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Old 6th June 2013, 10:17 PM   #1
borys is offline borys  Poland
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Default FET-hex explendit amplifier

Hello

Recently I have build VSSA amp (shaan version bit modyfied) and I am very happy with it.
I had few irfp240/9140 pairs in stock so I decided to build another version (as I am not an expert some upgrades may be needed).
Bellow schematic, board, and measurements. The measurements were done on prototyp board and all components weren't matchet (just taken stright from the box).
Bias is stable, cold amp seted to 100mA (15C) hot amp 92mA (78C), I didnt have irf540/530 so I used irf840 instead. I think that amp can use bit higher power supply than +/-35V.
Amp is playing really good.
Thanks to LazyCat and Shaan


Ps
I was thinking If it would be recommended to leave 0,1R source resistors and put 47R gate resistors instead 100R ?
My sound card is not the top notch and is creating some high order harmonics artefacts (there are present at the same place on different amplifiers measurements).
Attached Images
File Type: jpg DSC_0583r.jpg (70.0 KB, 4398 views)
File Type: png fet-hex 20V.png (69.6 KB, 4217 views)
File Type: png fet-hex 3khz20V.png (50.7 KB, 3973 views)
File Type: png fet-hex 5khz20V.png (49.6 KB, 3844 views)
File Type: png fet-HEX 8R plus 0.47uF square.png (117.2 KB, 3824 views)
File Type: png fet-HEX compensation.png (154.7 KB, 704 views)
File Type: png fet-HEX 8R plus 0.47uF.png (130.0 KB, 621 views)
Attached Files
File Type: pdf FET-hex ccs v4.pdf (12.0 KB, 1509 views)
File Type: pdf FET-hex ccs v4 top.brd.pdf (43.7 KB, 658 views)
File Type: pdf FET-hex v4 zelazko.pdf (55.5 KB, 739 views)

Last edited by borys; 6th June 2013 at 10:22 PM.
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Old 6th June 2013, 10:39 PM   #2
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Very nice VSSA variant! I was curious about a HEXFET version of the VSSA. I see you used CCSs as well.
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Old 7th June 2013, 04:36 AM   #3
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cute and nice measurements Out of curiosity what was the output power for the 3 different THD you show ?
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Old 7th June 2013, 07:12 AM   #4
borys is offline borys  Poland
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All thd measurements are done with 20V output amplitude at 8R load.
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Old 7th June 2013, 07:12 AM   #5
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Great little amp you have there borys. Good idea to find Rg sweet spot. Enjoy in music.
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Old 13th June 2013, 08:47 PM   #6
borys is offline borys  Poland
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I moved the vas stage under the board. There are 2 caps added just before each o/p transistor. Places for fuses if someone are going to use them.
I have tested the amp how it would react in case of one of burned fuse.
If the ''core'' of the amp is permanently supplied there is no DC at the output, so there is safe to use fuse protection in the amp.
Attached Images
File Type: jpg wzm1.jpg (48.7 KB, 1111 views)
File Type: jpg no fuse 1.jpg (128.4 KB, 1103 views)
File Type: jpg no fuse 3.jpg (144.2 KB, 839 views)
Attached Files
File Type: pdf FET-hex ccs v6 schematic.pdf (12.0 KB, 1196 views)
File Type: pdf FET-hex ccs v6 top.brd.pdf (44.2 KB, 459 views)
File Type: pdf FET-hex ccs v6 bottom.brd.pdf (17.6 KB, 366 views)
File Type: pdf FET-hex ccs v6 zelazko.pdf (58.5 KB, 428 views)
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Old 13th June 2013, 11:56 PM   #7
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Quote:
Originally Posted by borys View Post
I moved the vas stage under the board. There are 2 caps added just before each o/p transistor. Places for fuses if someone are going to use them.
I have tested the amp how it would react in case of one of burned fuse.
If the ''core'' of the amp is permanently supplied there is no DC at the output, so there is safe to use fuse protection in the amp.
Hi Borys,

Nice to see vssa variant. How does SQ compare to 2sj162/2sk1058? Can I use IRF540/IRF9540? Thank you.

Regards,
Boyet
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Old 14th June 2013, 06:23 AM   #8
borys is offline borys  Poland
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I am not able to compare sq at the moment but I must say that irfp version sound excellent, only one think I can notice is that bass is bit different.
I You can use any hexfets I think 540/9540 will be ok.
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Old 14th June 2013, 08:50 AM   #9
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Quote:
Originally Posted by borys View Post
I am not able to compare sq at the moment but I must say that irfp version sound excellent, only one think I can notice is that bass is bit different.
I You can use any hexfets I think 540/9540 will be ok.
Thank you borys. I will try your FET-hex explendit amplifier

Regards,
Boyet
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Old 14th June 2013, 02:33 PM   #10
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Nice!
I've got some N-channel IRFP250N only.
Could anyone draw a variant of this circuit to fit only N-channel hexfet outputs?
Thanks!
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