My amp used to be 75,000 uf a channel, but now I use 280,000 uf per channel , then 1 mh chokes then 50,000 uf of Blackgates. (almost 700,000 pie filtered total in a stereo amp)
It has better definition, tighter bass control, greater dynamics, and now very good low level detail. Formulas give a minimum, but my ear likes more uf.
It has better definition, tighter bass control, greater dynamics, and now very good low level detail. Formulas give a minimum, but my ear likes more uf.
I imagine Germany is also being overrun by our less than scrupulous neighbors. I see that China are now cloning Rolls Royces and BMWs so the World will never be safe again.
Hugh,
Yes, it's not simple. But it sounds like you are on the right track, although I shouldn't presume that my opinion has much value. Your experiences are valuable. Two other "interests" that I have right now happen to be 1) the importance of the decoupling capacitance at the load (versus the importance of capacitance in the power supply) and 2) the problems associated with return currents, probably mainly from sharing of conductors and "back-propagating" voltages induced across their inductances.
I think it's best to distribute as much of the capacitance as possible to the points of load. But I didn't take that into account in post 106.
The high currents should probably be confined to small-geometry local loops whenever possible. And I still think that transient response accuracy ("speed"?) is what separates the merely great amps from the exquisite ones. After all, it appears to be relatively easy to make an amp with vanishingly-small THD (i.e. almost-perfect steady-state response) that still doesn't sound good-enough. So therefore the key must be in the transient response, right?) So focusing on decoupling cap configurations seems like a key, to me, which has been neglected too much, by most (apparently). It's not always easy to get the decoupling good-enough, even at audio frequencies, especially when high currents are involved. It usually requires accuracy to hundreds of kHz and the physical geometry becomes a significant problem, with most DIY construction methods. The main thing there is to even think about it in the first place, and actually calculate the minimum required decoupling capacitance AND the maximum tolerable inductance in its connections. THEN we might see that it's sometimes VERY difficult to get a low-enough impedance to be seen by the pins where it's needed.
It's ridiculous to talk about a PSU's low output impedance without also talking about the inductance of the conductors from its output to the load, for example, and about what the load's actual impedance vs frequency requirements are, specifically, and at what current levels.
Regards,
Tom
What caps are you using though. Just to say that 0.7F is better can only be justified with a particular choice of caps.
I'm using 0.12F of Dubillier in a 100W Class A set-up.
Gootee I agree. How many people take each component as a separate issue and dont treat the whole amp as an entity ?
I've just been sorting out a Pass F5 build that was humming with over 100000uF of Siemens Computer grade caps.
His grounding layout was good but the gauge of the cables was appaulling. After replacing his 0V cables with decent 4mm cables the hum went away.
My Aleph uses crazy cabling but only because I could get 6mm cable at a bargain price.
I've just been sorting out a Pass F5 build that was humming with over 100000uF of Siemens Computer grade caps.
His grounding layout was good but the gauge of the cables was appaulling. After replacing his 0V cables with decent 4mm cables the hum went away.
My Aleph uses crazy cabling but only because I could get 6mm cable at a bargain price.
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Yes they do but are only for sale in China, that was the agreement. Problem is the wealthy Chinese does not want to buy these products made in China either.
Hi TicknPop, there is no doubt that some DIYers would want to personalize their products, but we need to establish a good basis to start from.
There is no point to specify or discuss the type, color, brand or whatever as this has no scientific relevance, and up to the user to choose.
The reason I choose Krummer or Siemens is because the manufacturers have a quality system and reputation to uphold unlike the example that I posted earlier.
Whether the caps sound better or worse with the plastic sheath removed or whether the sheath is gold or blue printed makes no scientific sense that I believe is purely cosmetic or where science and subjectivity parts ways.
Like I said earlier when I listened to 4700uF instead of 80 000uF supply rails I opened myself to be strung up and dried because this was scientifically inconclusive. However, if the majority of DIYers found the same results it can become a rule of thumb or popular belief.
I would like to keep this thread as "scientific" as possible until we establish the base line. It remains 3300uF/amp which has been verified to some extent by Tom. If the argument tends to become subjective then state why so that we can add some weighting to it. We have some for and some against at the moment so they balance each other leaving the result at 3300uF/amp.
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I thought the name was a deliberate joke.....
Seriously, I use them. They have nothing to do with exclusivity. When I started negotiating with Krummer I found out that they branded their capacitors for other manufacturers that needs compliance with various other "specialist" requirements such as medical and aerospace.
Krummer-Kondensatoren
Just go ahead and try them. You will never establish a definitive brand as everyone has their own ideas.
