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jtwrace is working on some custom enclousures which are going to be available at reasonable price to anyone interested in dressing up there class D-amp. Those interested can contact Jason ( jtwrace) for more info. P.SLooking forward to some pictures Jason ...... ones they are finished. CheersMariusz
To use who are currently using these units, how is the bass performance? Tom told me the damping factor was around 120 which seemed surprisingly low....
Michael Percy Audio sells the Vishay diodes and IXYs diodes, which are the ones I recommend. They are the fastest diodes on the market by far. The diodes need to be at least 2x the voltage of the TX. If you are using larger caps you should make it 4x to be safe. The problem is, that as the voltage gets higher the diode isn't as fast. So it's important to get a voltage rating that is just high enough, but not too high. The big thing with the diodes... and the caps for that matter... is what will fit on the board. You can always build a new PSU board, but it will be substantially easier to just replace the caps and bridge that are already there.
Is there a particular bridge rectifier you recommend, since digikey and I are so tight...
Hm, what about one of the supplies listed on this page:
yes it is 120
but I read the info from IR and the damping is 2000 before demodulator and at the class d output it is 120. I see other companies put there damping factor at 1000 and 2000. so it makes me wonder if they are using the factor before the demodulator too have the DF look better. I wonder..
They look nice, and the pricing is good. I wonder about the separate fusing (on some models) . . . that invites a single-rail failure which might not be good for the amp boards.
are you going w/ 15k each, for a total of 90k? or just 2 ( you mentioned 30k).
@Paul (pjchappy),The first 3 links that you posted all are the same classd boards which are 250 x 2 @ 4ohms. The first link has two boards and that is the reason you are getting the 1000W (250wpc with 4 channels). The 4th link is the 250wpc x 8ohm board. If you plan to go that route please make sure that you get the extra heat sink (the ones that Steve got for his 4ohm speakers and ones that were compared to wyred for sound), in case your plan to run 4ohm speakers with those boards. I would also check with Tom to be sure about the 4th link and your speaker requirement 4 v/s 8 ohms.
I totally understand that. As I mentioned in the paragraph discussing the 4th link, the upgraded heatsink is now standard, and therefore safe into 4 Ohms. (That info is straight from Tom)Anwyays, I decided not to use the kit I have in 4 channel mode and that is why I now have this "dilemma." (Which I added to the previous post for clarity)Paul
For my future speakers, I plan on going active and will need 4 channels of amplification. . .and I decided the kit I have, which can be used in a 4 channel "mode," just won't cut it. I don't feel like writing out all the different options I thought of regarding configurations of the Class D amps, so I will just post my current dilemma/options:
I have it narrowed down to a couple different speakers. The bass sections are known to be power hungry / like a lot of power.
The first experiment will be with 30k per rail (two pair of 15k, 60k total on board) and to use the third position for bypass and snubber parts. If that works well enough I'll clone it for the other amps, box 'em up and move on to serious listening. Apart from input coupling and power supply I haven't identified anything else that I want to change . . . yet . . . . . .
You may be spinning your wheels a bit worrying about power that you really don’t need. While the “1000 Watt” kit may be a little overhyped, especially considering the power supply, 4 channels at 125 Watts each into 8 Ohms is still a lot of power, and if you end up getting/building speakers with 4 Ohm drivers there is even more power available (though you’ll probably need to do some power supply improvement). Are the woofers in the speakers you are considering 8 Ohm or 4 Ohm? What’s their rated SPL at 1 Watt?Start by evaluating the actual power requirement of the speakers, and since you’re going to bi-amp consider the individual drivers in them. The IR amps *actually deliver* the rated power . . . there is no need to overbuy to get “headroom” (which is the word used to justify money spent for power never used). Look upthread for my post about the power actually needed for a Seas W22EX. My tri-amped speakers are spec’ed 120 Watts/side for the woofers, 60/side for the mids, and 60/side for the tweeters. It is specifically advised *not* to use amps larger than that, as they might damage the drivers. If things work out I’ll be powering the woofers and mids with two 120x2 boards (and two power supply boards, on one transformer). I didn’t buy the 250x2 boards because that’s *more* power than I need . . . .As for heat sinks . . . it’s better move a little air across a small heat sink than to put a big heat sink in a closed box. These things are in fact quite efficient . . . they don’t generate anywhere near as much heat as a Class AB amp delivering the same power. Even at painful listening levels they generate less heat than the typical laptop computer. They don’t need 20 lbs of Aluminum in a wind tunnel heat sink. That’s for the Class A guys . . . or pro sound at the coliseum.
So, I've been lurking on this thread for about a week, read the entire thing with great interest. I'm somewhat close to pulling the trigger on 2, 120w x 2, 240w x 1 to run as mono blocks (with upgraded power supplies).There's a point that several people have touched on, that I want to explore a little further. Several people have mentioned to keep signal leads as short as possible in order to reject as much RFI as possible, correct?My question is, does anyone think there would be any advantage in shielding the case with copper (or some other material) to reject RFI? They touch on it here - audioheritage.org/vbulletin/archive/index.php/t-14551.html.I've read that NUFORCE is 'notorious' for RFI issues. So, it would seem to me, that even if the RFI isn't audible as such, it would still have a harmful affect on the quality of the sound. It may even account for the 'wrongness' some people hear in the upper frequencies.
