Re: [ARSCLIST] Non-RIAA preamp

[Eric Jacobs <ericj@xxxxxxxxxxxxxxxxxxx>]

Hi Pillip,

The amplitude (loudness) of a frequency is not a function of the 
amplitude of the groove, but rather the lateral speed of the 
stylus.  The cartridge with its coil and magnet are effectively
a "generator" - the faster the lateral movement, the more output
the cartridge generates at any given frequency.  When you reduce
the lateral speed, you reduce the total dynamic range - the 
difference between the softest and loudest sounds.

When you half-speed transfer (not master), you reduce the output 
in a way that compresses the relative amplitudes, reducing the 
dynamic range.  Increasing the gain after adjusting pitch does 
nothing to the dynamic range and simply offsets the compressed 
signal.

The compressed signal is why it sounds "flat".  So some sort of
expansion is required.

Half-speed mastering on the other hand takes this compression 
into account, and they adjust the groove excursion accordingly
so that the dynamic range is correct when played back at full
speed.

Perhaps the analogy is that half-speed transfers increase your
sample rate density, but reduce your bit depth.

Hope that explanation (and distinction between half-speed 
masters and half-speed transfers) makes some sense.

Eric Jacobs
Principal

The Audio Archive
tel: 408.221.2128
fax: 408.549.9867
mailto:EricJ@xxxxxxxxxxxxxxxxxxx



-----Original Message-----
From: phillip holmes [mailto:insuranceman@xxxxxxxxxx]
Sent: Tuesday, September 12, 2006 4:24 PM
To: ericj@xxxxxxxxxxxxxxxxxxx
Subject: Re: [ARSCLIST] Non-RIAA preamp


That seems counterintuitive.  It seems like it would be the opposite: 
playing back at half speed would allow the playback equipment to better 
track the transients.  I can hear that half speed mastered LPs sound 
much better to me, and if half speed playback of vinyl sounds "flatter", 
would half speed playback of tape sound the same?  Or is it negated by 
doubling the speed of playback?  Wouldn't the same hold true if you 
played back a digital file at double speed?  Is it possible that it 
seems "flatter" when in actuality it's actually lower distortion, hence 
it sounds less aggressive (you know, lower distortion because the 
cartridge had an easier time of things)?  Have you analyzed things and 
found that it measures like you hear it?  I know I've been tricked into 
thinking things sound improved when they were actually worse 
(objectively measured to be worse).  Single ended tube amps "sound 
good", but measure awful and with the right music, sounds even worse.  
I'd like to see a 5 watt single ended amp driving dynamic (cone) 
loudspeakers playing a Virgil Fox spectacular without crapping out (not 
an issue with horns due to efficiency).  Electrostatic speakers "sound" 
good, and in some ways they are lower in distortion (no box resonance, 
crossover issues, etc..).  But the comb filtering is very noticeable to 
a spectrum analyzer, though not to human ears.  I've usually preferred a 
well mastered and pressed record to a CD.  Some of that has to be 2nd 
order distortions that are added making it sound fuller or sweeter.  
Some of my prejudice is that the high frequency response of a red book 
CD is not all that great (and MP3 is awful).
Hey, I'm not contradicting you.  I am interested in why it sounds flatter.
Phillip

Eric Jacobs wrote:
> On 10/12/06, don cox wrote:
>   
>> On 10/09/06, phillip holmes wrote:
>>     
>>> In the phase encode/decode discussion of RIAA, did anyone mention that
>>> speed is critical? If the disk was recorded slow or fast, you'll have
>>> a hard time getting proper frequency response. 
>>>       
>> Playing at the wrong speed affects pitch, but not really frequency
>> response.
>>     
>
> Often overlooked is the fact that the dynamics change as well when
> a recording is played back at the incorrect speed.  It is very
> noticable in more extreme cases of speed change.  If you playback at 
> half speed and then repitch the recording, it will sound "flatter" than 
> if it were played back at the correct speed.
>
> Has anyone tried to expand the dyanamics on a disc played back at 
> half speed?
>
> Eric Jacobs
> Principal
>
> The Audio Archive
> tel: 408.221.2128
> fax: 408.549.9867
> mailto:EricJ@xxxxxxxxxxxxxxxxxxx
>
>
>
>