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Old 18th December 2013, 01:46 PM   #11
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Yes, this is it.

Btw, I have compared price for Elektor kit Q-watt combi (110656-72, $244 regular, $219 for member) with set of parts from digikey (with exception of T4,T5 transistors which are available from Allied) I meticulously put together on vendor website and it turned to be $252 including PCB from Elektor but still does not include all small mechanical parts related to heatsink mount of components (screws, washers, thermal pads and paste not included). So at this point I ordered kit with parts from Elektor, as shipping within US ($5 for Ground) is also cheaper for some reason comparing for bare PCB shipping which are freighted from overseas for $20.

Then comes a set of "big" parts not included in the kit, namely: power supply bridge rectifier, bus caps, transformer, heatsink and enclosure. I found 500VA 2x40V toroid on amazon marketplace for $87 ea. plus $19 shipping for two pieces altogether, not bad considering the package weight (19lbs/9kg). The exact Fisher heatsink can be ordered from newark for $34 ea. plus $20 shipping for 2 pcs. As for the bus caps, I found on digikey 10mF/100V model with lowerst impedance of 7mohm which will ensure best dynamic performance free of compression at highest output levels, these are expensive around $36 ea. For stereo amplifier, you are going to need 8 of those so it is probably the highest expense. Bridge rectifier is just $7 ea so it wont break the budget.

Finally the enclosure, I still have not decided yet but I am looking over diyaudio store for one of those full size 12 or 15cm height available for preorder, alternatively there is some selection of these on siliconray website. Will decide after I get all the parts.

So here is a complete amplifier cost breakdown, for those who are interested:

$244 ($5 s/h) for Q-watt combi (110656-72) stereo kit from Elektor
$87 x 2 ($19 s/h) for 500VA 2x40V toroid transformer, 2 pcs
$7 x 2 ($5 s/h) for bridge rectifier, 2 pcs
$37 x 8 ($25 s/h) for 10,000uF/100V bus caps B41560A9109M, 8 pcs
$33 x 2 ($20 s/h) for Fisher heatsink
----- Total: $863 (including s/h)

and that does not include enclosure which may vary but just for the sake of example picking nice one 4U size in Deluxe finish from the website store for around $350 (including s/h), the total comes to little over $1,200.

If this amp will truly perform as advertised, this might be a bang for the buck considering prices for 300W per channel (@4ohm) off the shelf designs.
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Old 19th December 2013, 05:14 AM   #12
mabell is offline mabell  China
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Default Art-Tech

No Spice models. From what I see, cost/performance is a bit better than OnSemi.One critisism that I have with this Elektor project, is it is only a pcb or assembly, leaves the readers to figure out all the rest, PS,chassis.At least DIYAudio forum, have got it figured out, offering sources for cases/HS/PS's assemblies, etc.
Art-Tech
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Old 19th December 2013, 06:11 PM   #13
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The Elektor article contains all required information about the parts recommended for power supply suitable for this amplifier. As for power supply topology, I am sure folks who know how to use Spice models can figure this out, for those who do not, here is initial diagram of power supply I am planning to use in my build.
Click the image to open in full size.
The 120/240 voltage selector switch S101 is optional and shown here for the purpose of hard-wiring power supply for either of the voltages. The initial value for the F101 fuse is 6.3A (for 240VAC) or 11A (for 110VAC) slow blow for both voltages. The exact current rating for this fuse will be determined later. The main reason for it is that with such high capacitance of bus capacitor bank, I expect high inrush current when amplifier is turned on. If selected transformer impedance will turn to be very low, I might need to use inrush current limiter which will be designed after the need is determined.

As for enclosure, I have initially selected Deluxe 4U amplifier chassis available from diyaudio store. However, before I spend $300 I need to make sure, all main components of this amplifier will fit inside the enclosure. From store website I found the internal enclosure real estate is limited to 360 width by 300mm depth. This should allow me to install amp guts in few different configurations - some shown below. Only one most optimal configuration will be chosen to provide best supply performance with minimum interconnection length as well as interference from adjacent modules and parts. I have not marked connections yet, neither decided about front and back of the amp in each configuration. This will be determined next.

Two configurations with amplifier board positioned horizontally:

Click the image to open in full size.

