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Old 3rd June 2010, 01:12 PM   #1671
sendler is offline sendler  United States
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Default loop

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Originally Posted by v-bro View Post
The board already connects the RCA ground to PGND, so your star ground is in fact a loop then!

Try just one single wire between both PGND's, I've seen this work out fine a lot of times....but not on a Sure board....

MAN! The Sure noises still continue! Their first board was terrible, this one is better, hope the next one finally got it all right! Persons having been on the train from the start have not been off that cheap afterall.....
How is it a loop?
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Old 3rd June 2010, 02:39 PM   #1672
Baka is offline Baka  Montenegro
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Nobody here has a gain clone? I'm surprised.
Actually, I have.

Since I have received a 4*100W board as 2*100W (4-2X100 as you proposed) few days ago it is too early for any comparison.

I've accommodated a discrete linear supply from previous projects and changed input caps so far.

I am waiting for the Meanwell smps and Wurth coils you've suggested.

My take on 3886 is very serious one: 300VA trafo with 4 duals, separate discrete voltage regulators for each channel, boutique parts...

The DIY preamp is equally ambitious project.

We'll see. I'll let you know.

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Old 3rd June 2010, 05:27 PM   #1673
zdr is offline zdr  Belgium
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I have two GCs. I am slightly inclined to throw LM4780 out of both and repopulate nice boxes with tripaths. Too early to tell for sure, just got it yesterday.
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Old 3rd June 2010, 05:40 PM   #1674
sendler is offline sendler  United States
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Default supply

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I got my board today and hooked it up to a IBM PS, 19v, 3.4A. I think that voices are very slightly distorted.
You might want to try a better power supply.
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Old 3rd June 2010, 08:02 PM   #1675
v-bro is offline v-bro  Netherlands
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Quote:
Originally Posted by sendler View Post
How is it a loop?
Quote:
Originally Posted by sendler View Post
negative wire from left board, negative wire from right board,
Ok.

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Originally Posted by sendler View Post
left rca + to one input of the left amp, right rca + to the input of the right amp.
Ok.

But:
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negative from source rca cable, all connected at the same screw of the power supply terminal.
Either you are connecting source GND (which should go to AGND) to PGND or you (and then there's a real loop) connect the source GND to both (because there is already one single AGND-PGND connection on the board). Either case can result in noise, read the application notes.
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Old 3rd June 2010, 08:09 PM   #1676
sendler is offline sendler  United States
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Default Not both

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Originally Posted by v-bro View Post
Either you are connecting source GND (which should go to AGND) to PGND or you (and then there's a real loop) connect the source GND to both (because there is already one single AGND-PGND connection on the board). Either case can result in noise, read the application notes.
Source ground was connected only at the star for a test. No loops.
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Old 3rd June 2010, 08:34 PM   #1677
v-bro is offline v-bro  Netherlands
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So what was AGND doing?

Source GND shouldn't be at PGND at all, and certainly not bolted to any casing... Not that I care, but it's not really a good test then is it?

What struck me as well is that the Sure board uses a resistor of zero ohms to connect AGND and PGND. Even though this works according to Tripath application notes I noticed most designs use a small ferrite choke. I've connected whole bunches of amps together many times and used very sensitive PA speakers and never got such noise problems, so I may be able to help analize the problem, that's all...

I'm sorry, but I see a lot of work being done like the sorcerer's apprentice, no scientific approach whatsoever. Guys spending hours, perhaps even days listening to the sound of inductors. Even though it can be quite entertaining, technically it's not really getting anywhere.
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Last edited by v-bro; 3rd June 2010 at 08:44 PM.
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Old 4th June 2010, 09:23 AM   #1678
zdr is offline zdr  Belgium
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Quote:
Originally Posted by sendler View Post
You might want to try a better power supply.
I am using IBM Stinkpad 19V 3.4A PS, what can I improve there? Amp is totally silent with it and I am not sure I hear any distortion any more.

I am thinking into finally building an 2-way active speaker with linkwitz-riley active crossover in front of sure board. Anyone tried it already (I confess I did not go over all 170 pages in this thread)?
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Old 4th June 2010, 12:02 PM   #1679
sendler is offline sendler  United States
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Default Too small

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Originally Posted by zdr View Post
I am using IBM Stinkpad 19V 3.4A PS, what can I improve there? Amp is totally silent with it and I am not sure I hear any distortion any more.

I am thinking into finally building an 2-way active speaker with linkwitz-riley active crossover in front of sure board. Anyone tried it already (I confess I did not go over all 170 pages in this thread)?
For one thing that power supply is a little too small. That is only 65 watts and you are trying to power a 200 watt amp. Also, I have read many posts by people using various laptop power supplies that were disappointed with the results and then found a big improvement when changing to the 350 watt MeanWell. The feedback resistors in the amp are set to give the best sound at 32v so you may buy the 36v supply and turn down the front panel adjuster to 32. This voltage level will allow you to achieve the rated power. Less volts at 19v, less power. You will also want a seperate power supply for each amp board if you use more than one. This will prevent the odd noises we have been talking about and allow you to position the amps close to the left and right speakers in order to minimize the speaker wires for another improvement in sound.
.
The silver fan is also a known culprit for bad sound. Stop it momentarily while the amp is playing to hear it's effect. You will want to change it for a Zalman heat sink.
.
If you go active, you can sometimes get a decent crossover using textbook filters with something like a DCX2496 preceded by a DEQ2496 and adjusting the EQ by ear but you will eventually want to put together a measurement rig with ARTA to develop a better crossover.
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Old 4th June 2010, 12:22 PM   #1680
zdr is offline zdr  Belgium
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Quote:
Originally Posted by sendler View Post
For one thing that power supply is a little too small. That is only 65 watts and you are trying to power a 200 watt amp.
I am not playing even remotely close to 200W at all, and my mistake - it's 20V 4.5A, so 90W. I don't think I am playing more than 10 watts into 8ohm, but ok - I can give it a try with more muscle. I can also slip it into a GC, with two 220VA torroids and 35V on rails. Any benefits from running on heavy unregulated torroid PS?

Anyway, if I eliminate passive crossover losses, I am guessing that even 90W going directly to speaker drivers should be loud enough.
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