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#11 | |
frugal-phile(tm)
diyAudio Moderator
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Quote:
dave
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community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA |
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#12 |
diyAudio Member
Join Date: Jun 2002
Location: Left Coast
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"How can you give advice about a circuit you don't know what it even does?"
I've seen caps in series with the input before. Normally they are simply for AC coupling. But I thought I wrote the comment with enough uncertainty to express cautuion if need be. A 1uF cap in series with the input will roll off the low frequencies well into the audio range. This demonstrated by somevsimple arithmetic, by a simple spice simulation and by listening. In equipment from that period, this (low value AC coupling caps) seems pretty common. I'm guessing the reason is that the primary signal source was a turntable. Although very good for its price an NAD 3020 was still a budget item, and likely to be teamed with a budget turntable. Thus rolling off lows like this supressed "rumble" , and as there was less LF content on the typical LP of the day than CDs or modern vinyl, little hard was done. I suspect it was also justified by the expectation that speakers that were likely to be teamed up with the NAD didn't go too deep as well. I presume the posdter will be listening to CDs so the effect of the low values caps would have a greater impact on him than they would in 1980. In addition to the above, a 1uF electro at that point does more than just roll off the lows, it will add distortion as high up in the spectrum as 100Hz. This isn't just "capacitor lore", you can demonstate it with SPICE and it can be measured. Individual people vary as to whther they can hear it. |
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#13 | |
diyAudio Member
Join Date: Jul 2003
Location: S Yorkshire OK
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#14 | |
frugal-phile(tm)
diyAudio Moderator
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Quote:
dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA |
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#15 |
diyAudio Member
Join Date: Feb 2001
Location: USA
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"I've seen caps in series with the input before. Normally they are simply for AC coupling. But I thought I wrote the comment with enough uncertainty to express cautuion if need be."
Have you ever seen an active filter? Do you know how to figure the frequency and Q? Blindly messing with the RC time constants affects the PRAT of the amplifier. "Except the C for the output stage." There are limits to that too. How big do you think you can go before the rectifier will blow? Do you know how to calculate the % of ripple? What is the point of diminishing return? Considering that the voltage gainstages of the PA and the first current gain stage run off a fully regulated power supply, hows does that change things? |
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#16 | |
Banned
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Quote:
J |
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#17 | |
frugal-phile(tm)
diyAudio Moderator
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Quote:
dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA |
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#18 | |
diyAudio Member
Join Date: May 2002
Location: Switzerland
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Quote:
How does it behave when you turn the mains plug by 180 degrees ? How much current flows from the chassis to earth when you measure with a multimeter (use a series resistor to avoid fireworks or worse things !!!) ? Regards Charles |
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#19 |
diyAudio Member
Join Date: Apr 2004
Location: Hong Kong
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I would like to have a copy of the service manual. Please let me know where I can download it.
Thanks. |
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#20 |
Banned
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Thread | Thread Starter | Forum | Replies | Last Post |
Another NAD 3020 | jerryo | Solid State | 17 | 3rd May 2012 06:39 PM |
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