Hi all!
The filter bank of my single power supply for two amp modules consists of 2x10.000uF/50V Panasonic TS-HA per rail, so it's 40.000uF in total. Rail voltage is about 35V.
For testing purpose (and for the fun of it) I recently solderd in some bypass caps at the output of the psu (so these bypass caps would be the caps the amp "sees"). These are ELNA Silmic II, 470uF/50V each. I guess this is quite uncommon because most people use 0,1uF up to, say, 10uF here.
I'm not exactly sure about the result. I like the ELNA's very much in other applications, and I think there is a noticeable increase of musicality with these caps in the psu. On the other hand, I have the feeling that at very high volume levels the sound becomes slightly harder than it used to be before I soldered in these caps.
Unfortunately I don't own a o'scope to check how the output voltage looks like...
Any ideas? Has anyone experiences with such high-valued bypass caps in an amps psu?
Here's a pic...
Thanks a lot!
Martin
The filter bank of my single power supply for two amp modules consists of 2x10.000uF/50V Panasonic TS-HA per rail, so it's 40.000uF in total. Rail voltage is about 35V.
For testing purpose (and for the fun of it) I recently solderd in some bypass caps at the output of the psu (so these bypass caps would be the caps the amp "sees"). These are ELNA Silmic II, 470uF/50V each. I guess this is quite uncommon because most people use 0,1uF up to, say, 10uF here.
I'm not exactly sure about the result. I like the ELNA's very much in other applications, and I think there is a noticeable increase of musicality with these caps in the psu. On the other hand, I have the feeling that at very high volume levels the sound becomes slightly harder than it used to be before I soldered in these caps.
Unfortunately I don't own a o'scope to check how the output voltage looks like...
Any ideas? Has anyone experiences with such high-valued bypass caps in an amps psu?
Here's a pic...
Thanks a lot!
Martin
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Hi,
these bigger value bypass caps are more usually mounted on the amplifier PCB very close to the main current consumers. Here they are referred to as decoupling.
You have used two different values of electrolytic in your PSU. Due to significant ESR in the electrolytics there is much less likelyhood of incipient oscillation when very low ESR caps are used. Some low ESR electrolytics can cause ringing on the supply lines, but I don't have a rule for identifying which may cause problems.
Does your amplifier have HF and MF decoupling on board?
these bigger value bypass caps are more usually mounted on the amplifier PCB very close to the main current consumers. Here they are referred to as decoupling.
You have used two different values of electrolytic in your PSU. Due to significant ESR in the electrolytics there is much less likelyhood of incipient oscillation when very low ESR caps are used. Some low ESR electrolytics can cause ringing on the supply lines, but I don't have a rule for identifying which may cause problems.
Does your amplifier have HF and MF decoupling on board?
Hi Andrew,
yes, there are decoupling caps on the amp boards near the output devices, rated 47uF/100V, Nichicon Muse.
I'm aware of the fact that these bypass caps are usually mounted near the power consumers, but nevertheless I think of the amp boards and psu as two "separated" units. Even a completed amp board with decoupling caps near the output devices does react (sonically) to different psu topologies. Of course one might say there is no need for such psu bypass caps if they are on the amp boards already. But I think the psu does still "sound" different with different additional caps.
Recently I read an artikle about the idea that small psu bypass caps (like 0,01uF or 0,1uF) do actually degrade the performance of the psu. They performed a lot of measurements to proof their claims. Sorry, can't remember where I read it...
But in the end I'm left a bit puzzled about the possibilities of NO bypass, SMALL bypass or LARGE bypass values....
Martin
yes, there are decoupling caps on the amp boards near the output devices, rated 47uF/100V, Nichicon Muse.
I'm aware of the fact that these bypass caps are usually mounted near the power consumers, but nevertheless I think of the amp boards and psu as two "separated" units. Even a completed amp board with decoupling caps near the output devices does react (sonically) to different psu topologies. Of course one might say there is no need for such psu bypass caps if they are on the amp boards already. But I think the psu does still "sound" different with different additional caps.
