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Old 3rd March 2005, 10:57 PM   #1
Pano is offline Pano  United States
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Default Sonic Impact improvements. Great!

Hello everyone,
Well, after much measuring and thinking and fiddling my 1st modifications to the SI are complete.

What a difference a mod makes! It's not the same amp. I was about to declare that all the hype over the SI was pure B.S., but no longer. This little devil has some magic up its sleeve.

Now there is plenty of bass, and a much more dynamic sound. Gone is the thin brassy sound, hello roundness. Soundstage and details are vastly improved. The sound stage seemed to get much deeper and higher. Percussive sounds are now much better, the slap of the skin on a conga is amazing.

Musical phrasing is much better now too, more expressive. Detail is improved, with room sounds and reverb more pronounced.

I replaced all the in and out connectors, put everything in a tin box, PSU included. Replaced the input caps and resistors, including the pot. Replaced the output filter coils. Replace the power electrolytic with a Panasonic FM series.

The connectors and input caps made the biggest difference.

You can read more about these modification and the results on my site:

Sonic Impact News

I may offer these modified amps to those who are interested, see my site for details.
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Old 3rd March 2005, 11:32 PM   #2
joensd is offline joensd  Germany
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Great! Now you just have to find people who buy that.
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Old 3rd March 2005, 11:35 PM   #3
Pano is offline Pano  United States
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Buy what?
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Old 4th March 2005, 12:19 PM   #4
ohenry is offline ohenry  United States
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Nice site. I think smell a little envy.
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Old 4th March 2005, 08:45 PM   #5
Pano is offline Pano  United States
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Aloha ohenry,
Thanks for the kind words. I'm an ex tarheel myself. (from O'Henry's home town).

Everyone has a right to be scepitcal, I know I was. In fact it was just about time to cry "The Emporor has no Clothes!" The S.I. just didn't cut it for me. Even with a big beefy PSU unit connected thru the power jack, the improvement was nothing to rave about.

So I went into replacing the input circuit ond output coils thinking it was just "the right thing to do." Well, surprise, surprise, surprise! The changes were dramatic and all for the better.

All I can say is, try it. Working on this tiny PCB is a royal pain in the butt, it can be done though. Buy a pair of magnifying glasses.

Happy modding!
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Old 5th March 2005, 07:57 AM   #6
ohenry is offline ohenry  United States
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I had an SI and freaked when I saw how tiny it was. And I'm a bit surprised that there is enough heat sinking available for times the amp has prolonged party periods, but evidently it does.

I'm playing with an evaluation board, it has a little more room for the clumbsy guys like me. I'm still debating as to trying to mod it; I WILL need magnification as my older and tiring eyes still have trouble with fine work (even through bifocals ). I'll most likely order some parts and have a little electronic masochistic picnic. Then I'll change the subject when my wife inquires about the project.

BTW and surprisingly, Profusion PLC gave me a decent deal on that eval board (a little cheaper than buying it in the states). They probably think that I'll fry this one and be back for more. And they're probably right!

I'll be monitoring your progress.
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Old 5th March 2005, 12:40 PM   #7
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BTW and surprisingly, Profusion PLC gave me a decent deal on that eval board (a little cheaper than buying it in the states). They probably think that I'll fry this one and be back for more. And they're probably right!

I'll be monitoring your progress. [/B][/QUOTE]


The Evaluation Board is a much better circuit than the stock SI. I may have to break down and try ordering a couple from Profusion PLC. No luck with getting a response from the US distributors on purchasing two.
Looking over the detailed circuit of the EB-2024, the only thing I would change is maybe the inductors. Do not know what the output decoupling caps are stock, but the tech notes recommend 0.47 ufd for 4 ohm loads, and 0.22 ufd for 8 ohm. Getting these in the ballpark range should take care of topend rolloff and ringing also.

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Old 5th March 2005, 05:06 PM   #8
ohenry is offline ohenry  United States
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I think the board it looks pretty good as well. I think Wayne at Bolder typically leaves the inductors and adds Auricaps to the output circuit, bybees, etc.

Intuitively, it seems that someone with proper skills could use the eval board platform to eclipse the SI's performance. That platform does triple the starting price, but hey, it's still <$100 US.

Dealing with Premier (the US distributor) has been a hassle. I ordered a board last year and had to fax a copy of my credit card for the transaction. The sales contact there isn't very friendly. Profusion was friendly and their express shipping is quick.
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Old 5th March 2005, 09:00 PM   #9
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Quote:
Originally posted by Panelhead
... but the tech notes recommend 0.47 ufd for 4 ohm loads, and 0.22 ufd for 8 ohm. Getting these in the ballpark range should take care of topend rolloff and ringing also.
George, you mean the caps that are placed across the output connectors, yeah? Not the caps that are part of the low pass filter? If so, I replaced those when I did my 1st round of mods. My replacements were 0.01uF polypropylene. Maybe too small, but they seem to work well. I want to try larger values to see if they will reduce the RF coming out.

Of course I did the very unscientific thing of making a lot of modifications all at once, so now it is hard to know how much each contributed to the overall improvements.

I have yet to replace the .47uF caps in the output filters, that will be next, after I get a new SI board - I killed this one...

Quote:
Originally posted by ohenry I'm a bit surprised that there is enough heat sinking available for times the amp has prolonged party periods, but evidently it does


That little chip gets HOT! You can't even keep a finger on it if it's been running a while. It seems to me that the sound quality degrades as the chip gets hot. A heat sink is in order, to be sure.
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Old 5th March 2005, 09:37 PM   #10
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I've posted about these before, but here they are again.

Click the image to open in full size.

I use them on all my SI's and they fit like they were made for them. They come with thermal tape attached so all you have to do is peel and stick. They can be found here . Lucky for me, he lives in my home town and all I have to do is meet him at the post office if I need more .

Heres a pic of one attached.

Click the image to open in full size.
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