Yes, NP (non-polar) is better than "polarized" ones. But from my examples (caps on hand), BP (bi-polar) is better than NP.
NP is like putting 2 caps back to back: min-pos-pos-min.
BP is like: pos-min-min-pos.
I have tried using 2 caps (good quality ones) back to back but the result is inferior.
I think Bimo has never simulated FX8? Different circuit requires different compensation.
You can lower the feedback resistance to about 10K, add capacitance at the output and watch for the bump/peak at UHF. Fix this bump with e.g. the cap across the FB resistor. I will do this later, but cannot just using ears.
I think 10K is the lowest I have seen in VFA-LTP topology amplifier. Example is the Goldmund Mimesis.
Remove that capacitor. With 47pF you have increased amplifier bandwidth, but at the same time considerably reduced it's phase margin, which can result in oscillations (if your amplifier isn't oscillating already).
No one has said to use such high value. Egra was using 5.6pF in simulation and Bimo did not even use a capacitor at that place.
Ok, so I never knew the distinction between BP and NP caps - just thought they meant the same thing and either works the same way. Luckily, I have both on hand and will put the 100uF BP's in to see how that works.
I misread the 47pF - Egra's post said 5.6pF:
http://www.diyaudio.com/forums/solid-state/164093-100w-ultimate-fidelity-amplifier-688.html#post4673687
I just found a 2w 22k resistor - so I do have 22k's just not small ones. Probably overkill to swap out the resistor on the bottom right corner (what do you call that?).
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MKS2B044701K00KSSD WIMA | Mouser
Ok, so I never knew the distinction between BP and NP caps - just thought they meant the same thing and either works the same way. Luckily, I have both on hand and will put the 100uF BP's in to see how that works.
I misread the 47pF - Egra's post said 5.6pF:
http://www.diyaudio.com/forums/solid-state/164093-100w-ultimate-fidelity-amplifier-688.html#post4673687
I just found a 2w 22k resistor - so I do have 22k's just not small ones. Probably overkill to swap out the resistor on the bottom right corner (what do you call that?).
Erik777 (up late eh?),
Ideally, those Wima's would be sweet to have. For now, I will try the 50uF BP's with 1uF film caps in parallel. Hopefully, this will sound decent until some 4.7uF film caps come in. I also swapped out the 56pF for 5.6pF caps on FB resistor and for grins, put in a 2w 22kohm resistor to keep the Johnson noise low.
Edit: Just realized the 22k's are actually 2.2k's - would this be a problem to run 10 times more current here? Certainly, the resistor can handle the power.
Ideally, those Wima's would be sweet to have. For now, I will try the 50uF BP's with 1uF film caps in parallel. Hopefully, this will sound decent until some 4.7uF film caps come in. I also swapped out the 56pF for 5.6pF caps on FB resistor and for grins, put in a 2w 22kohm resistor to keep the Johnson noise low.
Edit: Just realized the 22k's are actually 2.2k's - would this be a problem to run 10 times more current here? Certainly, the resistor can handle the power.
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If you need simple but good sounding amp with minimum parts count you can use original APEX AX11 circuit. If you want best performance from the same topology you may prefer Bimo's AX11 De Luxe version. There are several useful improvements in Bimo's circuit (RC filtering for the input stage, supply rails bypass caps in the positions where they are most useful, sophisticated compensation, etc.)
Just hooked up the FX100 Supply (PSP100) with 2x1.500µF to two APEX A23 Boards (20mA idle) with additional 2x2.500µF each. As expected for the relatively low capacitance i'm getting quite a lot of 100 Hz hum on my speakers. The rail voltages have 60mV and 40mV ripple (the positive is higher because of the current draw of the psp 100 relays). Hum on the Speakers is about 2mV as far as I could correctly mesure that.
Do you think an upgrade to 2x20.000µF would eliminate the hum satisfactory?
Do you think an upgrade to 2x20.000µF would eliminate the hum satisfactory?
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I hooked up the FX8 with the above mods. So the 50uF BP + 1uF film cap certainly made a difference - it's like a new amp for the better. Substantial improvement in perceived sound quality from standpoint of bass extension. Highs still clear and midrange has amazing fluid like smoothness and clarity. Dynamics have improved too - overall this has been the Bomb of a mod. I am going to give more time to sink in, but first impressions with about 4 songs so far have really impressed me. Definitely a super amp
I am not sure if the 4.7pF made a difference but certainly this amp has very clear percussive and transients are very sharp and clear.
