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O-Noorus D1 - TPA3255 PFFB Stereo Amplifier - Front Display, Tone Control (with bypass) and Remote

I'm not familiar with the DA10 amplifier, the info I found says it uses a TI chip called TAS5352.
DA10 uses a fully digital signal, so the miniJack 3.5mm input is converted via ADC, which had a sensitivity limit of 1.5Vrms, as far as I remember.
Be aware that Amir's test used to be 0.16Vrms input signal with 29dB gain to produce 5W for the SINAD test.
The tests are of little use in real life, nobody uses 0.16Vrms signal, most audiophile devices have output signal greater than 2Vrms.
Снимок.PNG
 
I had no problems with topping, but when I measured the frequency response in RMAA for O-noorus DA10 via miniJack 3.5mm input I could not get results because of overload, the output signal was with large distortions. Recently I measured fosi ZA3 via TRS balanced input, when applying a signal above 1V I observed distortions greater than 1%, at 900mVrms everything was fine.
The za3 has 26dB gain or 20x gain. If you input 1v then you get 20V at the amplifier output. Assuming 4Ohms then 20^2/4=400/4=100W. Or 8ohms: 20^2/8=50W.
As already measured, that amplifier can provide up to 140W at 5ohms or 90W at 8ohms with its 48V power supply.
If you try this test with another amp with a different chip like the DA10 you mentioned, first this amp cannot privide that output. It only uses a 24V power supply which in theory can provide up to 70W at 4Ohms and 40W at 8ohms.
I dont know the amplifier gain. But let's asume is the same as ZA3 (26dB). If you use a 4ohm load then you will try to produce 100W from that amplifier which is impossible. It cannot produce output swings that high from a 24V power supply, and second the amplifier is not able to provide that output without horrible level of distortion which is what you saw on your test. Try lowering the input signal to 0.2V which translates to 4V at the output or 4^2/4= 4W and then you can try increasing input voltage little by little. For 5W output you need:
5=(Vout)^2/4=> Vout=sqrt(20)=4.47V.
And Vinx20=Vout so Vin=4.47/20=0.22V
 
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DA10 uses a fully digital signal, so the miniJack 3.5mm input is converted via ADC, which had a sensitivity limit of 1.5Vrms, as far as I remember.

The tests are of little use in real life, nobody uses 0.16Vrms signal, most audiophile devices have output signal greater than 2Vrms.
View attachment 390997
You seem confused. Did you forget what the amplifier potentiometer is for? You can connect whatever you want, the PS200 included with its 2Vrms output to any amplifier and the amplifier potentiometer will attenuate those 2Vrms into whatever is required for your desired music volume. Also note some potentiometers are linear and others are Logarithmic, so 50% on the pot position translates to only 10% of the input signal(2v into 0.2v) instead of 1Vrms or 50% of 2Vrms. And you say: ohh this thing is playing loud, while in reality it is only receiving 0.2V which the amplifier increases it to 0.2x20=4Vrms. And that means 4^2/4=4W at 4ohms. And you really think it is playing at 50% of whatever max power is able to produce(if 100W, then 50W).
Friend, enjoy your amplifier. You have nothing to worry about.
Also, remember music does not play at 0dB Full Scale. So, even if your DAC is able to produce 2V at 0dBFS (test tones), it only outputs 0.5Vrms max with music files which play in average at -12 to -16dBFS. You will never produce max power with music, unless you consider gunshots and cannons as music(which play for a fraction of a second).
 
You will never produce max power with music, unless you consider gunshots and cannons as music(which play for a fraction of a second).
Thanks for the detailed explanations. I heard distortion in the music, but it was only a moment, after which I started to worry and do tests. Modern dance music is quite dense in sound, a cannon shot is not uncommon in it :)
 
This is my measure 4Om 3W (3.5Vrms out) after update D1 (replacing resistors and put 220pF capacitor in hole place around operational amplifier)
1.PNG

2.PNG

3.PNG

This for 8Om 6.3W (6.5Vrms out)
1.PNG

2.PNG

3.PNG

4.PNG

I installed it according to this scheme, only 2 single capacitors, I didn’t install those that are in pairs.


