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Old 11th December 2006, 09:31 AM   #1
Dxvideo is offline Dxvideo  Turkey
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Default Recommendation needed..

Hi all,

After my 2+1 fiasco i decided to make a conventional stereo amplifier to drive my 4ohm 50W (pulse 80W) speakers. At this point i need some advices of you.. I can build all the system by my effort (designing, PCB, component purchase, etching etc..) but in Turkey i'm not sure that i can find high quality components (especially fake LM chips exist in Turkey). So i have two alternatives;

- I can purchase chips from an international distributor or order samples from the manufacturer (for National, they reject the free sample orders),
- Or i can buy DIY audio kits.

If i choose the second way i have two alternatives;

- I can buy a linear GC kit (from audio sector or chipamp) for example with LM3886 stereo or two LM4780 in parallel.
- Or i can buy a Class T stereo kit from 41Hz (like Amp1).

I have not enough knowledge about Class D and T technology. But it seems a good alternative.
I want to make a tiny size amp (PSU will be in another case). And will use them for my iPod and PC sound card not for turntable or casette tape...
Under that situation;

- Should i buy a linear or a Class T kit?
- Should i make a preamp (with tone controls) for them or not?
- What can you say to compare sound quality of Class Ts and LM series GC kits?

Thanks in advance for your helps..
Best regards,
Özgür
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Old 11th December 2006, 06:28 PM   #2
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Hi Dxvideo,

go see http://www.mhennessy.f9.co.uk/ I am sure that you will find exactly what you are looking for.

I have bought components directly from On-Semi and other manufacturers previously, they do not laugh at anybody as they know you may become their next big customer.

I am in South Africa and a sample order of six transistors from On Semi (USA), cost me only for shipping. Okay at $ 22 it was not cheap, but it was delivered within four working days to my door.

Kind regards

Nico

P.S. I have built a very succesful little 100W FET amp for our life saving club (we live by the beach). They use it for parties and is required to play very loud for many hours at a time. It sounds really as good, is well behaved and is very simple to construct.

If you email me I will send you the circuit, gerber files and whatever else you need. If you use my PCB layout and do not make any mistakes, it will work at switch on, no adjustments fiddling or tweaking, it just works.

At the club, it drives four old Wharfdale Linton to party levels in a hall about 25 x 30 x 3 meters
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Old 12th December 2006, 09:14 AM   #3
Dxvideo is offline Dxvideo  Turkey
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What do you say that?
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Old 12th December 2006, 09:16 AM   #4
Dxvideo is offline Dxvideo  Turkey
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And thats the PCB... Signal grounds "star"ed on right side with ground plate. Power grounds (with zobel's and mute circuits GND) stared on left side. Then will be connected with a 10ohm resistor on main star point in the enclouse...
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Old 12th December 2006, 04:34 PM   #5
AndrewT is offline AndrewT  Scotland
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Why buy 4ohm speakers and then ask why chipamps run into problems?
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regards Andrew T.
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Old 12th December 2006, 07:28 PM   #6
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Dear Dxvideo,

I say that you cannot make it any simpler. You can almost hide the PC board between the transformer windings.
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Old 13th December 2006, 09:27 AM   #7
Dxvideo is offline Dxvideo  Turkey
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For Andrew,

Do you say; 4ohm speakers is the centre of the problems? Should i use 8ohms? But i already have that speakers for a long time.. And i want to use them.

For Nico,

I plan to put transformer outside of the enclosure. Isnt it better? And have you seen any problem on my drawing?

Thank you all my friends..
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Old 13th December 2006, 11:05 AM   #8
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You have the smoothing caps on your PCB so I see no reason that you cannot put the transformer outside the cabinet. It will be less noisy because sometimes your amplifier can pick up transformer magnetic fields and causes hum.
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Old 13th December 2006, 11:10 AM   #9
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If I may comment on Andrew's question.

Sometimes IC amps are not very stable with load impedance of 2 or even 4 Ohms even if the manufacturer says so.

If you want to use 4 Ohm, I recommend that you use a lower supply voltage so that the amp does not have to work that hard.
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Old 13th December 2006, 12:22 PM   #10
Dxvideo is offline Dxvideo  Turkey
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Hi Nico..
I replied your mail. You may read.
For 4 ohm matter.. In the datasheet of LM3886, NSC says you can get "68W @ 4ohm" very clearly! What can i do about it? Should'nt i believe them?

Thanks a lot..
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