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Old 3rd December 2014, 04:43 PM   #1
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Default Larger Caps mod - worth it? Sane?

Hello!

First question here I have a Yamaha P2500S I would like to upgrade if that's easily possible. I've been reading that the peak power response of an amp depends on the size of it's filter caps.
The P2500S is rated 2x250W@8Ohm and has four 3300F 160V 85 filter caps.

Assuming that the filter caps where limiting the max peak power at lower freqs (as I think a could measure): It is as easy as exchanging its caps with larger ones?

Thank you!
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Old 3rd December 2014, 05:51 PM   #2
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After reading a little about the "EEV engine" power supply in the PS2500-7000 series amplifiers, it's clear these are not conventional transformer power supplies or even simple SMPS ones. The details are not clear but it would be unwise to assume the old class AB amplifier principles apply here. More likely the amp, or at least its power supply would come to early end if you simply upsize the capacitors.

I would try the more general question of upgrading in the Live sound- PA systems forum here: PA Systems - diyAudio.
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Old 3rd December 2014, 06:36 PM   #3
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Thank you! The more powerful ones, the P5000S and P7000S have a SMPS, but the smaller P3500S and P2500S seem to have a conventional power supply. It that were the case, would you stil think that the amp was likely to be damaged by exchanging the caps with larger ones?
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Old 3rd December 2014, 07:15 PM   #4
JMFahey is offline JMFahey  Argentina
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Hi Ian.
Intrigued by your
Quote:
"EEV engine" power supply
reference.
Mr google only brings up truck engines.
Care to link/explain something?
Thanks.
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Old 3rd December 2014, 08:37 PM   #5
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Quote:
Originally Posted by JMFahey View Post
....Intrigued by your reference.
Mr google only brings up truck engines.
Care to link/explain something?
Thanks.
Well, I think I have made an error in that quotation. I read "EEV" in one brochure and "EEE" everywhere else. My apologies, all.
It is only promotional blurb which tends to be misleading rather than informative but I think it has to do with the power management of these variations on a class D amp.

Here are a couple of relevant docs:
Technology | Self Training | Training & Support | Yamaha
http://download.yamaha.com/api/asset...asset_id=46663
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Last edited by Ian Finch; 3rd December 2014 at 08:46 PM.
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Old 3rd December 2014, 10:12 PM   #6
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So, Ian, do you stil think that the amp could get damage if I'd change the caps for higher ones?
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Old 3rd December 2014, 10:44 PM   #7
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Without knowing the specifics of how the power control circuit - the EEEngine - works, I'd be guessing, even though conventional transformer supplies have a lot of inherent variations such that 1,000uF or so may make no odds.

The point is though, that conventional thinking assumes more capacitance means larger instantaneous current from a conventional class AB power amplifier but that could be completely irrelevant or counter-productive to this type of amplifier where continuous (transformer) current may be the real limitation, apart from the design's safe operating limits, of course. At least I suspect this will be the case if the reactive circuitry in the "engine" works the way I think it does.

You may just waste money on bigger caps but you could also mess up the power delivery to the amplifier. Until you have proper advice from people experienced with modifying the design, leave well enough alone or get a bigger amplifier.
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Last edited by Ian Finch; 3rd December 2014 at 10:49 PM.
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Old 4th December 2014, 12:22 AM   #8
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BTW, we have looked at these in the past and parallels have been drawn with Labgruppen class TD, model FP3400. A small schematic is posted but the link to Jan Dupont's old site does not work. Earlier designs for bass amps by Bob Carver etc. and Yamaha's patents also refer: Class-AB meets Class-D: Yamaha's EEEngine Topology - where are this Diy Projects?
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Old 4th December 2014, 01:03 AM   #9
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In the service manual if found the part of the circuit after the filter caps. It's on page 72. The three connectors in the upper part of page 72 CN102, CN103 and CN104 come from the filter caps in page 70. I guess the circuit you were refering is around those connectors. Unfortunately I don't understand schematics so well yet
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Old 4th December 2014, 09:57 AM   #10
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Thanks indeed for posting the schematic. Many will be interested.

Yes, the switching power controller is the large section of power circuitry to the right of supply connectors. The issue though, is what you hope to achieve by more caps. They don't increase power, just provide charge storage for power demand between the 120 or 100Hz power supply peaks in a conventional rectified DC power supply. When you are driving a switching voltage supply with that DC, the old class AB thinking becomes a little dumb - well, not helpful in increasing peak power at least, because it is then regulated by a high frequency switching controller.

The main electrolytics become partly irrelevant to peak power delivery from the power amplifier and you get nothing for nothing - capacitors don't increase power. They simply make it easier for a low frequency supply to hold up over the rectified AC supply cycle. When you regulate or simply supply DC via switching control , that simple transformer/rectifier/capacitor model that sags between peaks, falls apart. It follows that the idea of maintaining a reserve of charge for a duty cycle many times faster than than the signal itself, also falls apart.

If the manufacturer has met his power specification with the supplied capacitors, you ain't gonna do much about peak power by messing with them. You simply need more raw power.
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