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Old 7th December 2008, 12:20 AM   #11
anatech is offline anatech  Canada
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Hi ostripper,
Quote:
My answer to this is the FA2, while saluting mike B's contribution to DIY, and not infringing on Ampslab's IP, offers a very superior Alternative to both. (prototyped and simulated symasym and found stability problems which were only balanced by "gross compensation" at OP stages)
I am always interested in amplifier designs. I can't prove or disprove what you say. However, my comments were simply to encourage Chris' efforts. I think there is a place for the original SymAsym, and also this slightly beefed up version.

Most of my comments directed to you were because you were in effect saying that Chris should simply stop and go with your design. However, that may not be in his best interest and certainly would eliminate the pride and confidence this project brings. It is everyones right to be able to create and build. This is the main point of DIY. I am unlikely to bin my SymAsym amplifiers.

Quote:
I know you all like your symasym's and I would not want to "bastardize" a good design, but I think there is MUCH room for improvement ,as some have bet their business on it.
Well, yes. Exactly.

Mine were built to drive wall speakers. Once I fired one up, I immediately realized that the basic design was very good, better than it looked (and I expected them to sound good). Once I found this out, my intentions turned to using these amps as a test bed to try different things out with them. Remember, it's just as easy to ruin the performance of the original design. I have even gone so far as to try them with both matched and unmatched parts. The diff pair always being matched. The original SymAsym is an excellent standard to judge other amplifiers on. You do understand that I am not saying they are the best. They are, however, much better than most commercial designs out there.

I am very interested in seeing your design, and may build it also. Your design will be competing with a Marantz 300DC and a pair of new Cyrus Mono X amplifiers. Those are high marks to hit or exceed, partly because I went over the Marantz matching parts and replacing capacitors. It's a much better amp now.

I will similarly encourage you to excel with your design. My hopes are that it should perform better than your expectations, and better than my commercial amplifiers.

-Best, Chris
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Old 7th December 2008, 01:04 AM   #12
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Default Re: Symasym PCB

Quote:
Originally posted by Khron
I implemented John's (MJL21193) idea of 22r//diodes for the small-signal ground "decoupler.

Hi Khron,
I can't take credit for that but I feel honoured that you would attribute it to me

I'm not sure what I'm seeing here. Is this a resistor in series with the output? Perhaps you left the load resistor in when making the board layout?
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Old 7th December 2008, 01:18 AM   #13
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Quote:
Originally posted by ostripper

My answer to this is the FA2, while saluting mike B's contribution
to DIY, and not infringing on Ampslab's IP, offers a very
superior Alternative to both.

Doing a bit of the old soft sell OS?

The Symasym may look like it has problems in simulation, but it is a proven design. Many of the things that make an amp sound good or special may be wrapped up in irregularities that show up during simulation. Who knows. I don't, that's for sure.
I haven't heard the Symasym to make a judgment on it's SQ, not that I'm any kind of discerning listener. I attempted to bend the design a while back to suit the parts that I had at the time but I didn't have the know-how. I met with a lot of opposition to my meddling and I dropped the idea and carried on on my own.
It's good to see others exercise their creativity and do something that could well go down as a worthwhile contribution. There is much to learn from all of these efforts.
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Old 7th December 2008, 01:20 AM   #14
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Since our fellow member , Andy C. introduced me to the "finer aspects" of spice I have modeled ALL the amps offered here.

Having only built quasi, DX, P3a,leach, symasym ...I wanted
something more. All the above relied on the accepted norms
of standard topology. As there are a lot of "off the wall"
ideas thrown around DIY land, I decided to see if any good
"hybrids" could be realized from all of this.

With a buffered widlar CM VAS in my "symasym clone" I've
totally done away with H3-5-7 leaving only minute H2 to
deal with. This amp does not need any comp. "after the fact"
The better aspects are related to the buffer which "ultra
linearizes" the VAS at ANY frequency.

As far as Scalability , I've run the first amp from 25v to
70v with no issues. FA2, (I shouldn't call it a clone) can do
40 to 100v no problem.
I won't go as far to say say the symasym is "flawed"
but we (MJL21193/myself) had a go at it and wondered
how it could be so revered.
OS
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Old 7th December 2008, 01:29 AM   #15
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Quote:
Doing a bit of the old soft sell OS
You just wait... some say sims are BS , but I've seen
how they relate to the real world.. that FA2 will "crush"
the Symasym... guaranteed. Even If I have to throw
nested feedback and all the other IP "tricks" in on top of it.
(with a high regard for individual specific IP)
OS
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Old 7th December 2008, 01:41 AM   #16
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Go get em tiger...
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Old 7th December 2008, 01:45 AM   #17
anatech is offline anatech  Canada
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Default Let's stay on track please ....

Hi ostripper,
Quote:
I won't go as far to say say the symasym is "flawed" but we (MJL21193/myself) had a go at it and wondered how it could be so revered.
I don't think it is revered. I do think it is straight forward to build with a high chance of success. What you get out of it depends on how much skill you can build it with. As I said earlier, the SymAsym is a good reference amplifier. Many people across the world have built them with success.

Now, I would really like to focus on Chris' version of the SymAsym. He started this thread for assistance with his version. Let's stay on track from here on please. I may be forced to do some cleaning here, just to preserve Chris' ideas. He seems to be directly building on the original design - and that is great!

-Chris
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Old 7th December 2008, 05:50 AM   #18
ReiMomo is offline ReiMomo  Puerto Rico
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I think it needs a resistor for each base of the outputs.
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Old 7th December 2008, 05:50 AM   #19
ReiMomo is offline ReiMomo  Puerto Rico
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oh wait thats the foil side!!!
but you still need to fix the emmiter resistors then.
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Old 7th December 2008, 08:11 AM   #20
Khron is offline Khron  Romania
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Quote:
MJL21193

I'm not sure what I'm seeing here. Is this a resistor in series with the output? Perhaps you left the load resistor in when making the board layout?
That's the 10 ohm // output inductor.

Quote:
ReiMomo

I think it needs a resistor for each base of the outputs.
oh wait thats the foil side!!! but you still need to fix the emmiter resistors then.
I'm gonna have to ask you to be a bit clearer, please


OS,

I never said this Symasym is the "be all, end all" holy grail of amplifiers, but it's just about the best (free, diy) design i've seen, buildable with "normal" parts, many of which i already have. Of course, if you have the knowledge, willpower and available funds, nothing's stopping you from designing and building an amp able to crush all "opposition"

I'm just a student trying to make the best of what i have available
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