$175 Class D amp--120 wpc

0 Members and 1 Guest are viewing this topic. Read 990607 times.

motosapien

Re: $175 Class D amp--120 wpc
« Reply #3620 on: 31 Aug 2014, 12:56 pm »
Been following this thread from the beginning.  My NAD C 275 BEE gave up the ghost recently so I ordered a CDA 258 kit.  Going to bread board it before I go to the trouble of putting it in a case.  Will be pushing it with a NAD C 165 BEE preamp at least initially.  Has adjustable output and tone controls.  Should be here Tuesday.  I'll post my impressions after a few weeks with it. 


mrhyfy

Re: $175 Class D amp--120 wpc
« Reply #3621 on: 31 Aug 2014, 03:21 pm »
Just curious if anyone is having heat issues (thermal shut down) with modules and/or evaluation boards.....

Sound-wise, is there a clear winner for low-cost DIY Class-D?

-Tommy O

I did have a problem with my SDS-470 overheating ,, just one channel.  I believe the amp was properly assembled with heat transfer tape.   I installed a computer fan right over the amp modules,, ran it on 5 volts and that fixed the problem.  The fan was very quiet.  The drive in my bluray player made more noise!
« Last Edit: 4 Sep 2014, 02:52 pm by mrhyfy »

motosapien

Re: $175 Class D amp--120 wpc
« Reply #3622 on: 4 Sep 2014, 01:59 pm »
Got my cda 258 kit bread boarded and energized.  Dead quiet, no harshness noted on the highs and no fm interference.  Sounds great with all my sources.  I'm happy with the purchase.  These offerings from Class D Audio represent high value.

mboxler

  • Full Member
  • Posts: 300
Re: $175 Class D amp--120 wpc
« Reply #3623 on: 4 Sep 2014, 02:16 pm »
Got my cda 258 kit bread boarded and energized.  Dead quiet, no harshness noted on the highs and no fm interference.  Sounds great with all my sources.  I'm happy with the purchase.  These offerings from Class D Audio represent high value.

Congratulations!  What speakers are you driving?

I'm still driving my Klipsch RF-83's with the SDS-224 amp.  Wonderful combo  :D

Mike

motosapien

Re: $175 Class D amp--120 wpc
« Reply #3624 on: 4 Sep 2014, 05:27 pm »
Right now a pair of Paul Carmody's Classix 2's.  They would definately qualify as "cheap and cheerful".  Yesterday I had John Busch's Manzanitas hooked up.  The amp is plush and quick, no rough edges.  The folks who have noted a harshness to the highs must have impedance issues upstream.  All the jibberish about special wires and cables is just that.  I would like to try one of Emotiva's Control Freak volume potentiometers between my dac and the amp just to see how it sounds without an active pre when I'm using my pc as a source.

Also, none of my speakers are very efficient.   84 db max.  So my next build will remedy that.  Now I need to get it in some kind of case.  Maybe just an ammo can with the tranny on top of the lid.  The price certainty would be right.

schweet1

  • Newbie
  • Posts: 2
Re: $175 Class D amp--120 wpc
« Reply #3625 on: 5 Sep 2014, 06:00 pm »
I need some help/input regarding 2 persistent problems I've been having with my CDA-254S amp.  I am using the amp in stereo mode fed by the pre-outs from my Yamaha RXV-1700 receiver.

Problem 1 is that the left channel has a hiss when the CDA amp is first plugged in and turned on.  My preference would be to plug the CDA amp into the AC output on the Yamaha 1700.  This way I can leave the CDA amp's power switch on and when the receiver turns on, the amp turns on, and when the receiver turns off, the amp turns off.  The hiss goes away on its own after the amp has been plugged in for 5-7 minutes, and then the speakers are dead quiet.  I am guessing that it has to do with charging the capacitors or transformer, or bringing certain components up to operating temperature.  However, for now, the solution has been to plug the CDA amp directly into the wall and leave it turn on 24/7.  However, this work-around is not my preference if there is an effective way to solve the problem.  I've tried the CDA amp in bridged mode and with other speakers the same problem exists.

Problem 2 is that the amplifier causes distortion or a buzz in the tweeter when sound is being played at above average (but not excessive) volume, particularly when the song or audio track includes heavy bass.  I've tried connecting the CDA amp to different speakers and tried both stereo and bridged mode.  I've also tried connecting the source directly to the amp bypassing the preamp/receiver.  None of those efforts have solved the problem.

