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[#1] 前石後膽怕燒機嗎    
聽人講比較危險 !!
dordorkam
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219.xxx.xxx.41
2010-03-08 12:10
[#2] 前石後膽怕燒機嗎    
To be safe, get the detail spec of the tube amp and solid state preamp and e-mail to the manufacturers to ask the engineers. If they say it's ok, then it's ok.
apprentice
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202.xxx.xxx.201
2010-03-08 13:23
[#3] 前石後膽怕燒機嗎    
>聽人講

Why would someone said that? What was the justification?
olddude
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202.xxx.xxx.82
2010-03-08 16:34
[#4] 前石後膽怕燒機嗎    
膽前石後就會,胆直出DC燒後級!

石前永無此問題!

這是impedence mismatch problem!!
cheunggerger
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121.xxx.xxx.85
2010-03-08 18:45
[#5] 前石後膽怕燒機嗎    
>膽前石後就會,胆直出DC燒後級!

Oh really? Never heard of that. If so, that has to be a serious drift in DC and it would sound very awful before the power amp blew.

>這是impedence mismatch problem!!

Why would impedance mismatch causing DC drift in the pre-amp output?
olddude
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116.xxx.xxx.127
2010-03-08 19:05
[#6] 前石後膽怕燒機嗎    
I'm not a tech guy.

But I blew my Mark Levinson 333 with a Tube Pre.

Excel warned me with stuff exactly I'd said.
cheunggerger
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121.xxx.xxx.85
2010-03-08 19:43
[#7] 前石後膽怕燒機嗎    
>Excel warned me with stuff exactly I'd said.

I am surprised that a reputable shop like Excel would tell a customer such BS. I wonder would Mark Levinson customer service concur to such statement.
olddude
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116.xxx.xxx.127
2010-03-08 19:50
[#8] 前石後膽怕燒機嗎    
有位c-hing教路,膽前石後有兩點要注意。

1. 胆前要先開幾分鐘,好讓輸出穩定下來。
2. 不可在中途轉source input,每次開機聽CD就CD,唔好跳去Phono。

各位c-hing有冇意見分享。

最後修改時間: 2010-03-08 20:36:03
micromegamah
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59.xxx.xxx.42
2010-03-08 20:32
[#9] 前石後膽怕燒機嗎    
""""I am surprised that a reputable shop like Excel would tell a customer such BS"""

唔通你想佢地會老實話部ML後級自己水皮燒左。

thomasc2
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61.xxx.xxx.176
2010-03-08 21:17
[#10] 前石後膽怕燒機嗎    
MICROMEGAMAH,

假如impedance not match( tube pre/solid state 後),無signal時 woofers of your speakers would move inward/outward spontaneously
cheunggerger
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121.xxx.xxx.85
2010-03-08 22:08
[#11] 前石後膽怕燒機嗎    
>假如impedance not match( tube pre/solid state 後),無signal時 woofers of your speakers would move inward/outward spontaneously

That would happen if your system is oscillating in a very low frequency.
olddude
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116.xxx.xxx.127
2010-03-08 22:36
[#12] 前石後膽怕燒機嗎    
olddude,

You might be factually incorrect!
cheunggerger
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121.xxx.xxx.85
2010-03-08 22:38
[#13] 前石後膽怕燒機嗎    
>olddude,
>You might be factually incorrect!

Please enlighten me on what was happening when the "無signal時 woofers of your speakers would move inward/outward spontaneously" then. I would really like to know how that would be related to the "mismatched impedance" between pre/power amp. Thanks in advance.
olddude
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116.xxx.xxx.127
2010-03-08 22:58
[#14] 前石後膽怕燒機嗎    
唔通你想佢地會老實話部ML後級自己水皮燒左。
______________________________________

講得好!

其實胆前石後, 石前胆後都冇問題.

唔通石前石後, 或者胆前胆後就一世唔會燒機?
Derek2A3
個人訊息 正式會員
58.xxx.xxx.137
2010-03-09 09:20
[#15] 前石後膽怕燒機嗎    
>其實胆前石後, 石前胆後都冇問題.

Exactly. Some people were just making excuses because they didn't know what was the real problem.

>唔通石前石後, 或者胆前胆後就一世唔會燒機?

I have been playing around with electronics and stereo equipment since the early 70's. The only time I blew a power amp was the time I was using a home-built power amp with some sub-substandard parts (poor college student could only afford to buy from supplies stores). I had used a very simple tube preamp driving a solid state amp for a good number of years without problem. Of course, in order to keep the preamp sound good, I kept the preamp powered on all the time and avoided surges at power on as mentioned by some others here.

Sometimes, I found it really amusing to see people perpetuating unsustainable myths just because they didn't understand the actual problems they had encountered. I was particularly surprised when a reputable store such as Excel would tell a customer that he blew his power amp (an expensive one too) because of "impedance mismatch" between his tub preamp and the soild state power amp.

