Add capacitors to RF 25 to Life Punch 150

0ldSch00lf00l · 27th February 2009, 07:20 AM

I can't seem to find this anywhere, but I recall reading a while back that extra capacitors could be added to the 25 to Life Punch 150 in the missing spots. I would like to know what, if anything, would be gained by filling the blank spots:

I guess my next question would be is that circuit board as hard as I think it is to remove from the heat sink?

Lastly, insomnia sucks!

Perry Babin · 27th February 2009, 07:26 AM

It's unlikely that there will be any audible improvement by adding the capacitors.

The circuit board comes out easily. Remove the T15 screws from the MEHSA strips and the circuit board and it lifts out.

0ldSch00lf00l · 27th February 2009, 07:37 AM

So in other words, it would be a waste of time, money, and effort. I want to say what I remember reading on them said that the only benefit was extra capacitance on the power supply side.

Oh well, this was one of those "I wonder if" situations that popped into my head while counting sheep

Thanks for the reply Perry!

1moreamp · 27th February 2009, 08:29 AM

Perry is correct in his statement that you most likely will not "Hear" any difference. It all depends on how poorly the supply was designed in the first place and the musical content you may be listening too also.

BUT, sometimes benefits may not be heard, but will be only seen in the overall performance of a amp design.
I have found in older amp designs that they suffered from a lack of stored energy in the supply. This was seen as a cooler running amp, and a reduction of over temp cut-outs under heavy demand after the addition of suitably matched caps to the supply rails.

Also a significant reduction of current draw and or 12 volt "hit" can be seen after such a upgrade. As the extra stored energy can smooth out the transients the Dc to Dc supply has to deal with. Although for the most part SMPS can handle just about anything music can demand of them speed wise, < recovery wise>, I am a firm believer in a very solid supply design and this means lots of micro-farads of storage. < but this is a small school of thinking in the real world>

Also this same board was most likely used for a similar design by RF so it still has the markups for the different amp design on the board. And that amp design may have a need for those extra caps power wise.

Also when you build big multi-cap banks like this you may also need to consider passive or active voltage balancing across the caps to keep them all operating in balance of one another.
You see this in those 12 volt mega caps using 200 little caps all adding up to one big value. resistors for passive and diodes for active balancing are pretty much the norm when you try to add that many caps in a circuit and try to get them to operate properly. the same effects may also happen on smaller banks like in your 25 to life.

Is it worth it ??? Who knows unless you try it and measure the differences it may or may not impart on your amp. As I said earlier on older 80's amps i found that it was noticeably an improvement up to a point, but after that given point it was simply a waste and the damage amp suffered upon failure could end up being magnified by the addition of TOO much energy storage.
I used to do this a lot in the past, so I am speaking from practical experiences of trying these ideas.
Adding the caps most likely won't hurt, unless you fail the amp. then it might show itself as a whole bunch more damage then you would expect to see in a un-modified amp... been there , done that , and got the Tee shirt...

jol50 · 28th February 2009, 12:02 AM

Are those amps sagging rail voltage at high output? I've read newer PS are smaller and more capable, but I do have old amps with BJT PS and sometimes wonder what difference there is. I don't yet have the setup to check rail voltage near clipping, but have checked amps where it dropped under heavy load. They were not mine so out the door they went.

1moreamp · 28th February 2009, 06:19 PM

Early BJT power supply's were not as efficient at the switching frequency's as mosfets are, so they had a tendency to make heat that ended up on the sink along with the amps outputs stages heat load. Changing to Mosfets just made the supply more efficient and faster. Mosfets were designed with high frequency switchmode power supply's hence the no brainer to leave BJT's behind as a switch....

27th February 2009, 07:20 AM	#1
0ldSch00lf00l diyAudio Member Join Date: Aug 2008 Location: Lafayette, Louisiana	Add capacitors to RF 25 to Life Punch 150 I can't seem to find this anywhere, but I recall reading a while back that extra capacitors could be added to the 25 to Life Punch 150 in the missing spots. I would like to know what, if anything, would be gained by filling the blank spots: I guess my next question would be is that circuit board as hard as I think it is to remove from the heat sink? Lastly, insomnia sucks!

27th February 2009, 07:26 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	It's unlikely that there will be any audible improvement by adding the capacitors. The circuit board comes out easily. Remove the T15 screws from the MEHSA strips and the circuit board and it lifts out. __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

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27th February 2009, 07:37 AM	#3
0ldSch00lf00l diyAudio Member Join Date: Aug 2008 Location: Lafayette, Louisiana	So in other words, it would be a waste of time, money, and effort. I want to say what I remember reading on them said that the only benefit was extra capacitance on the power supply side. Oh well, this was one of those "I wonder if" situations that popped into my head while counting sheep Thanks for the reply Perry!

27th February 2009, 08:29 AM	#4
1moreamp diyAudio Member Join Date: Dec 2005 Location: Northern California	Perry is correct in his statement that you most likely will not "Hear" any difference. It all depends on how poorly the supply was designed in the first place and the musical content you may be listening too also. BUT, sometimes benefits may not be heard, but will be only seen in the overall performance of a amp design. I have found in older amp designs that they suffered from a lack of stored energy in the supply. This was seen as a cooler running amp, and a reduction of over temp cut-outs under heavy demand after the addition of suitably matched caps to the supply rails. Also a significant reduction of current draw and or 12 volt "hit" can be seen after such a upgrade. As the extra stored energy can smooth out the transients the Dc to Dc supply has to deal with. Although for the most part SMPS can handle just about anything music can demand of them speed wise, < recovery wise>, I am a firm believer in a very solid supply design and this means lots of micro-farads of storage. < but this is a small school of thinking in the real world> Also this same board was most likely used for a similar design by RF so it still has the markups for the different amp design on the board. And that amp design may have a need for those extra caps power wise. Also when you build big multi-cap banks like this you may also need to consider passive or active voltage balancing across the caps to keep them all operating in balance of one another. You see this in those 12 volt mega caps using 200 little caps all adding up to one big value. resistors for passive and diodes for active balancing are pretty much the norm when you try to add that many caps in a circuit and try to get them to operate properly. the same effects may also happen on smaller banks like in your 25 to life. Is it worth it ??? Who knows unless you try it and measure the differences it may or may not impart on your amp. As I said earlier on older 80's amps i found that it was noticeably an improvement up to a point, but after that given point it was simply a waste and the damage amp suffered upon failure could end up being magnified by the addition of TOO much energy storage. I used to do this a lot in the past, so I am speaking from practical experiences of trying these ideas. Adding the caps most likely won't hurt, unless you fail the amp. then it might show itself as a whole bunch more damage then you would expect to see in a un-modified amp... been there , done that , and got the Tee shirt...

28th February 2009, 12:02 AM	#5
jol50 diyAudio Member Join Date: Nov 2007	Are those amps sagging rail voltage at high output? I've read newer PS are smaller and more capable, but I do have old amps with BJT PS and sometimes wonder what difference there is. I don't yet have the setup to check rail voltage near clipping, but have checked amps where it dropped under heavy load. They were not mine so out the door they went.

28th February 2009, 06:19 PM	#6
1moreamp diyAudio Member Join Date: Dec 2005 Location: Northern California	Early BJT power supply's were not as efficient at the switching frequency's as mosfets are, so they had a tendency to make heat that ended up on the sink along with the amps outputs stages heat load. Changing to Mosfets just made the supply more efficient and faster. Mosfets were designed with high frequency switchmode power supply's hence the no brainer to leave BJT's behind as a switch....