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Old 3rd October 2008, 05:52 PM   #11
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It's very difficult to make a technical business case for entering the manufacture of hi-fi amplifiers, other than perhaps class-D and other amplifiers benefiting from improvements in materials technology and the understanding of digital systems.

These development of these amplifiers does at least have the justification that they are increasingly efficient.

Hi-fi equipment is however a boutique market, bearing more resemblence to clothing fashion than perhaps any other electronic product.

Amplifiers of all classes entirely adequate to the task of hi-fi reproduction abound.

Given that wasting energy is going out of fashion fast, the case for your business looks better than it otherwise might, but very large companies are spending lots of money trying to make your efforts redundant.

It could be of course, that you feel that your talents lie more in the direction of sales than engineering; in either case, good luck.

w
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Old 3rd October 2008, 08:38 PM   #12
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Quote:
Originally posted by chicks


Sonos is a leader in the streaming market, with Olive http://www.olive.us/home.html aiming for the higher end. Logitech just introduced the SqueezeBox Boom, adding an amp and speakers to their streamer.

A compromise product that has the streamer and Class D amp, but allows external speakers for better separation and sound, at a price closer to the SqueezeBox than the Sonos, might work.

Here's my attempt a such a compromise: an Omnifi DMS-1 streamer with an added Sure Electronics amp:

http://www.chicksolutions.com/dms1/100_1040.JPG
http://www.chicksolutions.com/dms1/100_1041.JPG

Chick, could you contact me through either pm here or through my contact form on my site?

Regards


Blair
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Old 4th October 2008, 01:08 AM   #13
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Quote:
Originally posted by chicks

A compromise product that has the streamer and Class D amp, but allows external speakers for better separation and sound, at a price closer to the SqueezeBox than the Sonos, might work.
Thats a great idea, however i don't have much time to complete this project (college year including holidays is only about 26 weeks (approx), also i have other projects & assignments to complete during the year as well as exams at both christmas & summer, as expected i have deadlines to meet!

Quote:
Originally posted by wakibaki

It could be of course, that you feel that your talents lie more in the direction of sales than engineering

No thanks, id take engineering any day !
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Old 7th October 2008, 02:39 PM   #14
Pashley is offline Pashley  Canada
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Default Re: Some thoughts....

Quote:
Originally posted by ashok
I have used some classD amps and I think they do some things amazingly well. From a price point they are winners. BUT come to meaurements and they are poor in some areas.

...

MY opinion would be that they should refine classD ( which is very young right now ) to a stage when it can outclass the best tube and solid state equivalents. So ( design wise ) you have a challenge right there !
I wonder about a class-D amp using "feedforward". Quad did that in some of their amps http://www.quadesl.org/Album/Intervi...ealbinson.html and I recall one of the oriental companies advertising it as "their" latest great advance, mid-80s.

One way to make an amp more linear is to apply negative feedback. The basic notion of feedforward is that instead you take a sample of the main amp's output, compare it to the input (delayed to take account of the amp's delay), compute a difference signal, invert that, amplify it a bit and mix it back into output.

In theory, this is great. Say your main amp is 200 watts and 5% distortion. The error signal is just 10 watts, and even if your small amp gives 1% distortion, that's only .1 watt, or .005% of the 200-watt signal.

Of course, in practice it is far more complicated. That's why we need engineers!

Either or both amps in such a system could be class D. The overall design leaves the constraints on the big amp fairly loose. For the small one, a Tripath or other class D chip, or for that matter an op-amp might do.
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Old 9th October 2008, 05:09 PM   #15
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I am currently working on identifying customer needs, which is in the form of a Questionnaire. I am trying to come up with questions that will define Product Specification. The majority of questions are technical, regarding the specifications. Some of the questions include:

- How many audio channels would you require in an audio amplifier?
(2, 4 or 4+)
- What power (watts) would you require in each channel of the amplifier (assuming 8Ώ load)?
(50,100 or 200)

...etc

I have other questions regrading specifications like acceptable THD and desirable Frequency Response, S/N ratio, type of speaker connections...etc. I am sure there will also be subjective questions regarding the actual design & form of the amplifier. Although I was wondering if someone was to build you a Class D stereo power amplifier, what other specifications/details would you really look out for?
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Old 9th October 2008, 06:27 PM   #16
Pashley is offline Pashley  Canada
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Quote:
Originally posted by rob mullen

- How many audio channels would you require in an audio amplifier?
(2, 4 or 4+)
- What power (watts) would you require in each channel of the amplifier (assuming 8� load)?
(50,100 or 200)

...etc

I have other questions ...
Can you define the application? The target market?

