Purists hate loudness compensation, but unless you always listen at the "optimum" SPL, it can make the music sound "better" if not "more realistic." Face it, unless you're doing dedicated listening at "concert hall" volume, you're going to want some kind of frequency compensation.
A big problem with loudness switches is that they are hit or miss; they are only optimised for a certain speaker efficiency and/or room gain, line source level, etc. If you think your loudness compensation in your system sounds "perfect" just try listening to a more or less efficient speaker system with your system, or raise and lower your source level and see what happens. In fact somebody mentioned using source or power amp level to tweak loudness compensation.
Of course, some loudness switches just suck and sound terrible no matter what you do. A true loudness compensation circuit should do more than just bump the bass up a couple of DB. On some cheap units you only have a choice between no bass and nothing but bass. This of course is useless.
My old Nakamichi TA-2A has variable loudness, and if you're going to do loudness compensation this is the only way to go. You can really tweak the response with this particular loudness control. I have seen similar setups on other vintage equipment and I can't understand why the audiophile community has eschewed this handy device. Every variable loudness control I've ever seen works at least pretty well, and if you don't like it you can defeat it. I like them so much that I included a variant of the circuit in my latest integrated amp.
A big problem with loudness switches is that they are hit or miss; they are only optimised for a certain speaker efficiency and/or room gain, line source level, etc. If you think your loudness compensation in your system sounds "perfect" just try listening to a more or less efficient speaker system with your system, or raise and lower your source level and see what happens. In fact somebody mentioned using source or power amp level to tweak loudness compensation.
Of course, some loudness switches just suck and sound terrible no matter what you do. A true loudness compensation circuit should do more than just bump the bass up a couple of DB. On some cheap units you only have a choice between no bass and nothing but bass. This of course is useless.
My old Nakamichi TA-2A has variable loudness, and if you're going to do loudness compensation this is the only way to go. You can really tweak the response with this particular loudness control. I have seen similar setups on other vintage equipment and I can't understand why the audiophile community has eschewed this handy device. Every variable loudness control I've ever seen works at least pretty well, and if you don't like it you can defeat it. I like them so much that I included a variant of the circuit in my latest integrated amp.
Kenwood Basic C1 pre-amp also had a rotating loudness knob. While I didn't devote a lot of time to "studying" it, it seemed act exactly like the bass control (which was very rudimentary and lousy in line with the Basic philosophy of keeping the active element count low).
Funny thing, their C2 pre-amp is about the most knob-laden pre-amp you can imagine (choice of 3 bass filter turnover points). Doubly funny, "loudness" is now just a switch and it works really nicely and tracks the VC level.
Fast Eddie D is mistaken in saying you can't get a single-switch loudness circuit to track the room sound loudness level. No reason it can't be designed and adjusted by a simple level adjustment to do so. But it does depend on having sources supply signals at constant reference level.
Funny thing, their C2 pre-amp is about the most knob-laden pre-amp you can imagine (choice of 3 bass filter turnover points). Doubly funny, "loudness" is now just a switch and it works really nicely and tracks the VC level.
Fast Eddie D is mistaken in saying you can't get a single-switch loudness circuit to track the room sound loudness level. No reason it can't be designed and adjusted by a simple level adjustment to do so. But it does depend on having sources supply signals at constant reference level.
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You know, I'm an old guy that's not up to speed on all the software applications. For example, I don't even know how to draw a schematic on the computer. Any help would be appreciated; if I could just draw schematics online it would help me immensly as well as allow me to share with the community.
I hear about Spice simulations, but I know nothing about it. I suspect that when I design a circuit I do my own "Spice" simulations by applying KCL and KVL to all the nodes and loops of the circiut. I've been known to make a mistake or three too, but I can always figure out my mistakes.
I went to engineering school in the 70s, before computer modelling was in widespread use in engineering. We did everything the "hard way." Engineering calculators cost $150-200 in 1975 dollars too, and their capabilities paled in comparison to the engineering calculator I recently bought at Wal-Mart for under $20.
Anyway, the amplifier in question was the result of "Operation Junkpile." I have old amplifiers, recievers, boxes of parts, etc and I always said I would build something out of it. The circuit consists of a discrete preamplifier, passive tone controls, and a passive switched loudness compensation circuit with 6 different settings. Changing the settings changes how much loudness compensation is introduced into the circuit. It is simply some capacitors, the switch, and an array of resistors. The power amp section came out of a "50+50W" tabletop stereo, uses an unmarked chip, and after beefing up the power supply it delivers some real punch. Transformers are all salvage. Cheap, practical, and sounds pretty good. Not hi-fi but it's going in a second system. I also plan to add a dedicated chip amp headphone amplifier to it using a couple of those small LMXXX DIP chips rated for around 1W into 8 ohms. I will of course optimise the circuit for headphone use.
Of course you're correct, but a lot of recievers and amps just have a switch. You are referring to the variable loudness controls found on a lot of vintage equipment. And there is a reason it can't be designed like that- production costs.😉 But of course, we can design whatever features we want into our equipment.
Yes it does. Without having source levels uniform you will have to adjust the compensation when switching sources if you want to have uniform compensation.
If your loudness compensation circuit doesn't change with the volume control knob, then you are OK for only two room loudness levels: (1) as loud as the recording studio and (b) where ever that compensation fits. From here on, I am talking about the high-class type of VC-tied compensation.
Aside from complex notions about how to do compensation with DSP (of doubtful validity), there really is just a single parameter: how loud is the sound at your ear.
Therefore, in my view, just a matter of reducing the sensitivity of the power amps (or tricks using tape-out or external-processor loops). Piece of cake even if the power amps don't have their own input volume controls. And with just a single factor to listen for, not hard to do the set-up by listening to the same piece at different sound levels till you are happy with the bass at different levels.
Typically this means setting the pre-amp volume control way far higher than before. But that is the way the loudness compensation was built into the pre-amp volume control.
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