[Czilla9000]

Those of you who frequent the 'Cables etc' forum know I am very interested in digital amplification technology and have contemplated buying one of those Sharp 1-bit amplifiers.


So when I was browsing DIYCable.com (for parts for Project 1, the speaker I am building) and saw a link for "Digital Amplification" - my heart raced.

Inside the link was the "LC Audio ZAPPulse 2.1" - a digital speaker amp module. What is amazing is according to LC Audio, the unit is a credit card in size and capable of 400 WATTS!!!!!! (200 watts per channel)

However, the unit does not include a PSU, and one unit provides music for only one channel.


I have the following questions.



1. Anyone here familiar with the ZAPPulse?

2. The ZAPPulse, unlike the Sharp units which convert PCM (or analog) to a DSD-like 1-bit/5.8 MHz, converts analog signals to Pulse Width Modulation at a switching rate of 490 KHz. How does PWM differ from DSD?

3. Can I modify it to be a Headphone Amp? I would like to modify the ZAPPulse power amp to be a headphone amp and have the first digital headphone amp. Any suggestions (on how to do this)? (I also need a speaker amp for the speakers I am building, so if I could have it double as a speaker amp that would be great).

I assume the main hurdle is controlling the volume from being too loud and hooking up a headphone jack.



(As always, the standard disclaimer that I could using data from this thread build and sell a product for HeadFi-ers applies. If you have a problem with that please do not reply. However, keep in mind having a wide variety of amps on the market is good for ALL Headfi-ers.)


This is all, however, for later on. The parts I need for my speakers I am building have not arrived, and the speakers will be built before any amp.






As always........THANK YOU!!!!

 

[dd3mon]

Very interesting concept - LC Audio makes some damned good tweaking products. Haven't heard a thing about a digital amp product of theirs, any news on this on AudioAsylum? (I'd check myself, but bed is calling my name).

-dd3mon

 

[Glassman]

me also interested in digital amplification, see project DARPA (use google), it's very interesting.. as I am completely digital guy it attracks me much. Now I'm begining to understand why does Sony used DSD for SACD - they knew where's the future going! and of course DSD is the most suitable format for digital amplifiers..

as for headphone amp - you should use the very same technique as seen in ordinary amps - hook up your cans to the speaker out using some resistor.. or - try to decrease voltage from which the amp does the switching - I thing that the output voltage depends only on the input voltage from which the switching is made..


edit:
DARPA

 

[Czilla9000]

Shouldn't the variable resistor be hooked up to the RCA inputs of the amp....before the amping stage? Wouldn't that be better.....???


That reminds me........a big problem with the ZAPPULSE is that it does not have a PCM to PWM converter on board...........only an analog to PMW converter.



BTW, Glassman..........great minds think a like....

Back on the 16th of August I said the following in this thread: http://www4.head-fi.org/forums/showt...threadid=42538


Quote:

I know I am digressing....but I believe the main reason why SACD should win the battle against DVD-A is because of DSD Digital amplification. While DVD-A and high bit rate PCM may actually be superior to DSD/SACD, the fact that there is no such thing as a "PCM Digital Amp" makes SACD the better choice, because SACD gives the option to amplify without analog distortion (or PCM to DSD conversion distortion).

I would still love it if someone told me the differences between PCM, PWM, and DSD. I know how PCM and DSD work, but I do not know there relation to PWM.

 

[Glassman]

attenuation in front of ADC is always bad! we are happy for what ADC performance we have, we don't need to decrease it by attenuating it's level and making it more dificult for ADC to convert without quality degradation..

PCM - pulse code modulation
PWM - pulse width modulation
DSD - marketing name for PWM based digital format

I want DVD-A to win the battle but only if someone finaly cracks it's DRM

DSD is maybe too big revolution.. If DSD than I want to see PC DVD drives be able to read SACD and some psychoacustic-based compression algorithms and also lossless compression techniques (are they already implemented in SACD??).. Every format is bad if I can't use it on my computer and I thing that DVD-A has closer to be the good format

 

[Czilla9000]

So DSD = PWM? They are the same thing? If so, why didn't LC Audio just call it "DSD" instead of "PMW"?

Also, if it is DSD, isn't the 490 KHz sampling frequency of the ZPulse kinda slow?

 

[Glassman]

DSD is one implementation of PWM coding, not that they are one and the same.. PWM is a principe and DSD is concrete implementation.. it's the same like 8bit/22.05kHz PCM - is that a CD? it is also a PCM!

DSD now runs at 2.8224MHz with 64fs - 64*44.1kHz = 2882.4kHz but the switching ability of current digital amps is as you stated only about 500kHz for now..

