[matt_garman]

I am about to order a Par Metal Case and I have a couple of questions about it. 
Will the 16x12x4" case have enough height to fit the 400VA power transformer or will I need to go with a 5" tall case?

I have exactly that case (16x12x4), and my SDS-470 kit fits perfectly with room to spare.  In fact, on mine, the height from case bottom to top of the transformer nut is 3"; so you might be able to get away with a 3" tall case.

Also, according to my measurements, you might be able to get away with a 12x12 case... it looks doable with the SDS-470 (which is slightly bigger than other amp boards due to additional heatsink), so probably even easier with an CDA-254.

[firedog]

Added a Grant (Chinese) tube buffer between my SS pre and my SDS-470. Thought it would be an interesting experiment. Uses standard Shuguang 6SN7 J tubes.

In general, I like the results. The soundstage is definitely larger - especially wider. Most recordings have a more up front "live" feel.

On rock music from the 60's and 70's it sounds especially good. I was grinning last night listening to the Beatles remasters, both in mono and 24 bit stereo. I think the tubes make the music sound a bit more like LP's, and I think my brain has neurons that think this is how music like this is "supposed to sound". Mp3's definitely sound better run through the buffer. I assume that if I shelled out the cash for some really good 6SN7's it would sound even better.

On quality modern recordings I don't think it adds much. Even on a remastered old recording like the the hi-res Band on the Run (a very good sounding release) it didn't seem to make any great difference. I think it softens the sound slightly, which is a plus on many recordings - especially older ones with mediocre transfer to digital - but not a real plus if the recording is already a very good one.

Anyway, this is my first venture into tubes since I was a kid. It has me seriously thinking about a tube pre, a tube hybrid, or something like the new Peachtree Grand Pre, which has a tube buffer that can be engaged or disengaged as needed.

[praedet]

There is only ONE tube based item you should think about adding, and that is a Dodd Battery powered buffer, either DIY or Assembled. 

Nothing touches it for less then $5-10K...

[firedog]

Yeah, I've thought about the Dodd Buffer. But I'm not sure it fits my needs for a few reasons. One of them is that I'd like to reduce the number of boxes in my system. Presently I have built up through piecemeal experiments and upgrading:

1. Music Server
2. Empirical Audio Pace Car
3 SB Touch (clocks slaved to Pace Car)
4 DAC
5 Preamp (actually SS integrated being used as a pre)
6 Tube Buffer
7 Power Amp-SDS
8 Speakers

This is unwieldy and uses a forest of cabling and power cords. I also listen in a small room and it takes up a good chunk of space.

So I guess the Dodd could combine the functions of my present pre and buffer. I'm a little hesitant about having a system with only an attenuator and not a gain/volume control. Maybe that makes no sense, but I've just never had such a setup before. I'm sure if I asked, Gary would build me a hybrid Class D amp, possibly even battery powered.  Blair at Nightshade has already told me he'd be happy to build such a hybrid integrated (but on grid, of course).  I assume a hybrid amp built by one of them would sound at least as good - and probably better -than what I'm using now, and then I wouldn't need a tube buffer at all.

The new Peachtree pre sounds appealing to me, as it supposedly has a good quality asynch USB solution and could theoretically replace numbers 2-6 in the list above. Its tube buffer also has an engaged/not engaged setting. That appeals to me. The Peachtree Grand Integrated could replace the  Power Amp too. So I'm going to wait and see how those units sound and then decide on what I want to spend the not inconsiderable amount of cash involved. Obviously one of the considerations will be the quality of the tube buffer in the Peachtree. There are also other options, like a tubed DAC with attenuator.

[bruson2]

1. I have the 250 watt version SDS 258. About 8 months.
I've used 2 different power supplies and there is still an erratic noise, maybe every 1-3 seconds, low level around 200-500hz. It's been doing this since I got it.
Anybody else have this?

2. Setting gain with Vishay resistors makes this a great bargain amp. Ordinary resistors=ordinary sound.

3. I remounted the output inductors on the bottom of the board, same holes. Cleaner, clearer sound, not quite as large improvement as the Vishays. I think less interference for the magnetic/electric field they radiate axially. No metal caps nearby.
See confusing pic below:

[djklmnop]

Argh, look like I'm going to have to postpone moving my 250w kit into a chassis.  I received it today and the color of the chassis is Champagne!!!  I was almost going to use it, but after looking at it long enough, the color made me feel like a drug dealer living the "bling" life.

