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| [#54] Preamplifier for active speaker 謝謝 kit271師兄! |
kkfc123 正式會員58.xxx.xxx.71 |
2017-11-24 11:57 | |
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| [#53] Preamplifier for active speaker 我試吓解答你問題, 有錯請其它師兄更正 Gain只不過係voltage output, 還有許多因素會影響個transmission lose. Output gain會隨著Input impedance(Zi)減少而產生voltage drop, Zi越大,drop就越小, 同樣output impedance(Zo)越小, drop也會越小. 一般既output impedance(Zo)我地通常以1KHz去量度, 大約50ohm, 但大部分amplifier越高頻個Zo係越大, 20KHz可能已經講緊500ohm. 記住還有好多因素會影響個Zi同Zo, 例如cable既resistance同capacitance都會影響個Zo上升同Zi下降. 雖然Zo同Zi差佢多大無話絕對, 但最少二十倍以上會好點. 不過世事無完美, Zi越大, noise也會越大. 所以我地一般只考慮選擇Zo低既amp 如果power amp的Zi=10K, premap有50ohm Zo已好好. 記住,還有也要考慮埋cd player的Zo--＞preamp的Zi. 最後修改時間: 2017-11-23 17:27:10 |
kit271 正式會員 58.xxx.xxx.194 |
2017-11-23 17:24 |
| [#52] Preamplifier for active speaker #51 首先謝謝kit271師兄, 好詳細, 但係唔明白! 如果有源喇叭的Input Impedance是 10k Ohm, 前級的Output Impedance是 50 Ohm, 請教是否適合? 是否Output Impedance的數值越細, 個gain越大? 謝謝! |
kkfc123 正式會員 58.xxx.xxx.71 |
2017-11-23 13:54 |
| [#51] Preamplifier for active speaker 以icepower 500ASP 250W/8ohm做例子去計返個input voltage: Power*R(load)=V(rms)^2 V=44V(rms) Gain Av(db) = 20Log(Vout/Vin) **icepower 500ASP gain = 27db 27db=20Log(44V(rms)/Vin) Vin~= 2V(rms)  |
kit271 正式會員 58.xxx.xxx.194 |
2017-11-23 10:41 |
| [#50] Preamplifier for active speaker 很多師兄在這裏以講過, Pre-amp for active 一定要 gain 夠大,因為電子分音器會衰減訊号. 一般10倍 gain 以內的pre-amp 的driving 能力 是不夠的! |
akltam2009 正式會員 203.xxx.xxx.238 |
2017-11-23 00:05 |
| [#49] Preamplifier for active speaker 標準非平衡或平衡輸出都是2 volts. |
rcywong 正式會員 116.xxx.xxx.34 |
2017-11-22 21:57 |
| [#48] Preamplifier for active speaker #47 也有可能係source output唔夠，因為我CD player只有RCA輸出。RCA輸出2V而XLR輸出係4V, 應該會好啲。 我之前用過Jeff Rowland合併機配Genelec, 較果好好多。但後來覺得Rowland 啲聲唔襟聽（個人感受），所以換了部Audio Valve 膽前級，但較果唔好, 因為它的平衡輸出是假的。最後買咗部二手MFA，因為它有平衡輸出，點知個輸出又唔夠。？ |
kkfc123 正式會員 61.xxx.xxx.169 |
2017-11-22 21:43 |
| [#47] Preamplifier for active speaker #42 我會覺得係source output唔夠大 |
weds 正式會員 14.xxx.xxx.230 |
2017-11-22 19:00 |
| [#46] Preamplifier for active speaker 之前有師兄建議我用Mytek DAC(Preamp version) 或 GRACE DESIGN DAC去玩Genelec |
kkfc123 正式會員 58.xxx.xxx.71 |
2017-11-22 16:22 |
| [#45] Preamplifier for active speaker 一般 professional audio 個 line output, balanced 100 Ohm. Unbalanced 1K Ohm 已足夠match. |
rcywong 正式會員 116.xxx.xxx.34 |
2017-11-22 16:18 |
| [#44] Preamplifier for active speaker 還有passive amp個output impedance唔夠細 |
kit271 正式會員 58.xxx.xxx.194 |
2017-11-22 15:58 |
| [#43] Preamplifier for active speaker 溫馨提示，所有玩active喇叭嘅師兄一定要加preamp. 否則個gain唔夠力去推個喇叭. |
rcywong 正式會員 116.xxx.xxx.34 |
2017-11-22 15:48 |
| [#42] Preamplifier for active speaker 我用緊Music First Audio + Genelec 8040a, 較果一般, 我想主要原因係Passive前級個Gain唔夠大。 |
kkfc123 正式會員 58.xxx.xxx.71 |
2017-11-22 14:17 |
| [#41] Preamplifier for active speaker You should try a good quality TVC Passive Preamp..... such as Music First Audio. |
iangel 正式會員 112.xxx.xxx.199 |
2017-11-22 13:12 |
| [#40] Preamplifier for active speaker 簡單啲加個portable mixing console 最好.  |
rcywong 正式會員 116.xxx.xxx.34 |
2017-11-22 13:07 |
| [#39] Preamplifier for active speaker Active Speaker組amp既Input Impedance低. 而且passive preamp只用VR去分壓個input gain, 對個high-freq response不利 |
kit271 正式會員 58.xxx.xxx.194 |
2017-11-22 13:01 |
| [#38] Preamplifier for active speaker [#35] Preamplifier for active speaker Active speaker 唔好用passive preamp Kit CHing, Why?? 最後修改時間: 2017-11-22 12:31:40 |
rronaldleung 正式會員 203.xxx.xxx.79 |
2017-11-22 12:30 |
| [#37] Preamplifier for active speaker Why don't you reconsider that the excessive bass response was from the sources instead of the 8040a? Anything could happen. I got few pairs of active and listening in similar listening area like yours. All of them have bigger woofer units than yours including Genelec S30. Never have low freq issue. Used to Genelec 1030a & 1029a which I totally satisfied their full range response. I heard 8040 in some occasions with very tight bass and still a long way to comply as excessive. DOn't go to wrong direction. 最後修改時間: 2017-11-21 00:54:12 |
com-buddy 正式會員 58.xxx.xxx.201 |
2017-11-21 00:51 |
| [#36] Preamplifier for active speaker Thank you chings. |
Baristacafe 會員 42.xxx.xxx.147 |
2017-11-17 18:27 |
| [#35] Preamplifier for active speaker Active speaker 唔好用passive preamp 想清既買部Bryston BP26, 有XLR |
kit271 正式會員 58.xxx.xxx.194 |
2017-11-17 17:49 |
