| 100db |
Hi All,
Would like to hear your opinion on this...
Between these popular chips... LM3875/3886/4780 and also OPA 541 / 549... which one should be the best suit to my speaker ?
MTM, 4 Ohm ~90db, using parallel 15w-8530 with Vifa XT25 tweeter
thx.
:D |
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| jackinnj |
| you can parallel the LM4780 quite easily -- |
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| pinkmouse |
| The LM4780 and OPA549 both work well with 4ohm |
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| 100db |
Hi Jackinnj, Hi Al
I'm currently using inverted 549 with 10k input and 93.1k feedback... I wonder if this single unit enough for my speaker ?
I've tried to bridge them but can't away from Hum problem. Also when I turn the volume up and down, will be a "poke" sound come out from the woofer.
Will try the 4780 soon.
:D |
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| pinkmouse |
| Well, for 4 ohm loads, you should be looking at parallel operation rather than bridged. As for hum, the 4780 will be slightly easier in this respect as it is all on one chip, but if you're careful, and trace all the wiring in your existing amp, then you should get rid of the hum. As for the noise when you alter the volume, have you tried changing/cleaning the volume pot? |
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| 100db |
Hi Al,
I did try parallel 3875, but I found that it didn't sound as good as a single one, the other thing is I need to turn the volume more ( from 11am to 2pm ) to get the same loudness. Out put resistor is Mills MRA 0.1 R, 5 watt.... I don't think this output resistor will kill down the quality that much, isn't it ?
| quote: | | As for the noise when you alter the volume, have you tried changing/cleaning the volume pot? |
Yes, I've tried a DIY Stepped atten', a fake ALPS step', Noble 31 steps... all of them having this problem, maybe from somewhere else ?
:(
Ball |
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| pinkmouse |
| quote: | Originally posted by 100db
I did try parallel 3875... |
Bridging 3875s into 4 ohms wouldn't work that well, they are optimised for 8 ohm loads, and in your setup they would be seeing 2! Your Mills should be fine, though I would put two in series to get a little better current sharing with a bridge or parallel setup. What schematic did you use? |
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| 100db |
| quote: | | What schematic did you use? |
For 3875, all of them are inverted.
2.2uf Ci, 10k input, 220k feedback, 220k from + to gnd.
Toroidal 24-0-24, 20A through MUR1620/R, No snubber no regulated.
Ball |
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| v-bro |
| this one can drive heavy loads too (1 ohm!) , and can be parallelled... |
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| 100db |
Hi v-bro,
Thanks, I'm checking the data sheet :D
Any shematic recommended ?
Ball |
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| v-bro |
You can start with the schematic of the evaluation board...
The schematic is several pages down, also a recommended parts list is included:
http://41hz.com/downloads/TAA4100A....d%20taa4100a%22
If you want the joy of home-building paired with the comfort of haveing all parts served to you on a plate:http://www.41hz.com
(look at amp 9 kit). This one is more affordable than the next option, and they have a lot of choice in other kits.....
If you want to have it built and tested for you:http://www.autocostruire.com/catalo...4fd0c8e415bbfd9
This shop can provide you with a schematic to parallel the chips.
They have a 2/4/8 channel version with this amp.
The chip is fitted standard with 4 channels, so the 2 channel version doesn't use the whole chip (I have the 4 channel version of this one) as I've read...
The amp I have can drive my electrostatic speakers(on 12 volt operation) , they show an impedance at higher frequencies of aprox. 1 ohm!!
I must say soundquality-wise the electrostats reveal some limitations of the amp, but you would have to spend at least ten times this money to get the same sonic qualities. And the chip is vertually indestructible (secured very well). Brands like "audio research" use these chips (with their own schematic, would like to get my hands on one!)...
Making your own board with this chip (necessary to do the proper(and necessary!!) shielding) will be a lot harder than making a hardwired gainclone.
I would encourage doing that if you're capable of it, please keep me/us informed! |
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| v-bro |
Looks brilliant man!
Chip amps are the future ;) |
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| v-bro |
It only depends on what you want to do with it, I take my mc4x100 audiodigit amp wherever I go, and it really saves the battery.
Even in my livingroom I opeate it on a sla battery (35 amps)...
There is no cleaner power than a battery......
Don't know about the efficiency of that gainclone? |
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