hi there I have a few question's about the audio sector lm4780 amp in parallel ... I have searched and searched but cannot seem just quite what I'm looking for.
1. does anybody have any or direct me to where I can find hi-res photos (top and bottom) preferably with the 10000uf cap implemented on the ps
2. can someone clarify which are the correct components (on audio sector) as the parts list differs from the schematic
3.could someone explain why on the data sheet for the lm4780, the parallel example, uses 1 of the input resistor is 54.4k and the other is something like 49.6k now, I know that it's to do with offset and the balancing the two halves of the chip out but why does the audio sector use 2 x 22k
4.how much precision is needed 1% or 0.1% especially for the 680r resistor, have got 0.1% for everything else , but just cannot find a 680r resistor at 0.1%
In all haste, I have realised that trying run it as a parallel, is probably not the best way to go for noobs. but no-one achieved anything by giving up at the first hurdle
hopefully you guys and girls can help , many thanks in advance ( I'm sure the answers will help out a lot of noobs like me, that are in the same position)
1. does anybody have any or direct me to where I can find hi-res photos (top and bottom) preferably with the 10000uf cap implemented on the ps
2. can someone clarify which are the correct components (on audio sector) as the parts list differs from the schematic
3.could someone explain why on the data sheet for the lm4780, the parallel example, uses 1 of the input resistor is 54.4k and the other is something like 49.6k now, I know that it's to do with offset and the balancing the two halves of the chip out but why does the audio sector use 2 x 22k
4.how much precision is needed 1% or 0.1% especially for the 680r resistor, have got 0.1% for everything else , but just cannot find a 680r resistor at 0.1%
In all haste, I have realised that trying run it as a parallel, is probably not the best way to go for noobs. but no-one achieved anything by giving up at the first hurdle
hopefully you guys and girls can help , many thanks in advance ( I'm sure the answers will help out a lot of noobs like me, that are in the same position)
The 680 value is not critical, you can use 1k which I anyway prefer.
Here is one pic, but those are 4700uF. Can confirm that 10kuf also fit fine. Scroll down a few posts
Balanced power amplifier
Here is one pic, but those are 4700uF. Can confirm that 10kuf also fit fine. Scroll down a few posts
Balanced power amplifier
Sorry, that was from a cellphone camera.
Note that the caps, specially big ones, foul with the bolts fixing the chip to the sink. Since I use straight screwdrivers and Philips head bolts, I had to put them on the back of the board. If you use allen bolts and a right-angled key, this is not necessary to do.
I don't know what changes have happened over the last seven years, but the 22k resistors are for input and feedback, there are some 220 ohm units for adding in series with the input, and the bigger Panasonic ones are for the zobel - if supplied.
The small 10uF FC caps go on the PS board, and the large ones on the amp board. Additional buffer is highly recommended.
I am looking at the parallel amplifier schematic on the TI datasheet - April 2013 version - and there is a shared input resistor, and the feedback values are the same for both channels. Don't know where you saw different values?
Note that the caps, specially big ones, foul with the bolts fixing the chip to the sink. Since I use straight screwdrivers and Philips head bolts, I had to put them on the back of the board. If you use allen bolts and a right-angled key, this is not necessary to do.
I don't know what changes have happened over the last seven years, but the 22k resistors are for input and feedback, there are some 220 ohm units for adding in series with the input, and the bigger Panasonic ones are for the zobel - if supplied.
The small 10uF FC caps go on the PS board, and the large ones on the amp board. Additional buffer is highly recommended.
I am looking at the parallel amplifier schematic on the TI datasheet - April 2013 version - and there is a shared input resistor, and the feedback values are the same for both channels. Don't know where you saw different values?
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My Parallel AudioSector 4780
Here are the best shot I have to show any detail.
I can take some additional pictures at a later time.
The build guide that Peter provides should tell you everything you need to know.
If you have more specific questions please let me know, I will help however I can.
Here are the best shot I have to show any detail.
