Bricolo said:
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
MRehorst said:
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.
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
UrSv said:
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)
Attachments
Matttcattt said:[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
Matttcattt said:
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
Bricolo said:
You make a point but there are some other sides of the story. I use 1000 uF at 36 V. First of all, 1A at 36V is still 36 W. And this is for only one of the supply sides. Plus, after the peaks of the sinus on the mains supply the caps will not go down directly (they can't go under the dc supply of the toroid, well a little bit due to the voltage over the diodes). And then you have lost 10V, this is not very bad for the opamp due to the PSRR.
Still, the bass can loose some control. This is more of a 'choice' than a side effect. The effect is that the bass is more soft&pleasant and the high tones are fast&dynamic. This contrast is maybe the thing that makes this amp so wonderful.
Another point. I think this amp is not to be used as a 'Power Amp'. Purely for control, a more standard amp with large supply could be better. But when paired with good high-efficiency speakers (where hardly more than 1 W is used during normal listening conditions) this amp is awesome!
Fedde
p.s. Maybe 1000 uF is too low for my 36V supply. I have tried an extra 1000 uF and it has advantages and disadvantages...
I will go to 25 V supply lateron.
carlmart said:
As mentioned yu may use TO-218/247/264/3-P pads but there is also a dedicated MultiWatt pad which basically nobody carries it seems. Only place so far is Schuro (http://www.schuro.de/). If you use Aluminum oxide pads than there is no problem at all IMHO.
Cap types
Wima MKS4 are polyester types, which are probably good enough but far from extraordinary. Siemens stacked film types are probably better, for polyester.
Polyester is the less good of the film types. If you can find them you should try polycarbonate types or polypropylene, or go for exotic $$$ foil types.
For the gainclone, the value has to be at least 1uF or more, preferably 2.2uF or 4.7uF. Some report good results from using Black Gates at the input, though I never used them.
Carlos
fedde said:
Wima MKS4 are polyester types, which are probably good enough but far from extraordinary. Siemens stacked film types are probably better, for polyester.
Polyester is the less good of the film types. If you can find them you should try polycarbonate types or polypropylene, or go for exotic $$$ foil types.
For the gainclone, the value has to be at least 1uF or more, preferably 2.2uF or 4.7uF. Some report good results from using Black Gates at the input, though I never used them.
Carlos
having cake and eating it too
Some have suggested here that relatively high capacitance in the powersupply is good for bass and not so good for mid/high, and vice versa for low capacitance.
Accordingly, would it make sense - if
building a gainclone pair for bi-amplification - to tailor the PS differently for the woofer section vs. the mid/tweeter section? And could this be done by putting two pairs of bridges off of one secondary, with different filtering caps on each, or would it would require two entirely separate secondaries (or, more expensively) separate transformers?
TIA,
David
Some have suggested here that relatively high capacitance in the powersupply is good for bass and not so good for mid/high, and vice versa for low capacitance.
Accordingly, would it make sense - if
building a gainclone pair for bi-amplification - to tailor the PS differently for the woofer section vs. the mid/tweeter section? And could this be done by putting two pairs of bridges off of one secondary, with different filtering caps on each, or would it would require two entirely separate secondaries (or, more expensively) separate transformers?
TIA,
David
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.