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Old 22nd November 2015, 09:05 PM   #1
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Default Operation - no magic smoke

I am trying to mod a 6 mono 3 stereo 3 zone ab amp that has Lm3886t x 6. I know one of the gain pots needs to be fixed. This amp to me anyway has a useless feature of bussing the line outs to another 6 or 3x2 outs. It can be bridged to mono. Initially I planning on using jumpers and jumping out the gain pots that then are jumped into another board is 3 lm393ng 14 LEDs 7 green on bottom and 7 red on top to show clipping but may not need to do that. Bridging will give me over 360watts stereo at 8 ohms however I would like to get it to me over 720 4 or stable at 720 8ohms mono 1400 and change w a 4 ohm load. It currently only has 4 10kuf caps so i know I can use larger ones on the PCB. I would probably have to add a soft start circuit to it also. And I would have to have an AC filter on the plug as well as more caps before and probably after the capacitor. How much capacitance will be needed to make it 4 ohm stable in mono? The secondary's are 20v7 and 9a per winding at max and can be made to be 41v4 or 18 amps if I was to play with it. The power jumpers are currently 35-0-35 so may as well leave as is I guess. These are great and small 1 unit amps I get for almost nothing however I need to run them bridged have them 4 ohm stable or lower preferably lower and I will swap out the little opamps for my secret weapon and possibly swap out the lm3886t also is there is a better solution. Can anyone please help?
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Old 26th November 2015, 12:00 AM   #2
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6 LM3886. Simply multiply the power rating of one chip times the number of chips.

Greater placidity at HF could help shorten clipping recovery time. That's part Cc and the applicable range is 180p to 330p. Here's the datasheet LM3886.PDF

Please re-state the nature of the transformer? Maybe a sketch showing windings and voltages? The only thing I could tell about it is, more than one 9A winding, and yes, that probably does need a soft start board.

4x10,000uF is suitable for the power supply board.

For stability during operation, you'd like to have several 470uF caps on the amplifier board itself.

I guess that you want what we call a "BPA300" parallel bridge amplifier (that within the quotes is your search term to find out more about it). Also, this document will help, AN1192.PDF
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Old 26th November 2015, 03:03 AM   #3
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2 secondary windings - think 24v 9a so could be wired 48v or 18a. I was gonna swap out the little opamps for my fav ones for line level things as well and have a bunch of 4700uf 65v 85 degree caps. Are you talking about filtering caps or oil and tin or what and will they effect tonality. Where on the amp board should the caps go? Their is some caps already and I can just up their values. How many uf per channel will allow me bridge the 3 stereos to 1 at 4 ohms and ideally add something for mono out. I'm 4 ohm mono I should have the power needed. It's a plitron 1 primary that can be switched from 120 to whatever the other one is 240? 2 secondary pairs. It's packed tight and a solid design and with some tweeks it will be a monster especially in a 1 unit rack. These things I had for year turned on 24/7 365 no issues. Maybe I change the amp out also to a newer model but this is a slick package nice heat sinks 12v triggers Ir input etc. no switch as they were designed to be work horses. Ideally I need high current monoblocks also as I have some speaker systems that I made 4 ohm and in excess of 100db efficient. Sort of went overboard with this project. Please show me the way to the promise land. I'll probably add some other trickery and controls/circuits get new chasis machined and have the PCBs redone To be mono only. They currently have a loop out circuit which is basically unless for my needs so it can be a slick amp.

Lastly for power supplies is it best to have a lot of smaller value caps or less high value provided the uf is the same. I'm figuring redundency is best? I also saw a ps one time where the caps were run in series and parallel. What are the benefits?
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Old 26th November 2015, 06:14 PM   #4
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See also this: Simplest Ever Bridging Adapter for Amplifiers
Quote:
Originally Posted by JaredC79 View Post
2 secondary windings - think 24v 9a so could be wired 48v or 18a.
Single 48 would be inconvenient.
Two windings, 24vac 9a is usable.

(2x24)x9 is 432VA
Subtract an estimated 10% for power factor and then that's 389 Watts.
Quote:
Originally Posted by JaredC79 View Post
in a 1 unit rack
Class AB amplifiers are approximately 50% efficient when driving heavy load speakers. Therefore half of your available 389W will go into the heatsink, not the speaker. The remaining amount that may go to the speaker is 194 watts or less.

A 194 watt heat(er) dissipation in a 1u enclosure will cause shortfall of longevity (because oven). Also the 194 watt speaker output doesn't accomplish your goals of power output.

Conclusion: You need a more efficient amp.

You need Class D amplifier for your application. The 75% efficiency (with heavy loads) results in 389*0.75 = 291W to the speaker, and the remainder, 98W released as heat at that 1u enclosure. Considerably safer! In this case, Class D comes closer to your goals for power output. A PBTL Class D build may do a little better than my example. An additional bonus is that modules will be more straightforward to use and that means doable.

