Hi,
If you don't like the sound of caps, especially big lytics, I cannot see how you can stand a power amp output cap, but maybe they are small enough to be
film type since you go for those glowy things. Don't know enough about that stuff.
QUOTE]
Sorry, Christer one's got nothing to do with the other.
Whether interfacing a speaker with semi-conductors or a glowy things as you call it has got nothing to do with it as the value of the cap will still be the same for the same Z of that speaker.
Once again, that was not the question.
Cheers,
fdegrove said:Hi,
If you don't like the sound of caps, especially big lytics, I cannot see how you can stand a power amp output cap, but maybe they are small enough to be
film type since you go for those glowy things. Don't know enough about that stuff.
QUOTE]
Sorry, Christer one's got nothing to do with the other.
Whether interfacing a speaker with semi-conductors or a glowy things as you call it has got nothing to do with it as the value of the cap will still be the same for the same Z of that speaker.
Once again, that was not the question.
Cheers,
Then I must be missing your point entirely. What did I get
wrong??
Hi,
Sure, but they do so at the cost of having lytic output cap, unless they use a DC servo, that might fail.QUOTE]
And DC servos are fail proof you think? No more or less than any cap I'd say.
Now, would you put a DC servo at the output of that CDP and another on the input of the amp?
Cheers,
fdegrove said:Hi,
Sure, but they do so at the cost of having lytic output cap, unless they use a DC servo, that might fail.QUOTE]
And DC servos are fail proof you think? No more or less than any cap I'd say.
Now, would you put a DC servo at the output of that CDP and another on the input of the amp?
Cheers,
Hm, I did assume capacitors are much less likely to fail, since
they are one single simple component, which if run well within
limits should be very reliable. A DC servo on the other hands
contains a lot of components that might fail, including one
compelx one, the op amp. I find it hard to believe the occasional
failure of a film cap should be even close to the failure rate
of DC servos, but I may be wrong there.
The interesting thing is that despite your usual "allergy" to most
capacitors they suddenly seem not to bother you. However,
it is late, so maybe I'd better try reread what you have said
tomorrow.
Hi,
It's late for me too but the point was the usefulness (securitywise) of having a DC-blocking cap at the source side (CDP out) and at same time having a DC blocking cap at the input of the amp.
My point is that there's no point of having DC blocking at the amps input as there should be nothing to block and if there's DC present from the source it should be blocked, choose your means, directly at the source.
Putting the two blocking means in series by connecting one to the other is not a good idea and I pointed to the effect of two caps in series too as here C1+C2= C1/2 given equal values.
Cheers,
It's late for me too but the point was the usefulness (securitywise) of having a DC-blocking cap at the source side (CDP out) and at same time having a DC blocking cap at the input of the amp.
My point is that there's no point of having DC blocking at the amps input as there should be nothing to block and if there's DC present from the source it should be blocked, choose your means, directly at the source.
Putting the two blocking means in series by connecting one to the other is not a good idea and I pointed to the effect of two caps in series too as here C1+C2= C1/2 given equal values.
Cheers,
Think of the total signal path starting with the microphone. Then add the various amplification stages, mixers, EQ and what not. How many caps do you estimate trhe signal has gone through before it gets to your amp? I would bet that some of them were electrolytics, even.
Analogous to the same worry about op-amps by those dedicated to 100% discrete audio.
Analogous to the same worry about op-amps by those dedicated to 100% discrete audio.
Hi,
Unless you want to go "iron" all the way it's hard to avoid them altogether.
I've been trying to explain on hands and knees how to avoid yet another cap and you're thinking I'm wanting to add one???
Oh yeah, let's "Make things better". Why bother with audio anyway?
They messed it it up big time already, right?
Cheers,
Unless you want to go "iron" all the way it's hard to avoid them altogether.
I've been trying to explain on hands and knees how to avoid yet another cap and you're thinking I'm wanting to add one???
Oh yeah, let's "Make things better". Why bother with audio anyway?
They messed it it up big time already, right?
Cheers,
I'm one of those dedicated to discrete components but I do see your point. Using an input cap would greatly simplify my design. I still see no reason for an output cap as I can always get the offset within a few mV of 0v. Besides, it would have to be huge to allow low frequencies through a 2 ohm subwoofer. Something tells me an output cap placed between a 2 ohm sub and a 200w amp would fail rather quickly.
Hi,
How?
