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Old 3rd October 2003, 06:20 PM   #121
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Brian, I have no proper tools to measure noise, so I can not comment.
The control processor really expects to see a verification of the bus voltage, with disconnected amp section once I got more than 90V out of the supply.

I've tried the amp with 4 12VSLA, it really works great.

I'm trying to direct couple to a digital crossover, but sadly the crossover internal format is 24 bit left alligned, while the TAS chip has only 16 bit left alligned format. I have to convert to i2s, posibly can do it during the weekend...

Is there any detailed info available about the Equibit coding.
I'm (was?) a big fan of no oversampling dacs, but this "power DAC" with it's built in oversampling filter seems to be a better compromise, than a DAC plus an analog amp in my case.
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Old 4th October 2003, 08:57 AM   #122
Henckel is offline Henckel  Denmark
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Default Service manual XR25/45

HI

Has any of you guys obtaied the service manual - i have so not been able to obtain it in Europe so far.


BTW is the US version of the XR25/45 also capabel of 230 Volts AC input ?

Any pointers to the differneces between 25 and 45 would also be much appreciated - besides the differneces in DIgital input where the 45 supports 192 Kb/s


Thanks

Morten
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Old 5th October 2003, 10:01 PM   #123
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Default adding digital Xover in front of digital amps for each speaker

My new sound card has digital outputs for 5.1 HT.

How about adding a 2 way digital crossover in front of the TI stereo digital amp chip? Putting the Xover and amplifier at each speaker would allow customization for each speaker and allow digital cables between source and HT speakers. A 2-way Xover would cover 2-way speakers, as well as 3-way deisgns by using passive components between the midrange and tweeter.

If anyone is building PCBs for the TI digital amplifier, please consider adding the DSPs necessary for a FIR filter crossover?
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Old 6th October 2003, 02:12 PM   #124
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Default Re: adding digital Xover in front of digital amps for each speaker

Quote:
Originally posted by LineSource
My new sound card has digital outputs for 5.1 HT.

Do you mean 3 sets of spdif outputs? What card is that?

There are some SHARC modules available from Danville (www.danvillesignal.com) that might be suitable for doing a crossover directly in front of the amp, but they are a bit light on detail on their web site. They aren't bargain-basement, but they're not bad (start at $400 or so), but you'd have to do the I/O card on top of that.
For a 2-way system you could probably manage around 1024 tap FIR filters if I'm reading the SHARC data sheet correctly. This isn't too bad, but might be a bit short. Certainly more than enough for carefully designed IIR/hybrid xovers though.
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Old 30th October 2003, 08:32 PM   #125
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Just gonna throw this back up to the top of the list here. Wanted to see if there was an update on how things were going with it.
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Old 17th December 2003, 03:58 PM   #126
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Finally I was able to complete the one box crossiver/room corrector/5ch amp project based on the Pana receiver and a pro digit crossover.
The crossover and amp is in one 1U high 19" rack box now with direct i2s interface.The box has only digital I/O and speaker outputs. Configuration is done via an RS232 coupled computer GUI. The amp output sections are 4*12V SLA battery powered.

A couple of remarks:
To use the amp from SA-SX10 standalone with external bridge power it is enough to supply the following signals:

1. <digital_in> MCLK (256fs)
2. <digital_in> SCLK (64fs)
3. <digital_in> LRCLK (fs)
4. DGND
5. <digital_in> FRONT DATA (I2S 24bit data)
6. <digital_in> SURROUND DATA (I2S 24bit data)
7. <digital_in> CENTER / SUB DATA (I2S 24bit data)
11. <digital_in> DOUBLE SPEED (for audio data rate) (0: fs = 44.1KHz or 48KHz, 1: fs = 88.2KHz or 96KHz)
15. <analog_in> AMP RESET +5V
17. <digital_in> /MUTE HeadPhones (must be tied to +3.3V)
21. 12V_GND (DGND)
22. +B (12V)
23. 12V_GND (DGND)
24. +B (12V)

Note that the /MUTE HeadPhones input has no internal pullup, leaving it unconnected will disable the speaker outputs. Other MUTE inputs has internal pullups, can be left unconnected and the channel will be enabled.

18. <digital_in> /MUTE Front (0: Front speakers disabled, 1: Enabled)
19. <digital_in> /MUTE Center & Surround (0: Center and surround speakers disabled, 1: Enabled)
20. <digital_in> /MUTE Subwoofer (0: Subwoofer line out disabled, 1: Enabled)


The power supply for the output section can be disconnected and the bridge outputs can be directly fed from batteries. It is really efficient, can drive my speakers at full volume for several days.

One interesting thing: I always wondered why Panasonic decided to change the power supply voltage in the -20 - -40dB range for volume control.
Now, feeding the amp with a controlled digital signal it seems the the SA-XR receivers has greater than 1 gain combined with a kind of soft limiter in the 0 - -20dB range. It seems they decided that nobody will use this range regularly, only when the input volume is low.
Gain 1 seems to be at around -18db volume setting. Pushing the Panasonic receiver with high level input signal and closer to 0db volume setting will result digital limiting and clipping, maybe the reason for reported harshness at high volume.
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Old 18th December 2003, 03:49 PM   #127
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fcserei - very cool, thanks for the info.

Couple questions, of course :-)

How are you doing volume control? Are you using the control portion of the XR-10 at all for this, or did you just pull the power amp sections and do volume conventionally ahead of the xover?

