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Old 11th March 2008, 07:38 PM   #661
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Default It ain't pretty...part 2

The Power Supply:

Note that the transformers aren't what will be used in the end, but they were lying around with the right voltage specs. I have no plans to rock until the bigger transformer(s) are in place.

The power supply caps are 12,000 uF 50V Nichicon snap-ins from ApexJr's website. Not a bad deal considering they are $1.99 each. Compared to the $6.50 each for 10,000 uF Panasonics, it was a no-brainer for me. Your mileage may vary.

I'll take pictures of any smoldering wreckage after I power up here in a bit.
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Old 11th March 2008, 07:48 PM   #662
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Default Very good.... i was watching with my daugther and i feel great!


Thank you very much to share the images and your points of view about the unit.

Thank you once again...picture made rigth now, to you!

regards,

Carlos
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Old 11th March 2008, 07:58 PM   #663
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Default I love it, in special the wooden base


really!... i like it... i am not kidding!

regards,

Carlos
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Old 26th March 2008, 02:44 PM   #664
udailey is offline udailey  United States
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Default reactions

Guys I have been reading several pages of this post. It seems that the designer felt this amp sounded better than many chip amps. That sounds reasonable. There is a lot of talk, obviously, about Peter Daniel's LM3875 and LM4780 amps. I was going to build a LM3875 but this amp you all are working on sounds like it might be great.
I am new to this and have only built one amp... a tube amp. I like it and it was a lot of fun. Its going to the wife for her birthday along with a pair of DIY speakers once I get them looking pretty. So I need to build something for myself, but budget will restrict me to ONE project right now. Would you all recommend this over the gainclones? I know it is more difficult than a gainclone but thats part of the fun. I am most concerned about sound quality. I will be powering DIY Fostex 8" speakers of about 93db sensitivity and 8ohm. I hope my question is not intruding on the line of logic and discussion this post has been following.

Regards,
Uriah

I suppose I should ask also: If the preference were for a DX amp, would ones preference be the DX HRII or the Precision 1?
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Old 26th March 2008, 03:25 PM   #665
Nordic is offline Nordic  South Africa
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Hi Uriah, yes, I have no reservations saying these amps sound better than most chipamp implementations by quite a bit.

The path I would follow is to build the standard DX first, it is a simpler schematic, with fewer tricky sections to get right. Also replacement transistors are cheap for the innevitable error or 2.
These amps have a strong "long" bass and very low parts cost.

The original DX is medium power 50W @ 8R, 100W @4 R

The HRII is a little diffirent and lower power, with some of the supply rails regulated down in voltage, the result is a lower powered output, but a much improved fidelity, realy nice trebles and details, it is definately the lady amp of the bunch. providing about 40W@8R per channel in its basic form. I have a strong love for this one. This 40W of undistorted power and seem much much, much, more powerfull in real life.
Build cost is a little higher due to extra transistors, but not by much and the original DX supply can still be used.

The PI is the butch of the batch at about 250W@4R, very powerfull pushing bass from almost DC, with astounding detail in mid and bass regions. Construction costs are in the high-ish category as the power supply caps, transformers and heatsinks almost all double in size, not to mention the 4 extra output pairs...

I would suggest you aim for the HRII, I think it will complement those high efficiency drivers very well.
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Old 26th March 2008, 03:49 PM   #666
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Default Those chips are good, but, they cannot be better than discrete amplifiers... and this

Because the size limits.

If you try to touch a soldering iron, the small soldering iron tip, into a big heatsink, you will find that cannot transfer heat to the heatsink, or, the transference will be bad.

The correct transference may exist if you make a hole, the same shape and same dimensions of your soldering iron tip point, and introducing it into the heatsink hole you gonna have more contact area to heat transference... this way you gonna have, as a result, better heat transference.

The small case you have into those chips (exception are the better ones, in my point of view, some models from Sanyo, STK4141, for instance, sounds good)... the small metal cases, the small metal block you have into the chip back side is too small to allow you to transfer a big ammount of heat and very fast... this will limit the power transference...the maximum heat transfered.

You see that when you have an amplifier, alike the LM3875, or LM3886....well.... someone that can produce 50 watts clean, it will be dissipating more than that in heat..... because efficiency of class AB amplifiers that are around 65 percent maximum...so....there's a lot of heat to transfer to the heatsink to allow the unit to work into 55 degrees celsius...and the internal chip will be much more hot, maybe reaching the metal melting point.... the metal fusion point because heat..the junction damage may happens...so...this limits the power..... you see those chips have the same power into 8 ohms and 4 ohms....why?...because limited internally to avoid heat and problems.... those units, because of the limits they have, cannot pump big power into dinamic transientes...the chip will "eat", will block the peak, the overcurrent, overvoltage, over temperature, all this will enter in action to huck your sound.

The small distance from input to output can peak signal, and because of that, internal circuit is hardly compensated to avoid this pickup.... hardly compensated circuits do not sounds very well into high frequencies....and this happens...the treble is a little bit...very little bit...harshing.

The result of that, it that even sounding EXCELENT, those amplifiers, into chip form, cannot win ANY good discrete design...because the dinamic headroom you may have into discrete units...because the protection they have..and because the small distance between input and output.

I have, almost all chip amps here...i have listened all them, and tested, and compared....they are good, or very good, or even excelent, they are simple to assemble, they are very pretty, they are very cheap, very convenient to build pretty amplifiers, nice to multichannel amplifiers because very small, also easy, small parts count....but, in my point of view...subjective...hundreds may think the opposite (in special the ones have bougth those chip amplifiers)...but it is my point of view.... cannot beat a GOOD discrete design.

Not my designs beat those chips...i am saying that ALL GOOD discrete design can do that..because the dimension limits, and protections the chip amplifiers use to have, those small ones, the small chip amplifiers have a lot of protections.. each one of them plays some ammount into the highest possible audio quality KILLING.

regards,

Carlos
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Old 26th March 2008, 04:34 PM   #667
udailey is offline udailey  United States
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Default Thanks Guys

I sincerely appreciate the quick and thorough reply from you both. Are PCB boards still available for HRII?
It seemed that you may have exhausted the group buy for HRII. IF that is the case do you think that more people would be interested in another group buy? I am in the states and would be happy to have a board house manufacture some.
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Old 26th March 2008, 07:49 PM   #668
udailey is offline udailey  United States
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http://www.4pcb.com/

I dont know what their fees are. But they are offering a $500 coupon for any new customer. I dont know what minimum quantities or minimum dollar value of initial order must be to qualify. Just figured I would mention it if it is necessary to get more boards and if you think enough people would be interested.

Sincerely
Uriah
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Old 26th March 2008, 08:52 PM   #669
Nordic is offline Nordic  South Africa
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Hi I still have a small supply and haveing more boards made is normally about a week or less as they allready have prepared screens at the factory.
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Old 26th March 2008, 09:23 PM   #670
paudux is offline paudux  New Zealand
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I would be interested in in a pair if you have some spare, how much and how do I pay?

Cheers Paul
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