自製音頻解碼之路(2)

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本文僅為介紹,並非作業指引。內容涉及高電壓、高電流等危險工作,請遵照當地法規同安全指引執行。除非閣下為專業人士,否則不建議進行任何操作。所有、任何後果自負。

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Ian Canada DIY Project

DIY Audio社區卧虎藏龍,包括Pass Labs創辦人Nelson Pass都係活躍會員。Ian Canada DIY Project係上邊DAC區頗受歡迎嘅項目,之前以FifoPi出色嘅表現而廣受關注。宜家開發嘅產品涵蓋Streamer, DAC, DDC, PSU及時鐘等等,而且幾乎可以獨立使用。配合Pi或脱離Pi使用都得。本次講解嘅係配合Raspberry Pi 4B搭建嘅 串流解碼。開始前,略略提下設計要求:

  • 每部份獨立供電
  • 1U機箱容量(容易入架)
  • 長時間聆聽(4-5個鐘)

Parts嘅List

可以參考Ian Canada online Shop

  • 1D FifoPi Q7II
  • 4B ES9038Q2M Dual Mono II DAC
  • 6B OPA861 Zero feedback balanced I/V
  • 35C StationPi SMT
  • 49B MonitorPi Pro
  • 80A & 80 B SC-Pure Extremely-low Phase Noise Audio Clock
  • 32B LinearPi 共5個
  • 25C & 26C UcConditioner 3.3V(2個)、5V(3個)
  • 50A GPIO extension KIT4.
  • 50B GPIP spacer
  • etc

如果輸入界面要埋RCA, OPT, I2S over HDMI就加個

  • 19D ReceiverPi

如果要USB輸入(支持PCM、DSD更高碼率)就加

  • 70B Amanero Combo384

如果升級成UcPureMkIII,用超級電容供電會更好。呢個要視乎個人系統同埋筆直了。

砌機注意

砌OPA861 V/I嘅供電要用以下方法:

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Raspberry Pi儘量隔離,但係吾好造成短路! enter image description here

系統選擇

吾用Roon嘅朋友隨意。 用Roon嘅朋友,Raspberry Pi儘量作為Endpoint。個人測試目前較好嘅係 Silent AngelVitOS ,以直連方式傳輸。

  1. 用Raspberry Pi Imaginer 刷入Raspberry Pi OS for Pi4。
  2. 成功啓動後,將 根目錄 下邊16個 .DAT.ELF 文件,抄落備用。
  3. 刷入VitOS,上電,等10分鐘左右。呢個時候其實係啓動吾到。斷電,掹卡。
  4. 將16個DAT、ELF文件抄落VitOS根目錄。入卡,畀電。得咗。VitOS Manager見到Raspberry Pi 4。
  5. Windows用家,用PuTTY軟體SSH登錄VitOS後台。

pacman -Syu git gcc autoconf libtool libdaemon libconfig

update下。再:

pacman -Syu vi nano

裝編輯軟體。在 /boot/config.txt 裡貼上如下幾行就好,然後重開機。

# AUDIO HAT  

dtoverlay=i-sabre-Q2M   
force_eeprom_read=0

如果想降頻減少熱量,且讓頻率穩定,聲音也會比較穩定:

# REDUCE FREQ  
force_turbo=1  
arm_freq=600  
arm_freq_min=600  
gpu_freq=150  
core_freq=200  
core_freq_min=200  
h264_freq=200  
isp_freq=200  
v3d_freq=200  
sdram_freq=300  
sdram_freq_min=300  
avoid_pwm_pll=1  
over_voltage=-8  
over_voltage_min=-8  
over_voltage_sdram=-8  
over_voltage_sdram_c=-8  
over_voltage_sdram_i=-8  
over_voltage_sdram_p=-8

如果想關掉,所有樹莓派的LED燈:

# DISABLE LED  
dtoverlay=act-led  
dtparam=act_led_trigger=none  
dtparam=act_led_activelow=off  
dtparam=pwr_led_trigger=none  
dtparam=pwr_led_activelow=off  
dtparam=eth_led0=4  
dtparam=eth_led1=4

VitOS默認關掉了WIFI同藍牙,以下係以防其它系統需要:

