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Old 18th October 2009, 07:45 PM   #701
RKH is offline RKH  United States
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Quote:
Originally Posted by carlmart View Post
Where can I find the original symasym PCB design?
SymAsym5 - Project
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Old 28th October 2009, 09:30 AM   #702
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Quote:
Originally Posted by AAK View Post
Hi chalkandtalk,

I'm glad you liked the boards. I don't think that adding a seperate regulated PS would any value, plus I'd like to keep it simple. But I'm working on a external PS for those that would like to use a single transformer for two channels. I may also try just the amplifier without the PS on the same board. Since the amp alone measures 2.95" x 2.65" this may interest some. It would be no bigger than a chip amp but with better sound.

Regards,

Al
Sounds good to me. If it sounds better than version 5.3 I can't wait.

Any progress?

Aidan
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Old 5th November 2009, 06:07 PM   #703
AAK is offline AAK  United States
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Hi Aidan,

Progress is good. Been so busy working on the new amp and a new speaker design that I totally missed your post. Sorry about that. I'm very pleased with the out come. The amps have been on for over two weeks now without a glitch. It measures great and sounds beautiful. I'm currently finishing the BOM and schematics, and putting together several THD plots before I create a new thread. It should be any day now.

Regards,

Al
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Old 29th May 2012, 11:21 PM   #704
JZatopa is offline JZatopa  United States
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Could someone tell me if these transformers would be ok for the AAK symasym?

(1 PAIR) Avel Lindberg Toroidal Transformer AV-66938 (Ideal for Chip Amp) | eBay

If not should I be looking for something more in the range of 35V?
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Old 30th May 2012, 08:54 AM   #705
AndrewT is offline AndrewT  Scotland
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these 28.4Vac transformers look about ideal for a single pair Symasym.

35Vac is too high. That would allow ~ 100W into 8r0 and a single pair Symasym output stage would not be reliable at this level of input/output.
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Old 31st May 2012, 11:45 PM   #706
SteveA is offline SteveA  United States
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I have assembled 8 boards and tested them (thru bulb tester!!). Three failed the smoke test (ie, the 100R resistor smoked). The remaining 5 show a voltage drop of 1.4-1.7 V (all 8 boards show ~52.5V on each rail). I have Rev1.3 boards. The voltage drop according to the Rev1.4 assembly guide should be 2.5-3.5V. Is the expected voltage drop for Rev1.3 the same? If not, what should one see for Rev1.3 boards?
Thanks
SteveA
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Old 1st June 2012, 10:23 AM   #707
AndrewT is offline AndrewT  Scotland
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Could you tell us how many times/threads you have posted this same enquiry?
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Old 1st June 2012, 05:11 PM   #708
SteveA is offline SteveA  United States
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I have posted three or four times. I won't post again, I beg your pardon.
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Old 3rd June 2012, 07:14 PM   #709
AAK is offline AAK  United States
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SteveA, lets focus on the five amps that have the 1.4 to 1.7 voltage drop across each (+/-) safety resistor which sounds about right.

Take one of the five amps, remove the safety resistors, and insert the fuses making sure that bias pot R22 is turned fully counter-clockwise before powering up. Then set multimeter to lowest voltage setting, should be in the millivolts, then power up and measure the emitter voltage across U3 and U4. The meter should read near zero. If it's not near zero, stop and let me know what it is. Then adjust R22 clockwise until it reads about 20mv, then check the DC offset across T4 and T5. It should read less than 50mv. If everything checks out Ok, repeat with the remaining amps. Let me know how it goes before we move on.

Al
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Last edited by AAK; 3rd June 2012 at 07:22 PM.
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Old 3rd June 2012, 07:20 PM   #710
AAK is offline AAK  United States
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Just to make sure the amps output transistors U3, and U4 need to be attached to a suitable heat sink before testing.
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Last edited by AAK; 3rd June 2012 at 07:35 PM.
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