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Here is just an idea shunt circuit to add to the FX8. Its not too big, nothing expensive. Can design something more robust by adding a partner the TL431, but max is 100ma. But I left off the TL431.
It could make sense to give up a small fraction of real estate on the PCB to make way to do a much needed shunt circuit. With the goal to improve the PSRR = Improved SQ.
10uF
445-14933-1-ND
Digikey
Here is just an idea shunt circuit to add to the FX8. Its not too big, nothing expensive. Can design something more robust by adding a partner the TL431, but max is 100ma. But I left off the TL431.
It could make sense to give up a small fraction of real estate on the PCB to make way to do a much needed shunt circuit. With the goal to improve the PSRR = Improved SQ.
10uF
445-14933-1-ND
Digikey
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That's not a shunt regulator. In your circuit you're using standard adjustable 3-pin series regulator.
If you want to increase the PSRR of FX8, the simplest way is to add capacitance multiplier.
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Keeping the fx8 pcb miniature is important. Adding a Cs can create a problem if there is a large bank of caps. What is needed is an inductor, in the 1st stage. An LC filter is a great idea to really improve PSRR, which would sit between the psu and the amp.
Keeping the fx8 pcb miniature is important. Adding a Cs can create a problem if there is a large bank of caps. What is needed is an inductor, in the 1st stage. An LC filter is a great idea to really improve PSRR, which would sit between the psu and the amp.
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A simple amplifier like FX8 requires simple solutions. If you want to improve PSRR, a simple capacitance multiplier on the power supply rails before the VAS transistors will not take very much PCB real estate. Otherwise, if you want to to have fully regulated supplies, you can use APEX regulated PSU.
Here are the files for DIY for anyone, for the FX-8 mod by Bimo.
Here are the layout considerations,
1. 470u/220u caps have 13mm dia x 5mm pitch.
2. 1uF caps have 5mm or 7.5mm pitch.
3. On board inductor of ~13-14mm dia
4. holes for optional 10mm pitch silver mica caps
5. 3296W MT trimmer.
6. 0.5 w res have min pitch of 10mm, 1w has 15mm, 2w has 18mm
reg
Prasi
Here are the layout considerations,
1. 470u/220u caps have 13mm dia x 5mm pitch.
2. 1uF caps have 5mm or 7.5mm pitch.
3. On board inductor of ~13-14mm dia
4. holes for optional 10mm pitch silver mica caps
5. 3296W MT trimmer.
6. 0.5 w res have min pitch of 10mm, 1w has 15mm, 2w has 18mm
reg
Prasi
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Prasi,
Very nice. Could you also please post the associated Gerber files?
Thank you.
Very nice. Could you also please post the associated Gerber files?
Thank you.
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Since your volunteering to help. Would like to see a schematic showing your simple Cm with a range of 100-110db PSRR improvement.
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I have no interest in FX8 amplifier. However, mr. Mile did publish a version with added simple capacitance multiplier, but it went unnoticed (it was called AX13). You can see the circuit in post #2126: http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-213.html#post3482684
Attachments
So what is the PSRR gain with the added simple cm?
Would be helpful if you can support in LTspice a sim showing the PSRR 100-110db improvement of this simple added cm
Would be helpful if you can support in LTspice a sim showing the PSRR 100-110db improvement of this simple added cm
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I have put "+" and "-" symbols there (see zipped pdfs attached to post no. 7150). Do you want me write "Signal IN +" and "Signal GND-"😕.
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So that's all there is to it? A couple of BC639/40's a 1k resistors?
Hi
I know these include a capacitance multiplier, can U explain in a everyday language what does these to the IS. 🙂
Some amp use a resistor with a diode, is that for the same purpose
Thanks
Transistor in CM amplifies the filtration effect of R + C. There is less noise coming from the supply rails into sensitive IS. Sound of the amp is crisper and cleaner. But it's no guarantee that you shall like that sound more. Some people will probably prefer the sound of amp without CM.
Hi Gaborbela 🙂,
Look at the project 15 (Capacitance Multiplier Supply) from Rod Elliot's pages : it explains very well the capacitance multiplier and even offer a PCb for sale ...
Best regards
rephil
Best to put a clean PSU in front of the whole amp and keep the FX8 simple. Otherwise just build a different amp. If you add a CM to the circuit it is no longer an FX8