of 741 op-amps.....
Personally, I try to use recordings with woodwinds, as these has been my own instruments for 40 years. But on the other side,-if you don't hear the difference between Benny Goodman and Artie Shaw- why bother with the equipment...???
As an "electroniciot" by profession, I most sincerely beleive in the "no frills" idea, but sometimes you have to--
When I have to, I would love to have the parametric section of my old Soundcraft desk, - but at home I will do with simpler controls, - and a gold plated switch to get rid of them when I don't need them.
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