$175 Class D amp--120 wpc

Barry_NJ · « **Reply #2140 on:** 21 Oct 2010, 10:58 pm »

Upon further thought, I'm now realizing that the 2 boards likely have different voltage requirements, so you can't just swap them back and forth as I'd originally suggested.

dine1967 · « **Reply #2141 on:** 22 Oct 2010, 05:39 pm »

Quote from: wushuliu on 21 Oct 2010, 07:45 pm

The 254 sounds leaner and possibly cleaner, but I need more listening time. I guess I'm just surprised a 6dB gain difference would be so pronounced (assuming that the stock are still at 32dB as mentioned near the beginning of the thread).

I guess I am just really surprised by the difference between the two. I just finished an Aikido preamp and w/ the 224 music was warm and fuzzy, but w/ the 254 it's leaner and clearer, and by a lot.

Edit: I cam across this post from on diyaudio from someone at Coldamp that sums up the SMPS500R in the low end: "About regulation: linear power supplies are almost never regulated, and this is specially true as power increases, due to efficiency and heat dissipaton issues. On the other hand, it is easy to make regulated SMPS, that will hold rails voltage up to full power with no problem. This translates in a deeper and more powerfull bass, mainly, although it has sonic impacts in the rest of the audio band."

What is the value of the output cap you are using on aikido? I have the CDA254 connected to an aikido and Iam trying to get the right value.
thanks,
Dinesh

wushuliu · « **Reply #2142 on:** 22 Oct 2010, 05:58 pm »

Quote from: dine1967 on 22 Oct 2010, 05:39 pm

What is the value of the output cap you are using on aikido? I have the CDA254 connected to an aikido and Iam trying to get the right value.
thanks,
Dinesh
[/quote

As this off topic I will send pm

walkern · « **Reply #2143 on:** 22 Oct 2010, 08:09 pm »

I had some left over 3 pin Molex connectors and decided to try substituting a single resistor for each input level control on my SDS 254 amp. I tried 10 ohm Vishay metal film resistors first, and then switched to 4.7K ohm carbon film resistors so I would better match the volume control output characteristics of my Pass DCB1. The resistors both offered (a) a more 3D or holographic sound stage (2) more layering and extension both in front and to the rear of my speakers, and (c) a quieter background from which sound emerged (sounded much like adding good AC power conditioning). The Vishay metal film resistors clearly tipped up the treble balance, and initially sounded a bit gritty or spitty or splashy, and they also tightened up the bottom end a bit. The carbon film (generic... had 'em laying around from Radio Shack) resistors were smoother sounding with no emphasis in any particular region, but they did warm up the midbass a bit (fuller, but not bloated or tubby). All in all I would say the improvement is as great as the difference between the CDA amps and the SDS amps, and all for less than $10. The Molex connectors I used were not a perfect fit and had to be filed a bit (the locking system on them was different than Tom uses), but are snug and won't fall out. Mouser part number for them is: 538-10-11-2033, and you'd also need crimp terminals for them that will attach to the legs of the resistors (that must be soldered IMHO) - Mouser part number 538-08-50-0114.

Highly recommended cheap and cheerful tweak that won't void your warranty. I'm sure higher quality resistors would be worth trying. The 10 ohm value leaves the input impedance similar to having the control pots fully turned up. The 4.7K ohm value was equivalent to turning the control pots down by about 6 db.

Neil

Barry_NJ · « **Reply #2144 on:** 22 Oct 2010, 08:49 pm »

Quote from: walkern on 22 Oct 2010, 08:09 pm

Highly recommended cheap and cheerful tweak that won't void your warranty. I'm sure higher quality resistors would be worth trying. The 10 ohm value leaves the input impedance similar to having the control pots fully turned up. The 4.7K ohm value was equivalent to turning the control pots down by about 6 db.

Neil

Thanks Neil, that's great info!
Would you mind posting a couple of pix of the mod in place?

walkern · « **Reply #2145 on:** 22 Oct 2010, 09:36 pm »

I'll shoot a couple of photos when I get home. Not much to look at... but at least you could see the Molex housings both in place, and free standing.

Neil

roymail · « **Reply #2146 on:** 22 Oct 2010, 10:44 pm »

Quote from: walkern on 22 Oct 2010, 09:36 pm

I'll shoot a couple of photos when I get home. Not much to look at... but at least you could see the Molex housings both in place, and free standing.
Neil

Hey Neil,

How about just removing the molex connector from the amp board and solder the resistor to the board? What do you think? Great find for the SDS boards. Thanks!

Roy

walkern · « **Reply #2147 on:** 23 Oct 2010, 12:57 am »

Hey Roy,

You could certainly just remove the female Molex connector and solder the resistors directly to the pins on the male end of the connector on the board. I opted to use Molex connectors so I could check to make sure that the 10 ohm resistor value would work, and to try out different types of resistors. Once you find the sound you are looking for (and the input level that works best with your system) then that would be an ideal time to solder those puppies in.

Here are a couple o' photos (the Vishays not currently installed, and the carbon film resistors installed).

corndog71 · « **Reply #2148 on:** 23 Oct 2010, 03:49 pm »

Earlier in the thread there was a pic posted of the blue block-shaped input caps being replaced. Has anyone else done this mod? Pics?

Flounder · « **Reply #2149 on:** 23 Oct 2010, 06:18 pm »

Hi Everyone

I just finished doing the replacement of the gain controls with fixed resistors on my SDS-4. I just de-soldered gain controls and soldered the resistors (Caddock 220 ohm in a TO220 package) to the yellow/black wires from the molex connector.I didn't have any spare molex connectors and I just wanted to experiment to see if it made any difference.

Well, all I can say this should be a manditory mod.