Recently I read an artikle about the idea that small psu bypass caps (like 0,01uF or 0,1uF) do actually degrade the performance of the psu. They performed a lot of measurements to proof their claims. Sorry, can't remember where I read it...
But in the end I'm left a bit puzzled about the possibilities of NO bypass, SMALL bypass or LARGE bypass values....
Martin
Bypass capacitors can cause a rise in impedance at high frequencies if the main capacitor has very low ESR. Sometimes a bypass can help, sometimes not. This is a complex situation, made worse by myth propagation and fashion. If used, a bypass could be perhaps 100-1000 times smaller than the main cap. Alternatively, replace the big cap with two of half the capacitance each.
The unseen problem is the complex ESL and ESR of the capacitances interacting with the C & L & R of the connecting traces and/or cables when a fairly fast step change in current demand arrives.
Multiple caps increase this complexity and sometimes one hears the resultant SQ change.
Oscilloscope investigation is the only method I know, to go from heard to seen voltages
Multiple caps increase this complexity and sometimes one hears the resultant SQ change.
Oscilloscope investigation is the only method I know, to go from heard to seen voltages
You guys,
when we are talking about this bypass-thing I think the result is that it makes things not necessarily better or worse, but certainly much more complex and unpredictable.
I will rip the caps off. The simpler, the better! 🙂
Thanks a lot for sharing your thoughts!
Martin
when we are talking about this bypass-thing I think the result is that it makes things not necessarily better or worse, but certainly much more complex and unpredictable.
I will rip the caps off. The simpler, the better! 🙂
Thanks a lot for sharing your thoughts!
Martin
Ironically, I was about to post a similar question, but am reluctant to expose my ignorance. Nevertheless, here goes. While Mr Pass seems to recommend an 4.7uF MKP capacitor as the final component in the power supply. I have also seen 4.7uF capacitors used across the secondaries of a transformer although it has also been suggested in an old post that they might be better positioned across the +/- terminals of the bridge rectifier. While I accept that the use of such capacitors at the amplifier end might lower ESR I am puzzled by their use across the bridge or secondaries. Can anybody enlighten me as I believe it has something to do with inhibiting ringing in the circuit rather than an attempt to simply lower ESR of the first capacitor in the circuit. What effect does it have?
4.7uF seems much too high for the AC side of the rectifier - it could encourage ringing. 4.7nF may help with switch-off spikes.
"From simulations it seems that 4,7uF across the plus and minus of the bridge is more effective than across the AC inputs (= the secondary of the transformer). Smaller values (100n-1u) do work, but often require another bigger capacitor (470n-10u) with series resistor in parallel as a damper. Ratio of C's approx 5-10, resistor value depending on the inductance of the transformer secondary and the value of the C, but in the range of 5-15 Ohm."
Quoted from 'Choke for Pi Filter# in Solid State without permission - my sincerest apologies to Steven
Quoted from 'Choke for Pi Filter# in Solid State without permission - my sincerest apologies to Steven
Hi guys,
quick update: I did it, I removed the 470uF ELNA caps from the psu, and the result really is like I said before. The overall sound of the amp seems to be just slightly less musical (yet VERY neutral!), but its main sonic character now remains absolutely stable, even if I crank the volume up to really high levels. No more sign of "getting harder" or something like that at high listening levels.
Maybe this kind of bypass works for minimum current requirements, but fails at high current demands.
Anyway, great! I consider this part-removal a serious upgrade for my amp, that's why I want to thank you all for your participation on this topic!
Regards!
Martin
quick update: I did it, I removed the 470uF ELNA caps from the psu, and the result really is like I said before. The overall sound of the amp seems to be just slightly less musical (yet VERY neutral!), but its main sonic character now remains absolutely stable, even if I crank the volume up to really high levels. No more sign of "getting harder" or something like that at high listening levels.