Ровная АЧХ, 4 конденсатора 220пФ.png


I chose 27kOhm resistors, the heating at idle became a little less.
Шаг2_установка на позиции 1 и 3 резистора 24 или 27кОм.png
 
Thanks for all those details.
I don't plan on modding the amp nor using another power supply, but these results are really promising !
 
For me the best feature is the O-Noorus D1 and D3 is the remote control. Not every DAC has volume control, and for those special DACs the D1 is perfect.
I'm using a 24V PS with a DC filter and the amp does not heat at all. And believe me when I tell you there is plenty of power with 24V:

(24VDC x 0.707)^2 / 4ohm=72W, of those I normally use 1 or 2W
 
That's also my concern...
I'm using the little SMSL SU-1...
And even if I would switch to a new DAC with volume control, I'm also using turntable so I really need an amp with volume control !
 
Very interesting. Can you explain the changes/mods? Replacing coupling caps with Wima MKS 10uF, replacing Opamps with OPA1642, adding CA5 and CA6 Feedback capacitors WIMA FKP 220pF to the Opamp feedback resistor "RA5". This adds a first order LPF to the opamp output. I assume this reduces output noise?. Did you replace all the Melf resistors as well? The 220k, 10k ,15k and 2.7k? or those the stock values?. Did you also change the 10uF capacitors before the opamps as well?
No changes on the output filter? or the PFFB circuit?
I noticed the RA4 and RA6 have different values, but all the other equivalent resistor RA5 and RA7, RP1 and RP2 have the same values. This is intentional to adjust the gain (keep Unity gain) and just do the inversion of the signal on the second opamp stage, right?
 

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Very interesting. Can you explain the changes/mods? Replacing coupling caps with Wima MKS 10uF, replacing Opamps with OPA1642, adding CA5 and CA6 Feedback capacitors WIMA FKP 220pF to the Opamp feedback resistor "RA5". This adds a first order LPF to the opamp output. I assume this reduces output noise?. Did you replace all the Melf resistors as well? The 220k, 10k ,15k and 2.7k? or those the stock values?. Did you also change the 10uF capacitors before the opamps as well?
No changes on the output filter? or the PFFB circuit?
I noticed the RA4 and RA6 have different values, but all the other equivalent resistor RA5 and RA7, RP1 and RP2 have the same values. This is intentional to adjust the gain (keep Unity gain) and just do the inversion of the signal on the second opamp stage, right?
Gotcha!. I understand the changes now. Brighter orange underline or Brighter orange fonts indicate the changes. Replace with input resistors with 220kohm(what was the old value?) 0.1% (higher precision than before, right?) at the RCA input, Coupling caps with WIMA MKS 10u caps, replace all Melf resistors with same value but higher precision ones. and the new opamp FB capacitors WIMA FKP 220pF. I assume there are no issues soldering the capacitor legs to those empty small SMD pads, right?.

I'll take pictures this weekend to confirm the stock resistor values
 
People hi !

@ dr_mick51: You got it all figured out ;)

The 220pF capacitors are a modification identical to the one proposed by Lester (SYLPH AUDIO) on its PCB in order to correct the appearance of the frequency response for the extreme treble which have a very slight rise ->

Result - Curve graph.jpg


If soldering the legs of the FKP2 220pF is a problem for you in this area then you can use SMD components otherwise the other solution is to solder the FKP2 directly on the pins of the OPAMPS located below the PCB, it is much more convenient. Regarding the original input resistor, it's a 22K (it's easier for me to say because I have the O-NOORUS original diagrams :cool: ). It must be replaced by a 220K for obvious reasons of adaptability of the output impedance of the device that will be connected to it.

I will try to explain: the NJW-1194 volume control has an input impedance of 15 to 20 k, which is probably variable depending on the level setting, and which comes in parallel with this 22 k R... So it's in your best interest to increase this R, you can go up to 220 kO.

