[matt_garman]

Actually, your next little project should be the elimination of the two pots, in favor of two 1% resistors. You might see what your QSC is. If the standard for the QSC is 27DB, then if memory serves me right a 1.2? resistor for each channel should make a difference. Several pages back there is a chart with the correct resistor ratings to use. The pots Tom uses are cheap, and replacing them fixed with resistors will have a dusk and night result, that you might be able to hear. Just a suggestion or two.

If you put/mounted  those pots in your case, a search on the net you can find caps to cover the holes they made.

Yup, I've been planning to use fixed resistors in place of the pots all along.  I just wanted to use the pots initially to experiment/dial in the right amount of gain.  (Before I bought the kit, I read through this entire thread, taking notes.  One of the things I noted was the gain versus resistance table you mentioned. )

Also, for anyone who's interested, I asked Tom for a switch mode power supply (SMPS) suggestion for the SDS-470.  He replied with this link: ConnexElectronic SMPS800R.  He said, "Make sure the voltage is +/- 65 to 68 volts."

[matt_garman]

Also: is Front Panel Express (FPE) the only option for obtaining a professionally-machined custom enclosure?  I don't have the skill (or the patience) to make a nice custom case.  What I'd like is a powder-coated matte black steel case, complete with vent holes.  On the front, I'd like to have to big rocker switches (mains power and amp on/off) and LED cutouts.  On the back, IEC, fuse holder, XLR and binding posts.  Just wondering if FPE is the only game in town.

[toxteth ogrady]

I built another SDS-258 a couple of months ago and utilized a Par Metal desktop case I had on hand. I had it powder coated in satin black. For the front panel I used 1/4" black laser cut acrylic with very subtle rounded corners. Total cost including the enclosure was $110. It looks the business and I'm very satisfied with how it turned out. That said, it was a pain in the butt to drill and cut the openings in the rear panel. If I had to do it again I would order one of the cases from mudushop or vt4c. Much less muss and fuss.

[justinm]

I have a few questions for some of the experts out there. I just got my SDS470 a couple weeks a go and want to use it with my SDS254. I plan on putting them both in the same case. I also would like like to separate the transformers and maybe power supplies in a separate case below all hooked up with 2 neutrik powercon connectors. My questions are about cable length. 1st witch wire run should be shorter for best sound, power supply to amp board or transformer to power supply? 2nd would it be better to keep the transformers in there own case away from the other boards? 3rd which wire run should be shorter speaker binding posts or rca's? 4th does transformer and power supply need any type of ventilation like vent holes. Thanks for any suggestions you can make.     

[I.Greyhound Fan]

Also: is Front Panel Express (FPE) the only option for obtaining a professionally-machined custom enclosure?  I don't have the skill (or the patience) to make a nice custom case.  What I'd like is a powder-coated matte black steel case, complete with vent holes.  On the front, I'd like to have to big rocker switches (mains power and amp on/off) and LED cutouts.  On the back, IEC, fuse holder, XLR and binding posts.  Just wondering if FPE is the only game in town.

Matt, Par Metal will punch all the cut outs for you.  I'm not sure about the cost but the cases will be cheaper and come already vented.  I am going to order one this week.  12x12x5

http://www.par-metal.com/product-ttp-20series.php

[matt_garman]

Here are a couple pics I promised:

[Feanor]

Here are a couple pics I promised:


...

That looks great; congrats.

So is that the SDS-470? Pardon but I'm a bit out of touch on this thread, (now so long!), but I'm confused about what a 470 actually consists of.  From the picture, it strongly resembles an SDS-258, (like I have), with a larger heat sink. Is that appendage under the module also more heat sink or something else? Looks like a standard High Duty power supply; does it ushigherer voltage and/or higher powetransformerer?

(With due respect to Tom, the website does leave something to be desired in terms of technical info -- I'd suggest that he would spare him spare himself quite a few repetitive questions if he put a little more info on the site.)

