This is the bit I don't get. I've analysed quite a few recordings and most classical stuff has a peak to average of 20-30dB. The Foobar dynamic range plugin I don't completely trust though. Most modern classical CDs are normalised across the disk to around -0.1dBFS. To get the full majesty of a symphony you need max SPL on the peaks to be IIRO 100dB (actually figure cause of many arguments, but 100dB works in most domestic environments). This would give you an average level in the 75-80dB arena.
Pop music these days is compressed to death. So you would want to reduce the peak to around 85dB. Giving you 15dB of volume control range. Add your 6 for source differences gives 21dB, which gives another 10 for when you might want to listen more quietly at night to something soothing.
Can you see my confusion?
Classical music is not a problem from the standpoint of the volume control range (VCR), but rather one of the maximum SPL allowed. So I'm with you here, but I always get an uneasy feeling when I see a classical recording normalized to a value near the ceiling.
As I already mentioned, it is the heavily compressed stuff that dictates my VCR. Suppose I'm listening to a piece mentioned in my previous post at a peak SPL of 85dB, and call the corresponding volume setting VC1. Now if I want to listen to the same recording such that the peak SPL does not go beyond 50dB, then I have to attenuate by 40dB relative to VC1 in order to have the SPL varying between 45 and 50dB. Hence the VCR requirement in my case.
I abhor heavily compressed music, but as it happens I support a small Folk dance group in technical matters, and they have such recordings. Some of them are extremely rare, recorded by amateurs in the field with CompactCassette recorders of the time, and are nowhere else to find. Playing such stuff at 85dB SPL in a domestic environment located in a building with several more flats is a bit of a problem, at least in this country. And as a technical person, I like solutions with ample flexibility.
Regards,
Braca
The only thing that I have an issue with is that they don't tell you on the sleeve notes what the max SPL was in recording should you want to listen at the appropriate level. For example I have yet to find a reference as to how loud a string quartet should get if you are sitting in the front row. I suspect due to being close to them its not that much lower than a symphony, but only a suspicion.
50dB is extremely quiet even for late night listening tho? My solution to that is my old trust Koss ESP/950s! When I get my miniDSP working I would probably handle very low level digitally as you would need some EQ that low.
Fair enough. If you are using multiple analogue sources then you do need more gain swing. Fortuitously my phono stage pumps out close to the same level as the DAC so I am saved. My only killer is that the TV toslink out is about 12dB down on other digital sources. I am guessing its because there is an EQ capability in the TV, which cannot be overridden.
Bill
Well, most of the labels don't tell you almost anything about the technical aspects of the recording. Sadly, the classical music production copies increasingly the manners of the pop music market. And how about a compressed and clipped (at places) recording of a Shostakovich Symphony becoming a Record of the Year in the Grammophone Magazine a few years ago.
Re. the string quartet SPL, twelve First violins in a symphony orchestra produce (theoretically) approx. 11dB more SPL than a single one. Further calculations seem to be much more complicated.
It seems I've gone off-topic here.
Regards,
Braca
I think considering gain requirements, esp with a pre that can put out pro levels is on topic. I despair that Gramophone don't look at recording quality any more, BUT a number of the smaller labels are releasing stuff with close to full DR these days. You just have to be selective.
I have a (yet to be commissioned) MiniDSP 2x8HD. That can push out +20dB which is more than this preamp can take. Shame as would have been nice to run everything hot.
I have a (yet to be commissioned) MiniDSP 2x8HD. That can push out +20dB which is more than this preamp can take. Shame as would have been nice to run everything hot.
It's not too difficult to come up with a mechanical solution to this anyway. Just a little gear box or couple of cogs (which way would the original turn as per the design?) and can make remote control easy too.
If you want remote control, I would do relays or one of the PGA varieties. No need to hang on to mechanics.
Jan
A mechanical solution can give full turn on a volume knob whilst keeping the turn on the actual pot within it's good tracking limits.
That way you can have a proper volume knob whilst mechanising it with remote control.
The usual PGA volume controls (if we're talking about the same thing - I don't know the term but looked it up
) I don't think can work in this application and they use data wheels where aren't so nice to use.The active volume control uses the two resistances of the NFB to set the volume.
Those two resistances can be provided by a potentiometer with wiper tapping into the resistive track. The wiper tap is connected to the -IN pin of the opamp.
But, any TWO resistances could provide the same active volume control.
It does not matter that the resistances are selected manually, or by relays, or by a switch.
It does matter what happens DURING the switching period. The -IN pin must not be left "hanging" as an open circuit. Any rotation, or switching, must not open circuit the opamp.
Those two resistances can be provided by a potentiometer with wiper tapping into the resistive track. The wiper tap is connected to the -IN pin of the opamp.
But, any TWO resistances could provide the same active volume control.
It does not matter that the resistances are selected manually, or by relays, or by a switch.
It does matter what happens DURING the switching period. The -IN pin must not be left "hanging" as an open circuit. Any rotation, or switching, must not open circuit the opamp.
A mechanical solution can give full turn on a volume knob whilst keeping the turn on the actual pot within it's good tracking limits.
That way you can have a proper volume knob whilst mechanising it with remote control.
The usual PGA volume controls (if we're talking about the same thing - I don't know the term but looked it up
Yes in this app a digital pot would be a better choice.
You CAN do it mechanically, but I don't see readers here flock to their lathes ;-)
Did you check out Hans Polak's solution for this design?
And Andrews remarks about make-before-break are very important.
Jan
Andrew, thanks to point out the "open circuit" issue. I was thinking to use the R2R from AMB but I didn't think about it. I have to recheck the circuit to understand better how the switching is working.
Hi Jan, I realized the PCB for the Hans volume but I am not satisfied and I am looking for a better solution like the R2R from AMB. The minimum of the Hans circuit is still too loud and the steps are too big. The pot work much better but I have to say that I don't loose to much time to make it working better....
Regards,
Enrico
Lathes? A couple of lego gears and a lego remote control
Or even a weighted knob and a string pulley scavenged from an old tuner seperate. But toothed belt would be best, perhaps from an old inkjet printer found on the street.
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