TPA3255 - all about DIY, Discussion, Design etc

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#921
MirageZA said:
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
Click to expand...
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.
 
#922
voltwide said:
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.
Click to expand...
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!
 
#923
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-us/articles/115004486607-Class-D-Amp-Connection-Methods

a discussion on similar issue (though not class d):
http://forums.stevehoffman.tv/threads/rel-sub-high-level-connection-question.485994/
 
#925
seez said:
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
Click to expand...


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


vdevgon said:
Hi friends
Whats the recommended power supply for TPA3255 2.1 amp.
Please guide howz meanwell LRS-350-48 for this amp
Click to expand...


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.
 
#926
vdevgon said:
Hi friends
Whats the recommended power supply for TPA3255 2.1 amp.
Please guide howz meanwell LRS-350-48 for this amp
Click to expand...

doctormord said:
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.
Click to expand...

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.
 
#927
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
 
#928
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
 
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#929
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.
 
#930
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?
 
#931
doctormord said:
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?
Click to expand...
Good point Doctormord. I'm fairly new to diy and haven't dove into these possibilities yet. Do you have any specific recommendations?
 
#935
doctormord said:
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?
Click to expand...


doctormord, with all respect, there _are_ very audible differences in how various amplifiers sounds. The seems be be a hell of a lot of difference in how transients are handled, but I can't verify that. Even in amps that have seemingly equal frequency response and TDH.
Just dismissing reports of audible differences because they are not backed by hard evidence does not mean they not exists, just that they might be very hard to measure in a controlled environment. And most of us don't have the equipment and training to do such a thing.

Case in point; I have both the TPA3255EVM, a TPA3250 and a SureAA-AB32313. The EVM board and the TPA3250 lacks in bass and at first sounds a bit dull compared to the Sure, but in the end wins out by sounding more neutral. All this before any modification to the EVM (which I haven't had any time to do yet).

Apart from internal diffencencies in the boards there are the external reasons for that. It can very well be as you indicated input impedance; there's a difference between the boards. But also in how they handle the the speakers load, with it's frequency and amplitude dependent response.
 
#940
from volumio interface, volume can be changed (i am using my android phone as controlling device. phone's volume buttons work). but this is master volume.
i am looking for dedicated volume control of the tpa3255 board, because i am going to use this amp only for woofers in a bi-amped setup
 
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