Contacting the seller now..

[knireis]

Anyone knows what the powerconsumption is a complete CDA-254L amp?

[earflappin]

Anybody here tried jumpering the gain pins and forgoing either the stock gain pot or fixed resistors?  I had been using Vishay fixed resistors on my SDS's and just for kicks decided to remove them and just jumper the black and yellow wired pins.  There was a meaningful further improvement in transparency in my system.  I have 95db efficient speakers though.  YMMV.

[ptempel]

1. I have the 250 watt version SDS 258. About 8 months.
I've used 2 different power supplies and there is still an erratic noise, maybe every 1-3 seconds, low level around 200-500hz. It's been doing this since I got it.
Anybody else have this?

No, have never experienced this noise.  But am still using the CDA-254L kit with supplied Antek torroid.  No mods were done to it.  Maybe you can have your amp checked by classdaudio?

2. Setting gain with Vishay resistors makes this a great bargain amp. Ordinary resistors=ordinary sound.

Interesting.  I wonder if they use the same resistors on the non-balanced versions.  Which model Vishay resistors did you use? 

3. I remounted the output inductors on the bottom of the board, same holes. Cleaner, clearer sound, not quite as large improvement as the Vishays. I think less interference for the magnetic/electric field they radiate axially. No metal caps nearby.

Based on the pic I'm guessing that you mounted the amp board on its edge?  Another cool idea on the inductors.  If I did that mod, then I'd probably keep the same mounting scheme but use longer standoffs to raise it up.

[bruson2]

No, have never experienced this noise.  But am still using the CDA-254L kit with supplied Antek torroid.  No mods were done to it.  Maybe you can have your amp checked by classdaudio?

Interesting.  I wonder if they use the same resistors on the non-balanced versions.  Which model Vishay resistors did you use? 

Based on the pic I'm guessing that you mounted the amp board on its edge?  Another cool idea on the inductors.  If I did that mod, then I'd probably keep the same mounting scheme but use longer standoffs to raise it up.

Finally tracked down the noise problem, it is coming from my cable box, not the amp. And I've had 4 cable boxes in the past year, changed for other reasons, and all had the same noise.

Vishay SK102? earflappin a few posts above eliminated the resistor with a wire and had further audio clarity. Resistor or not depends on the gain structure of your system.

My amp is mounted on the back of some speakers I built http://www.diyaudio.com/forums/multi-way/167960-inexpensive-gedlee-bouska-waveguide-tweeter-midbass-idea-5.html

Now the amp is not mounted on stand offs any more, but hangs suspended by plastic ties stapled to the MDF box sides. The amp is "floating". Less vibration from the speaker. Cleaner sound.

Adding Vishays and reducing vibrations helps reveal the sound of this well engineered amp.

Anybody replaced the big electrolytic caps on the output side of the amp yet?

OT:
In the photo below you can see the speaker xover inductors, caps and resistors are all "floating" off the back of the speaker box. Result: Cleaner, clearer sound.

Most are suspended by plastic tie wraps stapled to the box. String or coated wire would work, too. "Floating" improves sound even in xovers mounted away from speakers. I had them glued down like Geddes does, but I wanted cleaner sound.

It's free and reversable if you don't like the sound.

Floating the inductors only made the most difference. Caps, a little added clarity.
These type inductors, no plastic core, sound better than a plastic core. Cut off of a plastic core and hear the diff.

[vlad335]

I have been researching these amps from Class D Audio and stumbled into this great thread. I have done searches and scoured the ClassD site and still have a couple questions. Many of which I am sure have been answered before and I humbly request your assistance.

This little obsession of mine began with a little Class T amp. The Lepai 20w to be exact. I bought this a couple weeks ago for my little computer system and began modding it as directed by a thread on Parts Express' forums. The modifications took this little amp to unbelievable performance and I realized it's the sound that I have been looking for. I became especially aware of this after I messed up the latest round of mods to the Lepai and essentially bricked it. It no longer works due to a mistake made somewhere in soldering so I ordered another. In the meantime, I swapped it out for a Crown D-75 and then a D-150A.

