Hi!
When you want to parallel two LM3886, you just use two similar amps and one 1kohm resistors on the input on each amp? That's how I've understood it when reading different posts and the AN-1129. Is that correct?
To bridge two amps is a bit trickier, isn't it? It's not just to switch the inputs on one amp, right? Which is the easiest way to bridge?
(I've got plans to build an amp that can be switched between bridge and parallel, depending on the impedance of the speaker. Is that a good idea?)
When you want to parallel two LM3886, you just use two similar amps and one 1kohm resistors on the input on each amp? That's how I've understood it when reading different posts and the AN-1129. Is that correct?
To bridge two amps is a bit trickier, isn't it? It's not just to switch the inputs on one amp, right? Which is the easiest way to bridge?
(I've got plans to build an amp that can be switched between bridge and parallel, depending on the impedance of the speaker. Is that a good idea?)
Well, what NS datasheet? AN-1129? I've read it and it seems that it's not possible to make an amp that can be switched between bridge/parallel, because you have to change some components from the original schematics. Correct?
When you parallel the amps each amp needs an output resistor. This is to take care of any difference in the dc offset between amps I believe a small value like .1ohm will probably do.
Your power supply could be quite different for different speaker impedances. Chip amps are cheap. Why not just build two amps?Ulew said:
Re: Re: How easy is it to bridge vs parallel?
Oh, that's a bit problematic! I'll skip that plan. I just thought it would be a fun thing to build!
paulb said:
Oh, that's a bit problematic! I'll skip that plan. I just thought it would be a fun thing to build!
To me, parallel is more difficult because the resistor tolerances must be better (0.1%) so that the output is close to the same so the chips don't "fight" each other.
I think the easiest idea for a switchable 8 ohm to 4 ohm setup would be a switch to change the power supply voltage.
I think the easiest idea for a switchable 8 ohm to 4 ohm setup would be a switch to change the power supply voltage.
But what I want is to get full power into 4 or 8 ohm-speakers. If I go for a parallel amp and use 8 ohm-speakers I won't get as much power as from a bridged one, right?
http://sound.westhost.com/project20.htmUlew said:
You will not achieve that with bridged and parallel versions.Ulew said:
A parallel configuration gives you double the power into 2 Ohm than a single or parallel configuration into 4 Ohm.
A bridged configuration gives you double the power into 8 Ohm than a single or parallel configuration into 4 Ohm.
Parallel configuration needs double the transformer rating and heatsink capacity as single configuration. Bridged needs double the transformer rating and heatsink capacity as parallel.
Exactly.Ulew said:
A solution would be to use a transformer with two pairs of secondaries. E. g. 2*18 V for 4 Ohm and 2*24 V for 8 Ohm. That maintains output power, transformer rating and heatsink size the same. The transformer will have to be custom made, thus a bit more expensive, though not much.
Yeah, but what for? Because it's there?
You could use 2 back-to-back valve output transformers and use the multiple output taps for different speaker impedances.
Why do you think a custom transformer is required? It's because nobody else cares enough, and nor should you.
w
wakibaki said:
I don't think that. A custom transformer is one possible solution for Ulew's desire to achieve the same power output into different loads, no more, no less.
wakibaki said:
Let us ignore for a moment the facts that an audio transformer increases THD and leads to a less linear frequency response. Below 4 Ohm the LM3886 is current limited and above 8 Ohm voltage limited, so you would need an audio transformer with primaries of 6 ±2 Ohm to make best use of its output power capability. If tube amps could drive such loads, they would not need output transformers in the first place. Sounds like such a transformer would also have to be custom made then, doesn't it?
wakibaki said:
Since that statement implies that you care, what is better? Buy one customized power transformer? Or buy a standard power transformer and a customized audio transformer with unpredictable influence on the sound?
Post #9 is not a permitted answer, albeit the correct one.
pacificblue said:
Post #9 is not a permitted answer, albeit the correct one.
Okay, thank you!
I won't bulid this amp that apparently is a rather sensitive subject to some.. 🙄 I just thought it would be fun to build, for the sake of building! Of course I don't need to change between 4 ohm and 8 ohm-speakers everyday, but there's a lot of things we don't need! 😉
Sorry, pacificblue. My answer was directed at Ulew, not you.
You are, of course, perfectly correct in your technical comments about how such an objective might be achieved.
My comments are intended to highlight the fact that although it's possible, thousands of amplifier designers just don't think it's worth the effort and expense.
w
Sensitive? Moi?
On the contrary, I just expect other people to have as thick a skin as I've got. If they haven't I'm quite happy to help them develop one.
You are, of course, perfectly correct in your technical comments about how such an objective might be achieved.
My comments are intended to highlight the fact that although it's possible, thousands of amplifier designers just don't think it's worth the effort and expense.
w
Sensitive? Moi?
On the contrary, I just expect other people to have as thick a skin as I've got. If they haven't I'm quite happy to help them develop one.
wakibaki said:
There's nothing wrong with my skin-thickness, but I think it's boring when people can't keep a discussion at a normal level, but no harm done!
Let's consider this subject done! 😉
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