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Old 27th February 2003, 09:56 PM   #861
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Quote:
Originally posted by Bricolo
but the 1000F TOTAL capacitance per rail seems really low.

A few mathemetics:

ask a 1 Farad cap to deliver 1 Ampere, it will loose 1 volt per second

do this with a 1000F one, it will loose 1000 Volt per second, in a 100Hz period (i'm in europe, 50Hz AC, 100Hz after the rectifier bridge) wich is 0.01s, it will loose 10V


this is with 1 amp, with 2.5 amp you totally discharge your cap between 2 transformer periods
Basically correct, except for one thing. You only draw near maximum current (say 4 amps) over an entire power line cycle for frequencies much lower than 2x the line frequency (50 or 60 Hz). For higher frequencies, the RMS current is significantly less than the maximum current (2.8 amps) and, more importantly, it is split evenly between the plus and minus supplies (now only 1.4 amps). The voltage drop is still more than 10V. This probably isn't a big big deal given the supply rejection of the chip. It just limits the transient power of the amplifier.

This same argument explains why the low bass firms up with more capacitance. You can get 4 amps draw from one supply at low, but not unreasonably low, frequencies. In this case, you will seriously drain the supply and be lucky to get even 15 good-sounding Watts for your bass.

Physics can't tell you everything about an amplifier, but it can certainly tell you when your capacitor runs out of electrons.

Jeremy
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Old 27th February 2003, 10:11 PM   #862
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Quote:
Originally posted by MRehorst
I can imagine no scenario where high ripple in a power supply is going to make an amp sound "better". It may make it sound different, but adding hum and/or distortion or whatever the effect of high ripple in the supply will be, is not my idea of hi-fi.
The key phrase here being "not my idea."

What may "sound better" is wholly determined by the particular individual experiencing the sound. And there's simply no arguing about individual tastes and preferences. To do otherwise is like arguing that the music you listen to is the only "real music" and the music others listen to is just a bunch of crap.

What is the purpose of listening to music if not for our own personal satisfaction? As long as one is satisfied with the result, who cares how that result was achieved?

Should music and the associated equipment used to reproduce it serve us, or are we to serve it? I don't know about you, but I don't care to be any sort of slave.

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It is a source of great personal frustration that so many people choose ignorance over education.
Why should you feel any sort of frustration simply because someone prefers the sound of their amplifier with far less supply filtering than you would prefer?

What has this to do with education or ignorance? Are you saying these people are too stupid to know what they subjectively like or dislike? That somehow if they become "educated" that their subjective preferences will somehow change?

Now, I can understand being frustrated when people make objective claims based on ignorance. But I fail to see how people simply subjectively preferring something which you may not subjectively prefer should be any source of frustration at all.

If 1,000uF filter caps gives someone more goosebumps or gets their foot tappin' more than using 10,000uF, so what?

se
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Old 27th February 2003, 10:12 PM   #863
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Originally posted by UrSv


Read back through the last few posts or the whole thread and make your choice. The orthodox GC followers seem to prefer 1000 uF for 18 VDC and/or 2200 uF for the higher supplies. People following other class AB recommendations like more. Some people like lots more. Others really don't know or care. I would say that this is where you will have to decide for yourself...

ok, for all the components, shall i just try the circuit with whatever components i have? (all the correct values and ratings)

for the capactitor here (see fig. 1) i have a load of capacitors that look like this (see fig. 2) (not the same writing on them by the way, just the same colour and shape), will they be ok, or do i need some completely different? like this? (ive seen a few of them used) (see fig. 3)
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File Type: jpg capacitors.jpg (24.6 KB, 1274 views)
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Old 27th February 2003, 10:26 PM   #864
Mad_K is offline Mad_K  Norway
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Quote:
Originally posted by Matttcattt



ok, for all the components, shall i just try the circuit with whatever components i have? (all the correct values and ratings)

for the capactitor here (see fig. 1) i have a load of capacitors that look like this (see fig. 2) (not the same writing on them by the way, just the same colour and shape), will they be ok, or do i need some completely different? like this? (ive seen a few of them used) (see fig. 3)
They look fine! Try all of them, and use the one you think sounds best! (I've heard good things about the MKS4)
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Old 27th February 2003, 10:29 PM   #865
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Quote:
Originally posted by Mad_K


They look fine! Try all of them, and use the one you think sounds best! (I've heard good things about the MKS4)

i dont know if they are MKS4's but they that picture looked the most similar (not having a digital camera to hand )
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Old 28th February 2003, 11:27 AM   #866
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Originally posted by Matttcattt
[edit]: i have just ordered 5 LM3875TF samples. where can i get samples of all the other components?

just got an E-mail from NS: i need to get them from a local suplier, only my local suplier (acording to the NS website) doesnt do samples

where in england can i buy them? maplin dont sell them. RS sell the LM3875T version but i would prefer the LM3875TF version .

i wanted free components
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Old 28th February 2003, 11:56 AM   #867
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Quote:
Originally posted by Matttcattt



just got an E-mail from NS: i need to get them from a local suplier, only my local suplier (acording to the NS website) doesnt do samples

Try to oder samples through a company. Then they normally don't disagree.

Marc, who got the samples he asked for
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Old 28th February 2003, 11:58 AM   #868
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Quote:
Originally posted by Matttcattt

just got an E-mail from NS: i need to get them from a local suplier, only my local suplier (acording to the NS website) doesnt do samples

where in england can i buy them? maplin dont sell them. RS sell the LM3875T version but i would prefer the LM3875TF version .

i wanted free components
Then you should start thinking of trying OP549s. The TI samples are backordered now, but they deliver.

About the 3875 T version, if it's available go for it.

BTW: does anyone know where I can get mica or silicone pads for 3875 or OP549 sizes? What is better?


Carlos
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Old 28th February 2003, 12:03 PM   #869
Mad_K is offline Mad_K  Norway
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Originally posted by carlmart


Then you should start thinking of trying OP549s. The TI samples are backordered now, but they deliver.

About the 3875 T version, if it's available go for it.

BTW: does anyone know where I can get mica or silicone pads for 3875 or OP549 sizes? What is better?


Carlos
OPA548 and OPA541 are also good!

You use ordinary top3/to247 pads...
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Old 28th February 2003, 12:03 PM   #870
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Quote:
Originally posted by Matttcattt


ok, for all the components, shall i just try the circuit with whatever components i have? (all the correct values and ratings)

for the capactitor here (see fig. 1) i have a load of capacitors that look like this (see fig. 2) (not the same writing on them by the way, just the same colour and shape), will they be ok, or do i need some completely different? like this? (ive seen a few of them used) (see fig. 3)
I tried the MKS4 once in a dac and I did not like it. Anyway, 0.047 uF is FAR too low! You need at least 1 uF, but 2-5 uF is better. I don't know the values of the other type. I think that I would prefer a standard 100 uF elco to a MKS4 cap...

Fedde
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