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| [#5463] 單端胆機同好會 Hi Johnny I am using Audion Golden Night 300B. We have discussed its circuitry elsewhere in this thread a few months ago. Remember the one with the cathode of 300B connected to the output transformer? |
Thanatos 正式會員104.xxx.xxx.132 |
2025-11-20 10:01 | |
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| [#5464] 單端胆機同好會 Hi Thanatos, Oh, thanks for your reminder. Yes I do remember now. What are the two small driver tubes in your amp? CVX100 and CVX120??? Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-11-20 18:42 |
| [#5465] 單端胆機同好會 1st stage EC806S, 2nd stage E280F |
Thanatos 正式會員 172.xxx.xxx.47 |
2025-11-20 19:01 |
| [#5466] 單端胆機同好會 EC806S u = 68, Ra = 5.5K E280F u = 60, Ra = 1.8K (Triode mode) Both tubes are having very high gain. There is no reason the Audion Golden Night requires any line amp at all. The B+ of the 300B is at 480Vdc with 1K resistor and 47uF bypass capacitor. That is appox 390V across anode and cathode, and the idle current is 80mA. I believe Audion designed this amp was striking for more output power. This really pushing the 300B close to the limit. Anyway, the quality of the 47uF capacitor would have significant impact on the sound too. Try replace it with film or oil capacitor and see if you would like. Johnny 最後修改時間: 2025-11-20 22:14:07 |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-11-20 22:03 |
| [#5467] 單端胆機同好會 This is the plate curve graph of the 300B with 390V and 80mA with 3K load.  最後修改時間: 2025-11-20 22:19:16 |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-11-20 22:18 |
| [#5468] 單端胆機同好會 Just found E280F triode strapped is a great tube and stunningly 10000 hours lifetime, can be the substitute for 5842. However the price is high, more than 2K HKD NOS, just wondering why people would not consider twin triode ECC99, superb linearity, 2 sections parallel run give you 1.15K tube impedance at awesome 30mA, price? 300HKD only!!!    最後修改時間: 2025-11-20 23:13:39 |
niceday009 正式會員 182.xxx.xxx.165 |
2025-11-20 22:52 |
| [#5469] 單端胆機同好會 Thanks Johnny, I am currently using Black Gate Non-polar electrolytic cathode bypass cap. And I only have 68uF (63uF measured by Fluke 289). Do you think I should strictly adhere to 47uF? Many people claim that a slightly larger cathode bypass cap would not be detrimental. But in Audion's case the 300B cathode is connected to one of the primary coils of the output transformer. Would this configuration form a special LCR circuit which requires a very precise capacitance? Much obliged to your exceedingly helpful advice. 最後修改時間: 2025-11-20 23:56:45 |
Thanatos 正式會員 172.xxx.xxx.230 |
2025-11-20 23:55 |
| [#5470] 單端胆機同好會 HI Thanatos, The capacitance of the cathode capacitor isn't critical at all. I don't think the BlackGate non-polarized capacitor is good for this application. Try to get the DC link or MKP capacitors. My audiophile friends prefer OIL caps but they are just too big to fit in the chassis. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-11-21 00:02 |
| [#5471] 單端胆機同好會 I have considered Mundorf Supreme EVO Silver Gold oil, but it measures 76x67mm ! EVO silver gold is smaller and cheaper, but receives less praise than Supreme |
Thanatos 正式會員 172.xxx.xxx.230 |
2025-11-21 00:09 |
| [#5472] 單端胆機同好會 Hi Thanatos, I recall you was saying your amp didn't have feedback tap as the schematic you posted early, meaning the version of your amp is completely zero feedback circuitry. And yes to your question that if the amp in open loop not having flat LF response(for example lesser cathode bypass capacitance causing roll off in LF frequency), the use of feedback could help to flatten the frequency response. However if the circuitry is completely zero feedback the flatter frequency response depends on each stage's own frequency response property. 300B biased at cathode bias may use 47uF to 220uF(Audionote for example). It depends on which -3dB roll off freq you want. I normally set 300B at 16Hz and 845 at 13Hz https://www.learningaboutelectronics.com/Articles/Bypass-capacitor-calculator.php#answer ＞＞using Black Gate Non-polar electrolytic cathode bypass cap. I don't think non-polar in cathode bypass would be necessary. The cathode of 300B is 75V above ground. The bipolar electrolyte capacitor in fact is two cap connected in series but negative to negative connected. During signal transfer, one of these two capacitors is shorted in upper phase and another does the transfer. During lower phase it does it another way around. In fact, in cathode bypass application, using bi-polar cap means it has to go through one more component, meaning the intrinsic distortion would be higher. As I know bipolar is normally used in output capacitor or used in speaker crossover. There is an article describing the cathode bypass using bipolar VS non bipolar. The author indicated bipolar has lesser distortion in such application. Someone may ask why top grade audionote would use non-polar electrolyte as cathode bypass. Only Audionote can answer this question.  最後修改時間: 2025-11-21 00:52:00 |
niceday009 正式會員 42.xxx.xxx.28 |
2025-11-21 00:32 |