Reminder:
In electronics (not limited to audio), any active system has a resistance (input, output, etc.) that is never linear but varies +/- depending on the frequency of the signal. We therefore use the notion of impedance to differentiate from pure resistance. To come back to the pairing of devices. In the case of HiFi, the ideal is for the output impedance of a device to be very small compared to the input impedance of the device to which it sends its signal. The smaller the output impedance, the more current the device can "send", and therefore not be disturbed "too much" by its load (the load, here, is the device to which it is connected). Conversely, the smaller the input impedance of a device, the more current it will "consume", and potentially disturb the source device.
If output = low impedance --> not easily disturbed If input = high impedance --> doesn't disturb much We quickly understand that the 2 together is even better! On the contrary, if the output impedance is high and the input impedance is low, very large signal disturbance in perspective (attenuation, distortion,....) If the impedances are more or less equal, we will experience a good attenuation (math shows that if the impedances are equal, the amplitude of the signal is divided by 2 exactly), and we also run the risk of disturbance (distortion).

Here is an explanation by an image of the PCB for a better understanding of the MOD ->

D1 MOD.jpg


In this photo, the amplifier's gain is increased to 27.6dB with the 24K resistors. On my diagram (with the resistors of 15K instead of 24K) the amplifier's gain is 23.5dB.

As you have understood: the changes are in orange. The two capacitors are removed because they are absolutely useless since link capacitors are already present upstream of the TPA3255 and concerning the NJW194, nothing is indicated in the datasheet. It is good to remember that the use of bipolar type operational amplifiers is not recommended with this diagram since the resistance to the inputs will have a high impedance and its impedances will not be equal elsewhere, which will cause OFFSET! So, we will use FET or JFET type operational amplifiers because they are almost insensitive to this imbalance and are adapted to high impedances (it's not me who says it but TI). References such as OPA1656 or OPA1642 are well suited for this tour. I chose the OPA1642 not because of the measurements but for their "subjective" sound rendering...

... I find that the OPA1656 created a kind of "spacialization" effect on certain tracks or channels, which is not the case with the OPA1642 which seemed more natural to me and also has a softer extreme treble that will avoid possible "phenomena" of sibilance. This cannot be measured, it is a personal feeling (which my friends also share), however these two references will have very good results that are also very close to the measurements if we want to remain objective :)


@ FanatNsk::
You absolutely have to put the 4 capacitors of 220pF because as it is, you create an imbalance of the signals that are expected as "symmetrical" by the TPA3255 chip.

PS: I take advantage of this post to talk about the "heating problems" with the D1: there is none! This feeling is felt by the fact that the material (and its thickness) of the case used is different from those of the competition (FOSI., AIYIMA,...). I invite readers to read TI's datasheet about the TPA3255 amplifier chip and to look carefully at the temperatures measured for a given voltage: on the tables it is indicated 75°C for a voltage of 51V and the Tjmax.de the chip is 125°C. So with the 42°C that I read with the laser thermometer in the center of the top of the case of my D1 powered by 42V/8.3A, I am in completely normal conditions of use even if the feeling of heat is slightly greater than with other amplifiers on the market. Another explanation comes from the use of PFFB which leads to a higher heating rate unlike amplifiers which are not equipped with it.

NOTE: my sytem with 8 Ohms speakers -> (42 VDC x 0.707)^2 / 8 Ohms = 110 Watts

PSU.jpg


For example, to "counteract" this feeling effect, AIYIMA on its A70 model which has the PFFB used a large aluminum "cube" as a contact sink in its case. However, the TPA3255 chip still works under the same conditions as the O-NOORUS D1 amplifier ->

the cube.png


It's a bit like I gave you a pair of insulated gloves with the amp to reassure you (LOL).

In addition, the advertisement for the A70 model is false because even with a 48V 10A Gan power supply, the 300W advertised is not reached with 4 Ohm speakers ->

(48 VDC x 0.707)^2 / 4 Ohms = 287.91 Watts.

