100W Ultimate Fidelity Amplifier

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#2,863
My first Apex AX20 channel was tested with transformer from a burnt Inter-M L2400 amplifier, as you can see in the picture, this transformer is good to feed the Apex H900. But for my AX 20 stereo amplifier I gona use 1000 VA. About PCB layout, no problem, here is for those wants do de some amplifier. You should star doing the protection first and teste it, than the amplifier, try to avoid component mistakes and dont forget de diferent grounds (in ground and normal ground). And we should say thanks to Miles Boss 🙂

Regards
 

Attachments

  • SAM_0814.JPG
    SAM_0814.JPG
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  • Apex AX 20 components.pdf
    Apex AX 20 components.pdf
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  • Apex AX 20 copper side.pdf
    Apex AX 20 copper side.pdf
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  • NE555 Protect 1.JPG
    NE555 Protect 1.JPG
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#2,865
kandimba said:
My first Apex AX20 channel was tested with transformer from a burnt Inter-M L2400 amplifier, as you can see in the picture, this transformer is good to feed the Apex H900. But for my AX 20 stereo amplifier I gona use 1000 VA. About PCB layout, no problem, here is for those wants do de some amplifier. You should star doing the protection first and teste it, than the amplifier, try to avoid component mistakes and dont forget de diferent grounds (in ground and normal ground). And we should say thanks to Miles Boss 🙂

Regards
Click to expand...

Thank you for pdf files,
Regards
 
#2,872
AX17

I have simulated the AX17 schematic in LTSpice, but I obtain poor THD results, 0.18% at 10khz 1V input.
What can be done to increase the performance of this schematic?
Have somebody measured real THD after building this amplifier? what were the results?
See attached files.
Thanks
 

Attachments

#2,874
AndrewT said:
post your asc file. Some sim expert/s can look at how you implemented the THD question.
Click to expand...

It is posted there, look more carefully.

Here is a new one, with minor changes that lead to 20x less THD, and has -91deg in LoopGain, so it should be perfectly stable (-91 + 180 = 89deg).
Is it correct and better than the original one?
 

Attachments

Last edited:
#2,876
A few more images: schematic, thd, loopgain.
THD is strongly dependent on the chosen VAS transistors, these
2SA1381/2SC3503 with aprox 5mA collector current obtain the best results in simulator.

I have also prepaired a PCB layout for this AX17 schematic with two pairs of output transistors.
 

Attachments

  • sch v3mod.png
    sch v3mod.png
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  • sch v3 mod.png
    sch v3 mod.png
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  • loopgain v3mod.png
    loopgain v3mod.png
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  • apex ax17 v3 mod.asc
    apex ax17 v3 mod.asc
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#2,878
vlasinalin said:
A few more images: schematic, thd, loopgain.
THD is strongly dependent on the chosen VAS transistors, these
2SA1381/2SC3503 with aprox 5mA collector current obtain the best results in simulator.

I have also prepaired a PCB layout for this AX17 schematic with two pairs of output transistors.
Click to expand...

There is many better VAS transistors than MJE340/350 but MJEs are easy available. Would you share your pcb?
 
#2,879
AX17

Here is the PCB for this AX17 schematic with two pairs of output transistors.
It is an extended version of the one firstly designed by AlexMM.

A double check across the schematic should be performed. Note that the components' numbers on my LTSpice schematic do not match the original numbering, please check considering their values only.

I will provide bottom copper layer pdf file in Private Message for those interested in building it.

Any suggestions for improving the PCB and/or schematic are welcome.

Regards

http://i1012.photobucket.com/albums/af241/vlasin_alin/apexAX17_v3_zpsffe74902.png~original
 
Last edited:
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