Legis, AVMania, does the XPA-1 in standard configuration use power supply caps in series/ parallel like on the XPA-2?
XPA-2 apparently has 2x 15000uf 50V in series with each other, and a bank of 3 on each rail, so this should be 7500uf x 3 = 22,500uf per rail.
How much capacitance is really in the XPA-1?
What are the voltage rails on the XPA-1? I guess about 63 volts?
What do you guys think of F&T capacitors? Apparently they are the OEM manufacturer of Mundorf?
I can get F&T 22,000uf 100V for about $60 which is half the price of the Mundorf of the same voltage and capacitance.
Thanks
XPA-2 apparently has 2x 15000uf 50V in series with each other, and a bank of 3 on each rail, so this should be 7500uf x 3 = 22,500uf per rail.
How much capacitance is really in the XPA-1?
What are the voltage rails on the XPA-1? I guess about 63 volts?
What do you guys think of F&T capacitors? Apparently they are the OEM manufacturer of Mundorf?
I can get F&T 22,000uf 100V for about $60 which is half the price of the Mundorf of the same voltage and capacitance.
Thanks
Hi erin, all the caps are in parallel, so 60,000µF per rail/120,000µF total. The rails are 58V, caps are rated 63V.
Does the XPA-1 have rather thin bridge rectifiers like the XPA-2?
I'm thinking of upping the capacitance on my XPA-2 but I think I should give it a bigger bridge rectifier. I have to wonder why Emotiva arranged the caps in the XPA-2 the way they did? They could have easily given it 90,000 uf per rail with a different track layout.
Its a bit annoying really. Since the XPA-2 theoretically has 45V rails, I could chop and rearrange the tracks and give it 90,000uf per rail?
I'm thinking of upping the capacitance on my XPA-2 but I think I should give it a bigger bridge rectifier. I have to wonder why Emotiva arranged the caps in the XPA-2 the way they did? They could have easily given it 90,000 uf per rail with a different track layout.
Its a bit annoying really. Since the XPA-2 theoretically has 45V rails, I could chop and rearrange the tracks and give it 90,000uf per rail?
XPA-1 uses 50A/(400A very short peak) RBV5006 diode bridge: http://www.digchip.com/datasheets/parts/datasheet/139/RBV5006-pdf.php
The inrush current limiter board affects also somewhat how big the capacitor charging peak is. If this board and and the diode bridge is the same in XPA-2 as in XPA-1, I would not be too afraid of trying 90000µF per rail. I'm going to try it in XPA-1 at some point.
When I turn on the amp I can hear a relay switch so I guess this is the inrush limiter swiching from the series resistance to full bypass when the relay swiches. I'll have to look again. The XPA-2 appears to be more of a PITA to get into than the XPA-1 hence my slowness with all my mods. I don't like having the amp out of action for too long or I get withdrawal. 
Yep. That is correct. 6 per side. I removed 4 and replaced with 2 M-Lytic 47000uF's. one per channel.
Hi Erin,
I think mines now around 87000uF per rail after the mod, taking the total to 174000uF. My electronics mentor, Sean say the transformer was able to handle more but I thought this should be enough of an upgrade at around a 50% increase. BTW Sean has taken me from electronics dummy to somewhat less than a dummy to be able to do this in a few weeks, So when you talk about other stuff you lost me.
I want to make the XPA-1's into a Krell buster. I think its already there but lets not stop. I have checked the size and I think I can fit the Mundorf Silver/Gold in Oil into the XPA-1. This will be my path as I want to use one type of cap all throught to the speaker drivers. This will mean sometime in the future even the 802D will not be safe. see below. the Silver Gold and the Supreme will be changed to Silver Gold Oil and the Mcap repalced with 2 Supreme's (one day). This is only for the mid and high range. The base can remain.
An externally hosted image should be here but it was not working when we last tested it.
What are the signal path caps on the XPA-2 (you see how much a dummy)? in the XPA-1 its the easy to but in your photo of the XPA-2 I could not identify the signal path caps. I have an XPA-2 for the rears (previous fronts speakers 804S) and would like to beef it up as well. Maybe the UPA-1 on the center will be after that.
Thanks
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Ok, next question. I could mod the XPA-2 to have 90,000uf per rail, using the original caps, but the voltage would sort of snake up and down the bus before getting to the output stage rather than just being a straight copper bus. If you know what I mean.
Is this a bad idea? Adding inductance?
Is it preferable to just buy bigger value caps and remove the other caps from the board.
Is this a bad idea? Adding inductance?
Is it preferable to just buy bigger value caps and remove the other caps from the board.
Signal path caps are small, and *sigh*, many on the XPA-2, I have changed the electrolytics for (red) Wima film caps, but I basically only chose Wima becuse they were the only ones that would fit. Believe me, if I could fit nice quality big film caps I would.
The voltage would stay the same, but would have to see the backside of the PCB to be able to say more.
Inductance is in relation to the area (square centimeters/- inches) of the loop, that includes also the physical size of the caps. The bigger the loop area, the bigger the inductance. Bigger inductance hinders RFI filtering of the supply, but it's not ultimate critical in analog amps, we need big power supplies more
.
Audioholics review gives insight into the layout of the caps. It may help
Emotiva XPA-2 Two Setup and Design Overview — Reviews and News from Audioholics
The maths in that audioholics article leaves a little to be desired.
how did he come up with 71 volt rails for 250 Watts into 8 ohms?
Yes. Noticed all the numbers are incorrect. Using the numbers specified in the XPA-1 for the XPA-2.
I only have the XPA-2 so I think this is a question for Legis.
those values are likeley to be in the signal path, or bypass capacitors, but would also affect the sound.
Hi, the 0,47µF (C205) is an "X-capacitor" that is between the + and - rails. The 0,22µF caps (C212 and C215) "Y-caps" to my knowledge, and they seem to be connected between the rail and the ground on a ribbon cable. The same goes for the two 1000µF e-lytics (C208 and C210), they are also Y-caps ("local bypass"). The red Wima (C216) near the ribbon cable is an X cap between the + - 64V rails and the smaller wima next to it (C213) appers to be Y cap for the same rail, as is the one (C214) below them.
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