Hello fellow digiamp fans.
Having found the little Sonic Impact amp with the Tripath chip here and read about it on other boards, I decided to undertake the little fellow as a project.
I have not yet made any modifications, but have been studying the amp, measuring, listening. Modifications will come next.
You'll find some useful info about the amp over at my site linked below. There are measurements, waveforms and such. As I continue further investigations and modifications they will be posted here and there.
Should be a fun project.
Sonic Investigations
Having found the little Sonic Impact amp with the Tripath chip here and read about it on other boards, I decided to undertake the little fellow as a project.
I have not yet made any modifications, but have been studying the amp, measuring, listening. Modifications will come next.
You'll find some useful info about the amp over at my site linked below. There are measurements, waveforms and such. As I continue further investigations and modifications they will be posted here and there.
Should be a fun project.
Sonic Investigations
An externally hosted image should be here but it was not working when we last tested it.
Sorry if any of you had problems with the link.
It's fixed now. (Server problem)
No coconuts.
Aloha
It's fixed now. (Server problem)
No coconuts.
Aloha
Cool project and website. It'll be interesting to see how the measurements change after everything is burned-in and how that correlates to what you hear. That's assuming your amp sounds better after a burn-in period. Most people report that it does.
My amps sounded edgy for a good while and then smoothed out. They sound clear but warm now.
Best,
KT
My amps sounded edgy for a good while and then smoothed out. They sound clear but warm now.
Best,
KT
Aloha Dave,
I've been to your site several times - good work!
Always know it's your site when I see that crazy "Seraphim".
MM
I've been to your site several times - good work!
Always know it's your site when I see that crazy "Seraphim".
MM
panomaniac said:
David Duke was certainly inspired with those... a very ambitious project... shows what can be done with a bit of imagination.
dave
Hi,
nice idea to tweak that lil bargain.
Nice website so far.
You wrote that the voltage rail on the regulated side dropped to 9V under load. That clearly shows that the chip is not regulating and that you didn´t provide the minimum input voltage to the chip (which is 14.5V but can vary).
That might even be worse for the chip than no regulator at all.
(soundwise)
12VAC should actually be enough but you´d need a bigger type that will have better regulation than yours. I reckon 50VA would do well.
greets
nice idea to tweak that lil bargain.
Nice website so far.
You wrote that the voltage rail on the regulated side dropped to 9V under load. That clearly shows that the chip is not regulating and that you didn´t provide the minimum input voltage to the chip (which is 14.5V but can vary).
That might even be worse for the chip than no regulator at all.
(soundwise)
12VAC should actually be enough but you´d need a bigger type that will have better regulation than yours. I reckon 50VA would do well.
greets
While you're testing, I'd be interested to see what current draw was when driving a 4 ohm load.
I wonder if it draws more current in this condition since it should be delivering more power...
I wonder if it draws more current in this condition since it should be delivering more power...
joensd said:
You are quite correct Sir! The little transformer can't keep up. It will be replace with toroidal 14V 60VA model. That should give the regulator enough headroom.
Lesson: Beware tiny transformers. Wallwarts? Maybe not. =)
Aloha MM
bwbass said:
I will test that and post results. My large speakers at work have 4 ohm woofers, so this would be good to know.
Thanks for the idea.
Aloha
MM
Try replacing your current wallwart with Catalog #ACTX-152 on this page:
http://www.allelectronics.com/matrix/AC_Wall_Transformers.html
15VAC @ 2.4 amps, or 36VA.
This should be plenty sufficient for your regulated PSU (after full bridge rectification you should get 21.2V.
Another option would be picking up one of the radioshack 12VAC/2amp transformers.
I don't think this little guy is going to draw more than 2 amps, so this should be plenty of juice.
http://www.allelectronics.com/matrix/AC_Wall_Transformers.html
15VAC @ 2.4 amps, or 36VA.
This should be plenty sufficient for your regulated PSU (after full bridge rectification you should get 21.2V.
Another option would be picking up one of the radioshack 12VAC/2amp transformers.
I don't think this little guy is going to draw more than 2 amps, so this should be plenty of juice.
panomaniac said:
No problem. For a little added dash of irony, these wallwarts are used to power the "Powerbite" amp listed on their site (Also rated at 15x2 watts):
http://www.allelectronics.com/cgi-bin/category.cgi?category=937&item=AMP-30&type=store
I picked up several of them -- they just seem like they'd be pretty handy for preamp power supplies. Little did I know that I'd wind up powering an amp with them!
