| Multi-chip amplifier - Concentra, GC, PBA200, multichannel (all in one) - Click HERE for Original Thread |
| veteran |
This is my project of simple, multi-chip amplifier. I'm thinking about something similar to Jeff Rowland Concentra but with LM3875 in output stage so this boards will be a part of it (with external, OPA1632 buffer/driver/inverter).
LM's can be connected in parallel or work in multichannel mode. Available options:
Concentra clone
GC
PBA200
Multichannel
Integrated PS board.
schematic diagram |
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| Gcollier |
Veteran,
That is a nice looking component layout! I particularly like the integrated PSU. So what is the final plan...to bridge two of these units? I am personally a bigger fan of the LM3875 than the LM3886 so I am happy to see that you used it here. I'd be interested in seeing the actual board layout with the traces.
A 3 way active filter in front of one of these boards run as independant channels would make for a great amp for a self powered speaker.
I am interested in seeing more on this design. Keep up the great work!
G. |
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| veteran |
Yes, to make easy to build but powerful amplifier in parallel/bridge mode.
Layout: |
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| Gcollier |
Very Nice! I like the supply routing, much easier than with the LM3886 and LM4780!
G. |
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| PierreG |
Very interesting.
Would it drive 4 Ohm Loads?
How many watts? |
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| jaudio |
| I never work with the lm3875, so I don’t know much about it dc offset. If it's in the range of the lm3886, how will you deal with it? |
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| veteran |
It's easy to drive low impedance loads with parallel connected amplifiers.
| quote: | Originally posted by jaudio
I never work with the lm3875, so I don�t know much about it dc offset. If it's in the range of the lm3886, how will you deal with it? |
I will have to make selection of LM3875 chips (similar offset voltage). I didn't wanted to use DC Servo circuit here. |
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| jaudio |
| I used a similar method. I purchased 2 times the needed chips. I got to within 2.5mv variation. How many chips are you planning on buy per parallel module? |
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| veteran |
| They are quite cheap so I will buy about 50 of them. Few of my friends are interested in standard, stereo version of this amplifier so the rest will not waste ;) |
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| jaudio |
| quote: | Originally posted by veteran
They are quite cheap so I will buy about 50 of them. |
How many paralllel module are you planning with 50 chips? I gathering OPA549 to make two bridge-parallel amps. So far I have 21 chips,I think I will get 3 more
| quote: | Originally posted by veteran
Few of my friends are interested in standard, stereo version of this amplifier so the rest will not waste ;) |
I made a couple of Carlos' non-inverted amp. I still have about 7 chips I need to find a use for |
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| ROVSING |
| Very interesting - as always when you come up with new projects.:D |
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| MikeW |
| How many boards are you going to make? |
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| veteran |
Standard order - about 20 boards. Minimal quantity to keep price on reasonable level.
Jaudio, I will make one stereo amplifier ;). I just need more chips to match them. I can sell the rest. |
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| traw |
| 20 boards ?... hmm, was hoping to pick up a 4 pack to do 6 chip per channel stereo amp... |
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| MikeW |
| quote: | Originally posted by veteran
Standard order - about 20 boards. Minimal quantity to keep price on reasonable level.
Jaudio, I will make one stereo amplifier ;). I just need more chips to match them. I can sell the rest. |
Can I have 2? |
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| troystg |
| quote: | Originally posted by veteran
.......
Layout: |
On the side of C1 and C2 there is a "node" on the power trace (facing up) but the same node and jumper is not there on C3.
May I ask what it is for on C1 and 2 and why it's not there for C3?
EDIT:
Sorry the picture was from post #3. Apparently the image doesn't copy when you quote. |
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| troystg |
Ah ha... I see said the blind man.....
The nodes are to connect C4-9 and the connections for C4 & 5 are allllllllll the way to the left....
Sorry I missed it earlier. :cannotbe: :angel:
But yes the boards do look good. I'd love to have a win-stamp pre to accompany them... ;) :D |
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| veteran |
I ordered them (30 boards - probably there will be few more).
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| paulb |
| quote: | Originally posted by troystg
Ah ha... I see said the blind man.....
. I'd love to have a win-stamp pre to accompany them... |
Any update on the WM Stamp? |
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| ppcblaster |
| Alot of forum readers were waiting on you |
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| veteran |
Finally some progress ;)
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| veteran |
It's working... Now I can place them on a bigger heatsink.
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| Bassterror |
Hi
nice projekt:D
How good is it compared to a paralleled 2x3886 or 4780 paralleled?
I think about a little amp for my 2*10 inch subwoofer... |
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| jaudio |
| What are the dc offsets? |
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| MikeW |
| Is +/- 43 volts to high? :hot: :hot: :dead: |
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| MikeW |
| Your right, two out of the three chips of onechannel blew up when I connected the input. The other channel is still working. I will drop the voltage a little.:hot: :bigeyes: |
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| halo0925 |
LM3886's ?? blew up on +/-42VDC? something else is wrong I run a BPA on +/- 48VDC and have never "blown up a chip":xeye:
PS thats unloaded voltage under load the supply puts about +/-43VDC never have I had a problem even under long term high output. |
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| Scribble |
So how does it sound!?
Im very interested in this project. Looks like something i can make point-to-point. How was the DC offset?. What transformer did you use?
Thanks for your time!,
Joel |
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| veteran |
It sounds quite good - with the softness of standard GC and power consequents from parallel configuration. If you have match chips proper output offset is minimal (about 70mV).
I'm using 2x24AV transformer for this amp. |
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| PierreG |
-By jaudio-
How many paralllel module are you planning with 50 chips?
| quote: | Originally posted by veteran
Jaudio, I will make one stereo amplifier ;). I just need more chips to match them. I can sell the rest. |
I understand that you need to buy 50 chips to match the quantity needed for a stereo amp? 6 out of 50? :bigeyes: |
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| halo0925 |
| Why match the chips:xeye:? do you match for the lowest individual offset? and if so why?it is a componding rule that applies to the DC offset, you will net gain for the lowest level of offset, but you will still have DC and higher idle dissipation, I would be curious to know what youre Idle current per chip is:) becuase idle current can be more of an issue then DC offset. Just take the normal 60ma per chip and mutiply by 3:D, I will bet ya its a lot greater then 60ma*3;) |
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| tschrama |
Hi, congrats on this very nice project. Very nice PCB! Are you selling PCBs. I would be very interested in 2.
regards,
Thijs |
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| samsagaz |
| maybe i want some too, i want to build 2 5.1 systemss. |
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| veteran |
PierreG, I just wanted to match them proper ;).
I have few more boards. Contact me please for details. |
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| PierreG |
| quote: | Originally posted by veteran
PierreG, I just wanted to match them proper ;).
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Do you mean that you can make the board without matching the chips ?
What would append then? |
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| sasmit |
| anybody got any ideas about a biamped setup using..4 * LM4780's and a 2 way active crossover..? |
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