[pelliott321]

I have been using a CDC 254 to drive the bass panels of my rebuilt maggy IIIa's for about a year now with no problems.  I did try it full range when I first got it and did not care for the high freqs.  I should go aback and give it another try

[firedog]

As far as Class D and the high end: yes, probably lacking a bit in relationship to the high end of conventional amps. In a few years the frequency of the chips will go to something like 4M instead of 1M, and then the filtering will be so far out of the range of human hearing and overtones that it will have no impact.

That said, Tom's amps are a bargain, and sound as good or better than anything near their price, including in the high frequencies. You have to spend double or triple to get something better, from what I've seen. The NCore seems to be better, but an assembled one will cost you over $2K. I've heard plenty of conventional amps in the $2-3K range that aren't better than my SDS. Some are.

[firedog]

Thinking of trying to upgrade my standard SDS build. Just for fun. At purchase, Tom said he'd tried all sorts of parts, and the ones he's using give equal SQ to more expensive parts at less cost than some of the audiophile favorites.

In spite of this,  I'm sort of a believer in the best hifi starts with the best power section:So I'm wondering: anyone used a better PS, transformer, or regulators?

Did it REALLY make a difference?

Or caps with more capacitance? Anyone turned one of these amps into something with very high current capacity? How did it effect the sound?

[Nick77]

Thinking of trying to upgrade my standard SDS build. Just for fun. At purchase, Tom said he'd tried all sorts of parts, and the ones he's using give equal SQ to more expensive parts at less cost than some of the audiophile favorites.

In spite of this,  I'm sort of a believer in the best hifi starts with the best power section:So I'm wondering: anyone used a better PS, transformer, or regulators?

Did it REALLY make a difference?

Or caps with more capacitance? Anyone turned one of these amps into something with very high current capacity? How did it effect the sound?

I just replaced the caps on the power supply board with larger 10k Panasonic TSHA series for a total of 60k capacitance. The result was increased dynamic's and micro details, well worth the $60 entry fee. 

[matt_garman]

I just replaced the caps on the power supply board with larger 10k Panasonic TSHA series for a total of 60k capacitance. The result was increased dynamic's and micro details, well worth the $60 entry fee. 

What voltage are those 10k Panasonic TSHA caps?  Where did you get them?

[Nick77]

What voltage are those 10k Panasonic TSHA caps?  Where did you get them?

http://www.diycable.com/main/advanced_search_result.php?keywords=panasonic&Cid=6027b26cbb56db7ef1820316e30b5860&x=0&y=0

[matt_garman]

http://www.diycable.com/main/advanced_search_result.php?keywords=panasonic&Cid=6027b26cbb56db7ef1820316e30b5860&x=0&y=0

Ahh, you used the 63V ones.  I'd like to use 80V, and it appears they don't offer an 80V 10k uF TSHA-series capacitor.  Not sure what the next best would be, without spending a fortune.

[Nick77]

Tom approved the 63v.

[w00dee]

Just finished reading that thread. Wow! I may need to read it again. Lots of great information. I have a CDA 254 and a SDS 254. I will be making some tweaks this weekend!

[rjyap]

Work in progress 8 channel power amp using 2 x SDS-258 module, 2 x CDA-258 module using SMPS. The amp is build with space saving concept in vertical position and will be install in a standard desktop PC casing. This project had been pending for almost 2 years. Still waiting for 28 AWG pure silver cable for input.

[runemaster]

Hi all. I own 2 SDS-224, each running in bridge mode. I was playing it in a minute, and then a channel when mute. Upon checking, the amp main board does not have the usual blue LED lit up, and the heat sink is quite warm. The other unit is running fine. When I switch the ON/OFF switch to OFF, the usual amber LED does light up, but when I switch it back to ON, no LED, no sound. I've checked all connection, reconnect them as well, still the same. I initially thought that it was over heating, but I tried it again after a 20 minutes break ( I turn off the main power ) and still the same symptom. Anyone encounter such a problem before?

Thanks

I dunno where to turn to, so i hope to shed some light here for me. Regarding the issue above, I have sent my amp to Tom, and the courier tracking log does show that the amp has been delivered 2 weeks ago, however, until now, there's no news from Tom.....I have even send follow up messages to him but with no avail. Just been wondering, is Tom still available, or is he on holiday? Cause I am kinda worried since there is no response from him at all.

Please help.
Thanks

[justd]

Relax. Tom is a man of very few words.