 

[Chipko]

They've been making the rounds on swedish DIY forums and the consensus seems to be that they are good. There have been some bugs but it seems that they are mostly working very well by now.

Peranders has a better knowledge of this stuff, might want to pick his brain about the Zappulse.

 

[maczrool]

I've actually been looking into making a portable digital headphone amp. The best option out there seems to be TIs Equibit system which can take PCM signals directly w/o first converting to analog, no DAC required. There are two basic components- the PWM processor and the ampifier stage.

The main obstacle for battery use is the high voltage that the PWM amplifier stage requires (over 20 volts). One would need some sort of voltable multiplier circuit.

Stu

 

[aos]

One thing you guys may be forgetting is that if you want to make and sell these kind of amps, you need to get FCC approval. Large sections of TI application notes (I've read quite a few on the subject) are about how to reduce HF to levels below FCC threshold.

The best chip is made by TI (I think) but is available only on a special license from some company that actually found a good method to do some of the steps in the process and sold them the rights. Kind of like Dolby Digital / DTS. They claim that they want to make sure only capable companies are building their stuff and not giving it a bad name by lousy implementations. There's quite a few inferior models sold by TI wihout strings attached though and I was tempted to try to build one for my own use. I think I'll wait until better chips are available for general population.

 

[maczrool]

Quote:

Originally posted by aos One thing you guys may be forgetting is that if you want to make and sell these kind of amps, you need to get FCC approval. Large sections of TI application notes (I've read quite a few on the subject) are about how to reduce HF to levels below FCC threshold. The best chip is made by TI (I think) but is available only on a special license from some company that actually found a good method to do some of the steps in the process and sold them the rights. Kind of like Dolby Digital / DTS. They claim that they want to make sure only capable companies are building their stuff and not giving it a bad name by lousy implementations. There's quite a few inferior models sold by TI wihout strings attached though and I was tempted to try to build one for my own use. I think I'll wait until better chips are available for general population.

I'm not one of them

. FCC cert. is not a cheap process. Assuming you get it right the first time, the testing etc. comes out to at least $10,000. It's important to at least get the basics down first before worrying about such minutiae. Hmm didn't see any FCC or CE logo on your amp aos

. Anyway most of the guys here just want one for their own personal use.

What TI chips have such restrictions put on them? I'm not aware of any.

Stu

 

[aos]

Audio amplifiers are not subject to FCC. Most digital electronics is as it creates radio frequency signals. Digital amps are particularly tough because they create VERY POWERFUL high frequency signal. I've mentioned FCC just because it is expensive. Although I'm doubtful it is THAT much, I thought it should be in the several thousands range (still a lot).

 

[maczrool]

Quote:

Originally posted by aos Audio amplifiers are not subject to FCC. Most digital electronics is as it creates radio frequency signals. Digital amps are particularly tough because they create VERY POWERFUL high frequency signal. I've mentioned FCC just because it is expensive. Although I'm doubtful it is THAT much, I thought it should be in the several thousands range (still a lot).

Fair enough, but your amp is not just amp, but a DAC. It has digital circuitry which to the best of my knowledge is subject to FCC regs. The FCC defines any device which is "An unintentional radiator (device or system) that generates and uses timing signals or pulses at a rate in excess of 9,000 pulses (cycles) per
second and uses digital techniques" as a digital device. More specifically, it is a Class B digital device. Technically I believe it should be FCC certifed, but given the small volume, I'm sure they wouldn't bother. And yes, it IS that expensive to have the FCC testing done.

Stu

 

[aos]

I believe you're right, but then, I'm not in the US

. Though we have our own equivalent of those rules I'm sure. Anyhow, I wanted to point out that in case of digital amps it's not just for show, they do generate high powered high frequency signal so you might cause some actual interference in your living room or beyond.

I assume you did FCC for your stuff so you're speaking from experience? Really, it's 10k? No wonder there's no competition to Sony, Philips and a few more of those. I'm wondering if the likes of Krell and Mark Levinson not to mention the smaller ones FCC test their stuff...

 

[maczrool]

Well a project we were working on a few years ago was going to require FCC work, but we never went through with it. $10K was the quote. My stuff hasn't got FCC approval mainly because it comes only partially assembled. It doesn't work without the end user modifying it a bit, so it's not needed as I understand it.

Although you may be in Canada, if your stuff is sold in the US, it is supposed to be FCC cert., but anyway the volume (qty.) of it is such that they won't care much. I play with Tesla coils and those things violate every FCC reg. there is, but then again I don't sell them. Yes, you're right about a digital amp being much more problematic than most electronics. I'm going to stick with analog for now.

Stu