PSU question for A30
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 25th April 2005, 03:07 PM #1 diyAudio Member     Join Date: May 2002 Location: Aalborg, Denmark PSU question for A30 In the phase of collectiong the pieces for my A30 amp, im a bit confused about what PSU design I should go for - a resistor in the area of 0,47 ohm in a CRC filter, or just a simple big old C ? My rough calculations gives me that a 0,47 ohm resistor will drop the voltage about 1,88 volts, and at approx. 2 amps pr. channel dispatch some 7-8 watts - not that much - and thus i will incorporate the secondary drop in the design, and use a 20 volt tranny, and thus end up around 24 volts - that is if I use a 1,3 instead of square root of 2 (witch I recall nelson suggested to use, for more life like calculations) In the haze of the post returned to me by the schearch machine, when entering CLC or CRC i found a thread that stated that CLC or LC was the only way to go.... Is the effort and heat of the R worth it ? I saw that Nelson uses it in the FW amp - or should i just go with with the C of about 220.000uF / channel, like the original alephs ? If I should use a resistor, is 0,1 ohm enough, or is 0,47 better ? Any other tips, besides the use of small polypropylenes acros the big C's ? Im not a fan of CAD-software, more the "better big than sorry" type of apporach....... And just a short 2. Q: the voltage ratings of the 220uF caps in the A30 - is 35 volts ok, or should I use 63 volts ? Cheers ! Hans
 25th April 2005, 06:28 PM #2 diyAudio Member     Join Date: Aug 2001 Location: Ingolstadt Germany Hi, since your bias won´t be that high I would go for a CLC approach. It wastes less energy and is much more effective. For example something like 44000-2.2mH-66000......... You can have a look at the effects of resistors and chokes with PSU Designer II (no CAD!) The 220uF caps can even be 25V without a problem (the coupling caps in the input and current source could even be 6,3V BG NX) William __________________ een ooievaar is geen konijn want zijn oren zijn te klein!
 25th April 2005, 06:31 PM #3 The one and only     Join Date: Mar 2001 I have built them successfully using a .47 ohm value per channel, which isolates the two channels and give a 1 volt drop across the resistor. This gives a reduction in the supply ripple by a factor of about 10.
 26th April 2005, 08:49 AM #4 diyAudio Member     Join Date: May 2002 Location: Aalborg, Denmark PSU for A30 Wuffwaff and Nelson - thnx for the answers - I would like to use R's instead of L's - as they are somewhat harder to get for me, and to be frank - i dont mind the extra heat.... ;-) I suspect that the the cap at the current source is C9 close to Q5 - or is it C10 ?? Wuff - you mention the use of BG caps here - is this location and the input coupling cap a good place to spend some extra \$\$\$ in trade of quality ? I plan on using Panasonic FC, as I have them lying in my "box O'goodies". Nelson, the use of Resistors that you mention to give isolation, as well as a factor 10 in reduced ripple (sounds as it is worth to include ??) - is that the "normal" use whare you place the resistor in the positive and negative rail between two banks of Caps ? How could this isolate the channels - is that because that you use a seperate cap bank for each channel ? and finally ( as if I didnt ask enough questions...) are there any pros by using a cap bank for each channel, with its own bridge ?(or two bridges, but I would like to thy and use one, as this i whats used in the A30 schematics) Thank you for taking the time to answer and contribute to my knowledge increase ;-) Cheers ! Hans
 26th April 2005, 09:39 AM #5 diyAudio Member     Join Date: Aug 2001 Location: Ingolstadt Germany Hi, the cap at the current source is the one connected to the base of Q5. BG NX 220uF 6,3V are not very expensive and I used them in my Aleph5. There is another thread "coupling cap in Aleph" were these caps are discussed at lenght ending with a bunch of BG´s used for the input cap and a panasonic FC + 10nF at the other position. William __________________ een ooievaar is geen konijn want zijn oren zijn te klein!
 26th April 2005, 12:29 PM #6 diyAudio Member     Join Date: May 2002 Location: Aalborg, Denmark A30 psu Hi again as I read the schematic, the only cap attached to the base of Q5 is C7, witch is 0.001uF ? C9 is connected acros the collector and emitter, and C10 to emitter, and to base via the R21@820 ohms - R9&R10 is 220uF ? I a bit confused now - ?? Cheers! Hans
 26th April 2005, 12:40 PM #7 diyAudio Member     Join Date: Aug 2001 Location: Ingolstadt Germany it´s the one connected to R21. Insome Alephs the cap comes first then the resistor. Here it seems to be the other way round....... sorry, William __________________ een ooievaar is geen konijn want zijn oren zijn te klein!
 26th April 2005, 12:51 PM #8 Account Disabled   Join Date: Aug 2002 Location: Near to the Pacific Ocean I think that 220uF of 35V grade is ok for C9 and C10. If you use 63V grade, the life of the caps could be vertually permanent. Regards
 27th April 2005, 08:20 AM #9 diyAudio Member     Join Date: May 2002 Location: Aalborg, Denmark PSU OK, good to know - I'll stick with the 35 volt - permanent is almost to good for me But still Im a bit confused about the use of resistors (or inductors) in the PSU - I suspect that nelson uses it in the FW amps because they have to drive very sensetive speakers, and/or the circuit itself is more prone to pick up noise from the supply ? I recall that some have said that they did not think that further regulation beyond a simple C of the aleph supply gave any improvement ? Ups, and another thing - I want to be able to play with BIAS (dont we all ??) and thus want to calculate for the greater current draw when ordering my toroid - how much does the A30 draw when R19 is removed - its about 2 amps/channel when not removed ? Cheers ! Hans
 27th April 2005, 10:36 AM #10 diyAudio Member     Join Date: Aug 2001 Location: Ingolstadt Germany Hi Hans, with 0,47 Ohm source resistors this will probably be over 3A / Channel. Instead of removing it you could also change it to a higher value. You will need a pot in this position anyway to set the amp up in the first place. Just change the setting and measure the pot so you´ll know what resistor you need for a given bias. All the Aleph´s were without C-R-C or C-L-C so this will work just fine. The nice thing about DIY is that you can try other things too without having to worry too much about cost or customers. A nice C-L-C supply will give you far less ripple. Why don´t you just try with and without. Measure the ripple voltage and listen to the changes in sound. William __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

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