Any ideas/suggestions on how to remedy?  Because of the above, the CDA amp has never found a home in my main system.  I keep it around as a utility amp when needed for speakers at the office, or in secondary zones.  Apart from the above issues, I've generally liked the clean sound it produces.

motosapien

Re: $175 Class D amp--120 wpc
« Reply #3626 on: 11 Sep 2014, 08:03 pm »
I would contact Tom at Class D Audio.  Maybe you have defective amp module.  Mine has worked flawlessly and is dead quiet.

srb

Re: $175 Class D amp--120 wpc
« Reply #3627 on: 11 Sep 2014, 08:28 pm »
My preference would be to plug the CDA amp into the AC output on the Yamaha 1700.  This way I can leave the CDA amp's power switch on and when the receiver turns on, the amp turns on, and when the receiver turns off, the amp turns off.

The switched AC convenience outlets on the Yamaha RX-V1700 are low-capacity 100W / .8A total designed for low-wattage components, like a CD player, turntable, etc.

I assume you've tried the amplifier plugged directly into the wall, but even if they are not restricting the operation of the power amplifier plugged into them current-wise, the receiver's power switch / relay / convenience outlet circuit is not designed for a power amplifier's load of that wattage, even being a relatively efficient Class D.

Steve

matt_garman

Re: $175 Class D amp--120 wpc
« Reply #3628 on: 11 Sep 2014, 08:51 pm »
The switched AC convenience outlets on the Yamaha RX-V1700 are low-capacity 100W / .8A total designed for low-wattage components, like a CD player, turntable, etc.

I assume you've tried the amplifier plugged directly into the wall, but even if they are not restricting the operation of the power amplifier plugged into them current-wise, the receiver's power switch / relay / convenience outlet circuit is not designed for a power amplifier's load of that wattage, even being a relatively efficient Class D.

For years now I've been using this Smart Strip 4941 Energy Saving Surge Protector with Autoswitching Technology, 7-Outlet as a poor-man's relay.  I have my DAC setup as the blue master on the smart strip, and my power amp (used to be SDS-470, now replaced by a TPA3116 amp) on one of the green auto-switched outlets.

SCM

Re: $175 Class D amp--120 wpc
« Reply #3629 on: 15 Sep 2014, 12:32 pm »
I would contact Tom at Class D Audio.  Maybe you have defective amp module.  Mine has worked flawlessly and is dead quiet.

Have any members here sent their Class D Audio in for repair/adjustment ?  And if so, what was the turn around time ?

schweet1

  • Newbie
  • Posts: 2
Re: $175 Class D amp--120 wpc
« Reply #3630 on: 16 Sep 2014, 06:37 pm »
Thanks all for the responses.

Yes, as mentioned, I now use the CDA-254S solely plugged into the wall.  When initially plugged in, it has a hiss in the left channel for about 5 minutes, which then goes away.  Therefore, I leave it plugged in and on all the time (since it does not seem to consume much electricity when idle).

I mailed the amp back to Tom at Classdaudio after first experiencing the problem.  He sent it back to me with a note that they didn't find any problem with it.  Unfortunately, when I received it back the same problem existed.  In response to SCM's question, I received the amp back about 3.5 weeks after I sent it (I paid for priority shipping when I sent it). 

When I first noticed the tweeter distortion, my thought was that I over-drove the tweeter, so I purchased a replacement tweeter from the speaker manufacturer and installed it.  But the same tweeter distortion existed.  So, I connected other receivers and amps to the speakers and tried both the new and old tweeter, and the problem was gone, thereby identifying the issue as coming from the CDA amp.

So while I was able to work around the initial hiss when power is connected (by leaving the amp plugged in at all times), the remaining problem of distortion in the high frequency range (when a track that also has heavy bass is being played at an above average volume) remains.  Unfortunately, at this point, I somewhat regret the purchase and wish there was more that I could do to help fix the issue.

SCM

Re: $175 Class D amp--120 wpc
« Reply #3631 on: 17 Sep 2014, 12:37 am »
PM sent

fmw

  • Jr. Member
  • Posts: 33
Re: $175 Class D amp--120 wpc
« Reply #3632 on: 22 Sep 2014, 01:50 pm »

The most common complaint of class d is that the highs sound off.  I don't know why that would be but I have my suspicions, and it has as much to do with what people are used to hearing.

The only class D amp I have powers my personal computer audio.  It is the bass that sounds a little off to me.  Perhaps it is designed to have bass boost for driving small speakers.  I don't know.  I do use a subwoofer with bookshelf speakers for the computer so it is a full range setup.

My impression is that comments about class D technology as a group probably depend more about when the comments were made rather than what they say.  Early class D amps were questionable.  The new ones really seem to be pretty good.  This little thing certainly provides high fidelity sound from my computer while I work.


