The thing that really grabbed my attention was the Cap Multiplier. I have tried cap multipliers in a Zen V3, and a few preamp circuits, and every single time I noticed an unpleasant change in tone. If the change of a transformer/choke/rectifier can have a profound impact on sound quality - how much more so a low grade regulator such as the cap multiplier.
Shoog
Shoog
this is a very cool kit.Oatley Electronics it drives my 4x12 guitar cad quite well. i would say it puts out about 1/4 of a watt. only powerd by a 9 volt battery!
Thanks for the all the comments.
I don't have the same experience. I two Zen-like amplifiers, both now equipped with cap multipliers, and they sound very good. I also tried big power chokes, either air-core coils (10mH) or Amveco toroidal chokes (120mH/5A).
The cap multiplier runs open-loop (no feedback), so the output impedance is relatively high. That's why it works better with constant-current amplifiers, such as SE or Class-A designs, which includes the Zen. I can't explain why you don't like a cap multiplier with your Zen (however, adding the Aleph subcircuit starting with the Zen v2 converts the upper transistor's operation from CCS to a variable current supply). Looking at the schematic in the Pass Zen v3 publication (page 2), did you increase C9 sufficiently? Using 220uF is much too small as shown in the schematic if you have the Aleph circuit connected (C7 and R19). You'll need >40,000uF, as Pass discusses in the text.
Chokes also act as constant-current sources, and will exhibit high AC impedance. That's why you need a reservoir (bulk) capacitor downstream of the choke (or cap multiplier), to provide low AC impedance output for Class AB (or Pass Aleph) designs.
In my case (300V B+ power supply), I used a cap multiplier as a band-aid to fix the SS rectification.
Yes, I used high-quality diodes from IRF. I'll check the numbers tonight. They are snubbed according to their characteristics (110 Ohm in series with 0.068uF). There are plenty of documents on the web on how to calculate snubber networks across diodes. Just Google "calculate diode snubber" or similar.
If you look at my previous post, you'll see I tested RF chokes, otherwise known as hash chokes. I also used Epcos capacitors designed to filter AC line hash.
Remember, I'm measuring low single-digit mV on my 300V B+ line, which is <10ppm. Yet, I can hear it on high-efficiency speakers, especially headphones. After many power supply designs (valve and SS) and much listening, I prefer valve rectification with passive CLC filtering far more than SS designs.
Therefore, why I started this thread.
I don't have the same experience. I two Zen-like amplifiers, both now equipped with cap multipliers, and they sound very good. I also tried big power chokes, either air-core coils (10mH) or Amveco toroidal chokes (120mH/5A).
The cap multiplier runs open-loop (no feedback), so the output impedance is relatively high. That's why it works better with constant-current amplifiers, such as SE or Class-A designs, which includes the Zen. I can't explain why you don't like a cap multiplier with your Zen (however, adding the Aleph subcircuit starting with the Zen v2 converts the upper transistor's operation from CCS to a variable current supply). Looking at the schematic in the Pass Zen v3 publication (page 2), did you increase C9 sufficiently? Using 220uF is much too small as shown in the schematic if you have the Aleph circuit connected (C7 and R19). You'll need >40,000uF, as Pass discusses in the text.
Chokes also act as constant-current sources, and will exhibit high AC impedance. That's why you need a reservoir (bulk) capacitor downstream of the choke (or cap multiplier), to provide low AC impedance output for Class AB (or Pass Aleph) designs.
In my case (300V B+ power supply), I used a cap multiplier as a band-aid to fix the SS rectification.
Yes, I used high-quality diodes from IRF. I'll check the numbers tonight. They are snubbed according to their characteristics (110 Ohm in series with 0.068uF). There are plenty of documents on the web on how to calculate snubber networks across diodes. Just Google "calculate diode snubber" or similar.
If you look at my previous post, you'll see I tested RF chokes, otherwise known as hash chokes. I also used Epcos capacitors designed to filter AC line hash.
Remember, I'm measuring low single-digit mV on my 300V B+ line, which is <10ppm. Yet, I can hear it on high-efficiency speakers, especially headphones. After many power supply designs (valve and SS) and much listening, I prefer valve rectification with passive CLC filtering far more than SS designs.