P.S.
Also, please find the enter/return key--No more textwall. Thanks!
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Last edited by danielwritesbac; 26th November 2015 at 06:21 PM.
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Old 27th November 2015, 06:48 PM   #5
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These are and have been functioning amps powered on 24/7 365 for about 10 year. Chasis can be made bigger if needed and the mfg may be sending me out 4 of the boards without the ps installed (1 group of 3 has its own PCB the other has the rectifier and filtering caps) running one on each of the 4 sizes with the sinks going around the edges. I have to put thr lcrs as big as they are on a pedestal, have extra dummy box for all my electronics because the crossovers are done totally differently and all the benefits of dsp without the D are implemented. There is also a small empty area at the top as well for more electronics and make the top flat most of the drivers are canted. So the power supplies can be remote with the actual amps themselves inside areas that would have been filled with sand or batting or braced depending on the location. I need several 4000 watt amps. I know those chips can handle more juice they their getting because there is circuits I don't need. Class D? No thanks I would rather hand wash a strippers thong although I do hear of some possible class D analog stuff but haven't heard any of it.

I have some older high end analog club amps I'm modding for now but not sure uncolored clean sound w no noise when I am done but worst case they are great solutions for the subs. This projects has been 7 years in the making and I ended up going a little nuts with these particular speakers especially the lcrs. It's a total of 51 different drivers. Basically everything will be powered by a monoblock. It's a different approach for theaters and a lot of unorthodox equipment was used from my former life so every this is basically a separate component system. No all in one pre pro or anything like that.

A few people in the industry have seen it and heard it as is without the perfect amp pairing. The LCRs are 2120 watts at peak 103db efficient at a 4 ohm load with a bunch of tricks no one has seen yet. I can make them a 1ohm load if needs be to cut the power needs but they are so sensitive I do need high current for them to shine. Word got out and a very popular well known - legand - may actually build and design the main amps so they are able to do the speaker system justice. I also have the ability to tri amp the speaker. Which makes my tricks for the crossovers easier and I'm sure different designs sound best for tweeters and high mids and low mids etc.

I haven't figured out the power needs or final design on side surrounds and the rear surrounds and been toying with a few different ones - the atmos spec is done. I basically use the rule of 2x peak for a speaker systems power needs and their is a ton for drivers in their so I can change thing up here and there so the amps can drive a series or a system - it's a full range line array with some custom 12"in coaxials. I have a few manufacturers and suppliers support which is great and it really seems like anyone who has seen it or heard it although not completed are pumped to experience the final result. Henry at Plitron laughs when we are talking about it and the power needs as well as current. My uncle who's a master electrician says I'm out of my mind. I know each sub amp and lcrs amp or series will need their own breakers. I went well beyond what any sane person would do for any portion of this build including medically isolated outlets and seperate grounds. Floated the floor, decoupled the room. Broke a few rules to show with some creativity obstacles can be overcome. It is sound proof or at least was before i throw the monster in there at peak. All the acoustical treatment was done in a way it is ornamental and the design it self was done with physics and their are slick design elements that are highly functional for sonic purposes.

What started off as a string "jcs winter project" became an obsession and 7 year job most of which was building custom stuff and testing things. It was supposed to be just a theater but turned into a whole house avd and automation system with energy harvesting and green solutions and a few other custom products in addition to some wicked design elements. The controllers and soon to be shown piece really are awesome and people a ton of money and sticks it to big businesses which I like the best. For instance the master bathroom has a kick as sound system and tv opposite the hot tub and a steam room/11 head shower. It also has chroma and aroma therapy. I like spas but escrew anything public so I made my own - if i have time I am going to remove the window by the jacuzzi and replace it with another fireplace and put Windows on both sides. (Not the os ******* iOS spell check). I missed this years CEDIA where the some of the line and the brand was to be rolled out so I figure I had another year to go absolutely over the top where my home is used as the showroom for the capabilities by entering the competitions. Safety and security were paramount (at least when explaining it to an ex) and can be programmed to be offensive and defensive. It thankfully consumed so much time my ex filed - I know if i did she would have gone for the jugular had 3 other women move out and i hardly leave the house I am so focused on perfecting every aspect and be an example of my wild imaginations future luxury home.

Sorry for the long blocks as I'm trypically on my phone. I hate my current career and occupation (sold the company and it is getting ready to go public) that the more I did the more I thought how everything was done from the beginning incorrectly and I was taken back by the costs of what is considered high end but is technically just a computer with some class d garbage. I used to be a DJ and producer, my dad was a huge AV head as long as i can remember and my family owned a legendary guitar company until the early 70s so it's in my DNA. I built anything and everything you could imagine over the years but had to learn a bunch of new skill sets for this and the further I got the more I realized I can make a superior product at a more than competitive price that is infinitely expandable with some components and perfs anyone can afford. A buyer isn't tied to a few select mfgs like a AMX, Crestron, Elan, etc allowing them to automate or control any lighting system, access entry, security, etc. Everything was pen tested to death and using some of my equipment and following some other guidelines your home will be a literal fortress.

Last thing to develop is the amps - if this guy ends up joining up his name alone will be a big win for the new company. I had other engineers and people assist with certain aspects and the concept is to make it so powerful and a frequency range so wide you have a 4d experience without fatiguing your ears and no tactical transducers - just pure analog hifi at its best. To make sure it isn't fatiguing at such high levels my friend was one of 3 engineers who built the Phazon system and basically won anyward possible for club sound systems. So while i may be new to certain aspects I have a lot of solid support but I feel it is important for me to totally understand every aspect so my vision is realized rather than slightly changed by the lack of knowledge capital.

