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| [#21] 5687牛輸出前級(Baker.Steven) ＞＞是否用cathode CCS？ Barker 師兄， For voltage amplification stage in cathode portion, cathode CCS is only applicable for differential VAS, not the single ended common cathode VAS. You don't need cathode CCS in single ended common cathode VAS. In your 5687 preamp, for single ended common cathode VAS, it's cathode need to see low impedance cathode R for AC bypass, the shunt regulator keep 死 the cathode to ground voltage, any variation of AC then bypass, the cathode R for AC component can be as little as 1 ohm While CCS in fact practically provide virtually large R. Exactly opposite, It is another way around 最後修改時間: 2024-11-01 19:24:14 |
niceday009 正式會員202.xxx.xxx.250 |
2024-11-01 19:18 | |
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| [#22] 5687牛輸出前級(Baker.Steven) The very nice thing about shunt regulator is that it can adjust the bias voltage for lowest distortion. Also, it doesn't have the phase distortion caused by the capacitor depending on the frequency especially at the low frequency end. I have tried using the Shunt Regulator in line amp, and power amps. I really like it. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2024-11-01 21:03 |
| [#23] 5687牛輸出前級(Baker.Steven) Johnny, the cathode shunt regulator schematic shown below seems to have got rid of zener, any improment?lower noise level and voltage stability ? |
niceday009 正式會員 182.xxx.xxx.102 |
2024-11-01 21:12 |
| [#24] 5687牛輸出前級(Baker.Steven) The schematic of the shunt regulator shown can be adjust down to 1Vdc with good voltage stability. The noise is very low which is good for use in low level signal circuit like the line amp. I have tried the TL431 programmable shunt regulator IC but it generates too much noise. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2024-11-01 22:51 |
| [#25] 5687牛輸出前級(Baker.Steven) ＞＞ having a low impedance resistor as load would cause a bit higher in distortion As low as 1K would not make just a bit more distortion, it would be a lot more distortion via the simulation of VTADIY The terminated R will be reflected as load through transformer voltage ratio. using 1K in secondary is reflected as 16K primary load through a 4:1 tranny. The line amp will finally connect to power amp assuming power amp input impedance as 100K, so 16K // 100K is 13.8K Now define the output voltage at secondary as 2V RMS, but the primary need to swing 4x of 2V then it will be 8V RMS or 11.2V peak or 22.4V peak to peak, VTADIY take peak voltage as measurement With simulation of VTADIY the one with 1K load secondary producing 2V RMS is THD 0.36 where 0.01 being the odd harmonic distortion The one without 1K secondary termination is 0.13 THD and no show of odd harmonic 0.36 is 270% of 0.13 where also need to take account of odd one  最後修改時間: 2024-11-02 00:03:20 |
niceday009 正式會員 182.xxx.xxx.159 |
2024-11-01 23:50 |
| [#26] 5687牛輸出前級(Baker.Steven) This is the one with 1K secondary termination  |
niceday009 正式會員 182.xxx.xxx.159 |
2024-11-01 23:53 |
| [#27] 5687牛輸出前級(Baker.Steven) correction！！！ power amp input impedance of 100K should be reflected to primary load as 100K x 16 =1.6M ohm with 1K secondary termination, primary reflexes as 16K //1600K=15.8K 1K termination come to 0.31 THD (at 2V RMS in secondary, x4 in primary) no secondary termination come to 0.11 THD(at 2V RMS secondary, x4 in primary) 0.31÷0.11=2.8倍  最後修改時間: 2024-11-02 00:55:44 |
niceday009 正式會員 218.xxx.xxx.164 |
2024-11-02 00:44 |
| [#28] 5687牛輸出前級(Baker.Steven) This one with 1K secondary termination And apart from harmonic measurement, listening to no termination interstage always feel more bold and concrete. That is why I always recommend no pure R termination, if no obvious overshoot in 10kHz square wave, just leave it not terminated, otherwise use snubber network  最後修改時間: 2024-11-02 01:05:43 |
niceday009 正式會員 218.xxx.xxx.164 |
2024-11-02 00:45 |
