Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 23rd June 2005, 03:07 AM   #21
diyAudio Member
 
sx881663's Avatar
 
Join Date: Nov 2003
Location: so. ca.
Default Re: Re: Caps on Output

Quote:
Originally posted by mb


IMO, the T-amps will suffer with 16ohm speakers. Once key bottlenecks like power supply and input caps are taken care of, the major sonic constraint is likely to be voltage swing, and the 12V power supply is clearly a limitation, esp. on higher impedance speakers that need voltage rather than current delivery.

My T-amps were ok up to very modest levels on nasty 4 ohm, ~84dB Gale speakers, but the lack of bass due to input caps and relative weakness of SLA batteries could be heard. With the 41Hz Amp3, good 13.4V linear power supply, the better parts on the Amp3, etc, the bass is terrific. I don't have the gear to measure, but with a multimeter I'm getting to 2-4W rms (peak reading, based on 8 ohms) and good, clean sound. Of course if I decide to yank it up another 6dB distortion, will be audible, but few amps of any size have the clarity and coherence I've heard on my Amp3.
Canít argue with that, 2.5-3 watts is just not enough to drive bass except in the most limited of manner. Yes, the SI amp is strictly entry level into good sounding class D. It makes sense only as a starting point unless you have very efficient speakers. I havenít played around with a 41Hz amp yet but the superior parts quality alone should make a big difference.
I will certainly agree that these little things do some things so right it amazes. Probably the first time I ever heard piano note attack and decay sound real and right. This was only true if driving a quality single driver speaker of reasonable efficiency (87db I think).
The point I was trying to make was that in this case the problem may not be power related but some other factor. My little amp will only do 5.5 watts before it starts to clip but has no problem doing deep tuneful bass till you push it. Not a problem as I use it for near field listening. I am sure having regulated SMPS power is a factor here. It does flesh out the bass and give it some body. Sure doesnít hurt the sound stage either.
Roger
__________________
Happiness is being owned by a cat
  Reply With Quote
Old 24th June 2005, 08:00 PM   #22
jkeny is offline jkeny  Ireland
Banned
 
Join Date: Feb 2007
Location: Dublin
George,

Quote:
I finally figured out most of the SI output stage. The Zobel is there and the 0.47 ufd caps from the outputs to ground so I replaced the 0.15 strapping cap with the recommended 0.01 ufd.
I would be interested if you could post a schematic of the output stage (or nearly complete output stage. I am also running the T-amp with 15 ohm speakers - Rogers LS3/5A. The amp is poerful enough for non party listening but I'm trying to improve it -

I have changed - changed input caps to 2.2 uF Wima MKS (Polyester?) bypassed with arcotronics .047uF

- added 4,700uf ELNA Cerafine cap bypasses with panasonic FC 1200uF (remotely wired to power pins of SI chip - not such a good implementation as directly at pins I know

- removed EMI reduction cap accross speaker output posts

Although the sound is good I still find it lacks stage and depth _ I'm running on 7ah battery so should be enough power

I thought maybe changing the cap you mentioned in quote might be the next job

John
  Reply With Quote
Old 24th June 2005, 09:51 PM   #23
diyAudio Member
 
sx881663's Avatar
 
Join Date: Nov 2003
Location: so. ca.
Default Question of staging

Quote:
Originally posted by jkeny
George,



I would be interested if you could post a schematic of the output stage (or nearly complete output stage. I am also running the T-amp with 15 ohm speakers - Rogers LS3/5A. The amp is poerful enough for non party listening but I'm trying to improve it -

I have changed - changed input caps to 2.2 uF Wima MKS (Polyester?) bypassed with arcotronics .047uF

- added 4,700uf ELNA Cerafine cap bypasses with panasonic FC 1200uF (remotely wired to power pins of SI chip - not such a good implementation as directly at pins I know

- removed EMI reduction cap accross speaker output posts

Although the sound is good I still find it lacks stage and depth _ I'm running on 7ah battery so should be enough power

I thought maybe changing the cap you mentioned in quote might be the next job

John
Sound staging is generally related to power source. The stiffer, better regulated the source the wider the stage. This has to do with cross talk degrading channel separation. Depth almost totally relates to noise. Noise masks low level info and can reduce stage depth dramatically. Focus within the stage relates to signal coherence, dealing with the timing accuracy of leading and trailing edges. The difference of sound arrival times is what we use to locate where in space a sound is coming from. So if all that is true it looks as if you have some power supply work to do. Later I will be building a battery powered piece and will use a highly regulated DC/DC converter. As I havenít actually listened to this combo yet I donít know if it will solve all the battery problems/issues. You might try a very large cap to see what happens. Like one of the .1 farad units they use in cars. All those very big caps must be doing some good or they wouldnít be selling as they are. Let us know your findings.
Btw I don't recommend bypassing coupling caps as this causes a time smear of the signal and leads to stage placement confusion or a perceived out of focus sound. This is somewhat the same effect as clock jitter, a timing error. Splitting a signal into 2 or more paths is never a good idea as when it is put back together it is never the same as it was originally.
Roger
__________________
Happiness is being owned by a cat
  Reply With Quote
Old 24th June 2005, 11:30 PM   #24
BWRX is offline BWRX  United States
diyAudio Moderator Emeritus
 