What size batteries are you running? Have you tried lower rail voltages? I was thinking that 24V might be adequate, but don't know how the amp would react to this; two big batteries for 24v would be cheaper/easier than 4 smaller ones for 48V. Any suggestions on chargers?

Of course now that I think about it, 4 cells that could be configured as 12, 24 or 48 V would be the most flexible, and would emulate the variable supply topology. Have you done enough listening to eval how much degradation in amp performance there is with reduced-resolution input?
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Old 18th December 2003, 04:16 PM   #128
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Quote:
Originally posted by fcserei
Finally I was able to complete the one box crossiver/room corrector/5ch amp project based on the Pana receiver and a pro digit crossover.
The crossover and amp is in one 1U high 19" rack box now with direct i2s interface.The box has only digital I/O and speaker outputs. Configuration is done via an RS232 coupled computer GUI. The amp output sections are 4*12V SLA battery powered.
Nice!

A couple of questions:

- What is the AmpHour rating of the batteries you're using?

- Which digital crossover did you start with?

- Any comments on the sound?
Quote:
One interesting thing: I always wondered why Panasonic decided to change the power supply voltage in the -20 - -40dB range for volume control.
Now, feeding the amp with a controlled digital signal it seems the the SA-XR receivers has greater than 1 gain combined with a kind of soft limiter in the 0 - -20dB range. It seems they decided that nobody will use this range regularly, only when the input volume is low.
Of course!

I'm kicking myself for assuming that the dB values displayed were accurate.

When I was playing around with the amp board outside of the receiver, I still was using the receiver as my I2S source.

This makes a lot more sense now.

Perhaps the gain and compression above displayed -20dB could be considered a digital implementation of allowing the user to 'Turn it to eleven'.
Quote:
Gain 1 seems to be at around -18db volume setting. Pushing the Panasonic receiver with high level input signal and closer to 0db volume setting will result digital limiting and clipping, maybe the reason for reported harshness at high volume.
Compression certainly could be part of it, but...

I still have the observation that the original switcher power supply was slewing around at higher volumes. I found that replacing this supply with LA batteries made the supply nice and stiff. This was accompanied by a very substantial improvement in sound quality.

Are you using MLS measurements for room correction?

I'm still quite a bit away from being able to try this. It would be interesting to hear about your experiments.

Regards,
Brian.
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Old 18th December 2003, 04:20 PM   #129
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Quote:
Originally posted by dwk123

How are you doing volume control? Are you using the control portion of the XR-10 at all for this, or did you just pull the power amp sections and do volume conventionally ahead of the xover?
I've removed the power amp board and put it in an 1U box together with the DSP. I'm not using any other part of the receiver now. Volume control is in the DSP digitally, but I use rather power supply voltage switching. The DSP is freely configurable, it can have volume control either before or after crossover. It can also have different output dither for different volume settings.

Quote:

What size batteries are you running? Have you tried lower rail voltages? I was thinking that 24V might be adequate, but don't know how the amp would react to this; two big batteries for 24v would be cheaper/easier than 4 smaller ones for 48V. Any suggestions on chargers?
I'm running the amp on four 7Ah SLA. The volume is quite matched to my room and tastes, means 0dB volume at 48V is about just the right loudness, not party level, but quite enoug for classical. Switching to 2 (24V) or 1 (12V) batteries I have a cheap way of limited volume control.
I just charge the batteries with cheap chargers when the amp is not in use.

Quote:
Of course now that I think about it, 4 cells that could be configured as 12, 24 or 48 V would be the most flexible, and would emulate the variable supply topology. Have you done enough listening to eval how much degradation in amp performance there is with reduced-resolution input?
I can't hear any degradation with dropping the voltage, and I don't need big adjustment range in the digital domain as I almost always listen at arond 0dB level.
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Old 18th December 2003, 05:56 PM   #130
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Quote:
Originally posted by fcserei


I've removed the power amp board and put it in an 1U box together with the DSP. I'm not using any other part of the receiver now.
That's what I thought, but wanted to be sure. I had a similar idea when I saw a local place with very cheap 2U rackmount cases.


Quote:

I'm running the amp on four 7Ah SLA. The volume is quite matched to my room and tastes, means 0dB volume at 48V is about just the right loudness, not party level, but quite enoug for classical. Switching to 2 (24V) or 1 (12V) batteries I have a cheap way of limited volume control.
I just charge the batteries with cheap chargers when the amp is not in use.
Wow - a total of only 28Ah? Thats much less than I would have expected. I forget exactly what I was looking at, but I was thinking along the lines of 2x 80Ah. Sounds like that might be unnecessary.

How many channels are you using - all 5 or only 4?

One thing I did realize in my battery thoughts is that there shouldn't be much difference in battery life due to the voltage used. ie 28Ah should last about the same regardless of whether you use it as 4-in-series for 48V or in parallel for 12 - it will all depend on the power output used. This is very different from Class A/B topologies where the wasted power increases with increasing voltage, since output current will be constant.

Quote:

I can't hear any degradation with dropping the voltage, and I don't need big adjustment range in the digital domain as I almost always listen at arond 0dB level.
Assuming you're right about the 0dB level being around -20 on the volume dial, I can see this working. I usually listen around -30 or so and so *might* get away with 24V, but maybe not - there might not be much headroom.
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