Extraña situación digitalizando vinilos

DAG escribió:

O bien los cables no siguen las mismas normas y por eso la inversion de fase o bien los cables estan bien y es el Mytek el que invierte la señal.

euridia escribió:

¿ Por qué creéis que es un problema de ajuste de volumen si la parte positiva se digitaliza bien? Me he perdido algo? Yo entiendo que el recorte debería de ser en ambos lados por igual en caso de ser un problema de ajuste de niveles.

Alguien escribió:

Sources of Asymmetrical Waveforms

Most people probably tend to think that their music signal is relatively symmetrical, and this is usually true when averaged out over a long period (perhaps 30 seconds or more). However, there are a great many sources of asymmetry within the programme material itself, and these include ...

Human voice (spoken or singing)
Wind instruments (flute, horns, reed instruments, etc.)
Plucked and struck stringed instruments (guitar, harp, piano, bass, etc.)

This list is not extensive, but covers the major 'culprits' - there are obviously many others such as drums of all kinds, synthesisers or other electronic sources, and not all notes or tones will be asymmetrical. In fact, any instrument may be symmetrical or asymmetrical depending on how it is played, the note being played, specific fingering techniques, etc. The averaging effects of a large orchestral ensemble will tend to create an overall symmetrical waveform in the long term, but there are many periods where a solo of any instrument will be not only highly asymmetrical, but made louder in the mix to even out the sound level (compression).

Suffice to say that in any given piece of recorded music, it is almost a given that there will be periods of sufficient level and asymmetry to cause the problems indicated above if the amplifier is overdriven - the polarity of the asymmetry will vary as well, and often even within a relatively short period.

Any amplifier that is driven to even mild clipping will show the effects described, depending on whether it is AC or DC coupled. DC servo systems will not be fast enough to remove the DC component - these are usually made with rather long time constants to prevent the servo from interacting with the music material, and may actually make matters worse with some signals


Conclusion

There is no doubt that a clipped asymmetrical waveform will generate a DC component in the output of an amplifier. There is equally no doubt (as evidenced above) that a fully DC coupled power amp is the worst possible case. Since there is no requirement whatsoever for an audio amplifier to reproduce DC, it follows that designs that are fully DC coupled are of no benefit to the listener, and indeed may cause far greater problems than they are supposed to 'solve' (according to those who insist that DC reproduction is somehow 'better').

Wherever possible, amplifiers should never be allowed to clip - this much is well known to anyone who is interested in quality reproduction. That it very likely will happen at some point is also accepted - parties in particular being the worst offenders. For those who use relatively small (i.e. low powered) amplifiers as a matter of course, the risk is greater, although the DC voltages so created are also reduced because of the lower overall supply voltage.

For those who prefer valve (tube) amplifiers, they are only partially immune from this problem. Since transformers cannot pass DC by their very nature, the DC cannot get to the voicecoil. There is still the real risk that distortion will increase dramatically if an asymmetrical waveform causes amp clipping, since it is now the output transformer that takes the burden of the DC ... this may cause core saturation. The problem will be worse with push-pull amplifiers, and their distortion could easily rise to the levels commonly found in single-ended designs.

As noted, for power amplifiers used to drive a transformer, the DC component is even more of a problem. A typical transformer for these applications may have a primary resistance of well under 1 ohm, so even a small DC level will cause a very high current to flow. This will cause transformer saturation and possibly amplifier failure.

To what extent have the effects described here influenced reviewers (who typically never use any instrumentation, and usually never know if the amp under test is clipping or not)? I have no idea, but it is not unreasonable to assume that some degree of clipping must be experienced from time to time, and that will affect the outcome of a subjective test ... but with absolutely no technical detail to indicate the actual cause of the problem should it exist. Reviewer-speak will obfuscate the real issue(s), and the lack of instrumentation leaves us in the dark.

Finally, it must be pointed out that this shows that clipping with real-world (speech or music) signals creates not only the harmonics that have been described in innumerable web pages, but also generates a subsonic signal that is potentially very damaging to drivers, but is never mentioned. This signal has the capability to cause driver damage at worst, or unwanted cone modulation and additional loudspeaker distortion at best - neither can be considered a desirable outcome.

The moral of the story is to avoid clipping at all times - even momentary (supposedly inaudible) clipping will generate an unwanted low frequency or subsonic signal whose frequency will be completely unrelated to anything in the programme material. All it will achieve is cone displacement and increased intermodulation distortion.
http://sound.westhost.com/clipping.htm

yerbas07 escribió:

He probado moviendo jumpers y Nagra atenuado. Jumper en 1 ó 2 ó 3 implica una señal de igual intensidad para canal L que no se afecta por el movimiento del potenciómetro. Jumper en 4 ó 5 ó 6 es la señal del canal R que no se modifica por el movimiento del potenciómetro. Obviamente no puedo jumpear 1 y 2 por ejemplo, solo se ve un canal en el DAW y ruidos, clicks. Jumper en 1 y 5 por ejemplo, se captura canal L bajito e inmune al movimiento del potenciómetro, pero el canal derecho sí se afecta al girar el potenciómetro, pero la señal sigue siendo bajita. En definitiva, no consigo una onda más grande.

yerbas07 escribió:

Recordarle que en la priemra captura con Mytek-Roland el recorte ocurría por encima y debajo de los canales de audio. Supongo que la pila estaría a punto de agotarse. Fue cuando puse pila nueva cuando apareció el recorte por debajo únicamente. Ese recorte unilateral se mantiene hasta ahora.

A800MKIII escribió:

There is no doubt that a clipped asymmetrical waveform will generate a DC component in the output of an amplifier.

yerbas07 escribió:

No se si he dicho que el cartucho Lyra Delos es de los de alta salida, unos 0,6 mA, cuando lo normal en un cartucho MC es de 0,3-0,4mA.
Es posible que esa intensidad alta ya sature la entrada de Nagra

Alguien escribió:

Alguien habla de ciertos previos tienen demasiadas opciones como ganancia, carga impedancia...en micado,a pesar de mi ignorancia nunca he tenido problemas con eso.

Alguien escribió:

the polarity of the asymmetry will vary as well, and often even within a relatively short period.

Alguien escribió:

a fully DC coupled power amp is the worst possible case

A800MKIII escribió:

yerbas07 escribió:
No se si he dicho que el cartucho Lyra Delos es de los de alta salida, unos 0,6 mA, cuando lo normal en un cartucho MC es de 0,3-0,4mA.
Es posible que esa intensidad alta ya sature la entrada de Nagra


Hola Yerbas07,
Lo tuyo es un caso en principio no son "mA", si no mV ....y si, efectivamente tu cartucho tiene un voltaje mas alto de lo normal,... y dicho voltaje es de 0.6mV