$175 Class D amp--120 wpc

hottuner · « **Reply #1980 on:** 11 Sep 2010, 03:23 pm »

Quote from: raindance on 11 Sep 2010, 03:04 pm

Yup.

OK this may be interesting - I get more hum, but then with audio inputs disconnected I get NO hum, and usually that give me more hum.

hottuner · « **Reply #1981 on:** 11 Sep 2010, 03:45 pm »

well it was a nice try raindancer, appreciated. As I said it's not bad as is, but still a puzzle. I'm going to try revamping the lead routing as noted within a few days and see what that does, and I'll post an update. Meanwhile better get outside, it's a nice day.

wushuliu · « **Reply #1982 on:** 11 Sep 2010, 04:11 pm »

Quote from: hottuner on 11 Sep 2010, 03:23 pm

OK this may be interesting - I get more hum, but then with audio inputs disconnected I get NO hum, and usually that give me more hum.

Well sounds like that may be the culprit. Maybe try separating/disconnectng rca and xlr, then only connect one of them at a time to the amp board inputs and compare.

Also not sure if that long rca/xlr wiring running by the PS and then by the toroid is the best idea.

DougSmith · « **Reply #1983 on:** 11 Sep 2010, 04:38 pm »

I would check that there is no ground leak from the input connectors to the chassis and use only shielded cable to connect to the inputs. It is fine for the amps and power supply to be isolated from the chassis ground (as you have it). That's the way mine are, and they are dead quiet. If starting from scratch, I would try to keep the 120V AC stuff away from the inputs and outputs. In your case, you could add some aluminum channel (screwed to the base) to isolate the 120V wires.

One other thing I noticed with my case... the paint coating was precluding a good ground connection between the top, bottom, sides, front and back. After I added some countersinks (which removed the coating and enabled a clean look with flat head screws instead of the round heads that came with the case) I got a good connection. A picture of my amp is posted somewhere in this thread, I think.

poseidonsvoice · « **Reply #1984 on:** 11 Sep 2010, 04:44 pm »

Quote from: DougSmith on 11 Sep 2010, 04:38 pm

A picture of my amp is posted somewhere in this thread, I think.

Doug,

It wasn't in this thread but in the Lab when you were discussing your cool bandpass subs using the 12BX100. But anyway, here it is again for all to see:

Notice the cleanliness of Doug's work. Notice how you can draw a circle starting from the power supply all the way to the input/outputs. Notice how the AC lines are very far away from anything DC. This is the sign of a pro builder.

Anand.

DougSmith · « **Reply #1985 on:** 11 Sep 2010, 05:21 pm »

Actually, I'm no pro - just built a few Heathkit things in the old days. I appreciate the compliment, though.

raindance · « **Reply #1986 on:** 11 Sep 2010, 05:45 pm »

Quote from: hottuner on 11 Sep 2010, 03:45 pm

well it was a nice try raindancer, appreciated. As I said it's not bad as is, but still a puzzle. I'm going to try revamping the lead routing as noted within a few days and see what that does, and I'll post an update. Meanwhile better get outside, it's a nice day.

Actually you are now halfway there> You have narrowed down the problem for me. It is a ground loop (as we suspected all along). Leave the added ground wire in place. Now verify for me which of the other components connected to the amp are grounded? I suspect you'll need to add a cheater plug to your preamp or the power amp to break the loop. Once you go balanced, you can re-ground and simply drop one end of the shield on each XLR cable.

roymail · « **Reply #1987 on:** 11 Sep 2010, 09:04 pm »

Quote from: poseidonsvoice on 11 Sep 2010, 04:44 pm

Notice the cleanliness of Doug's work. Notice how you can draw a circle starting from the power supply all the way to the input/outputs. Notice how the AC lines are very far away from anything DC. This is the sign of a pro builder.
Anand.

And, notice the symmetry of the wiring. Beautifully done, Doug!

srb · « **Reply #1988 on:** 11 Sep 2010, 10:57 pm »

Doug, your wiring looks very clean. But I'm not sure what I'm looking at as the grey cables from the rear panel RCA jacks connect to the amplifier boards. It looks like they terminate into some kind of right angle RCA plugs and are plugged into RCA jacks on the boards.

If so, wouldn't it be better to eliminate a 2nd RCA plug/jack connection and solder the cables directly to the pads on the boards?

