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Old 7th November 2010, 08:35 PM   #1
syyma is offline syyma  United States
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Default Edcor CXPP-30-MS-3.8K OPT

Would this Edcor CXPP-30-MS-3.8K OPT able to make the cut for an EL84 paralleled pp mono block. The circuit in mind for the project will be TubeCad's PS-4 & PS-5 Tube Power Supplies or Tubelab's SPP in UL mode for a pair of moderate sensitivity bookshelf speakers(84-85db). Any commends are more then welcome.
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Old 7th November 2010, 10:48 PM   #2
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Let's apply Joppa's Rule, which states an amp/speaker combo should be capable of 102 dB. SPL peaks at a 1 M. distance, to 84 dB. Looks like you need (sic) 64 WPC. A quad of EL84s set up PPP seems to be inadequate, given the 24 or so honest W. UL mode will yield.

IMO, unless you go for some sophisticated partial feedback technique and no GNFB, the CXPP-30-MS-3.8K lacks adequate magnetic headroom. For a circuit with GNFB, pick a model rated for 50 W.

JMO, your speakers should be mated to KT88 stuff or "sand".
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Old 7th November 2010, 11:09 PM   #3
tinitus is offline tinitus  Europe
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Joppa's Rule, does it apply to any kind of speaker ?

I mean, a 84db speaker could be almost anything
but could be a small 2way with 5" woofer, that will never play loud, no matter what
or it could be a small fullrange with just 20watt power handling

but judging from the nature of your question, it might be safer to stick to something proven and tested
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Old 7th November 2010, 11:19 PM   #4
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Quote:
Originally Posted by tinitus View Post
Joppa's Rule, does it apply to any kind of speaker ?


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I prefer 120 dB capability, to avoid clipping on forte-fortissimo.
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Old 8th November 2010, 08:55 AM   #5
Ian444 is offline Ian444  Australia
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There are other opinions too, which are just that, opinions, in my case I find 15W driving 83db speakers to be more than enough.

Syyma those tranny's should be fine for PPP EL84. Something like that would near rattle the windows and blow the dust off the ceilings in my little cottage...
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Old 8th November 2010, 10:08 AM   #6
45 is offline 45  Italy
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Quote:
Originally Posted by tinitus View Post
Joppa's Rule, does it apply to any kind of speaker ?

I mean, a 84db speaker could be almost anything
but could be a small 2way with 5" woofer, that will never play loud, no matter what
or it could be a small fullrange with just 20watt power handling

but judging from the nature of your question, it might be safer to stick to something proven and tested
A small bookshelf 84 db can play louder than a more efficient floorstanding one. How? Simply because loudness for the listener is not just measured in dB's! It is measured in amount of "clean and unambiguous information". Of course with higher SPL and low end extention you can gain in impact but this always comes second to the above rule. If you start to think about the listening room + speakers as one thing and how better that small speaker fits the bill in a normal situation you will realize why in a medium-sized room (even more in a small-sized one), you can easily live with a Spendor SA1 + a good 10-15W amplifier and forget about the rest. Sizes according to the European standard, of course!
If you have a good-sized dedicated room (say, about 35 square meters of convenient shape) and a perfectly integrated with a 3-way 90dB bookshelf speaker you can't believe what a 10W amp is capable of.....
To get there is not easy though.

45

Last edited by 45; 8th November 2010 at 10:12 AM.
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