An "audio amplifier" is dreadfully vague. Even within a single system, say a home theater setup, requirements are different for main speakers, surround & sub. There are also "audio amplifiers" in cars, theaters, electric guitars, ...

Even for a single application, what's your market? High volume mass-market? Cost-no-object perfection? Best price/performance trade-off? Sounds better than anything else in price range X, or is cheaper than anything else with performance Y?

The power amp I want most would be three channels, to drive the front three of a home theater system. There are lots of choices in 2-channel amps to drive the surrounds. The main design goals for the three-channel would be that it be be moderately priced and extremely clean.

At least 70 watts because I consider 110 Db per speaker a design goal for adequate loudness, and if sensitivity is 92 Db for 1 w 1m, you need 64 W to get that. More power is good, but not entirely necessary.

Three Coldamp class-D modules and a power supply would give me 240 W/channel for about 500 Euros in parts, plus case, etc. There are also quite a few 5-channel amps available with various specs and prices. To be really desirable compared to those, the three-channel would need to be under $500.
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Old 10th October 2008, 02:24 PM   #17
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Sorry Pashley, I should have been more specific. I guess I am looking at Best price/performance trade-off. I was thinking about the Cost-no-object perfection, but given the nature of my subject I think the Best price/performance trade-off is more suitable. My target market is the HIFI/audiophile market, not home theatre, not automotive, not musical instruments...

The Questionnaire is not finished yet,but when it is i will be looking for people from these forums to fill it out.
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Old 10th October 2008, 03:24 PM   #18
Pashley is offline Pashley  Canada
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I'm not sure how hard it would be to design in, but extra flexibility for bridging would be a nice feature.

Say you are designing an amp whose basic spec is 100 W into 8 ohms. Typically, these would also be happy driving a 4 ohm load, or bridged for ~ 200 W into 8. Can you extend this? An amp that tolerates 4 ohm speakers when bridged? Or that can bridge four modules for a ~400 W amp?

If those are possible, can you reduce the basic amp spec? Make a 50 W module bridgeable for 100 or 200? This gives a lot of flexibility, hence a broad market. Depending on room size, speaker choice, budget, etc. one might choose 50, 100 or 200 for stereo. Home theater might use them all -- 100 for mains, 50 for surround, 200 for sub.
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Old 10th October 2008, 04:16 PM   #19
bwaslo is offline bwaslo  United States
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Two other things that Class D amps seem to do particularly well are (1) very high power and (2) driving very low impedances.

Seems like these in combination might be used to implement some otherwise impractical loudspeaker types. Such as a direct drive ribbon type speaker (very low impedance, and not usually very efficient unless the magnet structure is huge).

Though designing an amp AND a speaker makes for much more work, given your limited time budget. Maybe the amp could focus on those attributes, directed only to a hypothetical ribbon loudspeaker. Some planar magnetic speakers similar to ribbons are discussed in the Loudspeaker section of the DIY forums.
--
Class D also has possible advantages in terms of low level detail. Unlike class B or AB, there is nothing special about small signals in the region where positive and negative voltage outputs meet (a.k.a., no crossover distortion mechanism). In that way, it is more like Class A, except Class D also makes no particular distinction between large excursion and small excursion (even in Class A, the linear gain changes with signal level, better Class D types like UCD have about the same distortion at any level until clipping is approached).
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Old 10th October 2008, 08:26 PM   #20
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Bridging is something i have considered and it is part of my Questionnaire, as regarding the extra flexibility i am not sure yet if i can do that.

Bwasio, il check out those direct drive ribbon type speakers. Thanks
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