Maybe this kind of bypass works for minimum current requirements, but fails at high current demands.
Anyway, great! I consider this part-removal a serious upgrade for my amp, that's why I want to thank you all for your participation on this topic!
Regards!
Martin
Just guessing but, this might explain the hardening of the sound.
At low volumes the amplifier is giving the PSU lot's of gentle kicks. Result nice sound with and without the extra electrolytics. Could the extra detail with the extra electrolytics be very mild ringing when small value fast transients demand a small step change in current?
At high volumes the amplifier is giving the PSU some very big kicks and lot's of medium size kicks. The PSU reacts to these kicks differently depending on whether the extra caps are in place or not. Result, a different sound at higher volumes. This could be an indication of ringing in the PSU when it receives big steps changes in the current demand. The extra complexity of the impedances with the extra electrolytics promotes some instability in the PSU and some of this gets through the amp to the speakers.
At low volumes the amplifier is giving the PSU lot's of gentle kicks. Result nice sound with and without the extra electrolytics. Could the extra detail with the extra electrolytics be very mild ringing when small value fast transients demand a small step change in current?
At high volumes the amplifier is giving the PSU some very big kicks and lot's of medium size kicks. The PSU reacts to these kicks differently depending on whether the extra caps are in place or not. Result, a different sound at higher volumes. This could be an indication of ringing in the PSU when it receives big steps changes in the current demand. The extra complexity of the impedances with the extra electrolytics promotes some instability in the PSU and some of this gets through the amp to the speakers.
since the 470uF is in parallel to many mF I suspect the ripple current is quite small. Most of the fast transients will be met by the on board decoupling.
The slower current changes will be met by both the "big" caps and the 470uF.
I don't expect the 470uF to be stressed.
The slower current changes will be met by both the "big" caps and the 470uF.
I don't expect the 470uF to be stressed.
Well, my honest opinion is that the 470uF cap, if it isn't over it ripple current, will make no difference whatsoever 'sonically'.
It would make a proportionally sized reduction in ripple in comparison to the main caps which, in this case, would be very small.
It would make a proportionally sized reduction in ripple in comparison to the main caps which, in this case, would be very small.
At the upper end of the audio range 10000uF will look like a small inductance. 470uF might still look like a capacitance (not sure). If so, the two could form a low Q resonant circuit which will raise PSU output impedance - the opposite of what is desired. What is worse, the resonance could be in or close to the audio range.
Hi Andrew!
Well, this 'could' be an explaination. I don't know if it's the truth, but it sounds resonable!
Hi DF96,
well, this could also be an explaination, which sounds just as resonable as what Andrew said!
Hi John,
well, believe me, there IS a difference in sonics. Over the time period I had the additional caps in the psu I was always unsatisfied with the sound of the whole amp when it came to high listening levels. As said before, within the lower range of volume the sound was very nice, punchy, fast, flowing and with the so important 'boogie-factor'. But things got really interesting when I turned the volume up to something beyond 12 o'clock. Things happend to get somehow hard, stressing, fatiguing. No matter if Tracy Chapman was singing or if good old Focus played one of their bests. Things just got worse. Sometimes I was even of the oppinion that this whole amp was not my cup of tea, and I thought about selling it.
But today I played music all day long, many types of music, and this ill effect really is gone! There is absolutely no change in the overall sound up to insane volume levels.
I find all this quite strange myself, that's for sure. If someone was telling me about such a bad influence of two (in other applications very nice sounding!) caps, I would have declared him nuts...
Martin
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Certainly, if you say so.
The fact that entirely defies logic and quantitative measurement is what threw me. 😉
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Interesting thread - not the first time I've read of sound changes from psu caps. I've got myself a roll of SMD ultra low ESR electrolytics - I might give them a try as bypass caps and see what the effect is.
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