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Chip Amps Amplifiers based on integrated circuits

LM1875 in parallel configuration and used in a composite amplifier.
LM1875 in parallel configuration and used in a composite amplifier.
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Old 24th February 2020, 09:10 PM   #501
chermann is offline chermann  Austria
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Good to know...UTC 2050 are since 5 days at my bench...no test actually. +/- 25V max

the only concern what i have is that the 18VAC transformer gives about 26,7 Volts at idle with 2 mono boards and 8 ohm speakers. i used my open baffle 12/5 but the second woofer per side is of -so i have just 8R load.
the voltage drops at loud listening just short (heavy bass) at 24,4V....to closed i think.


the lm1875 is able to handle more Voltage but gets after my test with 25V and higher current earlier problems instead of +/-22V. (ebay kit thread).


chris
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Old 24th February 2020, 09:10 PM   #502
maxhifi is offline maxhifi  Canada
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Quote:
Originally Posted by FauxFrench View Post
I listened to the amplifier with all the test music from before and I could not hear any difference from last test.
You mean to say, between the composite and non composite versions?
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Old 24th February 2020, 10:10 PM   #503
FauxFrench is offline FauxFrench  France
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Quote:
Originally Posted by fdenys View Post
Originally posted by FauxFrench:


That exactly comfirms my findings!
Did you perhaps also check the dissipation/ temperature of the chip?
Given the very similar results you experienced (in comparison to the "LM1875") and the current limit of 5A peak of the UTC-TDA2050 isn't this chip the preferred choice?
Two paralleled UTC's will probably give comparable results to three LM1875's which might simplify the project somewhat.
Also the working built-in protections are an advantage at (almost) comparable cost.
Hi Fred,
I come to the same results as you. Two can be used in BTL coupling with an 8 Ohm load and an output power of some 70W or four in parallel/BTL with a 4 Ohm load and an output power of 120W. Fully enough for most. 1 Eur a piece and moderate delivery costs. Just what we need.
When I have finished this 3x2 fake LM1875 I will try the 2x2 UTC-TDA2050V just to confirm our findings. I will also think about a better amplitude clamp for the OP-AMP. Like that, a very well performing amplifier can be made with a modest budget. Letś hope the supplies from Taiwan are not being disturbed by the very sad situation on the continent.
I am very happy that you suggested this IC. I did not know about this active second source.
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Old 24th February 2020, 10:23 PM   #504
FauxFrench is offline FauxFrench  France
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Quote:
Originally Posted by maxhifi View Post
You mean to say, between the composite and non composite versions?
No, my last test was also composite but without amplitude clamp. I need to do an A<>B test to know if I can actually distinguish a plain LM1875 from a composite version. Or better, we let someone who has had his ears washed more recently than I, someone like Chris , do the comparison.
From what I have heard yet with my test-board, it is flawless.
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Old 24th February 2020, 10:31 PM   #505
maxhifi is offline maxhifi  Canada
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Quote:
Originally Posted by FauxFrench View Post
No, my last test was also composite but without amplitude clamp. I need to do an A<>B test to know if I can actually distinguish a plain LM1875 from a composite version. Or better, we let someone who has had his ears washed more recently than I, someone like Chris , do the comparison.
From what I have heard yet with my test-board, it is flawless.
It sure is looking good on the scope! Interesting to see how much faster the op-amp is, I'm looking forward to seeing how this ends.
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Old 24th February 2020, 10:34 PM   #506
FauxFrench is offline FauxFrench  France
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Quote:
Originally Posted by chermann View Post
Good to know...UTC 2050 are since 5 days at my bench...no test actually. +/- 25V max
the only concern what i have is that the 18VAC transformer gives about 26,7 Volts at idle with 2 mono boards and 8 ohm speakers. i used my open baffle 12/5 but the second woofer per side is of -so i have just 8R load.
the voltage drops at loud listening just short (heavy bass) at 24,4V....to closed i think.
the lm1875 is able to handle more Voltage but gets after my test with 25V and higher current earlier problems instead of +/-22V. (ebay kit thread).
chris
We could consider a regulated power supply, eventually as integrated part of the amplifier board. The one I use is homemade and a suitable regulator is not difficult to make. You can run a regulated version from most transformers you salvage from a broke-down AVR amplifier, found on a dumb. I even know a way to use two rather similar transformers in parallel for double current. I like re-use.
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Old Yesterday, 08:49 AM   #507
chermann is offline chermann  Austria
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Quote:
Originally Posted by FauxFrench View Post
We could consider a regulated power supply, eventually as integrated part of the amplifier board. The one I use is homemade and a suitable regulator is not difficult to make. You can run a regulated version from most transformers you salvage from a broke-down AVR amplifier, found on a dumb. I even know a way to use two rather similar transformers in parallel for double current. I like re-use.

Do you think about a LM317 and 337? - the max current is "just" 1,5A each rail. or you have a transistor additionally for more current...
turbowatch wrote that its a second best solution to use the existing transformer and add 2 diode to "waste" - 1,4V each rail...
i ahve no idea how much a rail can be sag if more then 2 chips are in operation. fix is that a UTC 2050 has max 25V supply.
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Old Yesterday, 09:06 AM   #508
FauxFrench is offline FauxFrench  France
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Join Date: Dec 2017
Location: The mountains, calm and quiet.
An alternative to a buffered LM317/LM337 supply is an LLC SMPS similar to the one Fred uses, with +/-24V, and then add a "voltage dropper" before the decoupling capacitors. Diodes can be used.
A traditional unregulated power supply can be less useful if you build a power version because you have to stay below 25Vdc under all circumstances and that will drop importantly when current is drawn at higher power levels.
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Old Yesterday, 12:16 PM   #509
fdenys is offline fdenys  Netherlands
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The SMPS i am using has a variable output voltage of +-21V to 29V, adjustable with a small potentiometer on board, so imo no further voltage dropping circuits or diodes etc are required.

Yes i can wholeheartedly recommend the SMPS. The max output specified is (about) 2x25V at 5A ie about 250W.

But for this project a "sister" power supply has an additional +/- 15v (max 1 A) supply onboard - for feeding eg the composite opamp(s).
See the following link: SMTP click

For this project obviously an advantage
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