It's not me who says it but the mathematical formulas :rolleyes:

Have a good day and happy listening to all.
 
Last edited:
People hi !

@ dr_mick51: You got it all figured out ;)

The 220pF capacitors are a modification identical to the one proposed by Lester (SYLPH AUDIO) on its PCB in order to correct the appearance of the frequency response for the extreme treble which have a very slight rise ->

View attachment 406201

If soldering the legs of the FKP2 220pF is a problem for you in this area then you can use SMD components otherwise the other solution is to solder the FKP2 directly on the pins of the OPAMPS located below the PCB, it is much more convenient. Regarding the original input resistor, it's a 22K (it's easier for me to say because I have the O-NOORUS original diagrams :cool: ). It must be replaced by a 220K for obvious reasons of adaptability of the output impedance of the device that will be connected to it.

I will try to explain: the NJW-1194 volume control has an input impedance of 15 to 20 k, which is probably variable depending on the level setting, and which comes in parallel with this 22 k R... So it's in your best interest to increase this R, you can go up to 220 kO.

Reminder:
In electronics (not limited to audio), any active system has a resistance (input, output, etc.) that is never linear but varies +/- depending on the frequency of the signal. We therefore use the notion of impedance to differentiate from pure resistance. To come back to the pairing of devices. In the case of HiFi, the ideal is for the output impedance of a device to be very small compared to the input impedance of the device to which it sends its signal. The smaller the output impedance, the more current the device can "send", and therefore not be disturbed "too much" by its load (the load, here, is the device to which it is connected). Conversely, the smaller the input impedance of a device, the more current it will "consume", and potentially disturb the source device.
If output = low impedance --> not easily disturbed If input = high impedance --> doesn't disturb much We quickly understand that the 2 together is even better! On the contrary, if the output impedance is high and the input impedance is low, very large signal disturbance in perspective (attenuation, distortion,....) If the impedances are more or less equal, we will experience a good attenuation (math shows that if the impedances are equal, the amplitude of the signal is divided by 2 exactly), and we also run the risk of disturbance (distortion).

Here is an explanation by an image of the PCB for a better understanding of the MOD ->

View attachment 406181

In this photo, the amplifier's gain is increased to 27.6dB with the 24K resistors. On my diagram (with the resistors of 15K instead of 24K) the amplifier's gain is 23.5dB.

As you have understood: the changes are in orange. The two capacitors are removed because they are absolutely useless since link capacitors are already present upstream of the TPA3255 and concerning the NJW194, nothing is indicated in the datasheet. It is good to remember that the use of bipolar type operational amplifiers is not recommended with this diagram since the resistance to the inputs will have a high impedance and its impedances will not be equal elsewhere, which will cause OFFSET! So, we will use FET or JFET type operational amplifiers because they are almost insensitive to this imbalance and are adapted to high impedances (it's not me who says it but TI). References such as OPA1656 or OPA1642 are well suited for this tour. I chose the OPA1642 not because of the measurements but for their "subjective" sound rendering...

... I find that the OPA1656 created a kind of "spacialization" effect on certain tracks or channels, which is not the case with the OPA1642 which seemed more natural to me and also has a softer extreme treble that will avoid possible "phenomena" of sibilance. This cannot be measured, it is a personal feeling (which my friends also share), however these two references will have very good results that are also very close to the measurements if we want to remain objective :)


@ FanatNsk::
You absolutely have to put the 4 capacitors of 220pF because as it is, you create an imbalance of the signals that are expected as "symmetrical" by the TPA3255 chip.

PS: I take advantage of this post to talk about the "heating problems" with the D1: there is none! This feeling is felt by the fact that the material (and its thickness) of the case used is different from those of the competition (FOSI., AIYIMA,...). I invite readers to read TI's datasheet about the TPA3255 amplifier chip and to look carefully at the temperatures measured for a given voltage: on the tables it is indicated 75°C for a voltage of 51V and the Tjmax.de the chip is 125°C. So with the 42°C that I read with the laser thermometer in the center of the top of the case of my D1 powered by 42V/8.3A, I am in completely normal conditions of use even if the feeling of heat is slightly greater than with other amplifiers on the market. Another explanation comes from the use of PFFB which leads to a higher heating rate unlike amplifiers which are not equipped with it.