I can take some additional pictures at a later time.
The build guide that Peter provides should tell you everything you need to know.
If you have more specific questions please let me know, I will help however I can.
Attachments
thank you very much, it was actually the audio sector lm4780 in parallel pics I was after ..... obviously just one p/s board and I can just make out that the R0 is solder underneath gives this away as stereo but thanks I'm sure this will help someone though ......I may ask peter ( probably the best person in the world to ask) if he has some hi-res photo's of the top and bottom of completed boards ( both of parallel and stereo of his lm4780's
a nice clear picture of what were supposed to be shooting for would help out a great deal .....you know, not just placement but metal film or carbon or what type caps , poly or alu.....
anyway thanks to your good self and to everyone
for their help
a nice clear picture of what were supposed to be shooting for would help out a great deal .....you know, not just placement but metal film or carbon or what type caps , poly or alu.....
anyway thanks to your good self and to everyone
for their help
hi there Sangram it is on the nat semi data sheet, i was a bit wrong here the input resistor for the left amp is 47k and ri for the right amp is 4.7k and rf1 is 46.4k and rf2 is 51.1k. I would have thought you would want to have a close a match a possible on both amps (with my very limited knowledge) or unless that's part of the circuit to actually create a defined amount of off set to create a *null offset circuit ( if thats the correct term)
I don't think I have enough posts to post a link but its in all the nat semi lm4780 data sheets in the parallel example
thanks for all your help
I don't think I have enough posts to post a link but its in all the nat semi lm4780 data sheets in the parallel example
thanks for all your help
Thank heavens. BTW use the TI versions, they are more recent and have a wee bit more information than the original NS ones, and also are annotated and hyperlinked. Very helpful indeed: LM4780 | Mid/High-Power Amplifier | Speaker Amplifier and Modulator | Description & parametrics
Bridged would have different values because one is used in inverting mode.
Bridged would have different values because one is used in inverting mode.
lm4780 parallel components
hello everyone , I just asked peter for some photos so hopefully he or i will be able to post some pics ..if peters not to busy.
Now in this spirit of this thread can anyone on you brilliant people give us newbs the minimum voltage ratings and wattage ratings you would go for .....for these on the Audiosector lm4780 board again im sure this would hel[ newbs like myself .....and please explain why? so we can learn!
for R1/R2 I'm guessing 1/2 watt and up?
for R3/R5 I'M guessing 1/2 watt and up?
R0/R4 I'm guessing 1/2 watt and up?
R6/R7 DITTO
Now R8/R9 I have 0.1R rated 3 watts wire wound powers ...thoughts?
RM the 10k SMD ...AGAIN 1/2WATT smd but in smd is quite hard to find , now I know I can just use a flattened through-hole ?
R7 I have 2r7 at 7 watts wire wound ...suggestions
Cz 0.1uf or 100nf if you prefer ... I have 1% at 100v again suggestions please
now which resistor set is critical ......for accuracy 1% or 0.1% and which can we get away with being just 1%
I'm hoping this thread will give us newbs a better understanding of the components and why they are used ....so please explain as though you are explainig it to newb and not stephen hawking, thank you diy audio members for all your help ....you will earn your place in heaven, paradise, valhalla or that big components storage box in the sky for this
thanks rosco_leuven
hello everyone , I just asked peter for some photos so hopefully he or i will be able to post some pics ..if peters not to busy.
Now in this spirit of this thread can anyone on you brilliant people give us newbs the minimum voltage ratings and wattage ratings you would go for .....for these on the Audiosector lm4780 board again im sure this would hel[ newbs like myself .....and please explain why? so we can learn!
for R1/R2 I'm guessing 1/2 watt and up?
for R3/R5 I'M guessing 1/2 watt and up?
R0/R4 I'm guessing 1/2 watt and up?
R6/R7 DITTO
Now R8/R9 I have 0.1R rated 3 watts wire wound powers ...thoughts?