Click the image to open in full size.

and three configurations with amplifier board positioned vertically:

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

and additional check for space on the enclosure heatsink to fit amplifier PCB in arrangements C, D and E:

Click the image to open in full size.

Note: all drawings based on internal dimensions of Deluxe 4U enclosure and its heatsinks. I have abandoned idea to use Fisher heatsinks as diyaudio the enclosure has these already.

Seems like Deluxe 4U chassis can be a good choice.
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Old 19th December 2013, 06:53 PM   #14
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Forgot to mention, the shown power supply except S101 and F101 is just for one channel amp. For stereo configuration we need two of these, hence two transformers and 8 large caps shown on preliminary chassis layout drawings. The fuse rating I mentioned is for two supplies in parallel fed through one fuse of course.
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Old 19th December 2013, 08:07 PM   #15
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Below updated power supply schematic for two Q-Watt amps (stereo).
Click the image to open in full size.
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Old 27th January 2014, 01:02 AM   #16
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Finally after 5 wks of waiting, the Q-Watt combo kit has been delivered. I already have all other accessories including: power supply part, awesome large VU meters, speaker biding posts, RCA and headphone jack sockets, even golden knobs and chassis feet jacks except chassis itself which design is being wrapped up as we speak and soon be sent to shop for custom machining.

I am planning to hold final design of the power supply, specifically the large capacitor bank carrying board until chassis is made and delivered. This is to make sure all components and assemblies fit where they supposed to.

Click the image to open in full size.

More coming soon.

Last edited by eskwadrat; 27th January 2014 at 01:11 AM.
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Old 27th January 2014, 03:20 PM   #17
rsavas is offline rsavas  Canada
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Quote:
$87 x 2 ($19 s/h) for 500VA 2x40V toroid transformer, 2 pcs
$37 x 8 ($25 s/h) for 10,000uF/100V bus caps B41560A9109M, 8 pcs
That is a significant turn-on surge current, could blow a breaker in your distribution panel.
I suggest a soft-start ckt, to limit the inrush I
A few references for you:
1) Pioneer high power amps such as Spec-4, SX-1250 or SX-1050 and others( You can get SM from www.hifiengine.com)
2) TI/National app note, AN1849-An Audio Amplifier Power Supply Design
3) This forum has Soft start ckts for sale as well

Good luck
Rick
Attached Files
File Type: pdf Power-Entry&soft-start.pdf (26.9 KB, 71 views)
File Type: pdf POWERENTRYASSY-A0-27-top-assy.pdf (37.5 KB, 53 views)
File Type: txt powerentryassy-a0-bom.txt (1.4 KB, 32 views)

Last edited by rsavas; 27th January 2014 at 03:26 PM.
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Old 27th January 2014, 04:16 PM   #18
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Thanks for good suggestion Rick. Indeed inrush current can trip the breaker, that is why I include inrush limiting circuit as I mentioned btw on my initial post. I happen to design SPS circuits from time to time for living and I have couple of soft start solutions here so implementing one of these in Q-Watt amp should not be a problem. Again, I appreciate the comment and accompanying materials which are always very helpful. Will keep you posted and appreciate your input.
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Old 27th January 2014, 05:19 PM   #19
rsavas is offline rsavas  Canada
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Quote:
that is why I include inrush limiting circuit as I mentioned btw on my initial post.
oop's!!
Quote:
SPS?
switching power supplies? SMPS, so you're good at designing transformers. I worked for a lighting ballast mfg of late, lots of bobbins/cores and a good LCR meter. :-)
Thx, keep me posted on your project

Cheers
Rick
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Old 14th June 2014, 02:35 AM   #20
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I finally received long waiting enclosure. It looks like $million$ dollars, champagne aluminum front with professionally printed labels and plexiglass window w/artwork for UV meters, looks like hi-end gear from top audio manufacturer. I will be doing final assembly for few weeks now, lot's of fastening prep and work as this is 1st amp of its kind and not everything was designed in Solidworks. Once completed, I will post some pictures. For now just a teaser of what's comin'

Click the image to open in full size.
~Patience is the key ~

Last edited by eskwadrat; 14th June 2014 at 02:44 AM.
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