# DIAABLE WIFI/BT  
dtoverlay=disable-bt  
dtoverlay=disable-wifi

系統直連

只推薦VitOS,因為人哋已經吾再update。Roon Bridge亦冇再update。 同樣SSH係後台,

ip link

睇睇用緊嘅Ethernet端口,例如:

enp0s25

wlp3s0

記低。然後編輯創建一個profile:

/etc/systemd/network/eth0.network

[Match]
Name=eth0

[Network]
Address=192.168.100.199/24
Netmask=255.255.255.0
Gateway=192.168.100.1
DNS=1.1.1.1
DNS=8.8.8.8

eth0 因應個人結果而改。上邊所有嘅字串因應個人需要而改,就返 Roon Server 直連端口嘅同一網段。 激活、啓動服務:

systemctl enable systemd-networkd

systemctl start systemd-networkd

systemctl enable systemd-resolved

systemctl start systemd-resolved

搞掂!

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自製音頻解碼之路(1)

# 自製音頻解碼之路一:ProtoDAC

前言

玩音響的發燒友,最終可能都會走上DIY嘅道路。畢竟玩音響同DIY有著非常共通嘅地方:。 從最初玩起,早期試過raspberry Pi製作串流、解碼,而接觸到幾個比較出名的播放軟體:Moode, Volumio等等。而ProtoDAC則是在Moode Audio嘅Forum發展而嚟。 enter image description here

從圖中可以睇出,呢個解碼構造非常簡單。負責嘅chip係飛利浦嘅古董TDA1387 模組(8塊並聯)。呢個模組最初係設計直換著名嘅TDA1541,飛利浦16bit旗艦芯片。 enter image description here

造呢個DIY解碼嘅理由,其實就係:

  • 簡單而有質素咁聽下歌,
  • 有古董頂班CD機嘅味道。

呢個DAC 需要

  • 夾Raspberry Pi,3或4都得,
  • 淨係食PCM,最高支持384khz,如果播DSD Files需要轉PCM。

組裝

係MoodeAudio Forum或者係作者ebay舖頭買返嚟,基本需要嘅經已齊晒,所有parts基本啱晒PCB上邊嘅位,因而並冇説明書。不過最好上呢到嘅指南睇睇介紹先落手。 enter image description here

需要注意嘅係:

  • 40PIN針腳插,方形 對返PCB嘅方形位,而且裝喺PCB下邊,
  • TDA1387 X8模組 扇形 對返PCB嘅扇形位,
  • R1、R2、R3電阻位置同模組嘅某幾個腳位好近,小心!吾好短路!但係R1同TDA1387最近嘅針腳係 相通
  • 電容正負極吾好搞錯。
  • Foil Resistors有字嘅係正面,要 背對 TDA1387模組,盡量 貼近低過 輸出電容(最大舊,圖中紅色部分)。 enter image description here

幫Pi裝好Player,例如Moode Audio Player、Volumio,Daphile之類,或者裝Ropieee、Silent Angel 嘅VitOS等等作Endpoint,插落畀電就搞掂。 要注意嘅係:

  • 設置左、右反相,
  • 某啲system可能要自行添加dtoverlay,
  • 如果鍾情VitOS,先用Raspberry Pi Imager update部Pi嘅firmware同核心,再裝VitOS。如果啓動吾到,將Raspberry Pi OS系統根目錄下邊16個 .DAT.ELF 文件,抄晒落 VitOS嘅根目錄,重新駁電就得。

升級

加reclocker、時鐘

要注意嘅係大家嘅電壓可能吾同,最好check清楚。譬如解碼要5V,reclocker係3.3V嘅話,電壓吾夠。要用stacking header疊高,PIN2同PIN4吾裝

Pi、解碼,甚至reclocker嘅電獨立行。

主觀感受

成個模組59美金,ebay買多10蚊+tax。加個Pi,呢個價錢,贏好多幾倍價錢嘅ChiFi。捨得升級嘅話,$2xxx嘅串流解碼吾洗考慮。注意,係串流解碼。 缺點:只可串流,只食PCM,要郁手,要盒… 聽感上,個人嫌低音肥咗啲,但係vocal真係冇得頂。似十足古董解碼,醇厚、從容、無數碼味。