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Old 11th January 2011, 01:34 AM   #1221
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yes it will help me to understand i dont learn fast but I make some progress .. merci beaucoup
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Old 11th January 2011, 12:52 PM   #1222
Macleod is offline Macleod  France
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Thank you OS for those datas. This gives a benchmark of the performances to beat.
Merci beaucoup.
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Old 11th January 2011, 11:24 PM   #1223
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While we're demystifying things.....


I've been looking at the AX/BX schematics just trying to make sure I understand everything (!) and realized I have no clue about the capacitance C3//C4. Looks to me like the purpose is to "AC couple" the feedback. I'm new at this, but I've read through Slone and Cordell, and I don't recall seeing this in either book.

So what's the deal ? Is it to keep feedback from screwing with the (precisely tuned to zero) DC offset ?
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Old 12th January 2011, 12:12 AM   #1224
solid is offline solid  United States
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Quote:
Originally Posted by js22 View Post
While we're demystifying things.....


I've been looking at the AX/BX schematics just trying to make sure I understand everything (!) and realized I have no clue about the capacitance C3//C4. Looks to me like the purpose is to "AC couple" the feedback. I'm new at this, but I've read through Slone and Cordell, and I don't recall seeing this in either book.

So what's the deal ? Is it to keep feedback from screwing with the (precisely tuned to zero) DC offset ?

The AC voltage gain of the amplifier is 1+R5/R4.
C3/C4 keep the DC gain equal to 1 to keep the amplifier from amplifying any DC offset.
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Old 12th January 2011, 01:07 AM   #1225
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Quote:
Originally Posted by js22 View Post
While we're demystifying things.....


I've been looking at the AX/BX schematics just trying to make sure I understand everything (!) and realized I have no clue about the capacitance C3//C4. Looks to me like the purpose is to "AC couple" the feedback. I'm new at this, but I've read through Slone and Cordell, and I don't recall seeing this in either book.

So what's the deal ? Is it to keep feedback from screwing with the (precisely tuned to zero) DC offset ?
Solids accessment is "solid" ...

(below plot 1) is the 40X gain of the AX/BX. {Plot 2} is the DC rolloff (green) of the blocking caps (C3/4) resulting in 0 DB gain at .2HZ at the output (RED).

I have "flopped" my woofers with my synthesizers at 2 HZ with -3db output. So these amps have a range of 2hz - 100Khz (-3db).

OS
Attached Images
File Type: gif AXgain.gif (23.1 KB, 612 views)
File Type: gif AXdc.gif (19.0 KB, 525 views)
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Old 12th January 2011, 01:18 AM   #1226
Art M is offline Art M  United States
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Default Measurements

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Originally Posted by Ed LaFontaine View Post
I have heard them at their home. I know the sim'd results are backed up by actual measurements by others.

I look forward to experiencing them in my home when they are available.

I have not located where the actual measurement data is. Could you please show me the way.
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Old 12th January 2011, 02:29 AM   #1227
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Quote:
Originally Posted by Art M View Post
I have not located where the actual measurement data is. Could you please show me the way.
Boy , I wish I had a $10K AP distortion analyzer.

To put this to rest , The "blameless" design is a very common one , both the AX/BX are based on it. This design is absolutely the most measured and documented of all the topologies. Read "Audio Power Amplifier Design Handbook - D. Self " any edition , or "Bob Cordell - Designing Audio Power Amplifiers" ... and you will see this circuit with all of it's data.

Self's "take" on this design is basic and actually measures with lower than average THD , Cordell's version is more like my AX and performs to a even higher degree. I add capacitance multipliers , a cascode , and high performance input pairs to cordell's design. On top of that , the AX has TMC , further reducing the remaining distortion mechanisms. The PB power stages are also "fine tuned" to the AX/BX, giving inaudible noise and hum and a large "first watt" as explained a few posts back.

With such a simple design , not much can go wrong. Performance would follow the rules of simple physics and the choice of components. I don't make enough money to afford expensive test equipment ... but the testing has already been done for me.

