I CERTAINLY don't mean to argue, but the comment was 250W and 350W and taken in the context of a lower powr amp with AMPLE current capability, and a higher pwr amy that is "just" squeezing by on specs...
Yes the difference from 200 to 350 is almost double which = 3 db.
Still most subs are current driven and not volatge drivven. High numbers of LM3886 chips will be as good as a a cheap high voltage output pair or two.
For the money it is hard to match the LM3886's.
Yes the difference from 200 to 350 is almost double which = 3 db.
Still most subs are current driven and not volatge drivven. High numbers of LM3886 chips will be as good as a a cheap high voltage output pair or two.
For the money it is hard to match the LM3886's.
thanks everybody.
well i will do this:
1- measure the + & - rails V,
2- take note of the part numbers of the output transistors (i think that are MOSFET's) & quantity
3- take note of the PSU capacitors value
4- look the transformer to see if there is some value printed
5- take some pictures of the amp.
What can I use for "output load" ? i was thinking to use the speaker... I dont have a 8 ohm 350W resistor
carlmart said:
well i will do this:
1- measure the + & - rails V,
2- take note of the part numbers of the output transistors (i think that are MOSFET's) & quantity
3- take note of the PSU capacitors value
4- look the transformer to see if there is some value printed
5- take some pictures of the amp.
What can I use for "output load" ? i was thinking to use the speaker... I dont have a 8 ohm 350W resistor
zafira1981 said:
What can I use for "output load" ? i was thinking to use the speaker... I dont have a 8 ohm 350W resistor
I don't think you should use the speaker as output load. First of all because a speaker's load is not constant. And second because you may blow it if you go too high on your test.
You need to use an 8 ohm resistor, at least 30w or 50w type, and heatsink it, as it will get quite hot.
Something which I do, but would not advise, is using a smaller wattage resistor wired to the amp's outpt and put it inside a plastic or glass bowl with water. The water will act as an isolator and dissipate the heat.
Carlos
(i didnt find lol smiley)
I used the highest quesant dissipation value listed on the datasheet, theres probably room for ~fudge. 20 watts or 40 watts, its not efficient but the lights in my listening room still eat more than this. Steep rails make for low diode drop and I2R wont be high at idle.
I composed my sig after seeing the MIT study that claimed that a foil hat actually reduces head protection from EMI/alien and/or goverment mind scans, thier hats arent properly grounded over there (because they like you to think foil hats wont help...?). Take heed!
The other smilies are found by clicking get more under the smiley selector box.
I composed my sig after seeing the MIT study that claimed that a foil hat actually reduces head protection from EMI/alien and/or goverment mind scans, thier hats arent properly grounded over there (because they like you to think foil hats wont help...?). Take heed!
The other smilies are found by clicking get more under the smiley selector box.
I think the study was the work of graduate students and didnt cost much. This sort of stuff isnt completely and utterly irrelevent to all. Non-ionizing ordinarily isnt of much concern to most, but it might be if your on a tower. Not that this study was really relevant to that. Id suggest allowing your foil hat to float might be better in the case of AM towers.
Oh yeah, forgot the magnetising current, this is probably the main psu related consumption, unless switchmode.
Oh yeah, forgot the magnetising current, this is probably the main psu related consumption, unless switchmode.
350W lm38---
I just proto-typed a bridged parrellel amp useing lm3875's 4 parrellel sets bridged for a total of 8 per channel, amp has less then .008 DC offset, only idles at 34 watts and produces 408 watts at .13 THD and is dead stable. Very carefull design in the PC board is key, most problems in single bridged and parrellel designs are input offsets and oscillations caused by impeadance variations. Referance signal to ground provide a low impeadance path for return , and dont use a dual tied bridge......
I just proto-typed a bridged parrellel amp useing lm3875's 4 parrellel sets bridged for a total of 8 per channel, amp has less then .008 DC offset, only idles at 34 watts and produces 408 watts at .13 THD and is dead stable. Very carefull design in the PC board is key, most problems in single bridged and parrellel designs are input offsets and oscillations caused by impeadance variations. Referance signal to ground provide a low impeadance path for return , and dont use a dual tied bridge......
350W lm3886's
Let me get some stuff together and figure out how to post some pics, I use a basic non-inverted design with 4 parrellel lm3875's the decoupling loop is through a 47uf tantalum cap tied through a 1kohm .1% percision resistor then a pair of high speed small signal diods then cap bypassed 100pf to provide a dual frequeny path to ground. Then both parrellel units are bridged via a DRV134 with gain removed and forced bias. It is actual a pretty simple circuit sounds more complex then it is. I was trying to achieve the same sound quality as my single chip, it has taken about 6 prototypes and a lot of samples and chips! but this one is almost identical except much more dynamic power.
Let me get some stuff together and figure out how to post some pics, I use a basic non-inverted design with 4 parrellel lm3875's the decoupling loop is through a 47uf tantalum cap tied through a 1kohm .1% percision resistor then a pair of high speed small signal diods then cap bypassed 100pf to provide a dual frequeny path to ground. Then both parrellel units are bridged via a DRV134 with gain removed and forced bias. It is actual a pretty simple circuit sounds more complex then it is. I was trying to achieve the same sound quality as my single chip, it has taken about 6 prototypes and a lot of samples and chips! but this one is almost identical except much more dynamic power.
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