打算造一部直熱單端膽機後級，廿幾年前在Neslon兄提議下買了全香港最後一套Tango X-2.7S Output, 電源牛，choke和NC20級間推動牛，打算造一對300B後級，後來Neslon兄說X-2.7S有40W輸出，做300B浪費了，不如做1605有廿W輸出更好，但電源牛不合用，放下來一等就廿幾年，由於條件不許可不能再玩HiFi，已經無玩近廿年，連好多電子工程的公式都忘記了，現在隨著戰後嬰兒潮世代老去，玩HiFi熱潮不再，好難再找到師父接訂造單，唯有自己頂硬上，一直都沒有接觸過膽機設計和直空管數據的資料，自從幾個星期前開始上來問人，多謝綱友提供有用的意見和資訊，特別多謝Johnny 兄私下幫忙，使我明白膽機設計的原理和竅門，也教我用網上模擬軟件協助，我再用Al幫助解決了所有問題，題，關於Al我本身是寫交易程式的，好清楚Al的盲點，如果無在行的人帶領，Al好似一個弱智的人一樣，但在專家帶領之下，只要你懂得用Al強如一隊軍隊，所以有人說有了Al知識不再值錢是真的，所以大家應該好好利用，稍後會再分享其他細節。

大家設計膽機線路時，不知道會要求THD是幾多%的？一般廠機是5個%，DlY是否應該有更高要求？

Hi JimmyDIY,

There are various design critieria for the tube power amp especially for the power stage. Most common is trying to get the highest power from the stage, i.e., max watts per dollars. However, few designers would look for the lowest distortion from the amp say for the 1/3 or 1/2 or the max powr. For example, the 300B SE amp can produce max of 10~12 watts rms. They might just focus on 4 watts range with lowest distortion. In this case, the max output power would be around 6~7 watts which doesn't look good at all for the marketing.

The AI needs to get your design concepts to provide you more details in Pros and Cons for the design. The AI is simply a tool for the design. It isn't that creative at all.

Johnny

Hi Johnny,

謝謝你幫忙解決線路設計問題,我相信比較少人有這方面經驗,應該跟廠家標準THD在5%以下就夠了,現在頭痛的問題是造機殼和用什麼零件?電阻,電平錶,掐座,濾波電容都仍然未有頭緒?

此外我查過

EML320B XLS 高頻頻寬約 75kHz (-3dB)

WE300B 高頻頻寬約 35kHz ~ 58kHz (-3dB)

EML1605 高頻頻寬約 73 kHz (-3dB)

845 高頻頻寬約 25 kHz 至 35 kHz（-3dB）

如不計價錢,用EML 1605 或 320B XLS應該比較好?

I have one pair of x-2.5 with feedback loop

New old stock Pair Hirata TANGO No.10495 OPT for 300B, 2A3, 808, 805, 45(para single) tube amplifier. Transformer itself is very new


Primary impedance is 2.5K ohm. Secondary is 4, 8,16 ohm. It is special order made for 300B, 808, 805 Shishido amplifier, same core, same size with X series.

tvbbb,

謝謝分享!靖問有沒有後級照片提供参考?現在我完全未有任何排位和設置安放的概念,想找多些不同設計來作參考.