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[#21] Transformer Volume Control preamp    
哈哈,無拿拿drchan兄會懷疑只TVC ???????
>對DAC產生harmonic distortion
需要在TVC輸入部分作出修補<
再睇真D, Primary indictance=110H ,兩只TVC Label 唔同 marking,哈哈,咁就出廠?????
Back e.m.f= L X di/dt,
試試用 5mA /1mS pulse current 輸入primary,看看primary winding的 back e.m.f

daniel-chui
個人訊息 正式會員
118.xxx.xxx.190
2014-08-03 13:57
[#22] Transformer Volume Control preamp    
上Oscilloscope看
cityguy
個人訊息 正式會員
61.xxx.xxx.87
2014-08-03 14:08
[#23] Transformer Volume Control preamp    
[#22] >上Oscilloscope看
絕對同意 cityguy兄的意見,用20Hz ~50KHz方波看看.
唔知POSHAN廠有無示波器同 signal generator
daniel-chui
個人訊息 正式會員
118.xxx.xxx.190
2014-08-03 15:17
[#24] Transformer Volume Control preamp    
Oscilloscope看通常牛低頻會差D.



最後修改時間: 2014-08-03 21:29:27
cityguy
個人訊息 正式會員
61.xxx.xxx.87
2014-08-03 21:24
[#25] Transformer Volume Control preamp    
話時話,我D排好得閒,求其買幾只POSHAN電源牛打打3KV Hi-pot,過唔到高壓測試,寄只sample去
HK E&M dept,都幾好玩,申請CE安全認證都要十萬八萬,請多個ehgineer每個月要多加三萬,
D個costing都好和味.
daniel-chui
個人訊息 正式會員
118.xxx.xxx.190
2014-08-04 08:07
[#26] Transformer Volume Control preamp    
吸收了敎訓
追求完美
最後決重新再做過一對火牛

Dr Chan

最後修改時間: 2014-08-05 14:23:26
drchan
個人訊息 正式會員
223.xxx.xxx.64
2014-08-05 14:22
[#27] Transformer Volume Control preamp    
drchan兄:

不知你有沒有看過台灣名揚音響的牛音量(TVC),淘寶有賣,或者可以省卻你很多焊接組裝功夫兼有靚聲呢。

http://www.magaudio.com/



最後修改時間: 2014-08-05 16:00:54
阿福
個人訊息 正式會員
210.xxx.xxx.94
2014-08-05 15:59
[#28] Transformer Volume Control preamp    
都幾靚仔.

阿福
個人訊息 正式會員
210.xxx.xxx.94
2014-08-05 16:05
[#29] Transformer Volume Control preamp    
三年前己經購買使用,前後推介給朋友己有10個,效果很好,我在台北買的,全部有大學測試結果,兼有台湾發出的專利繞圈設計。起碼省掉一大堆接線,電感問題減少很多,有朋友和多款外国品牌比較過,最靚。也有朋友試後,馬七前級都唔用。我不是專家,實話實說。
alex03chan
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192.xxx.xxx.35
2014-08-05 18:17
[#30] Transformer Volume Control preamp    
Find one full balance in/out model in the www.magaudio.com
and will try to get one as soon as possible.
Since they have spent many years to develop this TVC
It should be well perform.

drchan
個人訊息 正式會員
183.xxx.xxx.190
2014-08-05 20:31
[#31] Transformer Volume Control preamp    
除了當為無源前級外,還有一種玩法,有些人覺得無源比較清、比較淡,咁就將佢接到前級的輸入端,將前級音量按鈕設定最大(即by-pass個volume制),用這個TVC來控制音量,你會有驚喜,因為一般的Volume制用電阻、炭粉,對訊號損秏很大,特別是細音量時,據台湾的朋友講,這個做法在日本都很普遍。我自己試過,朋友都試過,結果都很正面,基本上用過都除唔倒,音響的東西很奇怪,一件不太貴的東西,比花幾萬元換部机更有效。不過試過TVC的音量控制器,再比較電阻式,AB測試後,你一定心裡有數。當然,電阻式好處係音量分得好細,做工好的話又無爆音,仲可以遙控。
alex03chan
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113.xxx.xxx.200
2014-08-05 21:26
[#32] Transformer Volume Control preamp    
I will try a full balance in and out model
from Magaudio which cannot be made DIY.

drchan
個人訊息 正式會員
183.xxx.xxx.190
2014-08-06 05:21
[#33] Transformer Volume Control preamp    
schematic diagram

drchan
個人訊息 正式會員
183.xxx.xxx.190
2014-08-06 05:23
[#34] Transformer Volume Control preamp    
[#20]
話時話, 我睇睇吓D “ PO山 “ 電源牛 唔係好夠clearance同 creepage distance,
等我拿去TUV問問engineer是否安全,睇吓可唔可以賣出街先 .
daniel-chui
個人訊息 正式會員
118.xxx.xxx.190
2014-08-06 08:24
[#35] Transformer Volume Control preamp    
引頸等候drchan的成果。
阿福
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42.xxx.xxx.17
2014-08-06 09:15
[#36] Transformer Volume Control preamp    
it seems nice and easy to play, just plug and play. Can I join to buy one ?
june01
個人訊息 正式會員
113.xxx.xxx.86
2014-08-06 15:55
[#37] Transformer Volume Control preamp    
After checking the detail construction of MagAudio TVC, I found the design will get some problem since they use autotransformer type circuit, such that the prelimary and secondary of transformer is not isolated, the digital noise will passing through the TVC.

One of the objective to use TVC is to isolate the digital noise between the DAC and power amp. Auto transformer is the cheaper way to resolve the volume control issue but allow a direct copper connection between DAC and power amp.

As a result, I have to re-design and order another pair of TVC.

Anyway I learned why harmonic distortion is found in the last exercise.


Dr. Chan
drchan
個人訊息 正式會員
121.xxx.xxx.220
2014-08-07 14:04
[#38] Transformer Volume Control preamp    
one of the best TVC circuit design by Luxman for reference.

Pls note this can be designed for both RCA/XLR input and output.

please check the difference between Luxman and Magaudio design!




最後修改時間: 2014-08-07 18:48:42
drchan
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183.xxx.xxx.190
2014-08-07 18:44
[#39] Transformer Volume Control preamp    
Years ago, I got a TVC preamp from HK diyXX shop.

I used it to replace the preamp of Accuphase E530 (it has separate premap bypass to function as a Class A power amp) the TVC preamp has much better transparency than the preamp part of the E530, However, later model of accuphase has the new AAVC which improve the preamp part which I have no chance to compare with.

But the dac output impedance matching for driving this type of amp is quite difficult, only dac with very low impedance can be used. Many tube dac cannot drive the system with sufficient dynamics or bass.

最後修改時間: 2014-08-07 19:09:27
promet
個人訊息 正式會員
113.xxx.xxx.59
2014-08-07 19:08
[#40] Transformer Volume Control preamp    
音响不是神秘東面, 更不是亂搞壹頓就可以的, 搞隻大火牛做响度制,簡直係大笑話, 所有前級音
源,輸出很小,絕不足以推動 " 大牛 ",就算有聲,細致地方都會消失.
kennethtam
個人訊息 正式會員
203.xxx.xxx.71
2014-08-08 09:37
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