Hey mod team, if this needs to be over in another section, please feel free to throw it there.
A BUNCH of folks have been following my LM4780 paralleled amp project, and I've gotten a number of E-mails asking about buying boards.
I mean, a NUMBER of E-mails.
I'm an old hand with bulk-buys, having orchestrated the moving of several thousand white LEDs direct from Nichia Chemical Corp. in Japan (and correspondingly several thousand dollars from about a hundred people), so I'm debating another bulk-buy - this one of PC boards of my paralleled LM4780 design.
The board will be double-sided with plated holes and vias, full solder masks and silkscreened parts locations. Each board will be 3.8" by 2.5" and will contain TWO AMPLIFIER BOARDS, panellized. These can be hooked up in parallel to double output power or run separately for stereo. With a supply voltage of 60 volts rail-to-rail the amps should hit 120W RMS into an 8-ohm load.
The board design includes integrades close-to-chip decoupler cap mounting points as well as integrated thumpless mute. The design has thus far proven itself surprisingly immune to noise and hum. You'll need to provide appropriate supply filtration and run the mute connect points to some form of SPDT switch or relay. Additionally, the board is designed first and foremost to be compact - its connect points are for soldered wire, not terminals or connectors. It's not meant for temporary installation.
I don't do bulk-buys until I do a feeler, as standard policy. To that end I have posted a feeler page in the Wiki for everyone interested to post their desired quantity of boards. The more the cheaper, and price per board is posted in the Wiki page.
Wiki paralleled-LM4780 board feeler page
Pics of the prototypes will come shortly.
oO
A BUNCH of folks have been following my LM4780 paralleled amp project, and I've gotten a number of E-mails asking about buying boards.
I mean, a NUMBER of E-mails.
I'm an old hand with bulk-buys, having orchestrated the moving of several thousand white LEDs direct from Nichia Chemical Corp. in Japan (and correspondingly several thousand dollars from about a hundred people), so I'm debating another bulk-buy - this one of PC boards of my paralleled LM4780 design.
The board will be double-sided with plated holes and vias, full solder masks and silkscreened parts locations. Each board will be 3.8" by 2.5" and will contain TWO AMPLIFIER BOARDS, panellized. These can be hooked up in parallel to double output power or run separately for stereo. With a supply voltage of 60 volts rail-to-rail the amps should hit 120W RMS into an 8-ohm load.
The board design includes integrades close-to-chip decoupler cap mounting points as well as integrated thumpless mute. The design has thus far proven itself surprisingly immune to noise and hum. You'll need to provide appropriate supply filtration and run the mute connect points to some form of SPDT switch or relay. Additionally, the board is designed first and foremost to be compact - its connect points are for soldered wire, not terminals or connectors. It's not meant for temporary installation.
I don't do bulk-buys until I do a feeler, as standard policy. To that end I have posted a feeler page in the Wiki for everyone interested to post their desired quantity of boards. The more the cheaper, and price per board is posted in the Wiki page.
Wiki paralleled-LM4780 board feeler page
Pics of the prototypes will come shortly.
oO
Prototype boards, and a couple LM4780s:
Prototype populated with parts:
Prototype built:
Prototype being tested:
oO
An externally hosted image should be here but it was not working when we last tested it.
Prototype populated with parts:
An externally hosted image should be here but it was not working when we last tested it.
Prototype built:
An externally hosted image should be here but it was not working when we last tested it.
Prototype being tested:
An externally hosted image should be here but it was not working when we last tested it.
oO
jhead said:
Only size. Mine's about the smallest of the designs. Since all of us are working off the datasheet's schematic the circuits will all be about the same.
That's the downside to having several people come up with working board designs at the same time - it's almost an eeny-meeny-miney-moe type thing to choose a board!
oO
Peter Daniel said:
I guess, you mean the smallest PS caps? What is the size of your board? I'm in an inquiring mood tonight
BTW, you use Zobel, right?