[justd]

Just finished reading that thread. Wow! I may need to read it again. Lots of great information. I have a CDA 254 and a SDS 254. I will be making some tweaks this weekend!

Can you give a comparison of the sound quality between the amps.

[runemaster]

Relax. Tom is a man of very few words.

Well, he should at least reply the emails I sent to him, just for acknowledgment sake.

[rjyap]

Thanks Mboxler,

The hum is coming from the speakers. I am using Mirage speaker OMD 15, OMD 5, OMD C1. Yes it does go away if i remove the interconnects.

I am using a UMC-1 as the pre-amp and processor. I  have tried lifting ground on all the equipments and it is not helping at all. in fact the problem is very peculiar. There is very little hum (almost inaudible) when everything is connected. But as soon as i play the source, and the hum volume increases. The volume of this hum is the same irrespective to the volume on the UMC-1. When i pause the source the and the music stops... the humm stops after a 2 seconds.

So it seems to me that a 50hz, signal is superimposing itself on the interconnects between the umc-1 and the amp boards. Or may be the amps are grounding themselves through the interconnects via the UMC-1 since the amps do not have a ground available to them.
 

Whats is IEC?  is it the power supply board? i actually do not  have a body as such for the amp. And i have not grounded it. May be i should do that.


 

In fact i am running all my equipment on an online ups now. So i am getting clean power.

I previously had the same electrical buzz. If the source is playing then the buzz go away. I trace the problem to the RCA cabling and high gain. Previously I'm using 2 conductor with grounded shield but somehow the shield pick up EMI/RFI. I change to pure silver 28 AWG wire and a few twist solve the problem. Also change the gain using fix resistor 5kohm and now the amp is dead silence.

[rjyap]

Finally completed the wiring and now testing all channels. My short impression between CDA-258 and SDS-258 are SDS-258 had slightly better separation. For my application, CDA will be use for surround speaker and SDS for Front and Center speaker.

[justd]

Thanks for chiming in rjyap. My problem was the opposite. I started getting more hum when the source was sending a signal to the amps. In my case the emotive UMC-1. It still remains a mystery, for which i have had not time in the past few months. I had sent the amps back to tom, because one of them had fumed on me. Once i get them back ill try to get put them in a more conventional case and see how it goes from there.

I see that you are using Connex power supplies. How is that working out for you? When you say separation, you mean between the various instruments?

[rjyap]

Connex power supplies doesn't have any noise issue. I like it due to the compact size compare to linear ps which I can't fit into a compact 8 channel amp chassis. Also, separation should be better as each ClassD amp module will run on different transformer. Regarding the separation I mention earlier, I do feel that vocal is more distinct compare to background instrument.

As for your hum issue, it could be the gain is too high that cause the issue. Your build show that you are using CDA series which doesn't allow you to adjust the gain. You might want to try out SDS series and try higher value around 5 kohm and see if this solve your problem. Also need to mention SDS board is slightly longer so it might not fit your existing casing. Tom should be able to do a swap from CDA to SDS. I asked him earlier and he say it is OK as long as your board looks like new.

[JohnR]

Finally completed the wiring and now testing all channels. My short impression between CDA-258 and SDS-258 are SDS-258 had slightly better separation. For my application, CDA will be use for surround speaker and SDS for Front and Center speaker.

Nice design and construction!

[justd]

Connex power supplies doesn't have any noise issue. I like it due to the compact size compare to linear ps which I can't fit into a compact 8 channel amp chassis. Also, separation should be better as each ClassD amp module will run on different transformer. Regarding the separation I mention earlier, I do feel that vocal is more distinct compare to background instrument.

As for your hum issue, it could be the gain is too high that cause the issue. Your build show that you are using CDA series which doesn't allow you to adjust the gain. You might want to try out SDS series and try higher value around 5 kohm and see if this solve your problem. Also need to mention SDS board is slightly longer so it might not fit your existing casing. Tom should be able to do a swap from CDA to SDS. I asked him earlier and he say it is OK as long as your board looks like new.

Exchanging CDAs for SDS was one of the reasons for sending the amps back to Tom. But as I said earlier, he is a man of very few words. I had a lot of question for him but he chose to answer them as briefly as he could. He told me the basic advantage of the SDS over the CDA was the balanced inputs, for which I had no use as of now. The output impedance of the UMC-1 is 1k ohm, which I thought was a concern given the input impedance of CDA amps is 7k ohms. I asked Tom, as well, but got no response from him. So I stuck to the CDAs for the time being.

I have used the CDAs without an issue also. I will re-investigate everything once the amps come back to me.