NOTE: my sytem with 8 Ohms speakers -> (42 VDC x 0.707)^2 / 8 Ohms = 110 Watts

View attachment 406198

For example, to "counteract" this feeling effect, AIYIMA on its A70 model which has the PFFB used a large aluminum "cube" as a contact sink in its case. However, the TPA3255 chip still works under the same conditions as the O-NOORUS D1 amplifier ->

View attachment 406279

It's a bit like I gave you a pair of insulated gloves with the amp to reassure you (LOL).

In addition, the advertisement for the A70 model is false because even with a 48V 10A Gan power supply, the 300W advertised is not reached with 4 Ohm speakers ->

(48 VDC x 0.707)^2 / 4 Ohms = 287.91 Watts.

It's not me who says it but the mathematical formulas :rolleyes:

Have a good day and happy listening to all.
Thank you very much. I really appreciate it. But you left me thinking because I'm using OPA1612 with this amp, and the A07 Max and any other TPA3255/51 based amp. You are saying I should not use Bipolar opamp on this amp? Is it because of the NJW194 which is only used on the D1 and D3? I have not had any issues with this amp and the OPA1612, but I also have a pair of OPA1656 laying around. You said these are better for this amplifier?
 
People hi !

@ dr_mick51: You got it all figured out ;)

The 220pF capacitors are a modification identical to the one proposed by Lester (SYLPH AUDIO) on its PCB in order to correct the appearance of the frequency response for the extreme treble which have a very slight rise ->

View attachment 406201

If soldering the legs of the FKP2 220pF is a problem for you in this area then you can use SMD components otherwise the other solution is to solder the FKP2 directly on the pins of the OPAMPS located below the PCB, it is much more convenient. Regarding the original input resistor, it's a 22K (it's easier for me to say because I have the O-NOORUS original diagrams :cool: ). It must be replaced by a 220K for obvious reasons of adaptability of the output impedance of the device that will be connected to it.

I will try to explain: the NJW-1194 volume control has an input impedance of 15 to 20 k, which is probably variable depending on the level setting, and which comes in parallel with this 22 k R... So it's in your best interest to increase this R, you can go up to 220 kO.

Reminder:
In electronics (not limited to audio), any active system has a resistance (input, output, etc.) that is never linear but varies +/- depending on the frequency of the signal. We therefore use the notion of impedance to differentiate from pure resistance. To come back to the pairing of devices. In the case of HiFi, the ideal is for the output impedance of a device to be very small compared to the input impedance of the device to which it sends its signal. The smaller the output impedance, the more current the device can "send", and therefore not be disturbed "too much" by its load (the load, here, is the device to which it is connected). Conversely, the smaller the input impedance of a device, the more current it will "consume", and potentially disturb the source device.
If output = low impedance --> not easily disturbed If input = high impedance --> doesn't disturb much We quickly understand that the 2 together is even better! On the contrary, if the output impedance is high and the input impedance is low, very large signal disturbance in perspective (attenuation, distortion,....) If the impedances are more or less equal, we will experience a good attenuation (math shows that if the impedances are equal, the amplitude of the signal is divided by 2 exactly), and we also run the risk of disturbance (distortion).

Here is an explanation by an image of the PCB for a better understanding of the MOD ->

View attachment 406181

In this photo, the amplifier's gain is increased to 27.6dB with the 24K resistors. On my diagram (with the resistors of 15K instead of 24K) the amplifier's gain is 23.5dB.

