[mboxler]

Hi...

First post on my first forum...hope I'm asking appropriate questions.  I'm attempting to build a tri-amp active system to drive my Klipshorns (I'm upgrading the mid and tweeter drivers as well).  I've have 3 SDS-224 amp kits fed by Marchand XM-1 active crossovers.  I plan on driving the woofer section at full gain, then lower the mid and high amp gains using the supplied potentiometers.  Has anyone tried to simply solder the yellow and black wires on the gain controls together rather than use a low ohm resisters?  Seems that would be an easy (and cheap) way to get full gain on one amp, then use pots on the other amps to adjust the amplitude.  Once set, I'd measure the resistance on the adjusted mid and high pots and replace them with fixed resistors.

Thanks, Mike

[wgscott]

Earlier in the thread there were observations from some that the sound improved when the gain was attenuated somewhat.  Also, wouldn't you want to be able to balance the gain for all six channels to get the flattest response?

[mboxler]

I did solder the wires...got full gain as expected.   Also got same hiss/hum that I got at full throttle with the pots.  Sound was best around half way, which measured 5k ohms.  I'm going to solder a 4.7k ohm to the wires and see what happens.  Yes, I will then adjust the gain on the mids and highs to balance to the bass (using the supplied pots).

Mike

[roymail]

Hi...

First post on my first forum...hope I'm asking appropriate questions.  I'm attempting to build a tri-amp active system to drive my Klipshorns (I'm upgrading the mid and tweeter drivers as well).  I've have 3 SDS-224 amp kits fed by Marchand XM-1 active crossovers.  I plan on driving the woofer section at full gain, then lower the mid and high amp gains using the supplied potentiometers.  Has anyone tried to simply solder the yellow and black wires on the gain controls together rather than use a low ohm resisters?  Seems that would be an easy (and cheap) way to get full gain on one amp, then use pots on the other amps to adjust the amplitude.  Once set, I'd measure the resistance on the adjusted mid and high pots and replace them with fixed resistors.
Thanks, Mike

Hello Mike and welcome to AC.  We welcome your posts! 

[matt_garman]

Right-sizing and Headroom / Dynamics

Hi all,

I've worked my way through about 80% of this thread, so I hope this hasn't come up.  Basically, I'm trying to decide how big of an amp to build.  I don't know this from personal experience, but the "internet audiophile community" seems to generally say that, with amps, more headroom is better.  I.e., it's better to have a much bigger amp than you really need.  I believe the rationale for this notion is that it helps with dynamics in music (and movies as well).

Right now my current setup is: FLAC CD rips on a computer, fed via optical to an Emotiva XDA-1 preamp-DAC, to a QSC RMX2450 "pro" amp via balanced XLR, to Salk Songtower speakers (4 ohms at 88 db).  The QSC amp has an obscene amount of power; I went with a pro amp because they offer good value (in terms of watts/dollar).

I'm really happy with this setup, and I think it sounds great.  But the QSC does require active cooling (although I fan modded it so it's inaudible), and uses a fair amount of power.  Our entertainment center is in a corner, so it sits out of sight behind the TV; I wouldn't want to keep it in an enclosed space.  So that got me thinking about class D amps in general, as they are known for high efficiency.  I started reading about the Wyred 4 Sound series of amps, as they get a lot of good press, and then I ran across this thread... Besides the rational reason for wanting a different amp, I'm a perpetual tweaker (I can't leave things alone; I'm sure many here have the same problem), so a great-sounding, low-cost DIY project is something I simply must do. 

Having said all that, I want to come back to the "more headroom" idea.  First question: is the extra headroom a function of the power supply, the amp, or both?

Second: I hooked a Kill-A-Watt AC power meter up to my QSC while listening at typical levels.  It's only pulling about 60 Watts.  I believe the QSC is a class AB amp, which have low efficiency, but let's assume that it's 100% efficient.  That means I'm sending actually sending considerably less than 100W to my speakers.  Realistically, I'm probably sending 30--50 Watts to the speakers.

That in mind, would I be well-served by an SDS-254 (rated at 250W @ 4 ohms)?  Perhaps with an upgraded power supply and transformer?  I should I hold out for Tom (at Class D Audio) to come out with something bigger?  I've got a question about that in to him now---if he does have something bigger, should I get that instead?