1.75" x 2.5" with the chip along the narrow end. I figure if I mount 'em like blade computers I could stuff probably sixteen into a 2U rack chassis. (Picture that kind of a setup, muahahahahah!
)No Zobel, unless you count the load-balancers the chip calls for in parallel as they sure look like Zobels to me.
Personally I think the three of us with 4780 boards should swap a board with each other and then come up with a single design that kicks the most backside. But, that's just me.
oO
Peter Daniel said:
They are small, as the board design moves all supply-rail filter capacitance off the main amp board. All that's on the board are local filters and decouplers.
Something has to give in order to provide for a small footprint - in this case the supply-rail filters are off-board.
Seems to work rather well in my tests though.
oO
So how much capacitance are you using off the main amp board? Our board isn't any bigger than yours, yet we were able to fit even very large BG caps (1000/50V). We didn't give up on anything, even Zobel
Our board's size is 4.08 sq inch, while yours is 4.375 sq inch.
BTW, having proper capacitors, right next to the chip, was quite important to me.
Our board's size is 4.08 sq inch, while yours is 4.375 sq inch.
BTW, having proper capacitors, right next to the chip, was quite important to me.
Peter Daniel said:So how much capacitance are you using off the main amp board? Our board isn't any bigger than yours, yet we were able to fit even very large BG caps (1000/50V). We didn't give up on anything, even Zobel
Our board's size is 4.08 sq inch, while yours is 4.375 sq inch.
BTW, having proper capacitors, right next to the chip, was quite important to me.
Oh come now, you know you love Zobels!
My first tests on a live system were with 6,800uF per rail - entirely not enough, which is why I intend to add a bunch more. Still have about twenty 4,700u/50VDC caps sitting here that I can call on to assist.
Apparently mine isn't smaller - no matter, there's not enough interest in my variant to bother mass-producing.
As for the chip caps, in my proto the two decouplers are immediately to the left of the IC, and in the revised version they are in front of it with shorter traces to the IC. Both approaches work though - there was not a trace of oscillation or waveform ringing visible on my scope regardless of what I fed them.
oO
There is still some grey area with regards to recommended capacitance with those chips. In my prototype (LM4780) I used 1000u caps directly at the chip. For rectification I used Brian's board (with additionnal 4.7u caps at the diodes). The sound was fine with that setup. Later, out of curiosity, I added 5,600 caps per rail and sound became very dull and mechanical, it lost completely any liveleness it posessed previously. So for me, no big caps with those amps (for full range applications).
As to this amp drivng subwoofer only, more capacitance may be recommended, but I still wouldn't be completely sure of it. It seems like the bass is loosing its speed and becomes sort of booming, without enough transparency.
I also didn't use Zobel in my prototype, and in all 3 systems the amp was tried, no problems were experienced.
As to this amp drivng subwoofer only, more capacitance may be recommended, but I still wouldn't be completely sure of it. It seems like the bass is loosing its speed and becomes sort of booming, without enough transparency.
I also didn't use Zobel in my prototype, and in all 3 systems the amp was tried, no problems were experienced.
Weird - I would have thought adding capacitance on the supply rails would have tightened up bass response by providing more energy for transients.
At any rate, right now I have 0.1u ceramics near-chip and 10u low-ESR caps on the board near the power tiepoints. When I build a supply-cap board I'll use 4,700u caps mainly, but bypass them with a pair each of 470u, 10u, and 0.1u as I've found that combo is excellent at trapping out various harmonics and noise from the supply filtration.
oO
At any rate, right now I have 0.1u ceramics near-chip and 10u low-ESR caps on the board near the power tiepoints. When I build a supply-cap board I'll use 4,700u caps mainly, but bypass them with a pair each of 470u, 10u, and 0.1u as I've found that combo is excellent at trapping out various harmonics and noise from the supply filtration.
oO
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