,,,I was able to understand the cause of the discomfort I felt by looking at the measurement report of Amirm.
Especially I think that FX-502SPRO is completely miss design. When the volume is raised the protection circuit works and the error lamp lights up, it is an incredible operation anymore!
i cannot agree......
if some of these guys read our thread here....they will try something i guess...
chris
Especially I think that FX-502SPRO is completely miss design. When the volume is raised the protection circuit works and the error lamp lights up, it is an incredible operation anymore!
i cannot agree......
if some of these guys read our thread here....they will try something i guess...
chris
,,,I was able to understand the cause of the discomfort I felt by looking at the measurement report of Amirm.
Especially I think that FX-502SPRO is completely miss design. When the volume is raised the protection circuit works and the error lamp lights up, it is an incredible operation anymore!
i cannot agree......
if some of these guys read our thread here....they will try something i guess...
chris
@chermann + 10
Edit: I need to amend the above. I had an epiphany realizing the TV Box volume is digital and should perhaps be treated as the volume control on a computer music player - i.e. resolution should be better as max volume. And lo and behold, 90% of the harshness/sibiliance problem went away, and it doesn't bother me anymore. The remaining 10 % means, IMHO, that the FX502S PRO leans slightly on the bright side. Though I've read here and there that it is a balanced amp, my ears don't agree. I'm no expert but can't help relate this to the amp's very poor test results on ASR.
It's still useable, and preferable for me to both a class AB amp and an AVR I had many times its cost and size. But given the 3520 is a reference chip, it is disappointing as it could have been a home run.
I think I have a good idea now of the amp's sound will try the op amp "upgrade" and will be able to hear if there is a difference or not. I remain skeptical: why would FxAudio skimp on a few cents and use crappy or even fake, as it was claimed, op amps? What if it is an engineering, and not a parts problem? The worst that can happen is I'll lose $20.
please try the opamp upgrade with a LME49720NA it cost about 6 euro with shipping = 2x 6 = 12 euros
a red WIMA cap under the board in parallel to the decoupling caps would be help too
In Switzerland the cheapest provider, Conrad, charges an extra 8 CHF "small quantity upcharge" so the cost will be ~$20. Changing caps is beyond my ability. If that is necessary, then the op amp upgrade is perhaps not worth it.
changing caps is not need now.just add a caps in parallel.
pic 2..the smal red capshttps://www.diyaudio.com/forums/class-d/315681-tpa3250-listening-53.html#post5423051
Hadn't seen that pic, thx a lot for your trouble.
The soldering is straightforward right? Can you use a regular iron or do you need a small, electronics one?
As it's the weekend and I had a little time on my hands, I retried my class AB amp... and contrary to my initial impressions, liked the sound better.
In particular, all harshness was gone. Will do some more comparing later.
The reasons for the above may have been :
-inflated expectations (you warned me against this IIRC)
- new toy syndrome
-lack of proper level matching
Never mind, it's been a fun and instructive experiment. My thanks to you and other members in this thread.
Chris ~ just curious, have you done any mod for removal of speaker-pop during power-down?
as i wrote pages before...i do not have this issue....
and...
if i am ready with my YJTPA3255 mods i restart the FX502spro journey...
Hi,
My first post in this thread.
I bought the FX502spro and trying to find out how much sound I can squeeze out of it.
Changed all electrolytics for better Q and 50V. Opamps 4562. filter the noise on the LM317. exchanged the 33uH for 150mH after the buck regulator. Exchanged the air coils for shielded types (lot of work as in these where glued...) and took filter caps out and smaller value polyprop. 470 uF on AVDD.
Bought 32V adapter, so its running on 32 V now. (much better than 24V)
The sound has improved dramatically. And it is really interesting to see what can be squeezed out. Generally I like the sound of this class-D, it is still not perfect. Sound stage is wide and high, but lacking real depth.
After exchanging the 33uH after the Buckregulator the hum with volume turned down has gone. With my ear at the speaker I hear still some noise.
But the strange thing is, when I turn up the volume, at a certain point the hum is back. But turning it further (last quarter or so) the hum disappears again. Ofcourse the hum is in the range I would listen to.
Someone any idea how this can happen? And how to resolve?
Many thanks.
My first post in this thread.
I bought the FX502spro and trying to find out how much sound I can squeeze out of it.
Changed all electrolytics for better Q and 50V. Opamps 4562. filter the noise on the LM317. exchanged the 33uH for 150mH after the buck regulator. Exchanged the air coils for shielded types (lot of work as in these where glued...) and took filter caps out and smaller value polyprop. 470 uF on AVDD.
Bought 32V adapter, so its running on 32 V now. (much better than 24V)
The sound has improved dramatically. And it is really interesting to see what can be squeezed out. Generally I like the sound of this class-D, it is still not perfect. Sound stage is wide and high, but lacking real depth.
After exchanging the 33uH after the Buckregulator the hum with volume turned down has gone. With my ear at the speaker I hear still some noise.
But the strange thing is, when I turn up the volume, at a certain point the hum is back. But turning it further (last quarter or so) the hum disappears again. Ofcourse the hum is in the range I would listen to
.Someone any idea how this can happen? And how to resolve?
Many thanks.
Hi,
My first post in this thread.
I bought the FX502spro and trying to find out how much sound I can squeeze out of it.
Changed all electrolytics for better Q and 50V. Opamps 4562. filter the noise on the LM317. exchanged the 33uH for 150mH after the buck regulator. Exchanged the air coils for shielded types (lot of work as in these where glued...) and took filter caps out and smaller value polyprop. 470 uF on AVDD.
Bought 32V adapter, so its running on 32 V now. (much better than 24V)
The sound has improved dramatically. And it is really interesting to see what can be squeezed out. Generally I like the sound of this class-D, it is still not perfect. Sound stage is wide and high, but lacking real depth.
After exchanging the 33uH after the Buckregulator the hum with volume turned down has gone. With my ear at the speaker I hear still some noise.
But the strange thing is, when I turn up the volume, at a certain point the hum is back. But turning it further (last quarter or so) the hum disappears again. Ofcourse the hum is in the range I would listen to
Someone any idea how this can happen? And how to resolve?
Many thanks.
Hi
oh....nice that you did a lot of changes...do you have some pics for us.
@hum
hum like 50Hz-100Hz...or e.g. pink noise over the speakers?
lg
Do you have no thermal problems with the LM317. originally it is set for 24V output...but if you push 32V you should have at least 1 Watt Dissipation.
e.g.
8V different , 160mA drawn by all elements (post #222)= 1.28Watt
from post#222
I checked again, but the lm2596 is fed directly from powersupply, not from LM317. So only the 2 opamps are behind the LM317.
Rectifiers are there to prevent wrong polarization of power.
I think for PBTL you need 4-8 ohm speakers, because 8 ohm speaker become 4 ohm at PBTL