I know design is paramount but will a superior chip design outperform a superior solid state design? If I do tri amp the lcr system will a chip design perform better sonically in certain ranges?
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Old 29th November 2015, 07:20 PM   #6
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Quote:
Originally Posted by JaredC79 View Post
I can make them a 1ohm load if needs be to cut the power needs but they are so sensitive I do need high current for them to shine.
Audio amplifiers would perform optimally with 20 ohm speakers.
The lower that figure goes, the worse audio amplifier will perform.
So, 1 ohm is something you very much want to avoid.
A heavily loaded amplifier will put the majority of the power into its heatsink, Not your speaker.
Lighten the load, man!
3.3DCR (max load) is about as far as you can go without seriously hindering the amplifier.
Quote:
Originally Posted by JaredC79 View Post
I also have the ability to tri amp the speaker. Which makes my tricks for the crossovers easier and I'm sure different designs sound best for tweeters and high mids and low mids etc.
Yes, Tri-Amp will greatly improve the fidelity at those power levels. That would be fantastic for alleviating amplifier straining. Then, only the bass and midbass amplifiers would be straining.

Tri-Amp or Quadruple Amp can make the prospect doable.

It would be good to have a list:
How many treble speakers of 3.3DCR and lighter load?
How many midrange speakers of 3.3DCR and lighter loading?
How many midbass speakers of 3.3DCR and lighter loading?
How many bass speakers of 3.3DCR and lighter loading?

In the above questions, I'm inferring that you would, of course, un-group the unit enough to make the load doable.
Quote:
Originally Posted by JaredC79 View Post
I know design is paramount but will a superior chip design outperform a superior solid state design? If I do tri amp the lcr system will a chip design perform better sonically in certain ranges?
Due to the tiny size of the internalized output transistors, sealed inside that little black casing, the chip amp will perform best when it is least loaded. Paralleling also decreases loading. SO, a paralleled chip amp might be very nice for your tweeter/treble amplifier.

Since we don't run 2000W through an 18ga lamp cord to a near-short load, likewise, we can't use tiny output devices for such an application; and, therefore, the solid state discrete amplifiers are required for that task, mainly because you can choose very big power transistors. At this power level, use the big discrete parts for bass and midbass amplifiers.
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Old 30th November 2015, 04:35 AM   #7
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I recognize what your desires are. And the most meaningful responses I had to that are two:
Start with Tri-Amp (or quadruple amp), and
Lighten the load by un-grouping some speakers (the ohmmeter shouldn't measure a figure lower than 3.3 if you want goodly power out from the amplifier rather than only into it instead).

Those two things can install a whopping huge dose of "doable" into your project.

P.S.
Please employ a decibel meter and relevant safety procedures. And when you've failed that and can't stop hearing the teakettle whistle, ask me what to do about that--there is a slight chance to heal and reduce the whistle torture. This level of power is not safe indoors. Injury is a certain result. But, you don't know that until after you've done it. This sort of success should be approached with utmost caution. You'll need a big-enough area, and very wide dispersion. . . or else the consequences are very annoying for at least a couple of years (probably, permanently).
Currently, I have been attempting to calculate an estimate on appropriate wattage per square foot, but that is going to be too late because I'm very bad with the maths. I sincerely apologize and urge you to purchase the decibel meter. Please buy one with ranges--it is the treble that will corrupt your ears most quickly, such as even 4 hours can make long lasting pain. However, so far as I have researched, you could blast the bass so long as you have the additional protection of a well done passive crossover to limit harmonics (consider that opinion). Meanwhile, decibel meter or else teakettle that won't stop!!!!
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Old 30th November 2015, 05:51 AM   #8
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If said rather awkardly, a decent safety approach would be to pound out the bass, in the order "the lowest note the loudest" and then fill in with just barely adequate everything else. The bass is least dangerous to the ear. So, if one concentrated on really pretty effective bass, and also employed a decibel meter to monitor the treble for safe levels, then there is some chance that one's ears might survive a concert experience more frequently.

That might be really nice, so you could enjoy realistic music more often. These power levels do have me worried. What is the venue size in sq ft?
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Old 21st December 2015, 03:06 PM   #9
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sorry for the delayed response. the 15s are 4 ohms in separate boxes. the lcrs are 2 10s, 2 5.25s and a tweeter. a lot of the power is in frequency ranges we cant hear but feel. method to the madness. using the 2 8 ohm 5.25s and making them 16 ohms will only increase the amount of wattage needed. These are all very fast and high current amps.

Don't worry about the power levels - always good to have a ton of head room. sq ft isn't as important as cuft. but its a little over 500 sqft with 10+ foot tall ceilings
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Old 21st December 2015, 03:24 PM   #10
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Good so far.

Amplifiers for the "feels" should be entirely separate (especially power circuit) to amplifiers for the more easily heard signals. Therefore, tri-amp is a good place to start.
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