[chlorofille]

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?
Kevin

Hi Kevin,

That is exactly how I found the Class D amps. I have not heard Tom's boards but I own a Class D TK2050 100W into 4ohms . It has a tube like sound with warmish bass. Highs are not rolled but they are softer than a good class AB amp. I am using Aussie Amplifiers Nxv200 as a reference amp for comparison.

I think the great thing about the Class D amps is their ability to make any speaker sound good. They even made my Bose cubes sing. (these are my test speakers). Also they have superb value for money considering they can be driven by el cheapo chinese SMPS power supplies.

[hottuner]

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

Thanks Doug. Just downloaded the PDF's available at those links, on first glance look excellent.

[wushuliu]

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

These amps will put out whatever you put in, including low level resolution. Your experience w/ the power cords and footers are indicative of this transparency imho. I believe they excel at low level resolution and micro-details, depending on what's up and downstream.

As for the PS, increasing the amount will definitely improve the low end punch. If you are comfortable with the soldering iron, easiest thing to do is replace the caps that come w/ the stock board with higher values. Otherwise, one of the Connex should be fine. Can't vouch for their SMPS, but from all the research I've done just seems like more care has to be taken when implementing SMPS w/ any Class D/T amp.

The rolloff you're experiencing may be related to your speaker impedance. The IRAUDAMP design which the CDA and SDS amps are based on indicate a slight rolloff with 4 ohm speakers vs. 8. I am guessing this continues as the impedance lowers. But that's what the chip pdf says, I don't know if Tom compensated for that.

[Flounder]

Hi  Wushuliu

Thanks for your comments.

I guess I should have prefaced my comments in that I'm comparing the sound to a pair of $5 K tube amps that have been fully tricked over. The low level resolution just isn't there with this unit so far, compared to them. As you say this may be from how hard a load my speakers are.

I'm reluctant to dump much more money into this amp as it may be better spent putting it towards a big power SS amp which will sort out the bass issues and still give me a reasonable mid and treble.

Soldering in new caps would  not be any issue. I have a hand full or two of 0.47uF Auricaps and Multicaps I was thinking to try as bypass caps.

The internal wire I used is a combination of my favorite Mundorf silver /gold hook up wire for the input wiring and Vacuum State Audio pure silver ribbon for the speaker wiring. I used Kimber rhodium RCA jacks and Eichman speaker pods.  The system is a Wadia 861 CD player to a Tom Evans Vibe Pre with the Pluse power supply and S.F. Cremona speakers so the rest of the gear is fairly good.


I'm going to give the amp about another week or so as it is right now for more burn in. Then I'll evaluate the amp with the various speaker cables and make a final descision as to it's long term survival in this system and whether to spend much more on it. The give or take 50 bucks for the Connex power supply seems like a good deal for the better bridge rectification and the additional filtration. We'll see how it all plays out I guess.

Best regards
Kevin

[wushuliu]

Hi  Wushuliu

Thanks for your comments.

I guess I should have prefaced my comments in that I'm comparing the sound to a pair of $5 K tube amps that have been fully tricked over. The low level resolution just isn't there with this unit so far, compared to them. As you say this may be from how hard a load my speakers are.

I'm reluctant to dump much more money into this amp as it may be better spent putting it towards a big power SS amp which will sort out the bass issues and still give me a reasonable mid and treble.

Soldering in new caps would  not be any issue. I have a hand full or two of 0.47uF Auricaps and Multicaps I was thinking to try as bypass caps.

The internal wire I used is a combination of my favorite Mundorf silver /gold hook up wire for the input wiring and Vacuum State Audio pure silver ribbon for the speaker wiring. I used Kimber rhodium RCA jacks and Eichman speaker pods.  The system is a Wadia 861 CD player to a Tom Evans Vibe Pre with the Pluse power supply and S.F. Cremona speakers so the rest of the gear is fairly good.


I'm going to give the amp about another week or so as it is right now for more burn in. Then I'll evaluate the amp with the various speaker cables and make a final descision as to it's long term survival in this system and whether to spend much more on it. The give or take 50 bucks for the Connex power supply seems like a good deal for the better bridge rectification and the additional filtration. We'll see how it all plays out I guess.

Best regards
Kevin

Gotcha. No doubt custom $5k amps certainly should have the edge. Are you using only 1 or 2? Seems like using one amp per channel might be better for those speakers.

Given the quality of your gear, Tom's amps would probably want a little more lovin' as far as PS caps (both in capacitance and quality), toroid, etc. to give you what you need (not sure what transformer comes w/ your amp). Some people here advocate 800VA toroid and 100+kuf for the PS to really bring out the best in the amps. For your gear I wouldn't be surprised if you also benefitted from the same investment.

