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-   -   Swordfishy/ASPEN FETZILLA power amp (http://www.diyaudio.com/forums/aksa/191053-swordfishy-aspen-fetzilla-power-amp.html)

sparkeey 8th July 2011 04:55 AM

to ian i can supply you with sinks sent directly to your door just mail me when the time comes and you know i`ll give you at the best price

AKSA 8th July 2011 06:32 AM

HI George,

Please post, I would be interested - though the soft start is not actually required.

Thanks for the legwork, appreciated,

Hugh

chlorofille 8th July 2011 09:24 AM

Can't wait to start building this amp! (Once Greg gives the "go ahead")
I already have a 44,000uF per channel PS using Evox Rifa PEH169 caps so all I need is to connect the +/- 35V to the board!! Currently running a P3A amp - I'm certain the Aspen Fetzilla will be more musical.

AKSA 8th July 2011 12:39 PM

Dinesh,

I really would discourage you from building a huge power supply. It will not sound so good.

I have done extensive testing with Class AB amps on this issue and found again and again that the very high charge pulses found in high cap power supplies actually militate against good sonic performance. The problem is that these very high charge pulses interfere with the voice coil earth return through the filter caps, causing intermodulation.

I find it's never necessary to go much more than 4,700uF on a 50W amplifier.

The FETzilla uses two 3,300uF caps separated by interelectrode resistors, each of 0.15 ohms. This quarantines the charge pulses principally to the first cap after the rectifier, with the second cap handling much reduced charge pulse and all of the speaker return current. This arrangement gives palpably better sound.

Cheers,

Hugh

chlorofille 8th July 2011 01:12 PM

Hugh,

Noted, will follow your recommendation.

JKC 8th July 2011 03:30 PM

1 Attachment(s)
Hugh

Here is schematics for separate PSU. This is only a general idea if you are planing to use separate power supply instead of the one included on amp PCBs. You can change all the major components to your personal taste. I used here 24VAC 300W transformer. 24VAC is more common than 25VAC and is much easier to get. You don't need 300W transformer for this project, 160W will probably be enough. I used 300W for economical reasons, it costs only $15 more and is bigger by 7mm than 160W one. Soft start circuit is optional in case you plan to use large filtering capacitors to prevent blowing fuses on start-up.

Attachment 230402

Regards
George

AKSA 8th July 2011 11:22 PM

Lovely work, George, many thanks.

Agree about the 24Vac trafos, plenty around, some at disposals prices.

I do feel you might have too much capacitance there, which incidentally can be mounted onboard at the pcb. I have found that onboard caps improve the sound since the connection to the output devices is not so inductive as a long wire.

Thank you for your excellent contribution!

Hugh

Woody1911a1 9th July 2011 01:03 AM

put me down for 4+P :)

2+P JoMo Adelaide SA Australia
2+P Ian Finch Coffs Harbour NSW Australia
2+P Gennaji Hyderabad India
2 Ken Lewis LA USA
2 Ron Russell Kent UK
2+P John Kenny Dublin Ireland
2+P Francis Morrin Dublin Ireland
2+P Vitalica Bucharest Romania
2+P Erik Deinum Groningen Netherlands
2+P Keith Correa ? India
2 Igor Polyakov California (city?) USA
2 Steve (aka SRH) Whangarei New Zealand
2+P George (aka JKC) Calgary Canada
2+P Anthony Mills Gold Coast Australia
2+P Dinesh (aka Chlorofille) Christchurch New Zealand
2+P Colin S. (?) (city?) NSW Australia
2 Chris Powell Sydney Australia
2+P Danny (?) Lierde Belgium
2 Sonnya (?) City (?) Denmark
4+P Jozua Cape Town South Africa
2 JT (? aka Sandyhooker) City (?) Arizona USA
2+P Nicola City (?) Vincenza Italy
2+P Sparkey (?) Melbourne Australia
2+P Chalkandtalk (?) City (?) NW England UK
4+P Woody1911a1 Marblehead , Ma USA

cheers Woody

AKSA 9th July 2011 02:25 AM

You're in, Woody. Now at 54 boards and building!

2+P JoMo Adelaide SA Australia
2+P Ian Finch Coffs Harbour NSW Australia
2+P Gennaji Hyderabad India
2 Ken Lewis LA USA
2 Ron Russell Kent UK
2+P John Kenny Dublin Ireland
2+P Francis Morrin Dublin Ireland
2+P Vitalica Bucharest Romania
2+P Erik Deinum Groningen Netherlands
2+P Keith Correa ? India
2 Igor Polyakov California (city?) USA
2 Steve (aka SRH) Whangarei New Zealand
2+P George (aka JKC) Calgary Canada
2+P Anthony Mills Gold Coast Australia
2+P Dinesh (aka Chlorofille) Christchurch New Zealand
2+P Colin S. (?) (city?) NSW Australia
2 Chris Powell Sydney Australia
2+P Danny (?) Lierde Belgium
2 Sonnya (?) City (?) Denmark
4+P Jozua Cape Town South Africa
2 JT (? aka Sandyhooker) City (?) Arizona USA
2+P Nicola City (?) Vincenza Italy
2+P Sparkey (Brian ?) Melbourne Australia
2+P Chalkandtalk (?) City (?) NW England UK
4+P Woody1911a1 (?) Marblehead , MA USA


Thanks for the support, this is going very well......

Cheers,

Hugh

JKC 9th July 2011 05:23 PM

Hugh

As I said before those values can be changed. I think that the best compromise will be to use two big capacitors just after the bridge in the range 6800uF to 10000uF and another pair of smaller capacitors 3300uF to 4700uF directly on the boards. In this case length of the wires you ran from power supply to the amp will be not that critical. If you need to get low ripple voltage on the rails you will need quite big caps. In this case at 50W into 8ohm impedance will produce 3.5A peak current. With four 8200uF you looking at ripple voltage around 0.76Vpp at peak current. In reality it will be little smaller than that because of those series resistors between caps (those resistors should be an inductive wire-wound type for the best filtration). However, if you are looking for the worst case scenario let say 100W into 4ohm impedance load then your ripple voltage on the rails will double to 1.5Vpp at peak current of 7A which is quite high. Because of non-linearity of the speakers you should be expecting that kind of situation on a transient basis.

Regards
George


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