- #4018 [niceday009], 24-05-04 04:56
- #4017 [niceday009], 24-05-03 15:00Having tried to put a 2.2K 2W resistor between CCS and plate, and tuned the CCS R set value accordingly, it sounds smoother, less pronounced S and T
I guess the resistor work as plate stopper somehow
最後修改時間: 2024-05-03 15:03:13 - #4016 [johnnykmtang], 24-05-03 03:31Hi Niceday,
I haven't seen adding a resistor to the CCS circuit so far. Anyway, this is something you may try.
Johnny -
- #4015 [niceday009], 24-05-02 02:16有關CCS 同plate 中間加电阻,我揾到網上有人分析,好詳細
I see I'm in the minority on the positive aspects of using a series CCS resistor.
A series resistor with the output of a CCS offers protection for the CCS. It is useful to limit current during arcs (tube and transformer), leading edges of shorts (oops, I shorted the output leads again), rapid reductions of the B+ (the B+ arced/ failed/ shorted or another tube on the B+ arced), the tube went into oscillation and other nasty oopses. 5 to 10% of B+ is a good starting point for the voltage drop on this resistor.
A series resistor also helps with stability of the CCS/ tube combination. At high frequencies the CCS appears as a capacitor and possibly a negative impedance if you are using a Hawksford cascode or if you have long leads (> 1 inch) on a standard cascode. This resistor buffers that capacitance (and negative impedance.) 1 to 5 times the current set resistor value is a good start point for this resistor value.
A series resistor helps when the CCS saturates. It softens both the recovery after saturation and at the start of saturation. 5 to 10% of B+ is a good starting point for the voltage drop again.
There are times when we don't need a series CCS output resistor, but they are fewer than what many would expect. It is easier to just design the resistor in, even if it doesn't drop as much voltage as the rules of thumb above. Sometimes the CCS damage from an arc is latent or just degradation in CCS performance, I don't want to risk that. This resistor doesn't have to be an expensive resistor either. A non-bargain basement metal film works pretty good.
Agreeing with somebody else's post, a resistor in the output is not a reliable way to reduce the voltage stress on the CCS. A resistor across the final CCS output stage is useful for reducing the power dissipation in the CCS. If you drop 20% of B+ on the CCS and 40% in the series resistor, when B+ drop 10% (the air conditioner kicked in, the neighbor's playing with big power tools again etc.) you now only have an output swing of two times 10% of B+ instead of two times 20% of B+. Now if the plate voltage bias point shifts up another 10% because of tube variations, we can't get any clean power out at all because the CCS is in saturation.
The negative comment on CCSs I get most often is "I replaced my output choke with a CCS and can't get any power out and the sound sucks." A CCS doesn't store energy like a choke. So the plate voltage can go down below B+, but not above B+. This is made worse by the CCS voltage drop.
CCS like to have voltage headroom. Both BJTs (rated > hundred volts) and FETs like to see several, if not 10s, of volts from base to collector (or gate to drain.) This is from both Early voltage and capacitive effects.
The plate voltage on CCS fed tubes tends to vary more than usual with CCS loading. Even with the CCS current set dead on. This is because the cathode to ground voltage for the tube is fixed (V = Iset * R_cathode) with CCS loading. It sort of looks like a battery from the cathode to ground!
When we have resistance between the B+ and plate, the tube current is allowed to change as the plate to cathode voltage changes. This is because the change in grid to cathode voltage (from the plate voltage variation) causes the plate current to change via the cathode resistor. This local feedback (from the cathode resistor) reduces the variation in plate bias voltage from tube to tube. With a CCS fed tube, the voltage across the cathode resistor is fixed so we don't get the local feedback.
So if you use a CCS, the B+ tends to be
B+ CCS estimate = Voltage cathode to ground + 2 * Voltage Plate to cathode at the tube's bias point + Voltage drop in the series resistor + 10% more.
最後修改時間: 2024-05-02 02:21:01 - #4014 [johnnykmtang], 24-04-26 22:59#4012
The circuit looks very fancy. However, I doubted how the circuit works. It doesn't seem practical.
In fact, simple is the best. There are many good design circuits available.
