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Class D Switching Power Amplifiers and Power D/A conversion

Beomaster refit - controversial?
Beomaster refit - controversial?
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Old 21st September 2019, 05:53 PM   #41
Turbowatch2 is offline Turbowatch2  Germany
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Solder it out or take only the wires leading to it. You replace it by the slider, which is a pot as well. So the slider is digitalized, the value compared to the table you gave the DSP and the volume set in the digital domain. This way you loose no digital resolution and have no nearly 50 years old pot in the signals way, distorting the sound.

Last edited by Turbowatch2; 21st September 2019 at 05:59 PM.
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Old 21st September 2019, 06:21 PM   #42
planet10 is offline planet10  Canada
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Beomaster refit - controversial?
I have not read the thread, but having been a B&O dealer & going to BeoSchool (i never sold a B&O product again after that), i applaud taking the good part (the cosmetics) and improving the insides.

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Old 21st September 2019, 11:36 PM   #43
tallnutt is offline tallnutt  Australia
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Quote:
Originally Posted by Turbowatch2 View Post
Solder it out or take only the wires leading to it. You replace it by the slider, which is a pot as well. So the slider is digitalized, the value compared to the table you gave the DSP and the volume set in the digital domain. This way you loose no digital resolution and have no nearly 50 years old pot in the signals way, distorting the sound.
This is for the DSP volume control. What about the power amp pot?
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Old 22nd September 2019, 12:22 PM   #44
Turbowatch2 is offline Turbowatch2  Germany
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Solder it out or set it once, if the power amp has a pot.

The gain of the amp behind the DSP should be matched to the max. output voltage of the DSP.
In the end, if you put the B&O volume at 100% this should be maximum output of the amp. Maybe the max. level you ever want to hear, if you are sure that will be enough.

Last edited by Turbowatch2; 22nd September 2019 at 12:26 PM.
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Old 26th September 2019, 04:08 AM   #45
tallnutt is offline tallnutt  Australia
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Another question.. I have seen that some people have used the DSP for RIAA equalisation. So can it replace the preamp entirely by coupling it to the phono switch to activate that mode? I don't know if it would provide the amplification also. My TT is a Pioneer PL-S40 that the manual says is MC. However, it seems to work best in MM mode on the Little bear.. which I suspect is actually the MC circuit which they have labelled incorrectly. The 'MC' circuit has a lot of pops and whistles, so I think it may be faulty.

Thanks
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Old 26th September 2019, 11:29 AM   #46
Turbowatch2 is offline Turbowatch2  Germany
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Yes, it can be done, Im sure, but this would require some linear amplification first, as the MC signal is to weak to enter the DSP directly. Also, it might use a lot of the DSPs limited CPU power and memory.
I may be wrong, but I see no advantage over a hardware solution.
The Little Bear should be a good phono -pre, so maybe have a look inside, what may be wrong.
The MC input is a very sensitive amp, it may be upset by the smallest problem. This is why putting it into the player is such a good idea.
Have a look what the cartridge with the needle is called and look for a manual. There are high output MC, which run better at a MM input. These distort at a "real" MC input.
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Old 10th October 2019, 03:25 AM   #47
tallnutt is offline tallnutt  Australia
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Hi,


I have most of my parts now. I have the DSP and a 3116 two chip amp:


150W TPA3116 D2 Dual channel Stereo High Power Digital Audio Power Amplifier Board with TL074C OPAMP-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group


I can see the input caps for the balanced input which on this board look like they are connected to the single input via an op-amp. So do I just unsolder the opamp side of the caps and feed +/- balanced input through the caps? I have seen other balanced input mods where the -ve input has a cap to ground. Do I need to do this, because the data sheet, fig37 http://www.ti.com/lit/ds/symlink/tpa3116d2.pdf does not show it.


Also, what do I do with the DSP ground output for each channel? It has three outputs for each channel: +ve, -ve and gnd. Do I just connect L and R grounds to the common ground of the amp (pin 1)?


Thanks, Theo
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Old 10th October 2019, 04:20 AM   #48
tallnutt is offline tallnutt  Australia
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Also, I have just realised that the DSP did not come with the USB interface so there is no way to program it. Any ideas?


I have messaged the seller but no reply. Looking at SigmaDSP studio it also looks a bit beyond me without any simple guides online that I can find... I may have to go with a simple analog tone preamp that I also bought, which is very dissappointing.

Last edited by tallnutt; 10th October 2019 at 04:39 AM. Reason: edit
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Old 11th October 2019, 01:13 AM   #49
tallnutt is offline tallnutt  Australia
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Ok, got the inputs working and modded that horrible amp board so now it has almost no noise. Removed the opamp and have balanced input from the dsp. Only problem is the dsp channels are setup as a stereo crossover, so I will need to get an interface and reprogram it.
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Old 11th October 2019, 01:40 AM   #50
Turbowatch2 is offline Turbowatch2  Germany
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You have to get some interface to run Sigma studio and load other options. No way around that.
The cheap interface from eBay or Amazon works well, if you reprogram it, as described.

Popular product EZ-USB FX2LP Cypress CY7C68013A USB2.0 Developement Board | eBay

Prices are different, product always the same.
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