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Old 25th November 2009, 11:25 AM   #21
AAK is offline AAK  United States
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Hi Piersma,

I'm away from home for the Thanksgiving holidays, I'll run the IMD test this weekend when I get back. Do you have any specific frequencies that you'd like me test?

Before I left I tested the new boards and everything looks great. I'll put you down for four boards.

Regards,

Al
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Old 27th November 2009, 08:01 AM   #22
Piersma is offline Piersma  Netherlands
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Hi Al,

Please use: 60Hz/6kHz and 250Hz/8kHz
Amplitude ratio: 4:1

I am confident that this IMD measurement will also show fine results.

Time to start a threat in "Group Buys"?

Thanks,

Piersma
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Old 29th November 2009, 02:50 PM   #23
AAK is offline AAK  United States
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Hi Piersma,

Attached are the IMD plots you requested. For each picture the top plot is the IMD of the input signal, the bottom plot the output IMD. Each was taken using an 8 ohm load.

I'll start a group buy thread sometime this week. I have a count of six boards so far.

Regards,

Al
Attached Images
File Type: gif NewSym_60Hz_6Khz_IMD.gif (27.3 KB, 1265 views)
File Type: gif NewSym_250Hz_8Khz_IMD.gif (28.0 KB, 1242 views)
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Old 1st December 2009, 09:21 PM   #24
Piersma is offline Piersma  Netherlands
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Hi Al,

Thanks again for doing the IMD measurements, I am satisfied by now

Looking forward to build some of your boards !

regards,

Piersma
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Old 2nd December 2009, 09:29 PM   #25
lgreen is offline lgreen  United States
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I have not built one of these symasyms but would like to. Will you be posting a parts list or do we just take the parts from the schematic?
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Old 3rd December 2009, 07:03 AM   #26
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Hi Al,

Even with MJL3281A/1302A, the 50V rail voltage seems to high for me espacialy if speakers impedance is seeking near or under 4ohms....Will a 40-42V rail version not be more aware with output Device SOA : MJL4281/4302; MJL3281/1302; 2SC2922/2SA1216. I am not enough expert to indicate how to switch from 50 to 40-42V even nore if it's possible toward your design....

regards Marc
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Old 4th December 2009, 01:51 PM   #27
AAK is offline AAK  United States
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Hi Igreen,

I'll be posting the BOM before the end of the week.

Regards,

Al
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Old 4th December 2009, 02:24 PM   #28
AAK is offline AAK  United States
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Hi Marc,

At 40-42V rails the amp should work fine into a 4 ohms or higher with the MJL devices. Now if you go down to 3 or 2 ohms then there is a good chance you’ll have a problem especially at high output levels. At 40-42V rails you shouldn't have to change any components values on the amplifier. Just use a 30-0-30VAC transformer and your all set

My new board with dual pair output transistors my do the trick for loads under 4 ohms, I'll be posting more information on that amp shortly.

Regards,

Al
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Old 4th December 2009, 06:20 PM   #29
AAK is offline AAK  United States
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Hi All,

Here a pictures of the dual pair transistor version of the design. I added 0.865" to the length of the board to accommodate the extra pair of output transistors. The board now measures 5.865" x 2.95" including the power supply. The new design does require a heatsink with a 4" height instead of the 3" like the single pair.

Regards,

Al
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File Type: jpg NSym_DP_Amp.jpg (344.6 KB, 1170 views)
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Old 4th December 2009, 06:27 PM   #30
AAK is offline AAK  United States
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Here's a couple THD plots at 1khz at full power into 8ohms and 4ohms.
Attached Images
File Type: gif NewSymDP_100watts_8ohms.gif (33.1 KB, 1152 views)
File Type: gif NewSymDP_190watts_4ohms.gif (33.1 KB, 1014 views)
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