As you have understood: the changes are in orange. The two capacitors are removed because they are absolutely useless since link capacitors are already present upstream of the TPA3255 and concerning the NJW194, nothing is indicated in the datasheet. It is good to remember that the use of bipolar type operational amplifiers is not recommended with this diagram since the resistance to the inputs will have a high impedance and its impedances will not be equal elsewhere, which will cause OFFSET! So, we will use FET or JFET type operational amplifiers because they are almost insensitive to this imbalance and are adapted to high impedances (it's not me who says it but TI). References such as OPA1656 or OPA1642 are well suited for this tour. I chose the OPA1642 not because of the measurements but for their "subjective" sound rendering...

... I find that the OPA1656 created a kind of "spacialization" effect on certain tracks or channels, which is not the case with the OPA1642 which seemed more natural to me and also has a softer extreme treble that will avoid possible "phenomena" of sibilance. This cannot be measured, it is a personal feeling (which my friends also share), however these two references will have very good results that are also very close to the measurements if we want to remain objective :)


@ FanatNsk::
You absolutely have to put the 4 capacitors of 220pF because as it is, you create an imbalance of the signals that are expected as "symmetrical" by the TPA3255 chip.

PS: I take advantage of this post to talk about the "heating problems" with the D1: there is none! This feeling is felt by the fact that the material (and its thickness) of the case used is different from those of the competition (FOSI., AIYIMA,...). I invite readers to read TI's datasheet about the TPA3255 amplifier chip and to look carefully at the temperatures measured for a given voltage: on the tables it is indicated 75°C for a voltage of 51V and the Tjmax.de the chip is 125°C. So with the 42°C that I read with the laser thermometer in the center of the top of the case of my D1 powered by 42V/8.3A, I am in completely normal conditions of use even if the feeling of heat is slightly greater than with other amplifiers on the market. Another explanation comes from the use of PFFB which leads to a higher heating rate unlike amplifiers which are not equipped with it.

NOTE: my sytem with 8 Ohms speakers -> (42 VDC x 0.707)^2 / 8 Ohms = 110 Watts

View attachment 406198

For example, to "counteract" this feeling effect, AIYIMA on its A70 model which has the PFFB used a large aluminum "cube" as a contact sink in its case. However, the TPA3255 chip still works under the same conditions as the O-NOORUS D1 amplifier ->

View attachment 406279

It's a bit like I gave you a pair of insulated gloves with the amp to reassure you (LOL).

In addition, the advertisement for the A70 model is false because even with a 48V 10A Gan power supply, the 300W advertised is not reached with 4 Ohm speakers ->

(48 VDC x 0.707)^2 / 4 Ohms = 287.91 Watts.

It's not me who says it but the mathematical formulas :rolleyes:

Have a good day and happy listening to all.


ICIETDIYEUR
Thanks for the helpful advice.
I noticed that the sound of the D1 is very dependent on the type of power supply. I have the best sound with a linear, transformer power supply.
Please tell us about your network power supply. Tor 300 VA, Shotki, 15 mF.
 
Last edited:
People hi !

@ dr_mick51: You got it all figured out ;)

The 220pF capacitors are a modification identical to the one proposed by Lester (SYLPH AUDIO) on its PCB in order to correct the appearance of the frequency response for the extreme treble which have a very slight rise ->

View attachment 406201

If soldering the legs of the FKP2 220pF is a problem for you in this area then you can use SMD components otherwise the other solution is to solder the FKP2 directly on the pins of the OPAMPS located below the PCB, it is much more convenient. Regarding the original input resistor, it's a 22K (it's easier for me to say because I have the O-NOORUS original diagrams :cool: ). It must be replaced by a 220K for obvious reasons of adaptability of the output impedance of the device that will be connected to it.

I will try to explain: the NJW-1194 volume control has an input impedance of 15 to 20 k, which is probably variable depending on the level setting, and which comes in parallel with this 22 k R... So it's in your best interest to increase this R, you can go up to 220 kO.

