peranders said:
Yeah, yeah...
Just try it, ok?
You will scratch your head later, I didn't think it was needed to go that far, either.
But that 100Khz thing I don't buy, sorry.
You need to think way above that, or else just use the cheapest electrolythics you can get, and don't bypass.
Anyway, the snubber discussion is closed.
Try what I suggest if you will, ignore if you must.
This is very tiring, I already gave to that peditory.
lower voltage rails
I am following this thread with much interest and my appetite is whetted now so much that I am ready to start building your amp, Carlos, according to your latest iteration.
I have a question though: I have 4 ohm speakers so my voltage rails should be a little lower. According to the data sheet I should not exceed 28 V or so, I was thinking of 25 V. Do you think the amp can be used with lower voltage too or will it be necessary to make amendments?
Thanks for your continuous good work!
Mick
I am following this thread with much interest and my appetite is whetted now so much that I am ready to start building your amp, Carlos, according to your latest iteration.
I have a question though: I have 4 ohm speakers so my voltage rails should be a little lower. According to the data sheet I should not exceed 28 V or so, I was thinking of 25 V. Do you think the amp can be used with lower voltage too or will it be necessary to make amendments?
Thanks for your continuous good work!
Mick
Re: lower voltage rails
Perfectly fine, it works very well with lower voltages that what you have in mind.
Yes, for 4 ohm speakers you should not pass 28~30V.
For the voltage you have in mind I would recommend a 2x24V trafo and regulate for +/-24V, or a 2x25V trafo and regulate for +/-25V.
Pick the voltage that suits the trafo(s) you have, having in mind a 'headroom' of around 10V.
EDIT: Ops... you don't specify the PSU you want to build.
This post was for the regulated PSU.
If you decide to go unregulated, a 2x20V trafo is perfect for your needs.
Mick_F said:
Perfectly fine, it works very well with lower voltages that what you have in mind.
Yes, for 4 ohm speakers you should not pass 28~30V.
For the voltage you have in mind I would recommend a 2x24V trafo and regulate for +/-24V, or a 2x25V trafo and regulate for +/-25V.
Pick the voltage that suits the trafo(s) you have, having in mind a 'headroom' of around 10V.
EDIT: Ops... you don't specify the PSU you want to build.
This post was for the regulated PSU.
If you decide to go unregulated, a 2x20V trafo is perfect for your needs.
OK, I've orderd a couple of 3886's and I'm going to build one of these things.
If for no other reason, just because it's so easy, a non electronics hobbyist could do it.
It's amazing that there is such a huge combined volume of experience, so much energy and brainpower devoted to just three chips, that there's probably more practical hands-on knowledge within this forum than there is in all of National Semiconductor regarding these chips.
If for no other reason, just because it's so easy, a non electronics hobbyist could do it.
It's amazing that there is such a huge combined volume of experience, so much energy and brainpower devoted to just three chips, that there's probably more practical hands-on knowledge within this forum than there is in all of National Semiconductor regarding these chips.
funberry said:
National's engineers were surprized (and embarassed) when Jeff Rowland started buying LM3886 chips to make high-end amps.
Give them a go, you can make it or break it, but you can make a very good amp.
You don't have to go through all the process now, this one is fully built, tested and sounds wonderful.
funberry said:
You can search.
It's a man, and it's a brand.
funberry said:
The NI, with low value resistors (as I posted here) is slightly more detailed.
Otherwise I prefered the inverting.
funberry said:
No, not at all, the only thing is that you can control DC-offset much easier with the inverting topology.
With NI you have to take care selecting the resistor values, if you don't want to use the caps from feedback to ground (Ci on the datasheet), as they will have some impact in the sound. Depending on the cap, it can be minimal, but even then...
Since you're discussing the PSU i'll just go ahead and ask something myself
I have two pairs of Chipamps LM3875 kits (dual mono) and nothing to do.
So i thought of either Parallell or bridge them. Brian said that putting them in parallell would do just fine and since it seems simple enough so why not? I'm planning on adding Russ White's freebird and yardbird in it also but that's another thing .
Apart from that i have the parts for either the regulated version or the unreg so either will do. The transformers available are two 2x24VAC 300VA toroids.
So, any pointers of what to use?
oh, yes.
The speakers are a pair of vifa diy bookshelves with 83dB sensitivity and 8ohms.
I have two pairs of Chipamps LM3875 kits (dual mono) and nothing to do.
So i thought of either Parallell or bridge them. Brian said that putting them in parallell would do just fine and since it seems simple enough so why not? I'm planning on adding Russ White's freebird and yardbird in it also but that's another thing .
Apart from that i have the parts for either the regulated version or the unreg so either will do. The transformers available are two 2x24VAC 300VA toroids.
So, any pointers of what to use?
oh, yes.
The speakers are a pair of vifa diy bookshelves with 83dB sensitivity and 8ohms.
kmj said:
That's great.
kmj said:
First try bi-amping your speakers.
I don't think you need to parallel (which has negative effects) or bridge.
kmj said:
Those are fine for the (high cap. snubberized) unregulated PSU.
kmj said:
Sensitivity and average impedance specs alone don't mean much, and those speakers can be easy (or not) to drive.
You just need more gain (preferably on the pre), because they have very low sensitivity.
Go for biamping (4-channel amp), and two unregulated PSUs, one for left and another one for the right channel (two chips each).
If you wanted to regulate, with those trafos you would have to do it at around +/-24V, which could be a better option if your speakers were 4 ohms, or if they have (hopefuly not) big impedance dips.
carlosfm said:
National's engineers were surprized (and embarassed) when Jeff Rowland started buying LM3886 chips to make high-end amps.
Give them a go, you can make it or break it, but you can make a very good amp.
You don't have to go through all the process now, this one is fully built, tested and sounds wonderful.
Geez, I talk to quite a few people at National Semiconductor. I think that the last time they were embarrassed was when they tried to roll out their 8-bit microprocessor line. Even there they produced some good assembly language routines...the NSM folks are first rate but they have some stunning competition in analog in the States.
I can't imagine Bob Pease being embarrassed.
jackinnj said:
Go talk to them again.
I'm not claiming anything, or inventing anything out of the air.
And I'm not selling anything.
Just read what those who know (or knew) them say:
http://www.diyaudio.com/forums/showthread.php?postid=247517#post247517
Thanks, I missed that 4-channel alternative but as for the PSU's, the part are already starting to arrive
. The speakers are REALLY difficult to drive by the way so this seems lika a good solution.Then it's of to the metalrecycling company for some nice and thick aluminum, to the uncle's metalworkshop and then to the company next door who does powderpaint (Probably the wrong word but color in powderform is applied to a grounded piece of metal and then melted on).
So again, thanks for the help. Have a nice weekend everyone.
> (Probably the wrong word but color in powderform is applied to a
> grounded piece of metal and then melted on).
Powder coating. I have always wanted to build an amp that was powder coated high-gloss black, then get all the letters machined out in a V-shaped groove with a C&C machine, so that they'd show through in tiny polished aluminium letters.
Unfortunately, that would probably cost more than I'd be able to spend on an entire amplifier. :/
Wes
> grounded piece of metal and then melted on).
Powder coating. I have always wanted to build an amp that was powder coated high-gloss black, then get all the letters machined out in a V-shaped groove with a C&C machine, so that they'd show through in tiny polished aluminium letters.
Unfortunately, that would probably cost more than I'd be able to spend on an entire amplifier. :/
Wes
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