hi ashok,
what is the point? aren't we living in a free speech country? are you under oath? did you sign non-disclosure agreement with that company? are you affraid? if your amp is better than some commercial unit, the consumers deserve to know which amp is it, don't you think?
maybe it's a good think actually, not only for the consumer about to purchase it, even for that company....
ed
FFT - 4 ohms at 10 volts rms
consort_ee_um ,
yes I measured the distortion. The recommended Zobel was in circuit at all times. 2.2 ohms and 0.47 uF.
The higher harmonics are lower than 2nd and third.
However they are very low at lower signal levels. Typically at 1 watt the distortion levels keep dropping with increasing frequency. Good sign. The amp sounds very good at low levels.
The supply hum ( 50Hz) is only -56db but that must be hum pickup as I cannot see any higher harmonics of the 50 Hz signal.
Like 100Hz or 150 and 200 Hz. You cannot see that in this FFT plot due to the linear scale.
It's also possible that it is due to the setup used while measuring with some unshielded signal wires etc.
During normal listening I never heard any hum even at the speakers.
Cheers.
consort_ee_um ,
yes I measured the distortion. The recommended Zobel was in circuit at all times. 2.2 ohms and 0.47 uF.
The higher harmonics are lower than 2nd and third.
However they are very low at lower signal levels. Typically at 1 watt the distortion levels keep dropping with increasing frequency. Good sign. The amp sounds very good at low levels.
The supply hum ( 50Hz) is only -56db but that must be hum pickup as I cannot see any higher harmonics of the 50 Hz signal.
Like 100Hz or 150 and 200 Hz. You cannot see that in this FFT plot due to the linear scale.
It's also possible that it is due to the setup used while measuring with some unshielded signal wires etc.
During normal listening I never heard any hum even at the speakers.
Cheers.
Attachments
final schematics request
Hi Ashok, I am building one of my own amp using TDA2050 also, using the schematics on the datasheet with a single supply design.
Do you have your final schematics available that you can share? those include any of the mods you have.
What are the benefits of using split supply compared to a single supply? currently i am powering my amp with +18v, a bit distortion coming out from my speaker at full volume.
I wanted to max out what TDA2050 can do with my vintage 30g12 speaker, with a clean and good sound.
Hope you can help me.
thank you.
Hi Ashok, I am building one of my own amp using TDA2050 also, using the schematics on the datasheet with a single supply design.
Do you have your final schematics available that you can share? those include any of the mods you have.
What are the benefits of using split supply compared to a single supply? currently i am powering my amp with +18v, a bit distortion coming out from my speaker at full volume.
I wanted to max out what TDA2050 can do with my vintage 30g12 speaker, with a clean and good sound.
Hope you can help me.
thank you.
This thread came alive again !
Casiomax : I had built the split supply circuit. A single supply will require a dc decoupling capacitor at the output. My schematic is the same as the one I posted earlier in post 9 . I did not do any further experiments. You could use the single supply circuit from the application note and also the pcb layout shown there. Unless you make a mistake , that should work out very well.
Split supply will eliminate the output capacitor and that I think that is it's greatest advantage. You cannot determine what your distortion is unless you look at it on an oscilloscope . You could use one of the free ( shareware) programs that uses the pc sound card to function as an oscilloscope .
I think your amp is just clipping and you expect it to sound louder ! Volume control position is not an indicator of the output of the amp. If the input level is very high then the amp will reach full output with a very small rotation of the volume control. So statements like the amp is distorting with a 30 degree turn of the volume control ( or... at 10 o'clock position etc. ) is meaningless without knowing the input signal level and the gain of the amp.
If distortion is still there at low volume it could be from the preamp ( if you use one ). I find it impossible to believe that the chip will distort at low volume levels unless it is defective.
Jpoole908: You can see the 2050 chip in the photograph at the beginning of the thread . Check out the pictures on post 1 and post 4 .
cpemma : Yes the same board layout can be used. I did use both chips ( LM1875 and TDA2050 ) on the same board layout. In fact I just exchanged the chips without any component change and it worked fine. Use the board layout given in the application note. You can't go wrong.
Casiomax : I had built the split supply circuit. A single supply will require a dc decoupling capacitor at the output. My schematic is the same as the one I posted earlier in post 9 . I did not do any further experiments. You could use the single supply circuit from the application note and also the pcb layout shown there. Unless you make a mistake , that should work out very well.
Split supply will eliminate the output capacitor and that I think that is it's greatest advantage. You cannot determine what your distortion is unless you look at it on an oscilloscope . You could use one of the free ( shareware) programs that uses the pc sound card to function as an oscilloscope .
I think your amp is just clipping and you expect it to sound louder ! Volume control position is not an indicator of the output of the amp. If the input level is very high then the amp will reach full output with a very small rotation of the volume control. So statements like the amp is distorting with a 30 degree turn of the volume control ( or... at 10 o'clock position etc. ) is meaningless without knowing the input signal level and the gain of the amp.
If distortion is still there at low volume it could be from the preamp ( if you use one ). I find it impossible to believe that the chip will distort at low volume levels unless it is defective.
Jpoole908: You can see the 2050 chip in the photograph at the beginning of the thread . Check out the pictures on post 1 and post 4 .
cpemma : Yes the same board layout can be used. I did use both chips ( LM1875 and TDA2050 ) on the same board layout. In fact I just exchanged the chips without any component change and it worked fine. Use the board layout given in the application note. You can't go wrong.
ashok,
thanks for the info. a mistake happen, input cap polarity in reversed order, change speaker to vintage 30G12 and it sounds great. although humming is still audible from the speaker, but almost unnotice. already make a star ground configuration, but still there.
should i split signal ground from supply ground?
thanks for the info. a mistake happen, input cap polarity in reversed order, change speaker to vintage 30G12 and it sounds great. although humming is still audible from the speaker, but almost unnotice. already make a star ground configuration, but still there.
should i split signal ground from supply ground?
