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Class D Switching Power Amplifiers and Power D/A conversion

TPA3255 - all about DIY, Discussion, Design etc.
TPA3255 - all about DIY, Discussion, Design etc.
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Old 11th November 2018, 09:31 PM   #921
voltwide is offline voltwide  Ireland
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Join Date: Jan 2010
Quote:
Originally Posted by MirageZA View Post

My question - is it worth to try? Coming from old school amplification, a little bit of negative feedback is good. How about 3255, can I expect lower noise floor (less hiss in my case).
In my view, PFFB is more elegant solution than coil/caps mods on the output.

Many thanks for your help!
Alex
My answer is NO! - for several reasons
Certainly you could reduce hiss with additional feedback. But at the expense of gain, i.e. input sensity.
TPA3255 is a real low noise device, so if you are experiencing noise you should trace its source instead of reducing power stage gain. More often than not noise originates from the input source, so the first question was: Does it disappear with shorted input terminals?
PFFB as stated by TI application implicates significant gain reduction of TPA3255 and that must be compensated with accordingly increased input level. As a consequence the driving OPA must deliver more output level at lower THD to improve performance in PFFB configuration.
And looking at the THD performance of TPA3255 w/o PFFB I consider these mods not worth the effort.
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Old 13th November 2018, 08:16 PM   #922
MirageZA is offline MirageZA  South Africa
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Quote:
Originally Posted by voltwide View Post
My answer is NO! - for several reasons
Certainly you could reduce hiss with additional feedback. But at the expense of gain, i.e. input sensity.
TPA3255 is a real low noise device, so if you are experiencing noise you should trace its source instead of reducing power stage gain. More often than not noise originates from the input source, so the first question was: Does it disappear with shorted input terminals?
PFFB as stated by TI application implicates significant gain reduction of TPA3255 and that must be compensated with accordingly increased input level. As a consequence the driving OPA must deliver more output level at lower THD to improve performance in PFFB configuration.
And looking at the THD performance of TPA3255 w/o PFFB I consider these mods not worth the effort.
Fair enough, I will check the noise after I remove NE to swop for OPA. If TPA3255 is dead silent, will look into power supply options for OP amps, have low noise LT1084 regulator, might give it a whirl.
Thanks!
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Old 13th November 2018, 09:11 PM   #923
seez is offline seez
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Hi All, this is my first post, I have been only lurking around here till now.

I have a question on connecting a REL Quake subwoofer to TPA325x (BTL - I think it matters).
REL recommends leaving the ground wire floating and only connecting other two to + speaker posts. The same scheme is advised for A/B class balanced amps.
Is this connection fine with TPA325x and will it have an effect on THD or stereo speakers SQ? The input impedance of the REL amp is around 10K ohms. Would it interact somehow with LC filter in the amp?

REL faq:
https://relsupport.zendesk.com/hc/en...ection-Methods

a discussion on similar issue (though not class d):
http://forums.stevehoffman.tv/thread...estion.485994/
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Old 20th November 2018, 09:23 AM   #924
vdevgon is offline vdevgon
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Hi friends
Whats the recommended power supply for TPA3255 2.1 amp.
Please guide howz meanwell LRS-350-48 for this amp
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Old 20th November 2018, 12:11 PM   #925
doctormord is offline doctormord  Germany
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Quote:
Originally Posted by seez View Post
Hi All, this is my first post, I have been only lurking around here till now.

I have a question on connecting a REL Quake subwoofer to TPA325x (BTL - I think it matters).
REL recommends leaving the ground wire floating and only connecting other two to + speaker posts. The same scheme is advised for A/B class balanced amps.
Is this connection fine with TPA325x and will it have an effect on THD or stereo speakers SQ? The input impedance of the REL amp is around 10K ohms. Would it interact somehow with LC filter in the amp?

REL faq:
Class D Amp Connection Methods – REL Acoustics

a discussion on similar issue (though not class d):
REL Sub High Level Connection Question | Steve Hoffman Music Forums

If they say so, they should know whats best for their products. I don't see any problems following their FAQ arcticle.


Quote:
Originally Posted by vdevgon View Post
Hi friends
Whats the recommended power supply for TPA3255 2.1 amp.
Please guide howz meanwell LRS-350-48 for this amp

LRS-350-48 is fine if you don't run the amp full-power all the time in a quiet environment as this triggers the integrated fan.
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Old 20th November 2018, 04:13 PM   #926
forestsgump is offline forestsgump
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Quote:
Originally Posted by vdevgon View Post
Hi friends
Whats the recommended power supply for TPA3255 2.1 amp.
Please guide howz meanwell LRS-350-48 for this amp
Quote:
Originally Posted by doctormord View Post
LRS-350-48 is fine if you don't run the amp full-power all the time in a quiet environment as this triggers the integrated fan.
Not sure if you need the power of TPA3255, am using FxAudio implementation of TPA3250 with LRS150-36 adjusted to 31V which has no fans.
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Old 21st November 2018, 10:24 PM   #927
startkapital is offline startkapital
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Join Date: Jul 2010
I am almost too afraid to ask but what shall I add to complete the BOM
  • amp 3e audio TPA3255 Board 2x260W EAUMT-0260-2-A
  • psu board ELTIM PS-UN63RQ , Power Supply module, 63V, 8A max
  • transformer ???
  • Case undecided, something compact but riggid
  • xlr connectors neutrik
  • on off switch with indicator light
  • fuse
  • inlet port C14 socket
  • speaker terminal 2 red 2 black banana socket variois cables for connecting
Is the psu board even the right choice? I will use this amp soley for a pair of1 JBL Control 5 Plus SYSTEM:
Frequency 45Hz to 20Khz
Power 180watts
Sensitivity 89db
Impedance 4 ohms
Crossover 2KHz
8 inch bass mid
2 inch titanium dome tweeter



any advice
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Old 22nd November 2018, 07:08 AM   #928
jimk04 is offline jimk04  United Kingdom
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I don't know anything about the psu you specify but the 3255 is 52v max with 48v the accepted upper end. I have ran mine at below that with no particularly negative effects apart from the bonus of it all running cooler.

Edit....I see the Eltim is a rectifier and smoother so yes it would work with a transformer as you are probably aware.
That psu board seems quite a lot of money.

HiFi Single Power Supply Rectifier Filter Board Kit For 1969 Amplifier PSU | eBay

This is one I have in mind for my 3255 psu

Last edited by jimk04; 22nd November 2018 at 07:14 AM.
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Old 5th December 2018, 02:02 PM   #929
somedude1 is offline somedude1
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I bought a yjhifi tpa3255 amp with a meanwell 600-v48 to power my elac uni-fi b5s. I just hooked it up last night and first impression is that there is not enough bass from this setup. Has anyone tried powering uni-fis with this amp and what has been their assessment? Thanks in advance.
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Old 5th December 2018, 05:11 PM   #930
doctormord is offline doctormord  Germany
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As the amp is most likely to amplify linear, there's no "bass enhancement" involved. Linear amplifiers are just like that, the don't color/enhance/hide/add anything, they just make it "loud".

From the years reading here in the forums, it is a common phenomenon that new amps "lack bass" at first but things start to get better when coupling caps are changed for expensive ones together with changing the input stage's opamps for some uber top-notch industrial ones like LMAsomething.


Have you tried changing polarity of one speaker to see if it's not just a phase thing?
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