This is a pic of my SDS-258 in home-made, MDF case -- with benefit of hindsight I wish I'd gone for a Par-Metal.  Note that I've made use of the Status LEDs and the Stand-by switch.

[matt_garman]

That looks great; congrats.

Thanks!

So is that the SDS-470? Pardon but I'm a bit out of touch on this thread, (now so long!), but I'm confused about what a 470 actually consists of.  From the picture, it strongly resembles an SDS-258, (like I have), with a larger heat sink. Is that appendage under the module also more heat sink or something else? Looks like a standard High Duty power supply; does it ushigherer voltage and/or higher powetransformerer?

Yes, that is the SDS-470.  Currently it's set up to run in stereo mode, which is advertised at 600 Watts/Channel at 4 Ohms.  (I'm toying with the idea of building a second, and running both bridged---i.e., monoblocks.  Supposed to do 800 Watts at 4 Ohms bridged.)

It's the only Class D Audio board I've worked with, but I'm pretty sure it's virtually the same as the SDS-258, except with the added heatsink (and electrical differences of course).  Yes, the appendage on the underside is additional heatsink.  There are actually two additional, one on each side.  (If you go back to page 140, I posted a stock photo of the 470 that Tom sent me.  There you can see the added heatsinks a little more clearly.)

I forget exactly what model xformer I got (at work now, can't check).

(With due respect to Tom, the website does leave something to be desired in terms of technical info -- I'd suggest that he would spare him spare himself quite a few repetitive questions if he put a little more info on the site.)

Hate to say it, but I agree.  This comment seems to be a fairly common theme throughout this thread.

[Feanor]

...
Yes, that is the SDS-470.  Currently it's set up to run in stereo mode, which is advertised at 600 Watts/Channel at 4 Ohms.  (I'm toying with the idea of building a second, and running both bridged---i.e., monoblocks.  Supposed to do 800 Watts at 4 Ohms bridged.)

It's the only Class D Audio board I've worked with, but I'm pretty sure it's virtually the same as the SDS-258, except with the added heatsink (and electrical differences of course).  Yes, the appendage on the underside is additional heatsink.  There are actually two additional, one on each side.  (If you go back to page 140, I posted a stock photo of the 470 that Tom sent me.  There you can see the added heatsinks a little more clearly.)

I forget exactly what model xformer I got (at work now, can't check).
...

Thanks for the info.  The SDS-470 shows six transistors rather than the four on the 258, plus the much larger heat sink.

If you get around to it, I'd like to know if transformer is the same as for the 258 or if it's higher output (which would make sense).  As I recall, my 258 gets +/- 64 VDC from the power supply which implies a 45 volt transformer (as I understand).

[Æ]

As I recall, my 258 gets +/- 64 VDC from the power supply which implies a 45 volt transformer (as I understand).

I'm following this thread with interest, and I may be off with regards to my understanding about this class of amps. But if you were using a linear supply and trying to get +/- 64 VDC, it seems to me that you would need slightly more than 45 volts. I'm thinking something more like a 90V center tapped secondary. 2 x 45V. And maybe even just a bit more than that if you figure in losses and voltage drops.

[srb]

But if you were using a linear supply and trying to get +/- 64 VDC, it seems to me that you would need slightly more than 45 volts. I'm thinking something more like a 90V center tapped secondary. 2 x 45V. And maybe even just a bit more than that if you figure in losses and voltage drops.

The linear power supplies for these amps use a toroidal transformer with dual secondaries (not center tapped), and when someone like Antek calls it a "45V transformer", dual secondaries are usually implied.
 
The voltage range for the SDS-258 is +/- 60VDC to +/- 70VDC.  I like to have a little safety margin, so 64VDC is right in the middle of the range (with a 45VAC X2 transformer)
 
Using Antek as an example, the next higher voltage transformer is 48V which would give an ~ 68VDC rectified output, but is only available in 800VA and 1000VA.  The next available voltage, 50V, would give an ~ 71VDC rectified output.
 
As far as voltage drops and losses, I don't know if they would be more than a volt or so.  Anyone measured their final DC output with a multimeter?
 