RM the 10k SMD ...AGAIN 1/2WATT smd but in smd is quite hard to find , now I know I can just use a flattened through-hole ?
R7 I have 2r7 at 7 watts wire wound ...suggestions
Cz 0.1uf or 100nf if you prefer ... I have 1% at 100v again suggestions please
now which resistor set is critical ......for accuracy 1% or 0.1% and which can we get away with being just 1%
I'm hoping this thread will give us newbs a better understanding of the components and why they are used ....so please explain as though you are explainig it to newb and not stephen hawking, thank you diy audio members for all your help ....you will earn your place in heaven, paradise, valhalla or that big components storage box in the sky for this
thanks rosco_leuven
The 0.1 ohm resistors should be around 2 to 3 watt, same for the zobel. For the rest, 0.125 watt is enough. 1/8w.
The PCB is very small and getting any resistor larger than what is supplied with the kit is quite awkward.
I think some cadock resistors will directly fit the board, as will the high end vishay foil resistors. Best to just ask Peter.
The most critical, where you need very close matches, are the two feedback resistors in each amp - 22k and 680 ohm. Then again, I run a bridged-parallel setup using just the default resistors in the kit and it works just dandy, for the last seven years. I wouldn't worry.
The PCB is very small and getting any resistor larger than what is supplied with the kit is quite awkward.
I think some cadock resistors will directly fit the board, as will the high end vishay foil resistors. Best to just ask Peter.
The most critical, where you need very close matches, are the two feedback resistors in each amp - 22k and 680 ohm. Then again, I run a bridged-parallel setup using just the default resistors in the kit and it works just dandy, for the last seven years. I wouldn't worry.
The attached pic shows how to install large caps on rectifier board (please note this is LM3875 PS board, for the LM4780 the diodes are reversed)
The schematic shows 270R resistors, I'm supplying 220R, the actual value here doesn't matter. The wattage is not critical and you can use anything (except for 0.1R which are 3W)
I assume you actually mean bridged version. My kit does not provide unbalanced to balanced conversion, you can only use it with balanced sources, the NS schematic shows the circuit that works with both, that's why different value resistors.
1% tolerance should be fine.
Attachments
hi thanks peter, thank you for your help ......I want to run this parallel (should have bought lm3875 dual mono boards..for a first board) .................
so the lm4780 kit in bridged OR parallel, I have to have a super duper hi-end cd player with xlr outputs.......I ask this because I see in a lot of peoples pictures and even on the build instructions (albeit) on the lm3875 people are using RCA'S instead of xlr ????????????????
even more confused now but I am now totally obsessed with diy audio
I may be lucky I have an audiolab 800 or 80 in the loft ...which I believe has both outputs
so the lm4780 kit in bridged OR parallel, I have to have a super duper hi-end cd player with xlr outputs.......I ask this because I see in a lot of peoples pictures and even on the build instructions (albeit) on the lm3875 people are using RCA'S instead of xlr ????????????????
even more confused now but I am now totally obsessed with diy audio
I may be lucky I have an audiolab 800 or 80 in the loft ...which I believe has both outputs
Parallel is similar to stereo, just more current output, so you don't need any special cd player (it will use RCA connectors)
Also you can build a simple LM4780 stereo amp using only one chip (half of the kit). A single LM4780 kit is good for 4 separate channels (or two stereo amps) and you don't have to bother with parallel or bridged configuration
Also you can build a simple LM4780 stereo amp using only one chip (half of the kit). A single LM4780 kit is good for 4 separate channels (or two stereo amps) and you don't have to bother with parallel or bridged configuration
I have just found your post on ...lm4780 in parallel and because both inputs and outs are connected, you do not need a balanced source phew that's a relief... just building the amp in parallel is complicated enough, not so much the design, but the vast choice of resistors and caps ..... can I fit this here, can I stand up an axial to be able to get more exotic caps..... I have probably done more research in this than I did for my degree hahaha
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