Therefore, why I started this thread.
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Umm, while resembling higher capacitance to an extent, the "multiplier" doesn't actually multiply the capacitance avaliable (as in: it cannot deliver more energy to devices downstream than the capacitors can provide). It will cut the peaks off the ripple in a fashion similar to using larger capacitance, but that's it; it is no substitute for actual capacitors.
Now as long as you have sufficient capacitance avaliable to take care of "valleys" in the ripple waveform, you might as well add a voltage reference to the pass transistor and call this capacitance multiplier by its name: series voltage regulator. Capacitance at pass element's controlling terminal provides nice soft start identical to larger capacitance on the supply line but shouldn't have any effect on supply (and therefore sound output) after the power-up.
Therefore I respectfully disagree with the underlined remark above. I feel there is no place for "capacitance multiplier" after the PSU choke in place of actual capacitance, regardless of its value.
Your respect is appreciated. I respectfully re-communicate.
Two power supplies were tried with my Zens, which run at 2 Amps.
1. C-L-C with big C (>40,000uF) and L (10mH and 120mH)
2. C-MOSFET-C with big C (>40,000uF) and MOSFET capacitance multiplier between.
A "capacitance multiplier" doesn't act like a big capacitor! It has high AC impedance, whereas a real capacitor has low AC impedance. That's why you need to follow the "capacitance multiplier" with a big capacitor!
A choke has a similar characteristic - high AC impedance. You also need to follow a choke with a big capacitor.
I don't see a reason why a capacitor multiplier and choke would be used at the same time.
So, please consider my original sentence below:
Please consider the same sentence using different words:
Thank you. It is sometimes difficult to communicate technical schematics clearly with words, especially in informal settings.
Indeed, I'm not a native English speaker (which sometimes leads to confusion on my part) and it was my understanding that the underlined text referred to the "bulk capacitor downstream" (meaning that cap multiplier could replace the actual capacitor), which it apparently did not.
With additional elaboration on your part it is apparent that we both agree that it is not capacitance multiplier's job to replace the big capacitance, even though one might be (mis)led to such conclusion by its name and accompanying calculation formula(-e).
Claiming that SS rectifiers create "noise" is "over the top". Claiming that PF is a "factor" in a full wave rectifier is "over the top".
Hearing power supply noise from ANY real cause is simply a symptom of inadequate filtering. Of course no amount of filtering can eliminate imaginary noise, so I can see the problem here.
Yes, my remarks about wasting power (both the power wasted by the heater/filament and that wasted by the inefficiency of any tube rectifier) was tongue-in-cheek. Note, however that millions ofare being spent on making cell phone chargers draw less idle current when not charging. You can win gold stars for shaving microamps off the power draw.
If you can cite a valid double-blind experiment that shows that listeners can actually hear the difference between SS vs tube/valve rectifiers in the power supply, I will think about reconsidering my brash judgement. Else you can put me down as a solid disbeliever.Perhaps he sould consider a big bank of batteries in the basement.
Im actually with you on this one. Ive stopped using my cell phone and I have a plan to enforce laws which havent been passed yet. One of my ideas is to ban music and all music making devices, throw all teenagers in jail for impure thoughts (ipods) and generally force my views on the world. Any one not know who I am?
Governments are outlawing incandescent light bulbs which serve a far more useful purpose than 19th century technology firebottles.
Yup, yup, especially yup, yup, and probably.
A computer uses about 200W idle (including monitor), so it will use 4.8kWh in one day. 6.3W for one year is 55kWh.
Of course, the weasel words "few hours" and "days I use it" leave the conversion factor to the imagination, so you needn't be technically incorrect.
Of course, that's shortsighted, as no one uses a rectifier for heat alone. Under normal operating conditions, the plate dissipation is typically higher than heater dissipation by a factor of 2-4, so the tube might not be burning 6.3W, but rather 18W (which would be pretty typical of a full height 7 pin type tube, e.g. 6AQ5's 2.8W heater, 2W screen and 12W plate).
At any rate, it should be clear why I explore such esoteric subjects as class D tube amplifiers and numerous switching power supplies.
Tim
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