Power and the Sonic
I tested yesterday. The Sonic does draw twice the current into a 4 ohm load. It can draw as much as 2.2 amps at onset of clipping into 4 ohms.
So:
Average draw on music - 200mA
Peak draw before clipping - 1.02A
Double this for 4 ohms. Measured at 12 & 13.2 volts.
Also - the amp is measurably bass shy. Response rolls off under 200 Hz. It's down 9dB at 20Hz 😱
I will be posting a graph very soon.
The amp inverts the signal. This is mentioned in the documentation, but you have to look for it. My measurements confirm it. Fans of absolute phase be advised.
More later.
Aloha
MM
bwbass said:
I tested yesterday. The Sonic does draw twice the current into a 4 ohm load. It can draw as much as 2.2 amps at onset of clipping into 4 ohms.
So:
Average draw on music - 200mA
Peak draw before clipping - 1.02A
Double this for 4 ohms. Measured at 12 & 13.2 volts.
Also - the amp is measurably bass shy. Response rolls off under 200 Hz. It's down 9dB at 20Hz 😱
I will be posting a graph very soon.
The amp inverts the signal. This is mentioned in the documentation, but you have to look for it. My measurements confirm it. Fans of absolute phase be advised.
More later.
Aloha
MM
Re: Bass Shy
MM,
This is about what I hear. My speakers only go to about 38 Hz before they roll off steeply. The SI is rolling off way before they do.
But you mentioned that this is not level dependent. Is it loading dependent? Do the 4 ohm and 8 ohm curves overlay?
My speakers are 15 ohm, I wonder if the power transfer is better into higher impedances. The zobel on the output may be adjustable to compensate a little.
It is surprising that the lowend roll off is not power related. Guess it shows that the inductors are not saturating.
George
panomaniac said:
MM,
This is about what I hear. My speakers only go to about 38 Hz before they roll off steeply. The SI is rolling off way before they do.
But you mentioned that this is not level dependent. Is it loading dependent? Do the 4 ohm and 8 ohm curves overlay?
My speakers are 15 ohm, I wonder if the power transfer is better into higher impedances. The zobel on the output may be adjustable to compensate a little.
It is surprising that the lowend roll off is not power related. Guess it shows that the inductors are not saturating.
George
Re: Re: Bass Shy
Well, George,
to be honest I did not run the curves at a broad range of powers, just typical musical levels. Those tiny little inductors are certainly suspect (maybe for ringing too). But my guess is that the input may be to blame.
I'll check again at maximum output and under 16 & 4 ohm loads.
Thanks for the suggestion.
FWIW, I find it surprising that you are able to use the SI with 15 ohm speakers. It just doesn't put out enough power at that impedance. Your drivers must be very efficient.
Aloha
MM
Panelhead said:
Well, George,
to be honest I did not run the curves at a broad range of powers, just typical musical levels. Those tiny little inductors are certainly suspect (maybe for ringing too). But my guess is that the input may be to blame.
I'll check again at maximum output and under 16 & 4 ohm loads.
Thanks for the suggestion.
FWIW, I find it surprising that you are able to use the SI with 15 ohm speakers. It just doesn't put out enough power at that impedance. Your drivers must be very efficient.
Aloha
MM
Re: Re: Re: Bass Shy
If the problem is in the input it is not easily fixable. That will also explain if not level or load dependent.
Also, the speakers are 100 dB efficient, so the 3 1/2 watts or so from the SI is more than enough. Even a 45 tube amp at about 1 watt is loud enough, just too soft and colored.
George
panomaniac said:
If the problem is in the input it is not easily fixable. That will also explain if not level or load dependent.
Also, the speakers are 100 dB efficient, so the 3 1/2 watts or so from the SI is more than enough. Even a 45 tube amp at about 1 watt is loud enough, just too soft and colored.
George
My guess on the bass-shyness of the Sonic Impact is the small chip caps used to block DC. I suspect replacing them with a larger value capacitor would probably fix this issue. I haven't been able to determine the value of the chip on-board, though. I don't have a capacitence meter, and there's no visible markings on the chip.
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