I am not sure if the 4.7pF made a difference but certainly this amp has very clear percussive and transients are very sharp and clear.
I don't agree on what is being stated for the electrolytics.
An electrolytic capacitor is polarised.
One can buy polarised and bi-polar.
Plastic film is not polarised although some plastic film have a tiny polarising effect which we normally ignore.
Plastic is therefore usually referred to as non polar.
A bi-polar electrolytic cannot be non polar.
The yellow electrolytic shown in post7026 is printed incorrectly. It is not NP. it is bi-polar.
I have some bi-polar electrolytics that are printed non polar or NP. These manufacturers don't know how to describe their own product ! They are bi-polar.
An electrolytic capacitor is polarised.
One can buy polarised and bi-polar.
Plastic film is not polarised although some plastic film have a tiny polarising effect which we normally ignore.
Plastic is therefore usually referred to as non polar.
A bi-polar electrolytic cannot be non polar.
The yellow electrolytic shown in post7026 is printed incorrectly. It is not NP. it is bi-polar.
I have some bi-polar electrolytics that are printed non polar or NP. These manufacturers don't know how to describe their own product ! They are bi-polar.
So it doesn't matter if they are -ve +ve +ve -ve. Vs +ve -ve -ve +ve as far as internally how they are connected?
Regardless, the large value of the cap (50uF) is probably what is making it sound great. I am really liking the sound of the FX8 with this upgrade. Highly recommended.
If it makes any difference - I have a huge 50uF 450v industrial motor run oil filled film cap that is not electrolytic and not polarized. I should hook it up for a comparison
Regardless, the large value of the cap (50uF) is probably what is making it sound great. I am really liking the sound of the FX8 with this upgrade. Highly recommended.
If it makes any difference - I have a huge 50uF 450v industrial motor run oil filled film cap that is not electrolytic and not polarized. I should hook it up for a comparison
I built up some test electrolytic coupling capacitors using 10uF and 22uF polarised capacitors.
A pair of 22uF back to back gives 11uF bi-polar
A quad of 10uF connected -ve to -ve for one pair and a second pair connected +ve to +ve and connected in parallel to the first pair gives 10uF bi-polar.
I compared these to a 10uF non-polar MKT and to a 10uF non-polar FKP.
I could not tell the difference in my set up.
To me the most important part of a coupling capacitor is: It must NOT act as a filter to the passing/wanted signal. Make sure any filtering effect is at least two octaves away or preferably a full decade away from the wanted frequencies.
A pair of 22uF back to back gives 11uF bi-polar
A quad of 10uF connected -ve to -ve for one pair and a second pair connected +ve to +ve and connected in parallel to the first pair gives 10uF bi-polar.
I compared these to a 10uF non-polar MKT and to a 10uF non-polar FKP.
I could not tell the difference in my set up.
To me the most important part of a coupling capacitor is: It must NOT act as a filter to the passing/wanted signal. Make sure any filtering effect is at least two octaves away or preferably a full decade away from the wanted frequencies.
So it doesn't matter if they are -ve +ve +ve -ve. Vs +ve -ve -ve +ve as far as internally how they are connected?
Regardless, the large value of the cap (50uF) is probably what is making it sound great. I am really liking the sound of the FX8 with this upgrade. Highly recommended.
If it makes any difference - I have a huge 50uF 450v industrial motor run oil filled film cap that is not electrolytic and not polarized. I should hook it up for a comparison
Hi xrk! You can try this:
USF0J101MDD Nichicon | Mouser
It has 2,5mm lead spacing only. Put 2 of them in series as can be seen in the picture. They cost less than 1 EUR.
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In your simulation, 4.7pF capacitor from VAS output back to the IPS inverting input forms what is called Miller input compensation (MIC).
It is depend on the compensation. My simulation did not show an overshoot on 100kHz square wave. Very high slew rate
I am new to this - what type of file is this simulation, and what program do I need to open and view it? Is it LTSpice? I have TINA installed and will that be able to open it?
It is LTSpice. TINA (what I'm using) is just a toy compared to LTSpice. Using the second one need much more electrical knowledge, but the result is more accurate.