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Old 13th January 2013, 07:35 PM   #211
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Since the trafo resonance is in the audio band I wonder if a person could hook up a coil to their amp input and put it near the trafo. Then listen to the output, adjust snubber for cleanest hum.

There may be higher resonance modes requiring their own snubbers but I found snubbing the 14KHz resonance made the biggest impact on sonics. It would be interesting to try and address each individual resonance that could be found.
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Old 13th January 2013, 07:49 PM   #212
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What are your thoughts on running the TDA7294 from LM317/LM337, and having the TDA7294 push nice big discrete output devices?
At first glance, if we're considering any added parts, it seems good to improve linearity and current capacity, as would be suitable for driving a speaker.
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Old 13th January 2013, 08:46 PM   #213
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That makes sense. Though it would not improve linearity over the unloaded distortion spec.
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Old 13th January 2013, 08:50 PM   #214
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Let me clarify a bit. I personally don't have a problem with what I called the "higher parts count"/off-board PS designs. If that method represents the fewest trade-offs for optimal performance of this specific chip, that's the desired way to go IMHO. I'm assuming KSTR (as the lead PBC maker for this project) has preferences that will allow him to escape the limitations of his commercial endeavors. I'm sure there are several PS designs that will work and work well. I just wasn't sure a consensus had been reached for a "no holds barred" PS development path.

The need for something between power for the existing eBay kits and the optimized developed board on this thread may or may not be necessary. There are a couple options/opportunities to pull a large number of potential participants from other threads that might influence that, based on cost and complexity.

At the moment I'm just trying to identify what will be used for the "top end" build.

Make sense ???
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Old 13th January 2013, 09:32 PM   #215
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Quote:
Originally Posted by danielwritesbac View Post
The series elements for the power supply of the MyRef front end power circuit are:
LM317, LM337. And the front end power caps are 100u.
(CQC, bigger voltage drop than CDC, but similar)
Sorry Daniel but the My_Ref has a simple zener shunt PS... one series resistor and one zener shunt per rail.
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Old 13th January 2013, 09:38 PM   #216
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Quote:
Originally Posted by ClaveFremen View Post
Sorry Daniel but the My_Ref has a simple zener shunt PS... one series resistor and one zener shunt per rail.
I was staring at this:
http://www.diyaudio.com/forums/attac...-schematic.pdf
Actually, MyRef-FE.
I just checked again. The regulated front end features LM317 series elements followed by 100u. Looks like really good quality there.
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Old 13th January 2013, 09:44 PM   #217
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Quote:
Originally Posted by danielwritesbac View Post
I was staring at this:
(...)
Actually, MyRef-FE.
Exactly, it's my variation.

Quote:
Originally Posted by danielwritesbac View Post
I just checked again. The regulated front end features LM317 series elements followed by 100u.
Those LM317s are CCSs, actually, and they replace the current setting resistors of the original My_Ref PS.

Also the shunt is improved by a shunt transistor that lower the zener impedance by transistor's HFE.

In fact the 100uF are completely optional, to the point they're left unpopulated in actual builds.

Quote:
Originally Posted by danielwritesbac View Post
Looks like really good quality there.
Thanks
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Old 13th January 2013, 09:44 PM   #218
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Bob, the PSU designs that I made are for supporting basic chip amplifier projects, such as TDA7294 board from e-bay.
This is definitely not optimal.
There's far too much room for unfortunate and confounding build variances that can make each build sound much different.
The MyRef people have it right with the all-in-one board Monobloc that reduces build variance (blocks errors) and avoids inductor roulette except for the transformer itself.
Quote:
Originally Posted by KSTR View Post
OTOH, now if there were some global preference for single-PCB mono-blocks here then let's zero in on those. . .
Yes, let's do that! Monobloc power and amplifier on one board allows you to choose series element much more predictable than a random cable, and Monobloc simplifies building because when one is built, it serves as a non-confusing point of reference.

Conversely. . .
Attached is the reliable old gal from post #82, now dressed up in high heels and lipstick and ready to party with a monobloc. The collection of black & gold Nichicon-FW 2200u is not only pretty but can recharge very fast despite a plaster cracking bass beat (actually drywall, not tested with real plaster). If this power supply is set too close to an amplifier board, there's somewhat less chance of dulling than if we had used huge caps. Unfortunately, attempting to mitigate cable variances isn't very effective from the power supply end of the cable. SO, whatever DC cable is chosen can affect the needed capacitance size on the amplifier board and vice versa. When it comes to build variance, that's unpredictable performance causing each build to perform differently. I can't block this problem with a power supply board design, but you could block this problem with an amplifier board design.
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File Type: gif TankAndSmoothingNosag-Monobloc.gif (28.5 KB, 2525 views)
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Last edited by danielwritesbac; 13th January 2013 at 10:09 PM.
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Old 13th January 2013, 10:59 PM   #219
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Thanks Daniel, that narrows down the options as required. I'm still planing to build the "reliable old gal" next week as I need the experience of doing so and want to determine hands-on what the audible differences are.

So Mr. K, can you give us your perspective relative to your board design plans?
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Old 14th January 2013, 04:24 AM   #220
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Quote:
Originally Posted by bcmbob View Post
I'm still planing to build the "reliable old gal" next week as I need the experience of doing so and want to determine hands-on what the audible differences are.
I needed a power supply with a bit higher voltage tolerance (for a discrete amp), so I'm making one too.
Click the image to open in full size.
Those are the Fairchild Stealth II 16A 600V soft/fast schottky in the bridge rectifier. Almost slightly confusing to hook up. I'm glad the schematic has clearly marked KBPC1004's!

I'll probably redo the "CRC resistor" section. But it has 0.31R and that series pair of 16a fast silicon diodes has 0.9V forward voltage drop (and half the diode capacitance). Some more significant wattage non-inductive resistors is planned for an upgrade later; however, I'm using on-hand materials at the moment.
Anyway, you're looking at a rather fast 19,800uF per rail, in a monobloc's power supply.
The transformer is 400va in order to assure that this is still enough capacitance even if 4 ohm speakers are connected to the discrete amp (or parallel TDA7293 might could do it).
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File Type: jpg Ladderback_II.jpg (318.1 KB, 2149 views)
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Last edited by danielwritesbac; 14th January 2013 at 04:44 AM.
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