Reminder:
In electronics (not limited to audio), any active system has a resistance (input, output, etc.) that is never linear but varies +/- depending on the frequency of the signal. We therefore use the notion of impedance to differentiate from pure resistance. To come back to the pairing of devices. In the case of HiFi, the ideal is for the output impedance of a device to be very small compared to the input impedance of the device to which it sends its signal. The smaller the output impedance, the more current the device can "send", and therefore not be disturbed "too much" by its load (the load, here, is the device to which it is connected). Conversely, the smaller the input impedance of a device, the more current it will "consume", and potentially disturb the source device.
If output = low impedance --> not easily disturbed If input = high impedance --> doesn't disturb much We quickly understand that the 2 together is even better! On the contrary, if the output impedance is high and the input impedance is low, very large signal disturbance in perspective (attenuation, distortion,....) If the impedances are more or less equal, we will experience a good attenuation (math shows that if the impedances are equal, the amplitude of the signal is divided by 2 exactly), and we also run the risk of disturbance (distortion).

Here is an explanation by an image of the PCB for a better understanding of the MOD ->

View attachment 406181

In this photo, the amplifier's gain is increased to 27.6dB with the 24K resistors. On my diagram (with the resistors of 15K instead of 24K) the amplifier's gain is 23.5dB.

As you have understood: the changes are in orange. The two capacitors are removed because they are absolutely useless since link capacitors are already present upstream of the TPA3255 and concerning the NJW194, nothing is indicated in the datasheet. It is good to remember that the use of bipolar type operational amplifiers is not recommended with this diagram since the resistance to the inputs will have a high impedance and its impedances will not be equal elsewhere, which will cause OFFSET! So, we will use FET or JFET type operational amplifiers because they are almost insensitive to this imbalance and are adapted to high impedances (it's not me who says it but TI). References such as OPA1656 or OPA1642 are well suited for this tour. I chose the OPA1642 not because of the measurements but for their "subjective" sound rendering...

... I find that the OPA1656 created a kind of "spacialization" effect on certain tracks or channels, which is not the case with the OPA1642 which seemed more natural to me and also has a softer extreme treble that will avoid possible "phenomena" of sibilance. This cannot be measured, it is a personal feeling (which my friends also share), however these two references will have very good results that are also very close to the measurements if we want to remain objective :)


@ FanatNsk::
You absolutely have to put the 4 capacitors of 220pF because as it is, you create an imbalance of the signals that are expected as "symmetrical" by the TPA3255 chip.

PS: I take advantage of this post to talk about the "heating problems" with the D1: there is none! This feeling is felt by the fact that the material (and its thickness) of the case used is different from those of the competition (FOSI., AIYIMA,...). I invite readers to read TI's datasheet about the TPA3255 amplifier chip and to look carefully at the temperatures measured for a given voltage: on the tables it is indicated 75°C for a voltage of 51V and the Tjmax.de the chip is 125°C. So with the 42°C that I read with the laser thermometer in the center of the top of the case of my D1 powered by 42V/8.3A, I am in completely normal conditions of use even if the feeling of heat is slightly greater than with other amplifiers on the market. Another explanation comes from the use of PFFB which leads to a higher heating rate unlike amplifiers which are not equipped with it.

NOTE: my sytem with 8 Ohms speakers -> (42 VDC x 0.707)^2 / 8 Ohms = 110 Watts

View attachment 406198

For example, to "counteract" this feeling effect, AIYIMA on its A70 model which has the PFFB used a large aluminum "cube" as a contact sink in its case. However, the TPA3255 chip still works under the same conditions as the O-NOORUS D1 amplifier ->

View attachment 406279

It's a bit like I gave you a pair of insulated gloves with the amp to reassure you (LOL).

In addition, the advertisement for the A70 model is false because even with a 48V 10A Gan power supply, the 300W advertised is not reached with 4 Ohm speakers ->

(48 VDC x 0.707)^2 / 4 Ohms = 287.91 Watts.

It's not me who says it but the mathematical formulas :rolleyes:

Have a good day and happy listening to all.
Your calculations are correct, but music is different. We listen to music, not continuous signals.
Theoretical power for DC48V is (theoretical) Power:
At an output voltage of 33.5 V RMS and a load impedance of R=4 Ω 280.56 W.