| [#5473] 單端胆機同好會 Typo I don't think non-polar in cathode bypass would be necessary. The cathode of 300B is 75V above ground. The non-polar electrolyte capacitor in fact is two capacitors connected in series but negative to negative connected. During signal transfer, one of these two capacitors is shorted in upper phase and another one does the transfer. During lower phase it does it another way around. In fact, in cathode bypass application, using non-polar cap means it has to go through one more component, meaning the intrinsic distortion would be higher. As I know non-polar is normally used in output capacitor or used in speaker crossover. Some Japanese soild-state preamp use non-polar electrolyte as output cap or as input cap for power amp(Accuphase, Technics etc) There is an article describing the cathode bypass using bipolar VS non-polar. The author indicated bipolar has lesser distortion in such application. Someone may ask why top grade audionote would use non-polar electrolyte as cathode bypass. Only Audionote can answer this question. 最後修改時間: 2025-11-21 01:25:18 |
niceday009 正式會員 42.xxx.xxx.28 |
2025-11-21 01:14 |
| [#5474] 單端胆機同好會 Non-polar electrolytic capacitor by using two polar e-cap back to back in-series is only a low cost solution for diy'ers. The real construction of non-polar e-cap should be somthing as shown in the below pic. To solve the cap's signal by-pass effect of tube amplifiers, the cap's impedance(Z) vs frequency(audio) should be studied carefully as shown in below curve.  |
mcc2018 會員 42.xxx.xxx.130 |
2025-11-21 08:30 |
| [#5475] 單端胆機同好會 The difference between cathode bypass capacitor and speaker crossover capacitor, is that the former is always "charged" with a DC potential (~82V in my amplifier) and the latter only has to deal with AC signals. If I am not mistaken, when a non-polar cap is used as a cathode bypass, one of the two internal caps is always shorted by the DC potential and the signal actually never crosses the zero volt line (unless the AC amplitude is higher than 164V which I highly doubt). Which means only one of the two caps is working, the other is always shorted. |
Thanatos 正式會員 172.xxx.xxx.42 |
2025-11-21 10:33 |
| [#5476] 單端胆機同好會 For audiophile applications, the major difference of biased capacitor vs unbiased is the THD+N vs frequency analysis as shown in the below curve.  |
mcc2018 會員 42.xxx.xxx.130 |
2025-11-21 11:50 |
| [#5477] 單端胆機同好會 有啲出人意料就係藍色嗰條線同紅色嗰條線。 |
DY2036 正式會員 182.xxx.xxx.156 |
2025-11-21 15:57 |
| [#5478] 單端胆機同好會 如果認識乜嘢係dielectric molecule alignment, 也許對此不會感到意外，值得一提是dielectric polarization 更會影響中高頻的互調失真（IMD），所以一些追求低失真的喇叭，其分音器都會有舊電芯養住D電容。  |
mcc2018 會員 42.xxx.xxx.130 |
2025-11-21 18:50 |
| [#5479] 單端胆機同好會 為了低失真，用9V電芯養電容：  |
mcc2018 會員 42.xxx.xxx.130 |
2025-11-21 18:51 |
| [#5480] 單端胆機同好會 Hi Thanatos, ＞＞If I am not mistaken, when a non-polar cap is used as a cathode bypass, one of the two internal caps is always shorted by the DC potential The non polar electrolyte capacitor is designed to work with AC mainly. In an AC circuit, the current direction constantly reverses. When the external voltage polarity reverses, one of the internal capacitor sections becomes forward-biased and stores charge, while the other, now reverse-biased, is effectively short-circuited but allows the first to operate. In a DC circuit, a non-polarized capacitor can be connected in either direction and will function like a standard capacitor, blocking DC current while allowing AC to pass through. That is why we see non-polar electrolyte is usually used as coupling capacitor allowing AC signal to pass through and most non-polar electrolyte application do not have steady high DC voltage across them, like speaker crossover (may be a 9V to help aligning polarity like mcc2018 indicated)or coupling capacitor for preamp or input cap for power amp. 最後修改時間: 2025-11-21 21:36:35 |
niceday009 正式會員 182.xxx.xxx.236 |
2025-11-21 21:24 |
| [#5481] 單端胆機同好會 #5474 Hi mcc2018, I interpreterp that those two constructions are the same result, cathode of each electrolyte connected, leaving the positive to be connected to either direction I used JBL K2 before(Friend of mine moved home and I kept it for sometime). The way JBL used 9V DC to bias the dielectric material is only for film capacitor, may be electrolyte would not function 最後修改時間: 2025-11-21 21:59:31 |
niceday009 正式會員 182.xxx.xxx.236 |
2025-11-21 21:41 |
| [#5482] 單端胆機同好會 #5481 我之前見過文章講改分音器，就是用JBL 的 DC bias 去减少Ecap 的失真。而並非针對 Film cap JBL’s trick: two polarized electrolytics + DC bias Instead of using one expensive non-polar electrolytic or film cap, JBL did this: Put two identical polarized electrolytic capacitors in series (so the combination becomes non-polar). Apply a small DC bias voltage (typically +15 V to +40 V, often taken from the amplifier’s power supply via a high-value resistor) across the whole series pair. Because of the DC bias, one capacitor is always heavily forward-biased and the other is only very lightly reverse-biased or not at all, depending on the audio signal level. Real-world JBL examples JBL 4350/4355 studio monitors: 150 µF + 150 µF electrolytics in series on the woofer, biased with ~+30 V JBL 4345: similar scheme Many L-series (L100 Century, L112, L150, etc.) charge-coupled crossovers from the late 1970s onward JBL called this technique “Charge-Coupled” or sometimes just “DC-biased” networks in their literature. 最後修改時間: 2025-11-22 08:41:23 |
WilliamsonAudio 正式會員 182.xxx.xxx.14 |
2025-11-22 08:38 |