[Flounder]

Hi  Wushuliu

 Humm that's an interesting thought and one Tom didn't present to me. I wonder if the SDS-4 could be bridged for my system. It would make massive power but might not cut it on the impedance side of things. If things don't improve, I'll see what Tom thinks of that idea.

I still think this is an amazing little amp for the money and one that doesn't need to appologize to very many much more expensive products. If a guy was a pure "music lover" rather than "audiophile", I could see someone being totally happy with one of these.

I was reading about the Ampino amp and family - the higher powered members of those might make a very good candidate for me as well.

Thanks for the feedback
Kevin

[wushuliu]

Hi  Wushuliu

 Humm that's an interesting thought and one Tom didn't present to me. I wonder if the SDS-4 could be bridged for my system. It would make massive power but might not cut it on the impedance side of things. If things don't improve, I'll see what Tom thinks of that idea.

I still think this is an amazing little amp for the money and one that doesn't need to appologize to very many much more expensive products. If a guy was a pure "music lover" rather than "audiophile", I could see someone being totally happy with one of these.

I was reading about the Ampino amp and family - the higher powered members of those might make a very good candidate for me as well.

Thanks for the feedback
Kevin

Cool. Oops I added a little more to my post above, in case you missed that.

[Feanor]

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.
...

Just some other observations thus far.
...

Thanks for any insights you can give me
Kevin

Kevin, you must listen to some pretty fine amps to notice poor low-level resolution problems -- or have some pretty fine ears.

I have the impression that Tom often recommends the 254 rather than the 258; does anyone know why this is?  I opted for the 258.

By low-level resolution, I presume you mean resolution at low volumes???  I haven't noticed this with my 258 and Magneplanar speakers; on the contrary.  It beats my $2.3k Monarchy SM-70 Pro monoblocks and at least equals my $3k Bel Canto eVo2 for resolution at any level -- but then these aren't tube amps or $5k for that matter.  I wonder if your experience is related to your particular speakers?

Good luck with your tweaking.  Sometimes these measures make a difference, but in my experience much less than basic component upgrades such as to speakers or amps.  In that regard the SDS amps are super high-value relative to, e.g., expensive interconnects.

I think we agree that the SDS amps are solid and pleasantly warm in the 40-100 bass range.  I find them a tad bright in the lower treble, but I suspect this has reduced a bit with burn-in.  In any case, for me, inserting the vendor-supplied 1 ohm resistors in series with my Magneplanar tweeters has substantially removed that brightness.

I don't hear the high frequency roll-off but then I'm deaf above 10 kHz so that might explain that.

- Bill

[Barry_NJ]

Snip...

By low-level resolution, I presume you mean resolution at low volumes???

...Snip

- Bill

Hi Bill, I believe that 'low-level resolution' refers to the ability to hear little details in the signal, and differentiate those sounds from the more prominent ones in the signal, at any volume setting.

Best, Barry

[Feanor]

Hi Bill, I believe that 'low-level resolution' refers to the ability to hear little details in the signal, and differentiate those sounds from the more prominent ones in the signal, at any volume setting.

Best, Barry

Humm ... OK then.  Strange though: to me the SDS-258 is exemplary in this respect, and I've heard some good amps over the years.

[JohnR]

I have the impression that Tom often recommends the 254 rather than the 258; does anyone know why this is?

Hi - I suspect that this is just because the 254 is more compatible with a wider range of speakers (impedance-wise) than the 258. I've not heard either altho I have a CDA-254 on the way (seemed like the best fit for my purposes).

[Barry_NJ]

Humm ... OK then.  Strange though: to me the SDS-258 is exemplary in this respect, and I've heard some good amps over the years.

Understood Bill. FWIW, please see, about mid-way down the page, here...

http://www.stereophile.com/reference/50/index5.html


You know you're a geeky audiophool when you start referring people to J. Gordon Holt's 'The Audio Glossary '
(speaking of myself obviously)

[Flounder]

I think there are a couple of things to keep in mind here.

The SDS-4 board must be fairly different from the SDS 25X series. Tom told me there are  some parts on this board which are very hard to get presently and are in short supply. He only recommends these to customers with very difficult loads.  Therefore, it seems entirely reasonable that this board may sound slightly different from the SDS 25x series.

Most of the low level  resolution I find lacking/poorly reproduced is in the treble region which I have already stated is rolled off /shelved down in my system. This may be unique to my system or a character of this series of board. I have a pair of monitor speakers which have a 6 ohm norminal impedance. If I have time in the next couple days, I'll hook  those up and see if the treble issue changes.

 The other area of mild concern is the very low bass which is not as articulate as my other amps but I think from suggestions here this may be overcome/ameliorated with a higher uF capacity or better power supply.
When I get some results I'll post them here.

Kevin

[wushuliu]

I think there are a couple of things to keep in mind here.