Even though the Crowns have more power and can get much louder, they both sounded like garbage compared to the $21 modded CLASS T Lepai. Huh? How could this be? This cheap little amp has a warmness and roundness to the tone that can be listened to for hours. I had an epiphany that the sound I have been seeking all this time is actually being hampered by class AB amplification! More power added over the years just increased the harshness and sterility that I tried to overcome with better equipment, speakers, interconnects, etc. Even added tube buffers in my home theater system to try to combat this inherent harshness.

Anyway, decided to try different amplification in my main home theater/music system and searched the internet for more powerful Class T amps. This led me here and to ClassD Audio's website. Would like to start by upgrading the front 3 channels of my main system.

Now the questions:

1. Do these Class D offerings compare to Class T amps in sound quality? I could not really find any "T" amps that were rated for higher power but the reviews here of "D" amps lead me to believe they have the same warmth and clarity.

2. Regarding the offerings on ClassDaudio.com: Should I go with the SDS line? What are the main difference between the SDS and the lower priced offerings? I see that they use balanced connections but could you use RCA's with them?  I have an Emotiva UMC-1 processor that is not balanced. Also they have attenuators for each channel. Would the channel pots be essential in obtaining the proper gain through the system?

3. Is it possible to build a 4 channel amp from the kits and just utilize 3 channels for the time being? Will this hurt the amp?

4. What is the consensus on using wood/MDF cases? Is this safe and acceptable? I read about the RFI concerns so could I say, add copper shielding to the inside of the case to combat this?

5. I am seriously considering the CDA-1000 kit and building my own case or buying one of the Antek cases on Ebay. Would this kit work with my processor's gain?

6. I have a Adcom GFA-5500 amp (125w into 8ohms) and my front three speakers are DIY and 4 ohm. It seems that some of the amp modules are not 4 ohm compatable. ( Maybe they are and the website is vague.) I would like to add more power for headroom purposes hence the CDA-1000 choice. If I would be better served by SDS modules in my system, what module and components would work best?

Thank you if you suffered through and read all this. Any help in answering these questions would be greatly appreciated.

[corndog71]

I built the SDS-258 and can say it runs on the slightly warm side and is very pleasant to listen to for extended periods.  This one isn't rated for 4 ohms but I believe all of the others are.  They're all made for unbalanced inputs and the SDS versions are designed for both balanced and unbalanced.  Supposedly the SDS boards sound better but I don't know all of the details.

You can certainly use multiple boards but you may want to confirm with Tom the power supply requirements.  Using only 3 channels shouldn't be a problem.  The pots are for matching the gain to your preamp.  Others have used wood boxes with no problems so you should be fine there too.

[MX48]

I have 2 CDA-1000 kits. One with an extra board and both with upgraded 500VA transformers (in case I want to add an extra board later).

I am completely happy with them and Tom is great to work with.

Here is a link to the output of the SDS boards, the CDA's have the same output.
http://www.audiocircle.com/index.php?topic=76400.2820
Post #2827

This is a pic of my 9 channel DSP/Amp case. the DSP's are the unbalanced MiniDSP with advanced plugin. I housed the transfomer and power supply in a seperate enclosure.

I am using the T-amp to power my compression drivers. I am planning to upgrade it as soon as I can find a high quality budget solution.

I have never heard the SDS's but those that have them seem to love them. If the money difference isn't an issue I would go with the SDS line.

Hope this helps,
Moto

[vlad335]

Thanks guys for the great information. Money is an issue and the main reason I was considering the CDA-1000 kit. Probably be better served by going with the SDS units. I can sell the Adcom when I get this up and running.

Will continue reading and researching this monster thread. Thanks again!

[vlad335]

Oh, MX48. Forgot to mention... That is one amazing build. Are you using this as a 3way front stage for a home theater? I just read up on the MiniDSP stuff and it looks like a perfect fit for these amps.

[MX48]

Thanks, it looks better in the pic than in real life .

Yes, 3-way front stage with Danley Synergy Clone HT speakers.

I love my MDSP's for the price especially, 3-in 12-out for just over $300 with plugin (you only need 1 plugin for multiple MDSP's if it is for the same use such as 3-way crossover and PEQ). The plugins are only $10 so it is easy and cheap to change cofiguration later if you change your system in some way.

Moto

[Piffle]

I am building a new system from the ground up with some brand new Magnepan 1.7s.  I've always been a headphone guy, so this is my first "real" system.  My listening room is pretty small (11'x16' or so), so I don't need tons of power for loudness, but I do know the maggies love power so I want as much as possible even though I'll be listening at low to medium levels.  Currently using an old Pioneer receiver (yuck) to drive them until I get everything else figured out.  Probably getting  the Dodd preamp and not sure about the DAC yet (though the Tranquility sounds like something I would like.  Need to find a way to hear one.)  100% of my current listening is directly from J River on my HTPC.