Music signals have a much higher peak-to-average ratio (PAR) compared to continuous signals such as a sine wave.

In pop or rock music, the PAR is usually between 10 and 12 dB. This means that the average power (RMS) is much lower than the peak power.

Assuming a PAR of 10 dB, the average RMS power relative to the maximum continuous power is: 10%.

This means that for typical music, the average power is about 10% of the maximum continuous power.

For highly dynamic music (e.g. classical or jazz), PAR can reach 15–20 dB, reducing the average power to just a few percent (e.g. 3–5%).
For pop music: the average power is around 10% of the continuous power.

In practice, audio amplifiers are designed with these characteristics in mind, which is why their power supplies often have lower requirements than the peak power rating might suggest.
 
@ dr_mick51
Here is a table that I think can provide you with some answers.
There would be a lot to say about operational amplifiers and this sometimes leads to controversial topics.
For my part, I am not inventing anything: I am only transcribing what can be read in the TI datasheets.
Table.jpg



@ UAN

What matters is that you are satisfied with it in terms of sound rendering according to your own feelings.
There is not a single way to achieve this but a large number: the goal is to obtain what is suitable ;)
For my part, my power supply is VERY simple, "basic" and suits me too, here are interior photos ->

3.jpg




4.jpg



@ LSPhil

Hello and thank you for your comment that I understand perfectly.
You will understand that I have tried to use the "notions" that are found in the usual commercial descriptions so that my post is understandable by all.

Finally, the purpose of my post is to share a beneficial "experience" in terms of operation for this amplifier and its sound reproduction capacity (the latter not being measurable, let's be clear).

There are other and different ways to achieve this or even better but it seemed to me that these few simple "points" to modify or replace were (almost) within everyone's reach and if this is not the case, this allows to have a 'guideline' for the technician to whom these modifications would be entrusted, that's all :)
 
@ UAN

What matters is that you are satisfied with it in terms of sound rendering according to your own feelings.
There is not a single way to achieve this but a large number: the goal is to obtain what is suitable ;)
For my part, my power supply is VERY simple, "basic" and suits me too, here are interior photos ->

View attachment 406915



View attachment 406916

In my opinion, this power supply is the worst.

I am 70+ and maybe these are my age-related quirks.
 
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@ UAN

This is indeed your opinion, let me share mine please.

A linear power supply can be better than an SMPS if it is really very well designed BUT...
... such a power supply will cost much more than the amplifier presented here (and than the SMPS that I am also presenting), will require knowledge that not everyone has for its realization and will also have a much lower efficiency (therefore a higher consumption), not to mention that it will also take up much more space.

So, in my opinion, this choice is not necessarily wise because if you spend a (quite) large amount of money for such a power supply then you can also do the same for the amplifier (which would be logical).

The modification I propose in this post is far from all this because it does not cost much (some components, the "procedure to follow" is described and does not require any particular knowledge).

In addition, the PSU is better adapted than the "famous Gan" 48V/10A sold in the shops and for a lower price then my choice has been made, everyone will make their own according to their own opinion, their means and their ability to implement.

Just for information, if we just replace the power supply with a linear type made according to the "rules of the art", the gain in "SQ" will be much less than just the modification part I describe here: you will probably tell me that my words are purely subjective or that it is "psychoacoustics".

To convince yourself of this, do the test with measurements but above all by listening because you should not stray from the main vocation (or rather the only one I would say) of this amplifier which is a quality sound reproduction as you are entitled to expect with a so-called "Hi-Fi" device.

Music is listened to, images are watched and it seems that these are "phenomena" shared unequivocally...

Kind regards.
 
In addition, here are some indicators for choosing your PSU.

(Personally for my 8 Ohm speakers, I felt that 100 Watts was enough for my needs.)

TI DATASHEET:
PO vs PSU.jpg


Comparison table with theoretical calculation:

X - Tableau correspondance des transfos.jpg




 
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