The SDS-4 board must be fairly different from the SDS 25X series. Tom told me there are  some parts on this board which are very hard to get presently and are in short supply. He only recommends these to customers with very difficult loads.  Therefore, it seems entirely reasonable that this board may sound slightly different from the SDS 25x series.

Most of the low level  resolution I find lacking/poorly reproduced is in the treble region which I have already stated is rolled off /shelved down in my system. This may be unique to my system or a character of this series of board. I have a pair of monitor speakers which have a 6 ohm norminal impedance. If I have time in the next couple days, I'll hook  those up and see if the treble issue changes.

 The other area of mild concern is the very low bass which is not as articulate as my other amps but I think from suggestions here this may be overcome/ameliorated with a higher uF capacity or better power supply.
When I get some results I'll post them here.

Kevin

Thanks Kevin. I agree. Look forward to hearing about the 6 ohm speaker.

[Feanor]

Understood Bill. FWIW, please see, about mid-way down the page, here...

http://www.stereophile.com/reference/50/index5.html


You know you're a geeky audiophool when you start referring people to J. Gordon Holt's 'The Audio Glossary '
(speaking of myself obviously)

Thanks, yes, I guess I haven't looked at that in while.  It's good to have a common vocabulary. 

[hottuner]

Most of the low level  resolution I find lacking/poorly reproduced is in the treble region which I have already stated is rolled off /shelved down in my system. This may be unique to my system or a character of this series of board. I have a pair of monitor speakers which have a 6 ohm norminal impedance. If I have time in the next couple days, I'll hook  those up and see if the treble issue changes.
Kevin

Hi Kevin, well it's nice to see another SDS-4 at the party    I'm also curious about the Connexet SMPS 500R. With this board in particular (600 watts 2 ohm) it would seem desirable, except I find it hard to imagine these tiny mosfets and heatsinks delivering that kind of power without a nice fireworks display!

I'm sure you know this since you mentioned it specifically - the psycho-acoustic effect of high frequency response variation on perceived transparency, resolution, and imaging is pronounced. I wonder if you have ready access to a way to adjust that as you listen? And I must admit I'm curious about your speakers!
Dave

[Flounder]

Hi Everyone

OK, some progress.

I was going to set up the monitors but thought while I was messing about I might as well start with the speaker cable swaps. It had a high probablity to be one source of problems as I had never tried Grover's speaker cable before. This was also the easiest to do first and might save a few steps.

And it did- this was a good 50% of my problem. The Grover speaker cables just did not totally gel with my speakers. Now I have much better high frequency information and low level detail retrieval than with the Grovers. It is still a good bit less than with my tube amps but within what I can live with( especially for the price differential).

The bass is a little tighter and now it seems in the relm of possibility that a power supply board change will get the bass close to what I can live with long term.

The down side for me is the Grover cables had the better midrange than the cables I have in at the moment.  I am going to miss that but the overall balance and detail recovery is much more critical to me.

Grover was excellent about the return.  I would say if you are in the market for a $300 dollar speaker cable, they would be worth a try - just for that midrange. Maybe with a speaker that isn't so hard to drive they might be perfect. By the way, his $200 Interconnects are simply great. I use them with ICs that are over $1K a pair and it's just flavours with non being "better".

I didn't have time to do much more today. I'm going to just let the system play for a few days. I think things show enough promise to warrent ordering the higher uf Connex linear power supply board and see what that will do. I'm going to chicken out on the SMPS - at least for now.

Best regards
Kevin

[bigdirty]

Hey guys,

 wired up one bridged sds224 today!!     blew 4 fuses in the process   the fuse im using is 6a 125v. on the IEC/fuse holder it states to use 250v fuses. oops? rewired everything tried it without fuse and it plays music.

also, im going to be running 2 transformers, 2 power supply, 2 amps, through one IEC/fuse, any problems with this?

thanks for your help.

[toxteth ogrady]

Who's plugging their amp into a power conditioner? Just for shits and giggles I plugged my sds-258 amp into a newly acquired cheap & cheerful power conditioner and got a noticeable improvement in the sound. Much better bass, front to back depth and more 3 dimensional with improved harmonics. If you have a decent power conditioner give this a shot and see what it does for you.

[wushuliu]

Who's plugging their amp into a power conditioner? Just for shits and giggles I plugged my sds-258 amp into a newly acquired cheap & cheerful power conditioner and got a noticeable improvement in the sound. Much better bass, front to back depth and more 3 dimensional with improved harmonics. If you have a decent power conditioner give this a shot and see what it does for you.

Yes, the cleaner the power the better the sound for these amps. Best bang for the buck is the DIY 193L choke conditioner I mentioned in the modifications thread. It's the one tweak I am a fanatic about. Once you try it you'll never go back (only forward, like with say, dbe's Buss's). You will poop your pants.

Ok maybe not. Like I said, it's the one thing I'm a fanatic about...