The Snake Oil vendors will always creep in too. Some top-end manufacturers use less than exotic brands- but that again comes down to cost.
Have a look at the really high-end manufacturers for real inspiration.
The Snake Oil vendors will always creep in too. Some top-end manufacturers use less than exotic brands- but that again comes down to cost.
Have a look at the really high-end manufacturers for real inspiration.
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There's always the phenomenon of "Purse Ears".
If you pay $100 for a component it will always sound better than its £10 adversary.
Only once did I hear a REAL improvement, and that was in changing a feedback cap from a 22uF Tantalum to a 22uF Elna Simic II. The tant had a definite Tsssss sibilance which completely disappeared with the Elna.
If you pay $100 for a component it will always sound better than its £10 adversary.
Only once did I hear a REAL improvement, and that was in changing a feedback cap from a 22uF Tantalum to a 22uF Elna Simic II. The tant had a definite Tsssss sibilance which completely disappeared with the Elna.
Also, I think that we should try to stop thinking of power supplies in terms of voltage and ripple, so much. The current delivery performance is what matters most, by far. The PSU and decoupling capacitors provide the current that makes the the music we hear, directly. Ripple and voltage variations might be somewhat important, when PSRR is a problem, but it is ridiculous to think that if a power supply has lower ripple then it will sound better. It might, or it might not, but by far the more important factor is how accurately it can deliver current when current is demanded. I'm just saying that a lot of people seem to think that all they need to think about is getting low ripple voltage, and that if they do that then their power supply is as good as it can get. It's the wrong metric. Luckily for them, it sometimes correlates with having accurate current-delivery capability.
How about looking at the output spectrum using an FFT to view the mains harmonics when the amplifier is loaded at maximum power. This could help determine how much capacitance is required. The higher mains harmonics need to be well below the noise in my opinion though I guess that the high level audio will tend to mask them.
Different amplifiers are going to have different power supply rejection ratios which is also going to vary with frequency which can be tested by injecting signals onto the power supply rails. It is a lot of work to test though.
Putting lots of smaller capacitors in parallel isn't necessarily going to reduce the supply impedance due to all the wiring required. The capacitors suggested by OnAudio are quite low impedance.
Different amplifiers are going to have different power supply rejection ratios which is also going to vary with frequency which can be tested by injecting signals onto the power supply rails. It is a lot of work to test though.
Putting lots of smaller capacitors in parallel isn't necessarily going to reduce the supply impedance due to all the wiring required. The capacitors suggested by OnAudio are quite low impedance.
Tom every time you open your mouth, I know that what you are going to say will make absolute logical sense.
Nico,
It would be a straightforward calculation, I guess, if there were no parasitic inductance or resistance.
The ideal capacitor discharges according to:
Vc(t) = v0(e**(-t/RC))
We want to start with v0 = 40 Volts across the cap. We want the cap to be able to supply 3.54 A into 8 Ohms for 20 ms and have its voltage not go below 28.32 Volts before the 20 ms has elapsed. So Vc(0.02) = 28.32, for the minimum capacitance that could do that.
So we have:
28.32 = 40(e**(-0.02/8C))
and just need to solve for C:
(28.32/40) = -e**(-0.02/8C)
0.708 = e**(-0.02/8C)
ln(0.708) = -0.02/8C
-0.3453 = -0.02/8C
C = (-0.02)/((8)(-0.3453))
C = 0.007240
C would need to be at least 7240 uF.
Tom you are a star, we have our base line can we then scale it simply to 7240/3.54= 2000uF/Amp. I must congratulate PChi on suggesting that number from the outset 156 postings ago. This is our base line 2000uF/amp so our original 3300uF/amp was a 30% over kill.
To conclude a 100 watt rms into 8 ohm amplifier requires 7240uF caps on each rail in order to meet its basic requirement. Anything less than this will impair the sound and anything more than this we will start to result warm subjective experiences slightly below the abdomen.
KatieandDad now we can bring out the various flavours of snake oil and massage more micro farads and color into them. I am so pleased that we came to a conclusion, thanks again Tom!
To conclude a 100 watt rms into 8 ohm amplifier requires 7240uF caps on each rail in order to meet its basic requirement. Anything less than this will impair the sound and anything more than this we will start to result warm subjective experiences slightly below the abdomen.
KatieandDad now we can bring out the various flavours of snake oil and massage more micro farads and color into them. I am so pleased that we came to a conclusion, thanks again Tom!
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Nico,
Thanks, but you are being far too kind and generous. I just happen to have thought about some of this particular stuff quite a bit, for a little while now. But I am beginning to think that I am on the Asperger's spectrum because in many other areas I am hopelessly clueless.
Regards,
Tom
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