I.Greyhound Fan

Re: $175 Class D amp--120 wpc
« Reply #3633 on: 22 Sep 2014, 02:06 pm »
Thanks all for the responses.

Yes, as mentioned, I now use the CDA-254S solely plugged into the wall.  When initially plugged in, it has a hiss in the left channel for about 5 minutes, which then goes away.  Therefore, I leave it plugged in and on all the time (since it does not seem to consume much electricity when idle).

I mailed the amp back to Tom at Classdaudio after first experiencing the problem.  He sent it back to me with a note that they didn't find any problem with it.  Unfortunately, when I received it back the same problem existed.  In response to SCM's question, I received the amp back about 3.5 weeks after I sent it (I paid for priority shipping when I sent it). 

When I first noticed the tweeter distortion, my thought was that I over-drove the tweeter, so I purchased a replacement tweeter from the speaker manufacturer and installed it.  But the same tweeter distortion existed.  So, I connected other receivers and amps to the speakers and tried both the new and old tweeter, and the problem was gone, thereby identifying the issue as coming from the CDA amp.

So while I was able to work around the initial hiss when power is connected (by leaving the amp plugged in at all times), the remaining problem of distortion in the high frequency range (when a track that also has heavy bass is being played at an above average volume) remains.  Unfortunately, at this point, I somewhat regret the purchase and wish there was more that I could do to help fix the issue.


I would email Tom and see if he would exchange the amp for a new one.  He should given the circumstances if his customer service is top notch.


wgscott

Re: $175 Class D amp--120 wpc
« Reply #3634 on: 17 Nov 2014, 12:59 am »
For years now I've been using this Smart Strip 4941 Energy Saving Surge Protector with Autoswitching Technology, 7-Outlet as a poor-man's relay.  I have my DAC setup as the blue master on the smart strip, and my power amp (used to be SDS-470, now replaced by a TPA3116 amp) on one of the green auto-switched outlets.

I am using the same thing with my Class D Audio amp.

wgscott

Re: $175 Class D amp--120 wpc
« Reply #3635 on: 17 Nov 2014, 01:00 am »
Have any members here sent their Class D Audio in for repair/adjustment ?  And if so, what was the turn around time ?

Yes.  I can't remember exactly, but it was fast.

zoula

Re: $175 Class D amp--120 wpc
« Reply #3636 on: 17 Nov 2014, 03:24 pm »
Hi guys,

It's been a wile since I came over here....   I'm the proud owner of a SDS-254.  I recently bought an other 6 channels for an active loudspeaker. 

I would like to use a fix resistor on all of my amps and replace the adjustable gain.  Is there a "consensus" for the value that sound the best???  or is it simply a jumper that sound the best??? 

matt_garman

Re: $175 Class D amp--120 wpc
« Reply #3637 on: 17 Nov 2014, 05:02 pm »
I would like to use a fix resistor on all of my amps and replace the adjustable gain.  Is there a "consensus" for the value that sound the best???  or is it simply a jumper that sound the best???

Here is the table for resistance versus gain:
Code: [Select]
resistance (ohms) versus gain (db)
560  31
1000 30
2200 27
5200 23
6200 18
7500 16

I don't think there is any consensus, and in general, I believe input gain is a matter of personal preference and/or impedance matching with source components.

In my case, I simply used the pots to dial in what I liked best ("tune by ear"), then used an ohm meter to measure the resistance, and purchased fixed resistors accordingly.

There was a lengthy discussion on type of resistor a ways back in this thread.  A lot of people reported success with those expensive thin film (I think?) resistors.  IIRC, they're around $30/each.  A bit too much for my wallet.  :)

dr_skoobie

  • Jr. Member
  • Posts: 20
Re: $175 Class D amp--120 wpc
« Reply #3638 on: 20 Feb 2015, 04:20 pm »
Hi guys,

Does anyone know a way to contact Tom directly?  I need to inquire about an amplifier repair.  If you have a phone number, please PM me.

thanks!

-v

vinylvalet

  • Jr. Member
  • Posts: 44
Re: $175 Class D amp--120 wpc
« Reply #3639 on: 6 Mar 2015, 08:42 pm »
I've managed to wade through this entire thread and would like to thank all the generous contributors.

One thing that doesn't make sense to me is some of the complaints I've seen that Tom at CDA doesn't answer emails or takes a long time to do so. I've emailed Tom several times over the last several months and he has always gotten back to me within the hour. Exceptional support. I use the support@classdaudio.com email.