Thanks!
Matt

[Meicheng]

The SDS-254 will have no problem driving the Songtowers easily.  I think its a fine combination. 

[srb]

Second: I hooked a Kill-A-Watt AC power meter up to my QSC while listening at typical levels.  It's only pulling about 60 Watts.  I believe the QSC is a class AB amp, which have low efficiency, but let's assume that it's 100% efficient.  That means I'm sending actually sending considerably less than 100W to my speakers.  Realistically, I'm probably sending 30--50 Watts to the speakers.

The Kill A Watt meter does not have the speed to react to a peak transient on the order of milliseconds, nor does it have a peak hold function.  Whatever your average power used is, a 10dB transient requires 10 times the power, even if it's only for 100 miliseconds, and that's where headroom comes into play.
 
Steve

[NeilT]

Matt, check out the SDS-470 from classD audio / Tom.
250 wpc @ 8 ohms.

I just started using one and what a diff over my SS 200 wpc amp.

Complete amp for 600+.

Neil

[roymail]

Neil, does the SDS-470 also do 4 ohms since the Songtowers are 4 ohms, I believe.  I know some of the Class D Audio amps do 4 ohms and some don't.  Just checking... thanks!

[matt_garman]

Neil, does the SDS-470 also do 4 ohms since the Songtowers are 4 ohms, I believe.  I know some of the Class D Audio amps do 4 ohms and some don't.  Just checking... thanks!

I have exchanged a few emails with Tom at Class D Audio regarding the SDS-470.  He said, "[the SDS-470] will give you a very solid 500W RMS per channel into 4 ohms and can also put out up to 1000W RMS per channel into 2 ohms."  He even sent me a picture of it:



I went ahead and ordered one (a kit) today. 

Matt, check out the SDS-470 from classD audio / Tom.  250 wpc @ 8 ohms.

I just started using one and what a diff over my SS 200 wpc amp.

Could you elaborate a bit more on your setup?  What make/model of amp did you replace?  What kind of speakers do you have?  What about the source and preamp?  Is your SDS-470 built from the stock kit, or did you do mods?  And of course, we all love pics! 

I think this will be a fun project!

[NeilT]

Neil, does the SDS-470 also do 4 ohms since the Songtowers are 4 ohms, I believe.  I know some of the Class D Audio amps do 4 ohms and some don't.  Just checking... thanks!

Hi Roy, looks like Matt answered your question.
Mine is a stock, complete amp from Tom. I believe it has a 500 VA trans.
It has more than enough power to drive my 92db OB7's.

Matt check your PM

Neil

[wgscott]

Maybe this is obvious to people who know way more about audio than I do, but the biggest improvement with a more powerful amp was how it sounded when I had the volume set to a low listening level.

If you put your kilowatt on the Class D amp, you will think you forgot to turn it on.     That is part of the charm.

[maxitonus]

I reply to Matt Garmann'
I am new here,and an audiophile located in south France.
I received three weeks ago one SDS470,which has been installed temporarily to replace my Ayon TritonII tubed amp which i sent to the mfr for a free of charge upgrading + a change of all tubes to "black treasure kt88" ones.
The SDS amp is fed by a Weiss DAC2 and connected to 2X Duntech Crown Prince speakers,impedance:4 ohms.
Its been a very big surprise to immediately face the fact the SDS is of the same league as the Triton for which concerns the global sound quality and transparency.
So surprising that two friends of mine,really golden eared audiophiles (and perfectionnists),when hearing the sound of my system with the SDS (they already heard the Triton),asked me to purchase for them to Tom 2x SDS,which i did last sunday....
The transparency and resolution are at least equal to those of the Triton,we can also hear that there is less harmonic2,which is easily understandable..in the medium-treble zone,the sound seems more "flat" means more natural,without any (small) presence proeminence,eliminating any fatigue when listening for a long time.
There are two other small differences:
-The extreme treble zone (15 to 20khz)although present,is a little "shy",which i had to compensate by reducing the linear capacitance of the interconnects and searching for all other compensations,which has been finally sucessfull.
-The bass and extreme bass area is extremely powerfull,a little bit more than with the Ayon...so I had to slightly reduce the section of the (+) cable feeding the boomers (i use bi-wiring) and slightly increase the number of litz wires feeding the medium- treble drivers.
Nota:changing the mains 220v cable modifies the level of low frequencies,a good compromise is easy to find out.

