I was playing the Verdi Requiem -- the "Dies Irae" is one of the loudest choral passages in memory -- decided to put it on the scope -- the result is about the same whether I use my cheappo Samsung player, or the high end Sony SACD player. The first 4 peaks are the tympani:
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Cool. My St70 manual indicates 1.3v rms in for 35 W out. 1.3X1.4=1.9v peak each way around zero. You're showing about 0.8 V peak, one way. This signal will need a little boost in the preamp to max out the ST70. My Pas2 has 340 V headroom on the low gain 12AX7 stage, my RA88a disco mixer has +-7.5V supplies on the op amp low gain stage. NO PROBLEM.
The signal I have to L-pad down is the reverb output of the H182 organ, it is about 8v PP.
The signal I have to L-pad down is the reverb output of the H182 organ, it is about 8v PP.
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Music is incredibly dynamic.
I found my first amp designs didnt work very well as they clipped very quickly.
I learned to use higher voltage power rails to cope with the transients.
I found my first amp designs didnt work very well as they clipped very quickly.
I learned to use higher voltage power rails to cope with the transients.
CD and other digital sources have a built in limiter. The output can never be greater than the analogue equivalent of 0dBfs.
Most CDP have an analogue output for 0dBfs of between 2Vac and 2.2Vac (~6Vpp, ~3Vpk). A test disc and a DVM will confirm the maximum outputs from your digital sources.
The only way to get higher than this is from interference being added to the audio signal. Just take action to ensure the interference is kept at a low and acceptable level.
The average level from CDP and digital can be set at any level below that 0dBfs.
Again, a DVM can measure typical music levels off any disc and allow one to compare them to 0dBfs. Some of the extracting software does this for you. Some software allows one to reset the average level so that all recordings can playback at similar levels. I have that facility in iTunes, but don't use it.
Most CDP have an analogue output for 0dBfs of between 2Vac and 2.2Vac (~6Vpp, ~3Vpk). A test disc and a DVM will confirm the maximum outputs from your digital sources.
The only way to get higher than this is from interference being added to the audio signal. Just take action to ensure the interference is kept at a low and acceptable level.
The average level from CDP and digital can be set at any level below that 0dBfs.
Again, a DVM can measure typical music levels off any disc and allow one to compare them to 0dBfs. Some of the extracting software does this for you. Some software allows one to reset the average level so that all recordings can playback at similar levels. I have that facility in iTunes, but don't use it.
I'm glad you bought a serious DVM. My Sears 82195 is totally insensitive to music from the organ except at 50 and 60 Hz. 8 VAC signals out are totally invisible to the DVM. Most of the hobby repair people on organforum also find that inexpensive dual slope integrating DVM's are not suitable for testing their organ output or even worse, intermediate signals. I found a used 20 mhz scope much cheaper than one of the prestige brands of DVM's. The Fluke sales brochures linked to on WWGrainger Consolidated Electric Supply etc do not specify what frequencies their AC scale is sensitive to.
The fluke meter designed for the factory floor I had from work was incapable of seeing music frequencies.
By contrast, the Simpson analog 100kohm/volt meter with the 2 VAC scale, was quite useful for testing out the ST70 in 1976-84 before I dropped it.
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I would question the use of a DVM to measure AC music signals. I would suggest you use a scope and then take a look at the peak and calculate back from this.
I have a range of DMM with AC & DC ranges.
I can confirm that none of them are any good at reading transients. They make a half decent attempt at averaging the signal.
I can confirm that none of them are any good at reading transients. They make a half decent attempt at averaging the signal.
As I mentioned earlier 0dBfs is ~6Vpp.
-20dBfs should therefore be ~600mVpp.
It seems the DVM is seriously under-reading the peak voltages of that warbled signal.
Try a simple 500Hz sinewave at -20dBfs.
-20dBfs should therefore be ~600mVpp.
It seems the DVM is seriously under-reading the peak voltages of that warbled signal.
Try a simple 500Hz sinewave at -20dBfs.
Sorry Jack - not sure what you're trying to say here. Nor why you posted it in Analog source.
It's a just a preamp question -- how much input voltage should the preamp front end be designed for -- my FM tuner is way down from the output of the CD player, so the CD sets the extreme.
if the input to the pre-amp is the track of the volume attenuator then the power dissipation of the track determines the maximum input that the pre-amp can accept. I would expect a domestic listening pre-amp to accept at least 10Vpp (~3Vac) but I would aim much higher, capable of accepting 10Vac.
10Vac into a 10k pot results in a maximum dissipation of 10mW (10^2/10000=0.01W). Any half watt pot can easily accept 10Vac or even 20Vac.
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The specs needed for a DVM to measure transient signals is for it to have "True RMS" AC voltage capability. The 2nd function needed is for it to have "Record Min/Max"...this capability registers the maximum transient signal at a preset time interval, otherwise you will be looking at an ever changing value or in other DVMs average value. Then Vpk=Vrms*1.414
For a "digital" source such as CD the "overhead" needs be only what the CD can output when the disc is recorded at 0db. In simple terms, if the max level is 2 volt RMS from a particular player then the preamp will never ever be asked to handle more than that. It's cast in stone. 2 volt RMS is a typical level although some players do have more output.
All you need is a test CD recorded at 0db and measure the output from the player. If the frequency is low, say <400hz then any DVM will measure it.
As an aside to this, and many of you will have seen it,
http://www.diyaudio.com/forums/soli...er-do-you-really-need-domestic-listening.html
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