Johnny - #4013 [niceday009], 24-04-25 21:55但声音唔啱,用大環路負回輸,入返differential stage另一端
前端用differential 失真應該好低,理應唔使用loop feedback
用EL34 direct couple 845 cathode, 而845 grid用fixed voltage supply, 等於佢唔可以令grid 推到正电压A2(唔敢肯定,可能drive 845 cathode 电压再向下可以A2,有冇師兄研究到此A2可能性), 浪費咗900 ohm 內阻EL34 triode strapped 直結,發揮唔到低內阻driver 推A2之原意
而EL34下面之MJE182射極以下射極电阻及大數值电解Bypass cap 可以唔用,改用P ch MOSFET power zener 令music ground return更純更直接
最後修改時間: 2024-04-25 22:11:17 - #4012 [羅密歐], 24-04-25 21:23的確很有創意,多謝分享!
訊號只通過兩個交連電容,又不用交連牛,成本有限。前半部份用來推300B,也許不錯。 - #4011 [niceday009], 24-04-25 20:58刚刚見到呢個頗為創新845單端線路,845係cathode入訊號(ground grid )+ cascode , 等於triode strapped EL34 直結845, 第一次見到用plate output 直結845,前面放大級特別不在話下,但SE845用cathode 入係第一次見,各位点睇? 好處係乜?
難明filament 同input transformer 点樣同時間work
係台灣人設計,敬佩! design concept out of the box
最後修改時間: 2024-04-25 21:13:56 - #4010 [羅密歐], 24-04-23 15:23Deleted
最後修改時間: 2024-04-23 15:35:03 - #4009 [Spong], 24-04-23 10:14細房組合
單端FU50 推街價$450老古董天朗Eclipse
老坑愛老媚娘 :-) - #4008 [Spong], 24-04-23 07:58又講番呢件cheap 嘢
先用大盾6j7G鋼屏,人聲帶microphonic,並不理想,且偏向中高頻;其實此乃膽本身基因問題而非作任何微調可以解決;
於是二話不說改用EF37A;問題解決了,這小管子推動力優異,音色是一貫Mullard 美艷動人。。。播老柴鋼一(Kissin 版本)完全冇趕收工感覺;而全程節奏包皮環境(緊臭);可聽性極高;
迼部單端cheap賃現在裝備可能是其中同欵一套*膽組合終極版本* - #4007 [johnnykmtang], 24-04-21 05:33Hello 伊雲士,
Switching mode power supply (SMPS) for tube amps are available at TaoBao and Ebay. I believe this is the way to go. However, there isn't many reports how they performs.
I believe the SWPS is the way to go. It just takes time to get it designed right for the tube amp application.
JOhnny - #4006 [WilliamsonAudio], 24-04-20 22:15#4004
我見過最瘋狂的shunt type regulator , 就是用211膽去做。
一支211做輸出膽。另一支211是為211輸出膽做穩壓。大約1250V 的高壓穏壓。
概念等同1 台845膽机,再加多一支845做高壓穏壓。 - #4005 [伊雲士], 24-04-20 20:50大陸有高手當胆机電腦咁玩用開闢電源
- #4004 [johnnykmtang], 24-04-20 20:27My friends asked me why the shunt regulator is better than the series linear regulators. I just found the following article from AudioXpress which has very detailed explanation.
https://audioxpress.com/article/shunt-or-not-looking-for-the-ultimate-audio-voltage-regulator
Johnny - #4003 [johnnykmtang], 24-04-19 21:26Mission 776 line amp
I built the 24V CCS-shunt regulator to replace the LM317 regulator in this line amp. It is a very simple design with few transistors. There's some improvement on the sound quality. It has fuller body, clean, dynamic and deep sound stage.
I used 120Vdc CCS-shunt in two of my tube line amp lately with great success too.
Johnny
最後修改時間: 2024-04-19 21:43:10 - #4002 [Spong], 24-04-19 08:08唔想傷害中國人民感情所以要等埋另外一隻轉插先至試另外一對網屏6j7及EF37A
^—^ - #4001 [Spong], 24-04-19 07:58非凡哥經典名曲
尾段一句老婆愈老愈可愛…唱得較*肉緊*而最尾呼喚飄紅姐姐亦有感性,
原來單端膽機升呢都係要借助(外國勢力) :-p - #4000 [Spong], 24-04-19 07:50冇*不愉快*意外發生
要播mono cd 比較左右聲道 - #3999 [Spong], 24-04-19 07:46^0^
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