You need to show the exact grounding scheme . Include a picture of the ground wiring. Remember that any 'wire' or copper trace which carries supply capacitor currents and is shared partly with the input grounding scheme will cause hum. More a buzz than 50/60 hz hum.
You should probably keep all signal grounds separate and ground them directly at the capacitor ground ( -ve ) and I asume that is where the transformer 0V is also connected.
Do you get hum if the input is shorted together directly at the input terminals ?
You should probably keep all signal grounds separate and ground them directly at the capacitor ground ( -ve ) and I asume that is where the transformer 0V is also connected.
Do you get hum if the input is shorted together directly at the input terminals ?
i will post a picture later, currently i am at the office. but to be simple, from the PSU 0volt i connect a wire to the TDA2050 body using a solder pin from the chip nut.
that 0volt from PSU is separated from the input and output ground which taken from capacitor ground that connects to pin 3 of the chip, then input and output ground connected to the capacitor ground.
when input signal not shorted to the ground, the amp is silent. but when not shorted, the hum is almost audible. I think this was from the PSU, not filtered correctly.
my psu design taken from carlosfm PSU design.
I powered the chip with +24volt.
that 0volt from PSU is separated from the input and output ground which taken from capacitor ground that connects to pin 3 of the chip, then input and output ground connected to the capacitor ground.
when input signal not shorted to the ground, the amp is silent. but when not shorted, the hum is almost audible. I think this was from the PSU, not filtered correctly.
my psu design taken from carlosfm PSU design.
I powered the chip with +24volt.
Attachments
Linuxguru, the Solens came from the US if I remember correctly and the brown polyester cap came from the Chennai market. These are supposed to be 'surplus stock' so they could not guarantee the same type again. However I did see similar brown caps later though they were slightly paler in colour and had more markings on it . I did not buy those to check them out.
Apparently 1uF/250V polyester caps are consumed heavily in this market !
I bought 10 dipped brown colour polyprop caps ( 1nF ) which were really good but couldn't find them again in the whole market in Chennai or Bangalore ! Also called 'surplus' stock. I discovered they were polyprop caps a few days after buying them .... too late to get more of them !
Does anyone sell dipped polyprop caps in Bangalore ?
If you want to experiment I could send you some of the brown ployester caps. I have a few spare.
Apparently 1uF/250V polyester caps are consumed heavily in this market !
I bought 10 dipped brown colour polyprop caps ( 1nF ) which were really good but couldn't find them again in the whole market in Chennai or Bangalore ! Also called 'surplus' stock. I discovered they were polyprop caps a few days after buying them .... too late to get more of them !
Does anyone sell dipped polyprop caps in Bangalore ?
If you want to experiment I could send you some of the brown ployester caps. I have a few spare.
I have found brown dipped polyester Panasonic 470 nF at Arihant, and generic brown dipped Chinese polyester 220 nF at Chetan. I haven't actually tested and done audible comparisons on these, because I wasn't expecting miracles from them.
I haven't seen dipped polypropylene at all here. Rolled axial polyproylene film (yellow) seems to be available at numerous places, including Universal, Kanchan, etc.
I was also able to obtain 4 uF EPCOS (Siemens) polypropylene with multistrand leads (mainly for use for AC PFC), but haven't tried them out for audio input coupling yet.
Boxed 1 uF polyester (gray) seems to be available, as well as Vishay orange-drop polyester up to about 820 nF/63v.
In electrolytics, I got Elna RJJ 100uF/35v, Panasonic NHG 22uF/50v, Panasonic FC 470uf/25v and Rubycon ZL 1000uf/35v from Arihant. No trace of Silmics, Cerafines, Stargets, Muse, Blackgates, etc.
BTW, which shop in Chennai had the brown generic polyester? Suraj, Swastik or somebody else?
I haven't seen dipped polypropylene at all here. Rolled axial polyproylene film (yellow) seems to be available at numerous places, including Universal, Kanchan, etc.
I was also able to obtain 4 uF EPCOS (Siemens) polypropylene with multistrand leads (mainly for use for AC PFC), but haven't tried them out for audio input coupling yet.
Boxed 1 uF polyester (gray) seems to be available, as well as Vishay orange-drop polyester up to about 820 nF/63v.
In electrolytics, I got Elna RJJ 100uF/35v, Panasonic NHG 22uF/50v, Panasonic FC 470uf/25v and Rubycon ZL 1000uf/35v from Arihant. No trace of Silmics, Cerafines, Stargets, Muse, Blackgates, etc.
BTW, which shop in Chennai had the brown generic polyester? Suraj, Swastik or somebody else?
ashok said:
Another clue is that in the Fender it will be bolted to a decent-sized heatsink.
At least that one doesn't have the printing misalignment in the LM1875 datasheet.
I was really thinking of some of the designs from here and elsewhere that attempt to get nearer the Gainclone philosophy of short signal path, particularly the feedback resistor position. The 2050 isn't only a fifth the cost of the LM3886, it's half the price of the LM1875 at my supplier.
ok, i try to rebuild my TDA2050 not using a pcb, directly soldered the components to the chip, and make pin3 as center of the start ground. Surprisingly, humming is reduce, almost unnoticeable, but if you really stick your ears to the speaker, then you can hear it. I guess this is a PSU problem, I am using a standard transformer instead of the toroid one.
any comments on my PSU from my last reply?
any comments on my PSU from my last reply?
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