I'm a newb too...looking for the post now, but can't find it. I thnk the suggestion was try it and see if you like it. But I'm curious as well. Hopefully you'll have better luck with people helping you out than I have around here.
Maybe it was here-
www.diyaudio.com/forums/showthread.php?s=&threadid=10813&highlight=
Maybe it was here-
www.diyaudio.com/forums/showthread.php?s=&threadid=10813&highlight=
There's not that much consensus on the best setting for an Aleph
current source. We have played with it anywhere from 0 (CCS)
to 100%. The listeners we have tested with seem to have
preferences ranging from about 30% to 70%, but this figure
encompasses different speakers, music, levels, and taste.
50% gives the best efficiency figure, but the optimum gain
sonically depends on the above variables and also the bias.
As you go toward 0, you must double the bias in order to reach
the same power spec, and typically increase the feedback by
12 dB or so to maintain a similar distortion spec.
As you go toward 100, you must also double the bias to remain
in Class A, but you can get theoretically get "vanishingly low"
distortion with such an approach.
If you don't increase the bias as you increase the gain, you will
run into cutoff on the current source at higher power levels, and
it's not pretty.
current source. We have played with it anywhere from 0 (CCS)
to 100%. The listeners we have tested with seem to have
preferences ranging from about 30% to 70%, but this figure
encompasses different speakers, music, levels, and taste.
50% gives the best efficiency figure, but the optimum gain
sonically depends on the above variables and also the bias.
As you go toward 0, you must double the bias in order to reach
the same power spec, and typically increase the feedback by
12 dB or so to maintain a similar distortion spec.
As you go toward 100, you must also double the bias to remain
in Class A, but you can get theoretically get "vanishingly low"
distortion with such an approach.
If you don't increase the bias as you increase the gain, you will
run into cutoff on the current source at higher power levels, and
it's not pretty.
I haven't seen a schematic for the J, so I can't comment on what caps there might or might not be.
The phrase 'in the signal path' is a subtle and dangerous one, and likely one of the most abused terms in the entire audio lexicon. What, exactly, does it mean? Most people can look at a series component and see that it's in the signal path. Show them a parallel component, however, and you'll be surprised how many of them will confidently inform you that you need not worry about that one...it's not in the signal path.
Hmmm...
To see the fallacy here, consider a simple 6 dB/oct filter. Place a capacitor in series with the signal and we have a high pass filter. Since it's in series, the capacitor is rightly regarded as having an effect on the quality of the signal.
Take the same cap and put it to ground, such that the signal scoots by the top of the cap on its way to the next gain stage. Not in the signal path? Well, actually, what we've got now is a low pass filter, something that everyone will agree does something to the signal. Hence, it's in the signal path.
Get out of the amplification circuitry and look at, say, the capacitors in the power supply. Surely we're out of the signal path now...aren't we? Nope. Power supply caps have a more complex job than many people imagine. One of their functions is to serve as a short to ground for audio frequency stuff that makes it into the rails. Suddenly the humble power supply cap takes on a brand new aura of importance. If it's not big enough, low frequencies won't get passed to ground. If the cap is of poor quality, high frequencies won't get passed to ground. Either way, you're degrading the performance of the amplifier.
In short, there's no such thing as a component that's not in the circuit path.
How many caps, and where they are in the J's circuit, I do not know, but I will guarantee you that there are caps in there somewhere and that they are in the signal path in one way or another.
It'll be okay. I'm sure the amp will sound just fine.
Grey
The phrase 'in the signal path' is a subtle and dangerous one, and likely one of the most abused terms in the entire audio lexicon. What, exactly, does it mean? Most people can look at a series component and see that it's in the signal path. Show them a parallel component, however, and you'll be surprised how many of them will confidently inform you that you need not worry about that one...it's not in the signal path.
Hmmm...
To see the fallacy here, consider a simple 6 dB/oct filter. Place a capacitor in series with the signal and we have a high pass filter. Since it's in series, the capacitor is rightly regarded as having an effect on the quality of the signal.
Take the same cap and put it to ground, such that the signal scoots by the top of the cap on its way to the next gain stage. Not in the signal path? Well, actually, what we've got now is a low pass filter, something that everyone will agree does something to the signal. Hence, it's in the signal path.
Get out of the amplification circuitry and look at, say, the capacitors in the power supply. Surely we're out of the signal path now...aren't we? Nope. Power supply caps have a more complex job than many people imagine. One of their functions is to serve as a short to ground for audio frequency stuff that makes it into the rails. Suddenly the humble power supply cap takes on a brand new aura of importance. If it's not big enough, low frequencies won't get passed to ground. If the cap is of poor quality, high frequencies won't get passed to ground. Either way, you're degrading the performance of the amplifier.
In short, there's no such thing as a component that's not in the circuit path.
How many caps, and where they are in the J's circuit, I do not know, but I will guarantee you that there are caps in there somewhere and that they are in the signal path in one way or another.
It'll be okay. I'm sure the amp will sound just fine.
Grey
I'm sure there are some somewhere...though my limited electronics knowledge could be wrong.
Can't inductors be used as an energy storage device?
To me, if you got rid of the coupling caps you would have to make up for the possible DC offset somehow somewhere else. Maybe a new circuit design idea to do that...or maybe a few resistors...maybe something else.
I, for one, am pretty excited to see a new Aleph amp...though that Mini based on a 10 year old amp sound pretty sweet. Must be like a fine wine, only gets better with time.
Can't inductors be used as an energy storage device?
To me, if you got rid of the coupling caps you would have to make up for the possible DC offset somehow somewhere else. Maybe a new circuit design idea to do that...or maybe a few resistors...maybe something else.
I, for one, am pretty excited to see a new Aleph amp...though that Mini based on a 10 year old amp sound pretty sweet. Must be like a fine wine, only gets better with time.
winslow said:
There is a single film capacitor in the feedback loop, and there
are no input or output capacitors. There are electrolytics
associated with the current source, but I'm not about to stack
up film caps for 220 uF's not in the signal path. (I regard lots
of things as outside the signal path, including the power supply)
I agree Nelson. They are not teaching what we want to know. They try to teach enough theory to get us by, out here??? They actually try to work with coorperate elec and provide what's needed for fresh outs to excell. Actually, today you need more political savy than real knowledge to survive. But, if you always keep real applications in mind during all this theory, you develope experience before you ever leave school. That having been said. I graduated high school vocational elec. with tubes, transistors, even a little computor knowledge. I graduated DeVry in '79, we spent a couple weeks on monolithic stuff(ICs). My first real job,,, I was probing chips equivalent to the relatively new 6800 but they went into PaceMakers!!!. Probing and even testing of ICs was not even taught!!!
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