I have read through this whole thread and I see there are a few other maggie owners.  Any recommendations for a particular version?  My first option is the SDS-470.  I was also thinking of the SDS-1000 kit.  Is that overkill?    And the fallback, basic choice is the SDS0254.  This will be my first ever electronics project of any kind, so I'm obviously a bit nervous about that, but these kits seem pretty friendly to newbies.   My January at work is shaping up to be nutty, so if I want to hear this thing before February I might just buy a prebuilt unit.

Thanks for any input!  I'll be sending this to Tom through the Class D website also to get his recommendation.

P.S. - if it matters, I listen to all kinds of metal, lots of prog-rock/post-rock, classical, opera, and a bit of jazz and other stuff.

[krikor]

I am building a new system from the ground up with some brand new Magnepan 1.7s.  I've always been a headphone guy, so this is my first "real" system.  My listening room is pretty small (11'x16' or so), so I don't need tons of power for loudness, but I do know the maggies love power so I want as much as possible even though I'll be listening at low to medium levels.

...

I have read through this whole thread and I see there are a few other maggie owners.  Any recommendations for a particular version?  My first option is the SDS-470.  I was also thinking of the SDS-1000 kit.  Is that overkill?    And the fallback, basic choice is the SDS0254.

I've got a pair of MG1.6 speakers and contacted Tom regarding which amp would work well with these operating as balanced XLR monoblocks. He recommended the SDS-450 over the 470 saying they would run cooler in bridged mode.  Finally got them built and hooked up, and though they sound fantastic from what I can tell during the all too brief listening sessions, they are running very hot with the protection circuitry shutting them down after about 30 minutes of listening.  I can't even hold my hand on the heatsinks more than several seconds... and this is occurring at any volume level!

Tom thinks I simply need larger heat sinks and is sending me out a pair to install, but that was a few weeks ago and haven't heard anything back (though I'm giving him the benefit of a doubt since it is the holidays and he may be closed up through New Year's Day). It troubles me a bit that an amp supposedly well suited for my Maggies can so readily overheat.  Perhaps mine were built with the incorrect heat sinks (small ones compared to the large ones on the 470).

I'm not the first to have had such problems with Maggies. Another member here got the SDS-254 for use with MMGs and had the same overheating problem, albeit only above a certain volume level, using either a single stereo amp or a pair as monoblocks.

As for ease of building, I found them very simple to put together, provided you are don't mind getting all the hardware and are comfortable with doing (or learning to do) chassis work and basic wiring/jack hookups. The built versions seem like a fair price if you don't want to go through the fun or hassle yourself (depending upon how you look at it).

[vlad335]

I bought a pair of used Magnepan SMGa's off of craiglist for a song awhile back. Brought them home and hooked them up to a Yamaha receiver I had at the time. (cant remember the model number) and they sounded glorious, albeit somewhat shy on bass. The soundstage and clarity was great and the best I had ever heard in my home. However, the amp ran real hot and would go into protect mode easily. I suspected that the impedence curve on the Maggies must be pretty brutal, (2ohm dips) so I hooked up a pro amp I have here.

A QSC RMX-1850HD
http://www.qsc.com/products/amps/rmx/rmx.htm

Built like a tank and designed for 2 ohm loads. The sound quality of the Maggies went up exponentially, bass was far more improved and the soundstage was tremendous. These little panels filled the house with sound and it seemed the instruments were right in the room with you. Unfortunately, one of the panels went dead after a couple days. I pulled off the sock and the wires were completely corroded from age. Something all too common with older used Magnepans I found out. Plan to send these back to Magnepan after the Winter to get them repaired.

What I am getting at is apparently Magnepans are very tough to drive by normal home amplification. The toughest load I have ever come across and perhaps a bit too much for the ClassD Audio amps. The QSC's fan would even engage at times and get quite loud. ( I planned on adding a silent 24v fan as I did with the QSC RMX-850 in my bass guitar rig) However, I had never really heard the fan with PA duty running at a 2.66 ohm load

[Rclark]

I run my Maggies on a Virtue Two and the combo is beyond superb. It drives the hell out of em.