Steve

wushuliu · « **Reply #1989 on:** 11 Sep 2010, 11:47 pm »

[quote author=srb link=topic=76400.msg834892#msg834892 date=1284245827

Doug, your wiring looks very clean. But I'm not sure what I'm looking at as the grey cables from the rear panel RCA jacks connect to the amplifier boards. It looks like they terminate into some kind of right angle RCA plugs and are plugged into RCA jacks on the boards.

If so, wouldn't it be better to eliminate a 2nd RCA plug/jack connection and solder the cables directly to the pads on the boards?

Steve
[/quote]

The 1st gen CDAs came with those RCA jack inputs, so I'm guessing they're older boards.

nwboater · « **Reply #1990 on:** 12 Sep 2010, 12:21 am »

Quote from: poseidonsvoice on 11 Sep 2010, 04:44 pm

Doug,

It wasn't in this thread but in the Lab when you were discussing your cool bandpass subs using the 12BX100. But anyway, here it is again for all to see:

Notice the cleanliness of Doug's work. Notice how you can draw a circle starting from the power supply all the way to the input/outputs. Notice how the AC lines are very far away from anything DC. This is the sign of a pro builder.

Anand.

Absolutely gorgeous work! I used to design and build industrial control panels and always prided our group on its good workmanship. I would have tried to hire you!

Only one question. If the two amp boards were rotated 180 would that have not kept the sig leads shorter and further from the supply? Not familiar with this amps layout, but I would assume that the low level stages would be on the side with the inputs. That would also keep that portion of the amp further away. Not trying to criticize - just wondering as I may soon build one of these. It would be my first amp since a tube amp from scratch in 1958.

Rod

poseidonsvoice · « **Reply #1991 on:** 12 Sep 2010, 01:21 am »

Quote from: nwboater on 12 Sep 2010, 12:21 am

Absolutely gorgeous work! I used to design and build industrial control panels and always prided our group on its good workmanship. I would have tried to hire you!

Only one question. If the two amp boards were rotated 180 would that have not kept the sig leads shorter and further from the supply? Not familiar with this amps layout, but I would assume that the low level stages would be on the side with the inputs. That would also keep that portion of the amp further away. Not trying to criticize - just wondering as I may soon build one of these. It would be my first amp since a tube amp from scratch in 1958.

Rod

It'll sound fine either way given the design of the input stage (on the SDS version, not sure of the CDA version that Doug used), however, yes, in my build the input side of the amp will be facing closer to the XLR/RCA jacks as it is a low level signal. But do notice that Doug used shielded cables to the RCA inputs (the grey wiring) due to the distance involved.

You just have to choose the right methodology depending on how you are going to orient the board. YMMV, JMHO, etc...

Anand.

jtwrace · « **Reply #1992 on:** 12 Sep 2010, 01:34 am »

....and yes done properly I HIGHLY doubt you could hear a sonic difference between the two.

DougSmith · « **Reply #1993 on:** 12 Sep 2010, 02:02 am »

Yes, those are the older unbalanced amps. I could have turned the boards the other way, but I thought it would be good to keep the speaker wires short and since I planned to use shielded cable for the inputs I figured that didn't matter. I also thought the convective cooling would work better in the configuration I used because of the layout of holes in my chassis. I also could have removed the RCA jacks, but didn't want to in case there was a problem with one of the boards and I had to return it or in case I decided to do something different with them in the future. It works fine in any case (by the way, that little board near AC-in has a 12V relay that can be used to trigger the amp on from my receiver). The nice thing about isolating the signal ground from the chassis is that ground loops are not possible.

I have been using these for around 8 months now for my subs. I drive them with a DCX2496 (unmodified), which gets its input from the sub-out on my receiver. This combination works quite well even though I am going from single ended to balanced and back again. The refinements on the new boards are nice, but I think the less expensive ones are sufficient for use as sub amps.

poseidonsvoice · « **Reply #1994 on:** 12 Sep 2010, 02:59 am »

Quote from: DougSmith on 12 Sep 2010, 02:02 am

The refinements on the new boards are nice, but I think the less expensive ones are sufficient for use as sub amps.

Wholeheartedly agree. And therein lies the answer to why we don't need to mess with replacing the integrated RCA jacks, etc...its for a sub amp for god's sake

Anand.

hottuner · « **Reply #1995 on:** 12 Sep 2010, 02:19 pm »

raindance - made the power supply ground lead a permanent addition and now understand the simplicity of it: if the amp is only connected to AC and speakers it should be dead quiet, and now it is (almost - see below). Problem solved with increased understanding of ground loops - thanks for both.