最後修改時間: 2010-03-09 09:39:04
olddude
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116.xxx.xxx.127
2010-03-09 09:34
[#16] 前石後膽怕燒機嗎    
>>>有位c-hing教路,膽前石後有兩點要注意。

胆前石後 or 胆前胆後, my experienc is turn on the 胆前 first to avoid the "ba ba" sound. on the other hand, when you turn off, the power amp first.
aftjv
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81.xxx.xxx.43
2010-03-09 11:45
[#17] 前石後膽怕燒機嗎    
For the real HI END solid state power amps, there are no capacitor in input/output stages---as capacitors induce their sonic characters.

Non-capacitor coupling hi end power amp, ML, KRELL, ......... WHEN match with tube pre, manufacturers demand their customers to have their amp altered by dealers

Excel put a capacitor to both L/R input stage for me.
cheunggerger
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203.xxx.xxx.136
2010-03-11 01:33
[#18] 前石後膽怕燒機嗎    
>Non-capacitor coupling hi end power amp, ML, KRELL, ......... WHEN match with tube pre, manufacturers demand their customers to have their amp altered by dealers


Oh really!?! Frankly, would you trust someone who claimed that "impedance mismatch between tube preamp and solid state power amp would blew a power amp" to modify your expensive power amp? Not me.

Isn't add a coupling capacitor to the power amp kind of defeat the whole purpose of buying a state of the art DC coupled power amp? Also, with the typical lower input impedance of solid state power amp, adding a coupling capacitor would probably reduce the bass in the system.

On the other hand, they could be adding a bypass capacitor to cut out the high frequencies. In which case, that would affect the high frequencies.

最後修改時間: 2010-03-11 09:23:15
olddude
個人訊息 正式會員
116.xxx.xxx.127
2010-03-11 09:07
[#19] 前石後膽怕燒機嗎    
0lddule 兄,

你很玄,你常常用問號"?"來結尾,究竟是譏諷?或不懂?
不如請大師您elucidate好嗎?

我一早講明我不是tech guy,我都是聽番來的:

1.胆前阻抗(impedance)如和石後不match,就算無signal/冇開volume,你對低音單元會自動出出入入。

2.支膽在on/off時,會有直流DC,如你件石後是極品----(極品石後通常在放大線路上不用電容,因為電容會過濾signal)-----non-capacitor coupling,就會燒機。


但如你的胆前是有輸出牛(output transformer)設計 eg. Audio Note, Modwright, Ayon........就無問題,可以用乜石都得。




以下是download KRELL 綱頁的warning:



http://www.krellonline.com/assets/support/0162_020_MAN.pdf

PAGE 13.

USING A TUBE PREAMPLIFIER
The high DC output of tube preamplifiers may
exceed the DC protection circuitry of Full
Power Balanced amplifiers. Excessive DC
level in a signal can damage amplifiers, speakers,
or both. The coupling capacitors in Full
Power Balanced amplifiers must be engaged
when using a tube preamplifier. An authorized
Krell dealer, distributor, or Krell must activate
these capacitors.
Coupling capacitors must be inserted into the
signal path by your authorized Krell dealer, distributor,
or Krell before you can use your Full
Power Balanced amplifier with a tube preamplifier.
IMPORTANT
Please read the Warranty, on page 20, to
understand the warranty limitations of Full
Power Balanced amplifiers when used with




Page 20

IMPORTANT
The user is responsible for notifying his or her Krell dealer,
distributor, or Krell that a tube preamplifier will be used
with the Full Power Balanced amplifier, so that the Krell
dealer, distributor, or Krell can activate the coupling capacitors.
If the user does not notify the Krell dealer, distributor,
or Krell and uses a tube preamplifier without the Full
Power Balanced amplifier’s coupling capacitor engaged,
Krell reserves the right to refuse warranty related service
due to DC-related damage.
Proof of purchase in the form of a bill of sale or receipted
invoice substantiating that the unit is within the warranty
period must be presented to obtain warranty


最後修改時間: 2010-03-11 12:46:10
cheunggerger
個人訊息 正式會員
121.xxx.xxx.122
2010-03-11 12:40
[#20] 前石後膽怕燒機嗎    

The reason for DC output during preamp power up is because the preamp has an output cap. Initially there is no charge in the cap. Upon turn on the tube output DC which then raise the output cap's voltage until it reaches the same DC level.

If the amp has high input impedance (i.e., many SS amp) then it takes quite a while to charge up the output cap in the preamp and during this time DC or close to DC signal will appear at the amp's input.

Thus this only applies to cap-coupled output preamp. Transformer-output has no such problem as the transformer has limited low freq response.

Some tube preamp prevents this by adding a relay to short circuit the output during power up so that the cap can be fully charge quickly.

For the same token, tube amp will not be affected as they cannot pass DC in their output (unless it's DC-coupled OTL).
shostakovich
個人訊息 正式會員
220.xxx.xxx.189
2010-03-11 15:02
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