The only justification for a cap at the input of an amp is the assumption of DC at the source?
Fine, no problem. I do have the same arrangement with my tubed OTL amps and haven't had any trouble with DC on the output for twenty years.
Not with the right cap for the job but 2 ohm subs??
That's very low impedance calling for alot of current from the amp.
Cheers,
How?
The only justification for a cap at the input of an amp is the assumption of DC at the source?
Fine, no problem. I do have the same arrangement with my tubed OTL amps and haven't had any trouble with DC on the output for twenty years.
Not with the right cap for the job but 2 ohm subs??
That's very low impedance calling for alot of current from the amp.
Cheers,
Because I had to add more circuitry to make sure that 0v on the input always = 0v on the output regardless of the output impedance of the source. If you short circuit the input terminals on the amp, the output will still stay at 0v. Adding a cap would allow me to get rid of those pots.
Yes, It lets my amp make the most of its +/-20v rails. It seems rock solid down to 1 ohm but a load like that makes my power supply very sad. The TIP35/TIP35 output devices can pass a continuous 25A so there's no problem there.
Even if I use a 6800mf cap on the output, it would still absorb around 30% power at 40hz. I don't think the cap would hold up too well, especially since half the wave charges it backwards.
Hi,
Assuming the pots are there for DC balance I can only say that the cap is going to be in the direct signal path whereas the pots are much less so.
Normally, once adjusted for DC balance they should stay that way for ages unless the circuit uses a fishy topology and the devices aren't matched and age differently because of that imbalance.
Up to you,
Assuming the pots are there for DC balance I can only say that the cap is going to be in the direct signal path whereas the pots are much less so.
Normally, once adjusted for DC balance they should stay that way for ages unless the circuit uses a fishy topology and the devices aren't matched and age differently because of that imbalance.
Up to you,
One pot is responsible for setting the "no signal" offset. Another is responsible for setting the signal "ground" which in reality is about 0.95v. The problem is that every channel has it's own set of pots. If a device was to be connected that has more than one channel, its signal grounds will likely be tied together (probably to its chassis). On my amp the signal ground of my left channel may be .93v and the right channel may be .97v. If you connect a CD player's L and R channels, these two pots would be shorted together and as a result, you would get huge DC currents on the outputs.
Hi,
Yes, of course that's going to happen. What did you expect?
Volts disappearing into the digital null?
You run a floating supply and expect it to somehow magically balance??
The problem isn't that every channel has its' own pots, its just that your source is already tying them to ground at the source.
It just ain't that simple my friend,
Yes, of course that's going to happen. What did you expect?
Volts disappearing into the digital null?
You run a floating supply and expect it to somehow magically balance??
The problem isn't that every channel has its' own pots, its just that your source is already tying them to ground at the source.
It just ain't that simple my friend,
Now it is early (hm, well, for me at least) in the morning instead
of late at night, but let's see if I can clear up what I meant.
If we have full control of the whole signal chain, and know we
won't swap any equipment, it won't matter much where we
put the caps, since we know what the input impedance of
the next piece of the equipment is. Franks resaoning makes
some sense, blocking DC at the output, but since we have
full control of chain it doesn't really matter at which end we
put the cap IMHO.
If we don't have this full control, we cannot know if a preceeding
piece of equipment can be trusted to have zero DC out, and
we cannot know what the input impedance of the following
piece of equipment is. As far as I can see, this means two
things, 1) an input cap is useful, and 2) putting the cap at the
output means we must use a larger one than necessary, possibly
a lytic, just to be sure we don't filter out to much bass even
with somewhat lowish input impedance following.
That's all from the armchair engineering department for the
moment.
of late at night, but let's see if I can clear up what I meant.
If we have full control of the whole signal chain, and know we
won't swap any equipment, it won't matter much where we
put the caps, since we know what the input impedance of
the next piece of the equipment is. Franks resaoning makes
some sense, blocking DC at the output, but since we have
full control of chain it doesn't really matter at which end we
put the cap IMHO.
If we don't have this full control, we cannot know if a preceeding
piece of equipment can be trusted to have zero DC out, and
we cannot know what the input impedance of the following
piece of equipment is. As far as I can see, this means two
things, 1) an input cap is useful, and 2) putting the cap at the
output means we must use a larger one than necessary, possibly
a lytic, just to be sure we don't filter out to much bass even
with somewhat lowish input impedance following.
That's all from the armchair engineering department for the
moment.
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