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Old 10th May 2004, 05:39 PM   #1
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Default My Class D PWM amp project.

Just finished my first major DIY project, it's a Class D switching amp using the ZAP Pulse 2.2SE modules from LC Audio. OK, so I didn't really do anything more than screw and solder the various bits together but hey, it's my first project

Here are a few pics detailing some of the project (there's a parts and cost breakdown at the end of the post):

The main parts, together with the main part of the case:
Click the image to open in full size.

The rear panel of the case with all the necessary holes drilled and sawed into it. This was by far the toughest part of the project!
Click the image to open in full size.

The rear panel now populated with sockets etc:
Click the image to open in full size.

The PSU, transformer and input sockets and front panel power LED all wired up. Just needing to solder the connections to the actual modules themselves:
Click the image to open in full size.

Everything wired up and powered up for the first time - yay! :
Click the image to open in full size.

Closeup of one of the modules in action. If you're very observant you'll see I wired up the -ve and GND wires from the input the wrong way around (I switched them). I noticed that and fixed it before trying it out :
Click the image to open in full size.

Another view of the completed amp, including front panel with obligatory blue LED :
Click the image to open in full size.

Now sitting in my rack, and sounding very nice indeed:
Click the image to open in full size.

Parts and cost breakdown:
http://www.luacheia.com/misc_images/...ifierCosts.htm

The cost could have been significantly lower if I'd made my own PSU instead of going for the LC Audio one but for my first project I wanted something as "plug and play" as possible. I also ordered WAY too much cable from LC Audio. I actually used about 1/10th of what I ordered. The case from www.par-metal.com is very nice and surprisingly cheap.

It sounds very, VERY good. Far better than the Arcam A22 integrated I was using (in power amp mode) previously. Particularly noticable is the bass control, but then you'd kind of expect that with 230W per channel (into 8ohms, 460W into my 4ohm Dynaudios!). Probably needs a bit of running in but I'm already very impressed and pleased.

Any comments appreciated.

Michael.
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Old 10th May 2004, 07:09 PM   #2
pburke is offline pburke  Germany
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sweet looking setup.

I just noticed the price of the 100,000uF power supply you have was slashed in half at DIYCable.com because of the new 2-channel setup they are selling.

Since i want to build a 4-channel unit for bi-amping, I may just get one of these, since at $150 it actually is a pretty good deal, including soft start and having 100,000uF on the board. And since I would prefer to build 2-channels first and compare to my existing amps, I'll probably end up building two 2-channel setups like yours (or I'll have one 2-channel for use with future subwoofers if it fails the comparison test with my Odyssey mono extreme edition amps).

Which chassis did you get from par-metals? The RFI shielding version, or just plain aluminum? I'm still thinking of just building something on top of a fat aluminum plate with lots of cool acrylic and copper to enclose the modules - Peter Daniel gainclone style in a way.

Do some more listening and then let us know how it breaks in

Peter
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Old 10th May 2004, 07:11 PM   #3
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Nice job... but if I were you I should try to keep all cables with as small loop areas as possible, meaning twisted speaker wires or at least keep them closer together, the same thing with the input wires. Since this is a switched amp, this must be even more important than for a regular one. That's all, nice job.
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Old 10th May 2004, 07:24 PM   #4
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Isn't that a CHORD below the TEAC there? How does it sound?

Chris
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Old 10th May 2004, 07:24 PM   #5
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Thanks guys .

Another reason I got the V4P PSU was because I might add a 3rd channel later to power the centre channel of my AV setup but tbh the thought of dismantling it all to drill the necessary holes doesn't fill me with warm thoughts

I got this case from Par-Metal. 16x16x4 inches, anodized front plate, grey painted rest. It's just standard aluminium.

peranders - you're not the first person to suggest I should twist the input wires. I'll definitely give that a try but there's no evidence of any RFI problems so far. As for the speaker wires, I'll try twisting them too but I wanted to avoid having the speaker wires running close to the input wires if possible.

Michael.
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Old 10th May 2004, 07:32 PM   #6
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Quote:
Originally posted by chris ma
Isn't that a CHORD below the TEAC there? How does it sound?
Yep - Chord DAC64. I just love the sound of it. It's the only digital source I've heard that really brings music to life. It's fast, detailed and just incredibly musical. I wouldn't change it for anything

The Teac is a T1 transport which has been modified: it has the Clock 4 clock upgrade from Trichord Research with it's own PSU which is also from Trichord Research - it's one of their new "Never Connected" PSUs. Other than that, the captive power lead has been replaced with an IEC socket and some of the internal power cabling has been changed. Also, the case has had Dynamat damping material liberally applied.

The pre-amp is a Bent Audio NOH transformer based passive pre.

Michael.
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Old 11th May 2004, 11:23 PM   #7
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Been listening to it for a while now and here are some more thoughts on the sound:

- incredibly fast and detailed, and I think this adds to the sense of transparency.
- extremely well controlled bass and excellent extention too. Absolutely no "bloat" or overhang.
- really fluid mid-range, I've only heard the same kind of fluidity in Class A and valve amps
- pin sharp and detailed treble but without any harshness or edginess.

I had the case open again to change the resistor infront of the front panel LED for a more meaty one as the existing one was pretty much burning up . At the same time I took the chance to twist the input wires and also to earth the casing (and hence have a hard rather than "floating" ground). None of this had any noticable effect on the sound though

Michael.
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Old 12th May 2004, 12:49 AM   #8
pburke is offline pburke  Germany
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you're making me yealous - I'm still saving for the parts

Sounds a lot like the reviews i have heard of other zappulse based amps (www.solar-hifi.com - see audioasylum amp forum for a review a few months ago)

did you ever check into their active filter? one thing I am missing on the web site is info on what kind of power supply I would need to run that crossover.

Peter
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Old 12th May 2004, 08:39 AM   #9
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Hi,

How is the temperature around the zappulse modules, I notice you don't use any specific cooling....just the bottom plate?

I also see you use both XLR and Cinch input parallel wired , do you hear any difference when you hook them both up at the same time?

are the speaker terminals WBT? I don't see them in your cost overview


I've build an amp using the same modules but a higher voltage and lower spec'd power supply:

500 VA / 2*50VAC transformer and this power supply module:

http://www.bmm-shop.nl/Product.asp?Product_ID=1170

Probably because of the power supply specs the results are a bit dissapointing, I don't think the suplly has the current capacity as mentioned on this website.
I compared the amp with 2 rotel RB980BX and with one Krell KSA 80B and in both cases but of specifically in comparision with the krell the Zap had sharp treble and lacking bass pressure. Also at louder levels the zap started clipping sooner than the Rotel.

I will rebuild it soon as 2 monoblocks with probably lower voltage and overdimensioned (1000VA / 132mF ) power supply. But I'm a bit more cautious as I don't want to make the same mistake but also don't want to spend more money than nessecary.
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Old 12th May 2004, 08:52 AM   #10
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I think that is a mistake that is often made: Implementing weak PSUs for switching amplifiers.

Some PA guys I know complained about bad bass reproduction of switching amps, though I experienced the contrary. I therefore think that also manufacturers sometimes take too weak PSUs for switching amps in order to save weight and money. Even a generously dimensioned PSU for a class-d amp would still give weight and cost savings, one should just not be too scrimpy.
Regards

Charles
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