OS
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Old 12th January 2011, 10:35 PM   #1228
Murdoc is offline Murdoc  Germany
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Hallo!
First of all I would like to say that it is a pleasure to read this thread! Since weeks I have come here and enjoy the progress and diskussion about amps, electronics and sound. Thank you for all this!
Now I am planning to build this amplifier, because it seems to me (noob) one (the?) of the best sounding diy amplifiers.
Since now I learned that some devices beginning with 2sc... can be found easier under KSA/KSC. So all parts could be bought from mouser in europe. (I'm thankful for every advice where to buy or which parts better to buy!)

From my diy speaker project (Duetta ADW mine looks a bit different, it's a one piece design) I learned that a capacitor is a mysterious thing because 4.7uF from one manufacturer can sound different to 4.7uF from another.
And now, to cut a long story short, my question:
Do you have any recommendations for C1-C9 for the AX1.3VB and the Cs in the PowerBoard?

PS:
Quote:
Os: ...but the testing has already been done for me
Os, do you have any results of your amps? Which one measures the best?

And another question:
I could read between the lines that the AX sounds "best". I am looking for a amp which comes the ideal amp ("a wire with amplification") the closest, but it should not only be as neutral as possible but also be able to deliver the soul of the music, so to make fun to listen to it! Is the AX the best amp for me, or have I to wait for the LX, or do I have to build a completely different amp?

Greetings
Matthias
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Old 12th January 2011, 10:58 PM   #1229
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Quote:
Originally Posted by Murdoc View Post
Hallo!

Is the AX the best amp for me, or have I to wait for the LX, or do I have to build a completely different amp?

Greetings
Matthias
If you wait a week or two OS will have another amp for you to consider! Then - a couple of weeks after that - - - - - - - - - another.....

Fortunately they are not expensive to play with after you get past the cost of having some spare transformers and heatsinks to prototype with.
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Old 13th January 2011, 02:33 AM   #1230
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Default PB250H "my baby".... documentation done.

I have been putting it off , just sharing bits and pieces. The "best" of the modular power output boards is done (below 1). It is in the mongrel root as "PB250H.ZIP". I had to take my wires off to photograph it for the package (below 2).

This is the PB I do my final high power tests on. I have had the AX , BX , and GX , each running for a month or more , this nice piece of fr-4. After the voltage stages get a test run on the new PB-60X2 , they get the final "audition" here.


Quote:
By murdoc- Do you have any recommendations for C1-C9 for the AX1.3VB and the Cs in the PowerBoard?
The BOM's are verbose. The best guidelines are to derate (100V caps) , low ESR. I use Nichicon , panasonic (excellent - from mouser) exclusively. Xicon and Dale power resistors. The only "made in china" part is the blue led.

The "AX" is the first one I will sell as a completed , fully integrated amp (Voltage stage -120W power stage- PS ... all in one) I will order 100 pro boards once I ABSOLUTELY perfect it 110% (I'm REAL close to that).

I have no regret's (I am satified - completely) on the PB250H layout. With the excellent NJW21193/4's and 20mm rail traces (soldered a 10mm copper bar all the way down them - like Nico Ras's "big booty amp" ) this PB is truly a "wire with gain". With these OP devices , 400w/4R is well within the SOA (DC SOA @ 65V is almost 10A w/ 4 devices) safety margin of this amp.

Quote:
By C2Cthomas - If you wait a week or two OS will have another amp for you to consider! Then - a couple of weeks after that - - - - - - - - - another.....
Yes I will , now that I "caught up" , I will design the (hopefully)excellent "CLX"
(below 3). It will only cost me 15$ for a pair to hook to my PB60/250's. Yeah , it is nice to not have to rebuild the power stage everytime !!

OS
Attached Images
File Type: gif pb250.gif (55.9 KB, 452 views)
File Type: jpg PB250H_PHOTO.jpg (166.0 KB, 449 views)
File Type: gif CLX.gif (25.3 KB, 434 views)
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