Тема: DIY ЦАПы
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Старый 30.11.2012, 12:03   #115
Rasetsu
 
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Регистрация: 06.04.2011
Адрес: Набережные Челны
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Спасибо за пояснения, буду еще копать. Вот этот отрывок:
Цитата:
Active divider decoupling also depends on DEM clock. Like mentioned before, DEM clock oscillator is
able to "lock" on (on-chip) BCK crosstalk. By selecting DEM clock capacitor values that produce
(almost) exact multiples of fs, the DEM clock will "lock" to BCK and jitter amplitude would drop
significantly. The often used 470pF and 680pF won't result in a "lock" and produce maximum DEM
clock jitter amplitude.
Here are some capacitor values that result in a "lock" condition, capacitance might vary slightly due to
TDA1541A tolerances:
235.2 KHz, 350pF
256.58181 KHz, 318pF
282.24 KHz, 300pF
313.6 KHz, 260pF
352.8 KHz, 250pF
403.2 KHz, 203pF
470.4 KHz, 180pF
564.48 KHz, 145pF
705.6 KHz, 122pF
Еще про обвязку:
Цитата:
The active divider decoupling caps do have clearly audible effect on sound quality. The decoupling caps
need to have low inductance, very low leakage current, and low microphonics. Some of the active
divider outputs have only half the ripple frequency (check TDA1540 datasheet), and the ripple currents
vary with the output current.
So capacitors filtering fDEM / 2 need to have twice the capacity of the capacitor filtering fDEM. fDEM is
typically around 200 KHz. Capacitors filtering lower currents also have lower ripple current to filter, so
capacitance can also be lower. When selecting capacitor values with respect to DEM clock ripple current
frequency and active divider output current, and using 1uF as maximum value, following would apply:
pin 13,18, 2mA, fDEM /2, 1uF
pin 12,19, 1mA, fDEM, half current (13,18), twice the frequency of MSB, 250nF
pin 11,20, 0.5mA, fDEM / 2, half frequency, half current (12,19), 125nF
pin 10,21, 0.25mA, fDEM, half current double frequency (11,20), 31.25nF
pin 9,22, 0.125mA, fDEM / 2, half current, half frequency (10,21), 31.25nF
pin 8,23, 0.0625mA, fDEM, half current (9,22), 7,8nF
pin 7,24, 0.0625mA, fDEM, equal current (8,23), 7.8nF.
In practice, 1uF (MSB), 220nF, 120nF, 33nF, 33nF, 8.2nF, 8.2nF. This would give equal ripple currents
on all MSBs.
Думаю стоит попробовать твикнуть так. Но пока вообще собрать и завести нада)
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Следующий пользователь поблагодарил Rasetsu за это полезное сообщение
Yoshimo (30.11.2012)