Testing the amp with the CD:"calle54 9 chico o'farill afro cuban jazz suite" is very impressive ,never heard it like that,you can be scared with the realism of percussions and ultra low frequency strokes.
500W on 4 ohm is well present on transients..but the low level information is neither erased nore even degraded..
Testing on "carreras domingo pavarotti en concert 16-17encore o sole mio,nessun dorma" is the best listening experience with my system,in spite of the fact this CD is very far from perfect,you can recognize the type of condenser microphones..

As a conclusion,the SDS is so resolving that any mod of any element of the system changes the colour of the sound,in particular the position of plugs,the digital cables,filtering the mains line of the CD/DAC,etc....
This is why the comments given about this amp could be controversial since for example it is used with high capacitance interconnects,the sound could be qualified of soft or round,if the speaker cables are not optimised,the sound is only "good" but not breathtaking,if your CD player is having jitter you will believe that the metallic harmonics are coming from the amp however not guilty for this frequent shortcoming....
The reason why,according to my own personal opinion,this SDS amp is a high-end one,is that it never limited me to search for a better sound by any mod of the system,I never heard a distortion which could be surely attributed to it,i never heard a loss of information(the silence of this amp is fully "black"),it is clearly worth being connected to other elements of the highest level .
The cables and interconnects must be chosen with care until obtaining an holographic image with a tremendous depth and wide scene,which needs less mediums and a little bit more extreme treble. Sincerely Mxt

[NeilT]

Maybe this is obvious to people who know way more about audio than I do, but the biggest improvement with a more powerful amp was how it sounded when I had the volume set to a low listening level.

If you put your kilowatt on the Class D amp, you will think you forgot to turn it on.     That is part of the charm.

Nail on the head wgscott. 

The dynamics at low levels is amazing.
I have to look to make sure my sub woofer is off.
I rarely feel the need to use it with music anymore.
Neil

[matt_garman]

^^^^^
To me, the easy way to control the power of your amp is use power console, like Belkin PureAV or Monster console, they can remote turn on your amp by your receiver.

My current power amp does not have a 12V trigger, so I use a Smart Strip Power Strip, and my preamp is the "master".  This is basically a poor man's 12V trigger.  Works great for my current amp, and I don't see why it wouldn't work for the Class D Audio amps.

[matt_garman]

I reply to Matt Garmann'
I am new here,and an audiophile located in south France.
I received three weeks ago one SDS470,which has been installed temporarily to replace my Ayon TritonII tubed amp which i sent to the mfr for a free of charge upgrading + a change of all tubes to "black treasure kt88" ones.
... snip ...

Thank you for that detailed account of your experience with the SDS-470.  It has only made me more excited to receive mine!

[I.Greyhound Fan]

I just bought a CDA254 for my son to run with his Maverick DAC/Pre.  I want to place it in this metal chassis-

http://www.par-metal.com/product-ttp-20series.php

Is there any thing special that I need to know about before I do this?

Has any one found a good round power button for the unit?

Will any of these work-

http://www.e-switch.com/product/tabid/96/productid/74/sename/pv3-series-illuminated-sealed-long-life-anti-vandal-switches/default.aspx

http://www.e-switch.com/product/tabid/96/productid/73/sename/pv2-series-water-resistant-long-life-anti-vandal-switches/default.aspx

http://www.e-switch.com/product/tabid/96/productid/77/sename/pv6-series-illuminated-sealed-long-life-anti-vandal-switches/default.aspx

Any help would be much appreciated.

Larry

[corndog71]

If you need to drill any holes into the aluminum, take it slow.

[TrungT]

For sheet metal

[firedog]

I just bought a CDA254 for my son to run with his Maverick DAC/Pre.  I want to place it in this metal chassis-

http://www.par-metal.com/product-ttp-20series.php

Is there any thing special that I need to know about before I do this?

Has any one found a good round power button for the unit?

Larry

Larry, I like some of those, but isn't that site selling wholesale? Can you order one or two switches?