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Class D Switching Power Amplifiers and Power D/A conversion

TPA3250 somebody is listening?
TPA3250 somebody is listening?
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Old 13th March 2018, 03:29 PM   #211
cronm is offline cronm  Hong Kong
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Thanks doctormord suggestion.

I will try it later but it is hard to buy just 1 or 2 SMD resistors for replacement.

I read a document in DIY solid amp board years ago, it said that most OpAmp are much good sound in listening test between +-10V to +-12V DC. I thinks the FX development team will follow this rule to set the voltage for OpAmp because this company is an OEM/ODM for solid and D-AMP.
Also, people willing to upgrade the power supply if the amp is good sound.
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Old 13th March 2018, 03:49 PM   #212
forestsgump is offline forestsgump
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thanks for confirming FX's Opamp are indeed supplied with +/- 12V.

Also like to correct earlier typo made by me:
The almost 24V comes from LM317, instead of LM2596HVS (this buck regulator provides 12V to downstream AMS1117 -3.3v)

Well, since FX development team dint factor the needed dropout voltage, does it mean better bring up DC Supply voltage beyond 24V for correct regulation by LM317?

can anyone confirm if FX back-stage is driven by whatever voltage from DC Supply voltage (instead of being internally regulated by LM317)

Last edited by forestsgump; 13th March 2018 at 04:12 PM.
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Old 13th March 2018, 04:01 PM   #213
irribeo is offline irribeo  Netherlands
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So on the 3250 ampboard that can't be powered by 45 V or more they use the HVS version that should have been on the 3255 ampboard ??? I don't understand some chinese.
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Old 13th March 2018, 04:06 PM   #214
forestsgump is offline forestsgump
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Quote:
Originally Posted by cronm View Post
The FX Audio FX502SPRO uses a LM317 regulator to step-down the input voltage to 24V single rail DC (single-supply DC) to the two unbalanced to balanced converter OpAmps. If sums up the +- supply voltages of an OpAmp is equal to or more than 24V DC, it is safe to use in the amplifier.

This board is direct step-down the input supply voltage to the OpAmps. So uses a cleaner DC supply will make it cleaner output.


There are used 35V DC capacitors on the power lines. The maximum power supply should be 30V DC, although the TPA3250 can be supply up to 35V DC.
cronm as you notice those 35V caps, there is also afew 50V caps, several 25V caps as well .

TPA3250 datasheet recommends normal operation voltage within 38V.
Thus for safety operation within limits of 35V caps power line, how high can we supply on DC connector?

Last edited by forestsgump; 13th March 2018 at 04:08 PM.
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Old 13th March 2018, 04:16 PM   #215
forestsgump is offline forestsgump
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Quote:
Originally Posted by irribeo View Post
So on the 3250 ampboard that can't be powered by 45 V or more they use the HVS version that should have been on the 3255 ampboard ??? I don't understand some chinese.

Does 3250 ampboard refers FX502spro?
Anyway TPA3250 max is 38V, but implementation depends remaining component such as onboard capacitors; but FX502spro's caps are even lower than 38V.
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Old 13th March 2018, 11:46 PM   #216
cacao ambiance is offline cacao ambiance  United Kingdom
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im feeling kind of lost about what your talking about but all i know is on e3-audio’s board of the tpa3250. its max recommended voltage was 32v. I’m using 30v, sure 300w dc-dc boost converter.

if websites fail to load, use tor browser for china firewall proxy. Tor Project | Privacy Online
TPA3250-2CH-50W | 3e Audio

Sure Electronics' webstore 300W BOOST Converter for CAR Audio - TL494

looking at the tpa3250 datasheet:
Quote:
Total Output Power at 10%THD+N
– 70-W Stereo Continuous into 8 Ω in BTL
Configuration at 32 V
– 130-W Stereo Peak into 4 Ω in BTL
Configuration at 32 V
Total Output Power at 1%THD+N
– 60-W Stereo Continuous into 8 Ω in BTL
Configuration at 32 V
– 105-W Stereo Peak into 4 Ω in BTL
Configuration at 32 V
so looks like tpa3250 is really meant to be powered by around 30v. Sounds like FX Audio amp was designed for 30v+ but then they included cheaper power supply? :/ perhaps 24v got better search results or reception from people familiar with tpa3116 amp boards?


i guess if only using 8ohm speakers a 150w power supply will do? and for 4ohm 200W+? just something i wondered when i was choosing what size of dc-dc boost converter to use. Ended up playing safe and going for 300w one. though the e3-audio board is described as 50w and looking that there thd vs watts graph ya dont want to get much more out of it... well when i asked the guy behind 3e-audio he said if i all really had the 300w and the 100w boost converters, then i might as well use the 300w one . Its heatsink fan has not needed to turn on heh.

Sure Electronics' webstore 100W BOOST Converter for Audio Amplifier in Car

Last edited by cacao ambiance; 13th March 2018 at 11:50 PM.
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Old 14th March 2018, 05:59 AM   #217
forestsgump is offline forestsgump
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Regardless of implementation: 3e-audio or FX502spro, the heart of the amp is
TPA3250, while varies on supporting components. it is right to say TPA3250 datasheet recommends 32V, while 38V is max for normal operation. (50V absolute max, not intented for operation)

Personal inclination:
Even using average sensitive speakers poll shows majority (70%) just need <25W,
; any extra watts are margins allow transient peaks; however quality power source gives quality audio output.

Even the bundle power source 24V@4A gives 96W (almost 48w/channel), which is more than plenty according to 84% of that poll. unless there is really an usage case for more power, i see no need to go fr 300W BOOST Converter.
by the way, I am using a 32V, 150W instead the bundle 24V. Just for example: I rather have 96W clean quality power, than 300W from noisy converter.

Last edited by forestsgump; 14th March 2018 at 06:03 AM.
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Old 14th March 2018, 12:09 PM   #218
cacao ambiance is offline cacao ambiance  United Kingdom
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thanks for reply, in my case, i want to use these amps for pa setups so i need all the power i can get . tpa3250 would for for little pa setups like portable boom box

I find Sure boost converters are very good. i don’t hear them adding any noise very quite, there designed for audio amp applications .

i think, if i get the fx amp, which i am finding quite tempting. Then instead use i would use a smaller boost convert for it. Found a 150w one that got my wondering-pondering mind, recently which ive ordered and will see if its any good.

Last edited by cacao ambiance; 14th March 2018 at 12:13 PM.
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Old 14th March 2018, 02:55 PM   #219
doctormord is offline doctormord  Germany
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Quote:
Originally Posted by forestsgump View Post
thanks for confirming FX's Opamp are indeed supplied with +/- 12V.
Who confirmed that?
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Old 14th March 2018, 03:19 PM   #220
cronm is offline cronm  Hong Kong
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Those capacitors used in my FX502SPRO amp are 35V caps except the 6 analog input DC blocking caps are 10V caps. So I will say the maximum DC input is 32V DC. Under the 10% safety factor, 35x0.9=31.5V DC.

I will read the LM317 set to 24V DC output for the OpAmp is a safeguard when it is higher than 24V DC power supply input. For example, 27V DC input will burn out an AD8610 if no the 24V DC limit, because the OpAmp is +-13V DC or 26V DC input voltage.

I am no concern of under voltage on the LM317 if it uses quality power supply.

If using 32V DC power supply for the FX amp, I am only concern the over heat problem. It is because the aluminum case is a no airflow holes enclosure.
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