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Old 28th November 2008, 05:36 AM   #1
chicks is offline chicks  United States
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Default Another Tripath Amp

I hijacked a thread over in the Fullrange section that was about bamboo speaker enclosures, but includes information on a cheap Tripath-based amp, with a pair of 3" fullrange speakers and 14V SMPS (and a remote control and control board in the bargain). $21 shipped for the lot, involves destroying a perfectly good speaker system meant for a first-gen PSP, but lots of fun and great Tripath sound, once it's fully modded.

http://www.diyaudio.com/forums/showt...57#post1622157
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Old 29th November 2008, 07:02 PM   #2
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The wife found a "50% off any one clearance item" @ Tuesday Morning in the Thanksgiving day newspaper. So, off we went. They have the sister product to the Nodus, the Sonic Impact T24, marked down to $59.95 on clearance, and had the 50% off coupon taped to every one of them, making them ~ $30 each.

Anyone looking for a SoundDock clone for your iPod, or just a cheap XMas gift for an iPod owner, might want to have a look.

You can check stock in your area by calling their automated product locator @ 1-800-901-0881, using your zipcode and SKU # 8389804.

A review:

http://www.ilounge.com/index.php/rev...l-audio-system
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Old 22nd December 2008, 12:17 AM   #3
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Alright, rather than continuing to derail the thread in the fullrange loudspeaker forum, i'm posting my nodus psyclone experience here.

I went so far as to cut off the EQ portion of the board completely, because i need to fit it into a tight space.

I did this all in the last couple hours.

The good news is, it doesn't burst into flames. The bad news is, I only have sound in one channel.

By the way, has anyone else noticed that if the markings on the amp board are correct, one of the speakers in the psyclone was out of phase with the other?

Anyway, attached is a picture of my board w/ mods as recommended in the other thread, near as i could follow them.
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Old 23rd December 2008, 05:47 PM   #4
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Looks like the portion of the ground plane adjacent to the two yellow input caps gets isolated when the board is cut. It appears that the negative lead of C337 (I can't quite make out the number, but it's a black electrolytic, 100uF @ 16V, right below the power connector and next to C315) is used to connect to the ground plane through the board. Try jumpering the negative lead of this cap to the non-isolated ground plane.
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Old 23rd December 2008, 07:19 PM   #5
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Yeah, I actually tried that. Well, i bridged the ground plane, at least. I haven't checked to see if that cap is really properly grounded.

Maybe i killed it. Got two more just like it. But i'd still feel bad if i killed it.

By the way, I've been wondering - is it really necessary to connect signal ground to power ground?

I'm wondering about that because the box that i'm shoehorning it into has a volume control that i don't want to lose. Which means i'm probably going to have to buffer the input with an opamp, which would connect it's input ground to a 'virtual' ground at something around 7v. I've done a fair amount of DIY work but I'm not sure if maybe that will cause a problem, or maybe just require that i leave the input caps on the tripath board intact.

(For those who haven't read the other thread, I'm attempting to upgrade a Stax SRD-X electrostatic headphone driver which currently uses 5.8w rated car radio chip amps from the seventies to drive a pair of transformers. The nodus amp board looks like it should fit if i cut off the EQ section.)
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Old 23rd December 2008, 11:19 PM   #6
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Quote:
Originally posted by ericj

is it really necessary to connect signal ground to power ground?
I wasn't able to get any sound out of this until I hooked these together. Your results may vary...
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Old 27th December 2008, 06:31 PM   #7
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Alright, I extracted another amp board from another PSC99.

So far I've done all the same jumper mods as my 1st board, cut the recommended traces, and manually severed everything that cutting off the speaten filter would cut except for the big groundplane.

And it's still working. Driving the heck out of some little Teac 6-ohm kevlar speakers. Freaky how the heatsink only gets a little warm, and then only after several minutes at high volume.

I've verified that the negative leg of C337 is indeed floating when that groundplane is cut, but reconnecting it to the rest of the groundplane doesn't help my 1st board. Maybe allowing it to float was a Very Bad Thing.

Sooner or later I'll have the nerve to chop off the speaten filter on the 2nd board, and I'll reconnect the groundplane before i apply power.

Edit: Did i mention that i never tested the 1st PSC99 before i tore into it? I did loan it to a friend of mine who has a PSP for a few days. Only now does he tell me that the sound only came out of one speaker. DOH!
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Old 27th December 2008, 07:05 PM   #8
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Alright, chopped the speaten filter off the 2nd board, bridged the groundplane back together, and it's working just fine.

fwiw a dremel tool near it's highest speed with a diamond cutoff wheel makes very short work of the speaten filter.

As for the heatsink, I find that it mounts ok with just the two screws on either end of the tripath chip.
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Old 27th December 2008, 07:33 PM   #9
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Great news! I'm not sure the heat sink is even required, most of the Tripath amps I've seen don't have one. The Tripath chips are amazingly efficient.

BTW, I can't quite make out the part number on the chip, is it TA-2024?
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Old 27th December 2008, 08:09 PM   #10
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Quote:
Originally posted by chicks
Great news! I'm not sure the heat sink is even required, most of the Tripath amps I've seen don't have one. The Tripath chips are amazingly efficient.

BTW, I can't quite make out the part number on the chip, is it TA-2024?

It's a TA-2021B, which has slightly better specs than the TA-2024. Rated for 25W output. Though as usual for class-D, only the 1st third of that is really all that good.

datasheet here: http://www.datasheetcatalog.com/data.../TA2021B.shtml

From the power vs. thd curve, it seems like it should give a few more watts of clean power than the TA-2024.

After several minutes driving the little 6 ohm kevlar speakers i have, the heatsink did get a little warm. The internal frame of the box I'm putting it in is thinner aluminum, but i think i can actually mount it directly to the frame and toss the original heatsink.
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