Join Date: Jan 2005
Location: Pennsylvania
Default Re: Question of staging

Quote:
Originally posted by sx881663
You might try a very large cap to see what happens. Like one of the .1 farad units they use in cars. All those very big caps must be doing some good or they wouldnít be selling as they are. Let us know your findings.
you mean the 1.0 F caps they use in cars. they main reason they sell is because of good marketing, but that's off topic... like you said, sound staging is related to the power source. a regulated power supply greatly improves not only the frequency response (you will hear more bass and smoother highs) but also the sound staging of the SI. find a higher voltage wall wart with ample current capability around the house, buy a good low dropout IC regulator from national or linear, build a simple regulator circuit described in the common applications section of the data sheet, and you're good to go.
  Reply With Quote
Old 25th June 2005, 12:30 AM   #25
diyAudio Member
 
sx881663's Avatar
 
Join Date: Nov 2003
Location: so. ca.
Default Re: Re: Question of staging

Quote:
Originally posted by BWRX


you mean the 1.0 F caps they use in cars. they main reason they sell is because of good marketing, but that's off topic... like you said, sound staging is related to the power source. a regulated power supply greatly improves not only the frequency response (you will hear more bass and smoother highs) but also the sound staging of the SI. find a higher voltage wall wart with ample current capability around the house, buy a good low dropout IC regulator from national or linear, build a simple regulator circuit described in the common applications section of the data sheet, and you're good to go.
I agree with the good marketing bit, putting gold plated screws into them along with a fancy label and charging twice as much. But all that aside they must do some good or the "fad" would have died out.
The message I wanted to give was dealing with power supplies. If you purchase a good quality SMPS type unit, one that has its own power cord. There are usually screws under the stick on feet or label to open it up. These units are usually adjustable and if not can be easily be made so. While you are at it you can up grade the caps with some larger low ESR units. These units usually have very good regulation using an lm431 reference as a high gain feed back element. It makes it not worth the bother to build one that wouldnít be as good anyway. Several more real advantages exist with these units aside from regulation and efficiency. Due to a very small influence from leakage inductance in their transformers and the high speed switching they are very quiet in the audio band. They respond fast to changes but run out of steam just as fast so for a 12 - 13.5 v unit I would recommend a 22-50,000uf buffer cap. At 16 volt rating these arenít too big. It can be done with 2 smaller pieces in parallel and put into the battery compartment of the original case, if that is what you are using. With this being done sound staging will not be a problem.
Roger
__________________
Happiness is being owned by a cat
  Reply With Quote
Old 26th June 2005, 04:05 AM   #26
diyAudio Member
 
sx881663's Avatar
 
Join Date: Nov 2003
Location: so. ca.
Default Big caps!

General information
I just did some checking on eBay for some larger 16 volt caps but the selection was very limited. Thought maybe searching for car type caps using the word farad would bring up something. Wow! Did it ever 7+ pages of caps from .5 farad to 60, yes 60 farad. These are apparently a hybrid design with no further info available. Not cheap either. These caps must have some merit in this application.
Roger
__________________
Happiness is being owned by a cat
  Reply With Quote
Old 29th June 2005, 01:07 AM   #27
jkeny is offline jkeny  Ireland
Banned
 
Join Date: Feb 2007
Location: Dublin
Thanks for your help - ypu are right it was the a power supply problem - even though I am using a 7aH SLA battery I put a 4700uF ELNA capacitor on fly leads connected to the pos and ground of the SI chip.

Once I took this out and put a low ESR panasonic FC cap right at the chip power pins everything sharpened up and sound stage opened up.

I am finding that the mid range is not as full as other amps I have heard (gainclone, etc). Has any else experienced this or is it the synergy with my 15 ohm speakers?

John
  Reply With Quote
Old 29th June 2005, 03:48 AM   #28
diyAudio Member
 
sx881663's Avatar
 
Join Date: Nov 2003
Location: so. ca.
John,
I am using Auricaps for my input coupling chores. These caps are exemplary in all respects including test results. I also am using small full range single drivers (Tang band 8 ohm 3Ē) in near field with a powered sub. Earlier when I tried quality 2 way speakers the sound all around the cross over freq was pretty bad. These amps canít handle complex loads with varying impedance, probably because the output filter is not in the feedback loop. As it stands it sounds wonderful and the midrange on up is its strongest good point. If you are stuck driving complex speakers then you might try upgrading the output filter components and change them to the proper value for 16 ohm. Tripath has all that info on their website.
Roger
__________________
Happiness is being owned by a cat
  Reply With Quote
Old 2nd July 2005, 08:46 PM   #29
jkeny is offline jkeny  Ireland
Banned
 
Join Date: Feb 2007
Location: Dublin
Roger,
Thanks, that was what I was thinking, although I will probably try to go the route of using the amps( I have two) to make these speakers active using computer and kxproject or BruteFir software for digital crossovers - this will remove the complex passive crossover s used on Ls3/5a's and may free up the sound

John
  Reply With Quote
Old 3rd July 2005, 06:35 PM   #30
diyAudio Member
 
sx881663's Avatar
 
Join Date: Nov 2003
Location: so. ca.
Default Bi amp

This is not an easy one. The Rogers have an extensive and complex crossover network. This would be a very good place for reverse engineering and circuit modeling. It would also be helpful to have the specs on the drivers used, to plug into the model. This would tell you what they are doing but not necessarily why. With a computer generated crossover and correction it should be possible to overcome the back row seat sound these speakers have. One real and immediate benefit would be the much better efficiency and control from direct drive. I think an excellent use for these amps. This could be very good when finished. Let us know as you progress.
Good luck,
Roger
__________________
Happiness is being owned by a cat
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
my latest box he he he east electronics Solid State 4 12th March 2008 07:54 AM
My latest Andrewbee Full Range 14 7th December 2005 03:14 AM
My Latest Subwoofer - with pictures soundNERD Subwoofers 7 1st December 2005 04:08 AM
pix of my latest jsalk Multi-Way 19 4th July 2003 05:57 AM


New To Site? Need Help?

All times are GMT. The time now is 08:18 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2