Steve

[Æ]

The linear power supplies for these amps use a toroidal transformer with dual secondaries (not center tapped), and when someone like Antek calls it a "45V transformer", dual secondaries are usually implied.
 
The voltage range for the SDS-258 is +/- 60VDC to +/- 70VDC.  I like to have a little safety margin, so 64VDC is right in the middle of the range (with a 45VAC X2 transformer)
 
Using Antek as an example, the next higher voltage transformer is 48V which would give an ~ 68VDC rectified output, but is only available in 800VA and 1000VA.  The next available voltage, 50V, would give an ~ 71VDC rectified output.
 
As far as voltage drops and losses, I don't know if they would be more than a volt or so.  Anyone measured their final DC output with a multimeter?
 
Steve

Thanks for explaining it to me.

You do get a small voltage drop from the rectifier(s). High speed rectifiers have less of a forward voltage drop, which is a good reason to use them. Your final filtered voltage will also drop depending upon the load.

If the transformer has dual identical secondaries and you tie them together in series, you can use the tie point as a center tap. The transformers in the pic I took (above) have four wires (dual) secondaries, which became a center tap when tied together.

[MX48]

My first classd amp kit should be here this week. I got the CDA-1000 kit with an extra CDA-254 board and larger transformer to power all 3 boards for my active 3-way speakers.
I have a couple questions:

1) This is a budget build so I will be using leftover MDF to mount them on. I tried to search for "Ground" but the search doesn't work to well here. What is the proper grounding procedure?
2) I will be plugging this into a smart strip. The power to the power strip comes on with the receiver. I am assuming I don't need to put in a switch since the strip will be turning it on and off. No power goes to the strip when the receiver is off.
Is that OK?

Sorry for the nube questions, this is my first amp build.
Also thanks to everyone here, without this thread I really wouldn't know much about classDaudio.

Thanks
Moto

[matt_garman]

2) I will be plugging this into a smart strip. The power to the power strip comes on with the receiver. I am assuming I don't need to put in a switch since the strip will be turning it on and off. No power goes to the strip when the receiver is off.
Is that OK?

I asked Tom (of Class D Audio) about this, and he gave it the OK.  I'm doing exactly this: I leave the switch on the SDS board to the "on" position, and didn't install any kind of mains switch.  I've only been using my build for a couple weeks, but it gets turned on and off at least once/day, and no problems so far!

I love the smart strip as a poor man's trigger.  Before the Class D Audio amp, I was using a QSC "pro" power amp with no trigger.  I used it for many months with the smart strip and had zero issues.

[MX48]

Thanks Matt.

I may ground mine as was done on page 90. But apparently it isn't necessary as best as I can figure.

Moto

[krikor]

Shot of the SDS-450 amp board.

[StevenZ]

Guys, a friend of mine said it was a horrible idea for me to build the amplifier in a wooden box and that it's most likely spraying RF frequencies into all of my other equipment.  Can anyone confirm this?  I'd hate to rebuild the enclosure.  In all honesty I haven't noticed any shortcomings so perhaps he is incorrect.

[Nick77]

     In all honesty I haven't noticed any shortcomings so perhaps he is incorrect.                                   

That makes two of us........

[roymail]

The OP, Steve K, built his into a wood enclosure which you can see on the first page of this thread and elsewhere.  Very nice job I might add.  Many others have done the same with no issues I'm aware of. 

[I.Greyhound Fan]

Guys, a friend of mine said it was a horrible idea for me to build the amplifier in a wooden box and that it's most likely spraying RF frequencies into all of my other equipment.  Can anyone confirm this?  I'd hate to rebuild the enclosure.  In all honesty I haven't noticed any shortcomings so perhaps he is incorrect.

I recently bought a CDA-254 in a wooden box and I cannot use my tuner with it due to the RFI.  I am placing it in a Par Metal chassi which should take care of the problem.  If not, then I will need to buy some 3M copper shielding tape and line the chassi.