It might be worthwhile to run the gain controls to ballpark the value of the resistor for a while. I just used Walkern's base line of 10 ohms and added a bit more resistance. My guess is for most, a value of around 500 to 1000 ohms would work out well to give that pre amp center of the volume pot positioning. My pre has pretty high gain and I can run it at around 9:00 for about low 70's spl output with the 220 ohm resistors.

I did this in my high eff system and these speakers have never had this much bass. The clarity has now popped up to close to the 300 B amp
Great stuff!
Thanks Walkern for the inspiration

Kevin

walkern · « **Reply #2150 on:** 23 Oct 2010, 07:44 pm »

Glad it wasn't just my imagination!

The 10 ohm resistor value suggestion came from Tom, and in my system it sounded like the level was comparable to the control levels when they were maxed out.

Thanks Kevin,

Neil

wushuliu · « **Reply #2151 on:** 23 Oct 2010, 08:30 pm »

Okay, FINE, I'll put in an order for an SDS amp.

You guys happy now?!

srb · « **Reply #2152 on:** 23 Oct 2010, 08:41 pm »

Quote from: wushuliu on 23 Oct 2010, 08:30 pm

Okay, FINE, I'll put in an order for an SDS amp.

You guys happy now?!

Not until we see completed photos!

Steve

wushuliu · « **Reply #2153 on:** 23 Oct 2010, 11:01 pm »

I asked Tom to increase the SDS254 voltage to +/-54v to accomodate the SMPS; though the SMPS can be manually dialed down 10% with a screwdriver, it just makes things easier...

guest1632 · « **Reply #2154 on:** 25 Oct 2010, 06:26 pm »

Quote from: Flounder on 23 Oct 2010, 06:18 pm

Hi Everyone

I just finished doing the replacement of the gain controls with fixed resistors on my SDS-4. I just de-soldered gain controls and soldered the resistors (Caddock 220 ohm in a TO220 package) to the yellow/black wires from the molex connector.I didn't have any spare molex connectors and I just wanted to experiment to see if it made any difference.

Well, all I can say this should be a manditory mod.

It might be worthwhile to run the gain controls to ballpark the value of the resistor for a while. I just used Walkern's base line of 10 ohms and added a bit more resistance. My guess is for most, a value of around 500 to 1000 ohms would work out well to give that pre amp center of the volume pot positioning. My pre has pretty high gain and I can run it at around 9:00 for about low 70's spl output with the 220 ohm resistors.

I did this in my high eff system and these speakers have never had this much bass. The clarity has now popped up to close to the 300 B amp
Great stuff!
Thanks Walkern for the inspiration

Kevin

Ok, so to beg the question Kevin, did the dynamics go up too? You had mentioned that the dynamics were such that all of the stuff seemed to be on the same level. Did that improve?

To those who have the SDS boards, rather than just pull the pots, just use a meter and bring down the value to something like 500 to 1K listen first, and then once the right value has been found, remove the pots, and put in the fixed resistors. Then you have to allow the value differences of each resistors, 5% 10% ETC.

Ray

Flounder · « **Reply #2155 on:** 25 Oct 2010, 06:52 pm »

Hi Ray

So far I've only run the SDS-4 with the new resistors in my second system with the high effciency Fostex based speakers.

This second system didn't suffer with the "dynamics" the Sonus Faber based rig did either before or after the fixed resistor replacement.

The changes to the high eff. system were a much stronger and more detailed bass and a much improved treble response.

After going back to the tube amps in the main set up with the cable changes and power conditioner in, I really like what I'm hearing there. The improvement to the second system is is well worth while so the SDS4 amp will stay with the Fostex based rig at least for a while.

I still haven't received the Connex board. When that comes and after it has burned in I may stick it in the main system again just to see if the issues I had have been resolved or ameliorated

Kevin

Barry_NJ · « **Reply #2156 on:** 25 Oct 2010, 07:41 pm »

Neil, sorry for the delayed reply. Thanks very much for the pix they're perfect.
When I finally do place my order, I'll likely ask Tom for some extra molex connectors in place of the pots.

wushuliu · « **Reply #2157 on:** 25 Oct 2010, 07:54 pm »

Quote from: walkern on 23 Oct 2010, 07:44 pm

Glad it wasn't just my imagination!

The 10 ohm resistor value suggestion came from Tom, and in my system it sounded like the level was comparable to the control levels when they were maxed out.

Thanks Kevin,

Neil

Thanks for the tip Neil. My one grip with the CDA/SDS boards is that there's really nothing to tweak. But now there is!

Edit: I also give a big thumbs up to the SMPS500R. At best it sounds cleaner than my 90k linear (probably because of the poor wiring layout I had frankly), at worst it sounds the same. Except for the bass. Unbelievable mid/bass. Ease of use and space/weight-saving make it a winner for me. Just be prepared for the 2-3 week wait time for delivery...

wushuliu · « **Reply #2158 on:** 28 Oct 2010, 09:47 pm »

I got the SDS254 up and running with the SMPS500R last night. I only got about an hour's listening in, with the gain dialed in to roughly the same as my CDA254. The sound was a little leaner and clearer but overall sounded the same as the CDA to my ears. My guess is the leaner sound is due to the impedance matching of the SDS w/ my Aikido as the difference is similar to going from the stock 1k B1 buffer output impedance to a somewhat lower value. I'll swap out the gain pots w/ resistors tonight.

jtwrace · « **Reply #2159 on:** 28 Oct 2010, 11:13 pm »

Quote from: wushuliu on 28 Oct 2010, 09:47 pm

I'll swap out the gain pots w/ resistors tonight.

I'll be curious to read what you think...

$175 Class D amp--120 wpc

guest1632