Anyone tried improving/modding these amps?
I've started playing around a little with the power supply and have a amp unit on the table to try and figure out what makes sense to do.
Generally they are quite nice and capable at lower frequencies but I find them rough, grainy and unrefined at high frequencies particularly when stressed.
The PS is SMPS and it has 2 sets of rail voltages and from what I can gather from the amp board the higher rails get switched on with an on board power mosfet. The rails are +-35 and +-70 volts.
The PS unit +-35 rail seems to have +-3300uF cap and the +-70 "only" +-100uF if I managed to read it correctly.
I've added +-10,000uF on the lower rails and +-4700uF on the higher rails plus film caps.
This improved the higher frequencies significantly and "calmed" the sound stage but it did not change the lower frequencies much which it usually does on traditional power supplies, I assume this is to be expected as the smps power supply is quite capable (3kw continuous) as is.
On the input side it starts with a TI 5532 that I have yet to figure out how its powered other that it only has a long set of cables, a set of ceramic caps and no larger caps close to the op amp which I find odd.
The film caps I added was close to the power supply so not optimal other than filtering high freq from the smps, there are quite a bit of cabling from there to the amp boards so I am now itching to add film caps direct on the amp board (there are none today) to refine the treble even more. I am however concerned this will mess with the higher rail voltage switching and particularly the IRF 3710 power mosfet that seems to be doing the on and off for the higher rail voltage.
There is also a set of diodes in a MUR 1610CT in line with the ps rails "before" the output transistors but I assume these won't be an issue.
The other concern is, as there is a IRF 3710 "in-line" with the power supply rail it's rd-on (even though it's only .23 ohms according to the datasheet) becomes part of the ESR of the PS/cap set up and adding filmcaps after the mosfet will sort of potentially make it less linear. Or it will not as the cables and mosfet increase the overall ESR that the output stage "sees" already so adding the film caps will make it more linear.
I've started playing around a little with the power supply and have a amp unit on the table to try and figure out what makes sense to do.
Generally they are quite nice and capable at lower frequencies but I find them rough, grainy and unrefined at high frequencies particularly when stressed.
The PS is SMPS and it has 2 sets of rail voltages and from what I can gather from the amp board the higher rails get switched on with an on board power mosfet. The rails are +-35 and +-70 volts.
The PS unit +-35 rail seems to have +-3300uF cap and the +-70 "only" +-100uF if I managed to read it correctly.
I've added +-10,000uF on the lower rails and +-4700uF on the higher rails plus film caps.
This improved the higher frequencies significantly and "calmed" the sound stage but it did not change the lower frequencies much which it usually does on traditional power supplies, I assume this is to be expected as the smps power supply is quite capable (3kw continuous) as is.
On the input side it starts with a TI 5532 that I have yet to figure out how its powered other that it only has a long set of cables, a set of ceramic caps and no larger caps close to the op amp which I find odd.
The film caps I added was close to the power supply so not optimal other than filtering high freq from the smps, there are quite a bit of cabling from there to the amp boards so I am now itching to add film caps direct on the amp board (there are none today) to refine the treble even more. I am however concerned this will mess with the higher rail voltage switching and particularly the IRF 3710 power mosfet that seems to be doing the on and off for the higher rail voltage.
There is also a set of diodes in a MUR 1610CT in line with the ps rails "before" the output transistors but I assume these won't be an issue.
The other concern is, as there is a IRF 3710 "in-line" with the power supply rail it's rd-on (even though it's only .23 ohms according to the datasheet) becomes part of the ESR of the PS/cap set up and adding filmcaps after the mosfet will sort of potentially make it less linear. Or it will not as the cables and mosfet increase the overall ESR that the output stage "sees" already so adding the film caps will make it more linear.
Hi,
I just saw this older thread...
Could you find out more about modding the XPA Gen 3?
There are at least two companies here in germany that
offer modification for these amps.
If you use facebook:
Log into Facebook
Features of the modification
-filtering of the power supply
-improving the power supply of the input stage
-exchange the operational amplifiers
-exchange the circuit parts of the opamps
-Interference suppression the input stage
-Interference suppression the output stage
-exchange the Emitter resistors
I post this just for information.
The costs are holding me back. I asked someone who has
a modified XPA Gen 3 and he says it is worth it. His XPA
would sound better then a MacIntosh 257. (His subjective opinion,
a matter of taste, synergy with speakers etc....)
This person owns a hifi or av shop. I don't think that he sells Emotiva products.
My tech finds that the thin cables for + and - voltages and ground
could be a weak link plus the fact that they are side by side.
Any thoughts about this?
I am using the XPA for my active 3.5 Way speakers. The Emotiva
has some advantages for me I would not find in other products.
Improvements are always welcome. If modding the XPA would really
make a difference I could avoid buying something else.
I just saw this older thread...
Could you find out more about modding the XPA Gen 3?
There are at least two companies here in germany that
offer modification for these amps.
If you use facebook:
Log into Facebook
Features of the modification
-filtering of the power supply
-improving the power supply of the input stage
-exchange the operational amplifiers
-exchange the circuit parts of the opamps
-Interference suppression the input stage
-Interference suppression the output stage
-exchange the Emitter resistors
I post this just for information.
The costs are holding me back. I asked someone who has
a modified XPA Gen 3 and he says it is worth it. His XPA
would sound better then a MacIntosh 257. (His subjective opinion,
a matter of taste, synergy with speakers etc....)
This person owns a hifi or av shop. I don't think that he sells Emotiva products.
My tech finds that the thin cables for + and - voltages and ground
could be a weak link plus the fact that they are side by side.
Any thoughts about this?
I am using the XPA for my active 3.5 Way speakers. The Emotiva
has some advantages for me I would not find in other products.
Improvements are always welcome. If modding the XPA would really
make a difference I could avoid buying something else.
The Input 5532 Power Supply is from a pair of 78/7912 and not very well filtered. I've cleaned that up with chokes and a big well filtered cap bank and local decoupling at each amp board which helps but generally I would not spend a lot of effort modding these. The dual high rail voltage switching is limiting the overall performance and there is no way to bypass that without rebuilding the amp. I think this is the reason for the high IMD at 100w plus that has been pointed out elsewhere.
I've got the DR3 now which plays louder without using the higher rails and the XPA is only used for the subs at up to 120hz these days.
Other that that your list is in line with what I've done even though I think the emitter resistors and the 5532 are not the limiting parts of the AMP.
That said the Emotiva AMPs still impress with simply stunning dynamics and a sense of live sound.
I've got the DR3 now which plays louder without using the higher rails and the XPA is only used for the subs at up to 120hz these days.
Other that that your list is in line with what I've done even though I think the emitter resistors and the 5532 are not the limiting parts of the AMP.
That said the Emotiva AMPs still impress with simply stunning dynamics and a sense of live sound.