Also great info on routing by other regulars of this thread. I put the Class D back on the Finals since they are more revealing than the 1+1's, and I do hear a tiny smidge of noise on right channel (ear smack on speaker), sounds like white noise I guess, and left channel dead quiet (amp connected to speakers only). Honestly it's so low in level I never would have noticed it without the other problem leading me to it. Based on the comments here my guess is the right channel input leads being longer, not shielded, and next to xformer are picking up some radiation and feeding that to amp board input. I might be imagining it, but it seems even pushing the leads away from xformer a bit makes a small improvement. So now I know what to do next, thanks for all the help guys!

DougSmith · « **Reply #1996 on:** 12 Sep 2010, 04:37 pm »

hottuner - you might find these links helpful on grounding and how to avoid ground loops:
http://www.rane.com/note110.html
http://www.rane.com/note151.html

Flounder · « **Reply #1997 on:** 12 Sep 2010, 05:15 pm »

Hi Everyone

I received a SDS 4 kit from Tom about a week and a half ago. First off I'd like to congratulate Tom on a very fine product especially at this price point. The kit is stock with the optional heavy duty power supply at the moment. Power rating for the SDS-4 is 150 WPC @ 8ohms /300 wpc @ 4 ohms and 600 @ 2 ohms.

It is working fairly well but seems to be taking a good bit of time to settle in. It also takes about 30 to 45 minutes to really get into it's own from start up. What has your experience been as far as these go?

Sonically, some things I have found, is it is lacking a bit on very low level resolution. The tone is very good and the bass is adiquate and very similar to my tube amps. The highs are rolled off but nothing dramatic. Has anyone else noticed these things?

My speakers are a very tough load - 2.8 ohms through the 30s and a very hard phase angle of 55 degrees at 70 hz. so this may have some bearing on my outcome as they will really tax an amp. The speaker measurements were why Tom suggested the SDS4 rather than the SDS 258 I had originally enquired about. I had wanted a very high power unit as I had tried an old SS amp with the ability to generate 450 WPC into 4 ohms and this really took the woofers under control. The rest of the frequency spectrum of the SS amp wasn't done as nicely and my big tube amps were much better everywhere else.

To the guys who have done the power supply upgrades, do you think either the Connex power supply board ( 6 x 10,000 uF@ 80 volts) or the Connex SMPS supply will be better than the stock heavy duty one and address the short commings above? (This power amp module has +/-35 volt rails so it APPEARS like I could use the SMPS500 )

Just some other observations thus far.

These things do respond to power cord and footer changes. So far I tried the following power cables: Stealth M5000 (1st place) Stealth Cloud 9 ( 2nd place) Virtual Dynamics Master Series (3rd place) and Black Sand Statement 1 ( last) Yes, these cords are all multiples in price of the amp but they do make a nice difference.

For footers, I have tried Symposium Roller Block Jrs ( 1st) Solid Tech Feet of Silence (a very, very close second) , Black Diamond Racing #4 cones ( 3rd) and Herbies Audio feet (last) none of these were anywhere as large a change as the power cords but still worth while.

I haven't gotten around to interconnects and speaker cables yet- once things settle in a bit more I'll do those. I'm currently trying out a set of Grover Huffman's latest speaker cable and this may be the source of the short comings as they are new to me. I have them on a 30 day trial so I'm using them as much as possible to give them a fair shot against my other cables.

Really, if this amp had just a bit more low level resolution it would have a long term home in my system. It cost less than a re-tube of my amps with a set of Gold Lion KT-88 re-issues. That was how I decided to even try this out.

Thanks for any insights you can give me
Kevin

Mariusz · « **Reply #1998 on:** 12 Sep 2010, 05:30 pm »

Welcome to AC Kevin
.......and interesting 1st post.
Enjoy your new amp

Mariusz

Nick77 · « **Reply #1999 on:** 12 Sep 2010, 06:09 pm »

Kevin welcome to AC, i have not heard much a want to the bottom end with these amps but upgrading the caps and capasitance on the ps did give a nice bump in low end grunt. I agree these amps do respond very well to internal wiring and power cords. I just put a Wywire power cord on my SDS254 and the result was overwelming. Felt like going from mono to stereo with increased resolution and depth of soundstage. Highly reccomend experimenting.
Thanks for sharing your thoughts.