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Old 22nd December 2016, 06:14 PM   #1
delange is offline delange  Belgium
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Default My Q-Watt project

EDIT: don't know what happened but I somehow created a double posting.

Last edited by delange; 22nd December 2016 at 06:45 PM.
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Old 22nd December 2016, 06:42 PM   #2
delange is offline delange  Belgium
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The Q-Watt amplifier from Elector caught my attention a long time ago. The project caught my attention due to its simplicity but yet interesting specifications. I finally bought the two kits a few months ago and I started building it this week.

Since I couldn’t find many posts about this amplifier I decided to post the progress of my project here. My project consists of two mono block amplifiers who will be placed right behind the speakers. The idea is to make them as invisible as possible. The project has been growing inside my head since a couple of months (and some parts are still growing). The enclosure was one of the points of attention. I couldn’t find anything on the marked so I decided to design and build the enclosure myself.

The first thing I did was to solder a 1.5mm2 wire across the pcb traces who need to carry a lot of power. I’m a bit skeptic about thickness of those traces… So this is what I did:

<see image 1>
<see image 2>

I left the electronics part rest for a while and started with some of the mechanical build of the enclosure. The back plane consists of an aluminum L profile of 50 x 20 x 2. It has the same with as the SK85 heat sink I’ll be using (160 mm). The back plane holds all the in- and outputs: mains, level adjust, input and speaker output connectors. I made the “front panel” myself and printed it on a label. After applying the label to the back plane I used a clear adhesive foil on top of the label. This must protect the label.

<see image 3>

The base plate is attached to the back plane by four screws. I used an aluminum plate of 160 x 150 x 2 mm. This will be the footprint of the enclosure.

<see image 4>

I’ll be using a SMPS for this project. Initially I planned on using a traditional transformer but the size and weight made me change my mind. I ended up buying two SMPS500R power supplies with 2 x 55 volts. These are 500 watts power supplies and they get very good reviews. The SMPS’s are smaller, lighter, cheaper and should provide better performance than a traditional transformer based power supply. I’m curious about how they will perform. The SMPS’s will be mounted inside the enclosure by this mount:

<see image 5>

The back side of the enclosure is largely made up of the heat sink. The amplifier PCB will be fixed flat against the heat sink in order to save space. There are two aluminum L profiles of 10 x 10 x 2 to fix the heat sink to the back plane. The PCB will be screwed on 4 metal standoffs of 10 mm:

<see image 6>

The mechanic construction is progressing well. Here is how the power supply is fitted in the enclosure:

<see image 7>

Before fixing the heat sing to the back plane I’ll be installing the amplifier’s PCB and transistors. Next on the ‘to do’ list is to populate the PCB, do the adjustments and finally install the heat sink to the back plane. I’ll probably do that tomorrow. To be continued…
Attached Images
File Type: jpg 20160906_Q-Watt_0001.jpg (626.2 KB, 1295 views)
File Type: jpg 20160906_Q-Watt_0002.jpg (563.2 KB, 1220 views)
File Type: jpg DSC_0044.jpg (204.8 KB, 1171 views)
File Type: jpg DSC_0046.jpg (194.8 KB, 1161 views)
File Type: jpg DSC_0048.jpg (175.8 KB, 1161 views)
File Type: jpg DSC_0053.jpg (218.5 KB, 492 views)
File Type: jpg DSC_0057.jpg (234.5 KB, 506 views)
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Old 23rd December 2016, 08:10 AM   #3
AndrewT is offline AndrewT  Scotland
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Could you attach a hand drawn schematic of what you have built?
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Old 23rd December 2016, 10:07 AM   #4
delange is offline delange  Belgium
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Quote:
Originally Posted by AndrewT View Post
Could you attach a hand drawn schematic of what you have built?
Andrew, I'm building the Q-Watt amplifier from Elektor.
Follow the above link if you want schematics, PCB files, documentation and so on. (You might need to create an account on the Elektor website to be able to download anything).
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Old 23rd December 2016, 11:11 AM   #5
AndrewT is offline AndrewT  Scotland
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It would be much more convenient for us Members to see everything here on the Forum.
What about attaching details here?
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Old 23rd December 2016, 11:44 AM   #6
delange is offline delange  Belgium
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Join Date: Jan 2012
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Quote:
Originally Posted by AndrewT View Post
It would be much more convenient for us Members to see everything here on the Forum.
What about attaching details here?
I attached the schematics and the PCB files.
Since I used a different heat sink (SK85), I have also attached my own drilling template.
Attached Files
File Type: pdf Q-watt.pdf (499.1 KB, 484 views)
File Type: zip 110656-1.zip (68.0 KB, 106 views)
File Type: pdf Heatsink template SK85.pdf (4.3 KB, 73 views)
File Type: pdf SMPS500R.pdf (651.7 KB, 127 views)
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Old 23rd December 2016, 04:38 PM   #7
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Hi delange!

I followed you from the Q-Watt forum. I'm using a bog-standard 3U 300mm deep case from hifi2000. Ordered today :-D

I see you are using a beefy speaker output connector. Is that a Speakon? Can anybody advise on output connector options for 200W system? Is there anything wrong with binding posts?
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Old 23rd December 2016, 05:07 PM   #8
delange is offline delange  Belgium
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Join Date: Jan 2012
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Quote:
Originally Posted by popchops View Post
Hi delange!

I followed you from the Q-Watt forum. I'm using a bog-standard 3U 300mm deep case from hifi2000. Ordered today :-D
Hi there, looking forward seeing your project!

Quote:
Originally Posted by popchops View Post
I see you are using a beefy speaker output connector. Is that a Speakon? Can anybody advise on output connector options for 200W system? Is there anything wrong with binding posts?
That is indeed a speakon.
Binding posts are okay but there more prone to short cutting your amp.
I like speakon because it can handle huge currents and it is a compact housing.
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Old 24th December 2016, 12:15 AM   #9
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Hello,
I also follow your project through the Q-watt forum, and an already at an advanced stage to build it.
But I have a question concerning the power supply. on connector K7 you'll need 2 times 40V AC, from where you'll apply that?
As somebody mention on the same forum I'll apply klixons on the heatsink to switch of the mains at 75 degree celsius.
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Old 24th December 2016, 10:24 AM   #10
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Hi guys.

I cannot believe the main heatsinks (300x120x40mm in my case) will ever get to 75 deg C. At 0.5 deg/W that's about 90W waste heat!

I like the idea of Speakon connectors but I also need some way to connect my high-impedance active sub to both left and right channels. At present on my old Rotel amp, I have wound these 4 wires (left signal+ground, right signal+ground) around the speaker binding posts on the amp. The sub side of this cable has a 4-way Speakon interface.

If I switch to Speakons out of my new amp then I need another (third) speaker output (4-way) for the sub. Has anybody done this? Am I barking up the wrong tree?
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