jackinnj said:
This is the Parallel version -- The Bridged amp, is, well, bridged.
With respect to "Quality" -- I guess it's an item which I'll let the "subjectivists" decide -- the objective measurement of THD is pretty good, but THD ain't everything.
I'm confused... is your board a board to bridge two 4780's together, did you make 2 channels of a paralleled 4780 (so 4 4780 kits) and then bridge that
I'm assuming the former based upon your power ratings
I'm also interested in purchasing these... I will take 6 whenever they're finalized
well, since I was running out of boards I had some new ones made up -- they are basically the same but I have spaced the caps a little so the chunky 4.7uF PP units from Mouser will fit, as well as the tremendous 10uF PS Spragues, or back to back electrolytics:
An externally hosted image should be here but it was not working when we last tested it.
JackinNJ, Sorry to jump in this thread a little late and I am not an expert by any means so sorry if this is a really dumb question. I tried following the pictures of your layout and looked at the layout pcis in the LM4780 datasheet. I don't understand what you mean about star grounding. It seems National has more of a star ground than your board has. Am I confused or am I not reading your board right? I have understood a star ground to look something like a star with all the traces coming back to one point.
The traces also seem a bit small for the other supply pins such as 10 & 11 and others of higher number. I noticed National has big fat traces going over to the other pins for the most part. Why did you run your input traces like that to where they are in the mess of output and power traces?
What will one of these boards cost? Do you offer only the blank PCB in the GB or parts too?
Thanks for the info and sorry if these questions are just dumb.
-SL
The traces also seem a bit small for the other supply pins such as 10 & 11 and others of higher number. I noticed National has big fat traces going over to the other pins for the most part. Why did you run your input traces like that to where they are in the mess of output and power traces?
What will one of these boards cost? Do you offer only the blank PCB in the GB or parts too?
Thanks for the info and sorry if these questions are just dumb.
-SL
it's more of a star blob i have run these amps for 24 hours full tilt and there's not been a problem with the traces.
here are some of the possible cap arrangements:
1) a pair of electrolytics bypassed with a wima film cap -- which can yield an f3 in the milli-Hz -- why anyone wants it I don't know -- perhaps for some instrumentation application.
2) a 10uF Sprague very, very low D Polycarbonate cap (0.0001)
3) a 4.7uF polypropylene
i have run these amps for 24 hours full tilt and there's not been a problem with the traces. here are some of the possible cap arrangements:
1) a pair of electrolytics bypassed with a wima film cap -- which can yield an f3 in the milli-Hz -- why anyone wants it I don't know -- perhaps for some instrumentation application.
2) a 10uF Sprague very, very low D Polycarbonate cap (0.0001)
3) a 4.7uF polypropylene
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Re: 4780 boards
I know the airport up there really well.
There are parallel and bridged boards, never bothered to make a dual board since the LM3886 seems up to the task.
We are enjoying the government shut-down here in Essex Cty. No white-haired old ladies getting on the bus to roll their quarters in AC -- probably means that Church attendance will be up on Sunday and that the Short Hills mall will be crowded.
jmateus said:
I know the airport up there really well.
There are parallel and bridged boards, never bothered to make a dual board since the LM3886 seems up to the task.
We are enjoying the government shut-down here in Essex Cty. No white-haired old ladies getting on the bus to roll their quarters in AC -- probably means that Church attendance will be up on Sunday and that the Short Hills mall will be crowded.
Hi Jack
It's going to be fun even though I don't go too much either to the
airport (forget it this year...) or to the church. Too bad because
otherwise I would learn something....
On the other hand "Little Britain" can be also very funny...
But...but... aren't those boards for the 4780?
I could use a pair, if you could tell me how can I get'em.
It's going to be fun even though I don't go too much either to the
airport (forget it this year...) or to the church. Too bad because
otherwise I would learn something....
On the other hand "Little Britain" can be also very funny...
But...but... aren't those boards for the 4780?
I could use a pair, if you could tell me how can I get'em.
yes, those boards at http://www.tech-diy.com/chipamps.htm are for the LM4780.
I am still slaving away on the LM4702, but haven't been able to get the disortion down below a few hundredths of a percent unless I run it in Class-A -- at least with the Sanken transistors. I have some of the On-Semi power Darlington's to try out but they use the VBE multiplier -- I managed to toast a couple of test leads on the heatsink which tells me that the idle current is set a little high Haven't blown up any transistors, however.
I am still slaving away on the LM4702, but haven't been able to get the disortion down below a few hundredths of a percent unless I run it in Class-A -- at least with the Sanken transistors. I have some of the On-Semi power Darlington's to try out but they use the VBE multiplier -- I managed to toast a couple of test leads on the heatsink which tells me that the idle current is set a little high
Haven't blown up any transistors, however.A problem with Darlingtons in general is that the bases of the drivers already have an internal connection to the emitter, so you are forced to have a split resistor between the bases of the pair (with a tap at the output).
In some brands (such as ST), it has a few 100 R at the most.
Not sure about the value of the internal resistor in the Sankens, but for most OnSemi darlingtons, it is in the 1 to 10 k range, so you can overide it with a 100 to 330 R resistor directly between the bases.
In some brands (such as ST), it has a few 100 R at the most.
Not sure about the value of the internal resistor in the Sankens, but for most OnSemi darlingtons, it is in the 1 to 10 k range, so you can overide it with a 100 to 330 R resistor directly between the bases.
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