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Class D Switching Power Amplifiers and Power D/A conversion

I AM D v200, Fx Audio d802, optimisation and TPA3116
I AM D v200, Fx Audio d802, optimisation and TPA3116
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Old 11th December 2018, 10:29 AM   #531
Hugh Jazz is offline Hugh Jazz  Taiwan
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Join Date: Feb 2013
Depends on the amp, speakers and some might say source too. If you want a rule of thumb I'd say design for 60KHz and 6 ohm, but I'd never do this. If I wanted a universal filter, I'd start at either 10uH or 15uH and 0.47uF differential, depending on the speakers, and see how it sounds.

40KHz and hybrid makes a lot of sense to me. How does percussion sound?

Last edited by Hugh Jazz; 11th December 2018 at 10:40 AM.
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Old 11th December 2018, 11:10 AM   #532
chermann is offline chermann  Austria
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Location: Vienna
Hi Hugh Jazz

i am not so experienced as you or others. i just follow the hint as described above. currently i am happy with the setup for 4 ohms.
i tried

7 and 1
7 and 0,68F
7 and 0,68 + CTL 0,033F - original opamp (TL072 or fake)
now i use 7H + 1 again with new OPA1602 or AD8599

percussions was never a problem. the KEF Q100 is a coax which sound pointed but partly hard....and very good for that price !
so for this speaker it would be make sense to cut of -3dB at 20kHZ...i will try if i have time to change amps and speakers...but not in this thread

but as jean paul decribed. china boards(amps) are.... cheap +cheap +cheap..
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Old 14th December 2018, 08:15 AM   #533
Hugh Jazz is offline Hugh Jazz  Taiwan
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I changed the 12v and 3.3V regulators, added a 47uH inductor for the 3.3V, and replaced caps in the D802 - and am very impressed with the sound now - that Rojon tcxo is good but it needed better power. I also got rid of the blue LEDs behind the volume dial - tacky. A minor re-route of the red/yellow/black button wires too.

The LM2596 and its bits are gone and instead there is a 550kHz switcher set to 12.8V that is fitted with an LT3045 set to 12V with fast start up and Cset of 22uF. I removed the diode (D3) that feeds 12V to the 3.3V reg and fitted a 47uH inductor. The 3.3V LM317 and its bits were removed and replaced with another LT3045. I'm using a linear power supply for the amp. The three 470uF caps were replaced with 1000uF Pansonic FR 16V, Rubycon 1200uF ZLH 6.3V and 1500uF 6.3V ZLJ.

Not much else worth doing to this amp now but it does sound really good. I'm impressed and very pleased :-)

I opened up the V200 again and pulled the coils - they are 11uH on my meter. I'll order some 10uH, some KDS xo, and a PCM1803 and then get to work on that. Can it sound as good as the D802....?
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Last edited by Hugh Jazz; 14th December 2018 at 08:29 AM.
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Old 12th February 2019, 08:48 AM   #534
dublin78 is offline dublin78  United Kingdom
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Location: Cheshire
Hello

Do you think that I could use an FX D802 to power some PA speakers? They would be very efficient - 99 or 100db sensitivity (1w 1M). Two way speakers with 15" + Compression driver. Either 8ohm or 4 ohm.

I wouldn't need it for serious party volumes, but mainly for background music outside. I'm thinking 24v battery power for a mobile solution.
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Old 26th February 2019, 04:00 PM   #535
jdbon is offline jdbon  United States
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I've been researching FDA amps, and I see that most of them offer a variety of EQ presets as well as tone controls. Do any of these amps offer manual EQ adjustments with a graphic equalizer? I see the Alientek D8 has some sort of visualizer, but it appears it is only aesthetic.
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Old 3rd April 2019, 08:54 AM   #536
dublin78 is offline dublin78  United Kingdom
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Well, I've just taken delivery of a D802C PRO. It looks like a nice little unit.

However, the Bluetooth is next to useless. It has good range and connects easily, but plackback is interrupted every few seconds with a half second stutter.

I have read a few reviews that report a similar problem. Others say the Bluetooth is great, so it may be a batch issue. Does anyone have any experience of this? I bought through ebay paving by paypal, so I am confident that I can get my money back, but I would rather fix it if possible.

I bought this for a mobile solution, so the Bluetooth function is primary.
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Old 3rd April 2019, 10:27 AM   #537
FauxFrench is online now FauxFrench  France
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Location: The mountains, calm and quiet.
It seems fine, with Bluetooth 4.2, and good reception range. I assume it supports APTX.
I use Bluetooth as well (different setup) and a disturbing factor is the general use of that radio band. If I'm not wrong, Bluetooth uses a general purpose band (with frequency swapping) that is used for a lot of other, typically control, purposes. I live in a rural area with good distance to the neighbors but anyway I sometimes notice a dropout. If you live in an urban area with close distances to neighbors and with many around the disturbance may be important. The problem is that for sound streaming the data packages have to arrive rather regularly. Next, I believe that the bandwidth of Bluetooth is a bit marginal for audio such that it cannot tolerate too many packages lost before the timing is insufficient. With printing using Bluetooth this is not a problem as the buffer will collect the packages when they arrive.
You may try to put the D802C PRO and your phone inside a big metallic box and see if the situation is improved.

Last edited by FauxFrench; 3rd April 2019 at 10:31 AM.
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Old 3rd April 2019, 01:25 PM   #538
dublin78 is offline dublin78  United Kingdom
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Location: Cheshire
Hi
I live in a rural area too.
I have used the amp with two alternative Bluetooth receivers (5.0) and (4.0) feeding the coax input. They both work fine.
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Old 3rd April 2019, 03:15 PM   #539
FauxFrench is online now FauxFrench  France
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Location: The mountains, calm and quiet.
Quote:
Originally Posted by dublin78 View Post
Hi
I live in a rural area too.
I have used the amp with two alternative Bluetooth receivers (5.0) and (4.0) feeding the coax input. They both work fine.
A very valid reply that unfortunately preempts most of my further suggestions.

Testing the unit with two other Bluetooth receivers on the coaxial input shows that the class D amplifier and the DAC as such work well. Further, that the Bluetooth source does not give problems and the radio transmission should be OK.
It hints that the flaw is in the Bluetooth module or in the interface to the DAC.

The Bluetooth experts are mainly in the section "design & Build > Parts" of this forum. Tell them what you just told me to see if they have a good idea.

You may try to remove the Bluetooth antenna of the D802C PRO (keep your Bluetooth phone nearby) to see if the receiver is jammed by another radio signal via the antenna.

Else, it seems like a "return to sender".
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Old 22nd April 2019, 01:09 PM   #540
pghvolt is offline pghvolt
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Does anyone know if the I.AM.D V200 has the ability to automatically power on/off in response to changes in input device? For instance, if connected to a computer via USB, could the V200 automatically turn on when PC boots up, then off when PC is shut down?
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