Amp Modification

[ratten46 10+ year member]

Has anyone ever performed a modification on an Old RF 200a4 to make it into a 400a4? I have the schematic for that amp, and it's 100% shared, except for what looks like about 6 components in the power supply. It looks like you can swap out 2 resistors, add 4 capacitors, and double your output. That seems too easy, wondering if anyone has ever done this (or similar) mod. If so, success and failure information is appreciated...

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[TeamMAXXSONICS 10+ year member]

i modded a 1501d buy removing the Q235 chip so that its able to run at 1ohm but never worked on a 4004a

 

[Ed Lester 10+ year member]

Has anyone ever performed a modification on an Old RF 200a4 to make it into a 400a4? I have the schematic for that amp, and it's 100% shared, except for what looks like about 6 components in the power supply. It looks like you can swap out 2 resistors, add 4 capacitors, and double your output. That seems too easy, wondering if anyone has ever done this (or similar) mod. If so, success and failure information is appreciated...

Highly doubt you will ever double output.

Maybe 10-15% increase in power but less reliability.

 

[ratten46 10+ year member]

Highly doubt you will ever double output.Maybe 10-15% increase in power but less reliability.

It really sounds too good to be true. Your statement is probably the most likely scenario. I found it interesting though, that the same schematic is used for 2 amps. Seems like there was probably a lot more profit for RF on the 400a4 - if this was truely the only difference. Maybe $5 worth of components difference.

 

[Haunz 10+ year member]

Id bet that the 400 uses heavier duty Fets along with larger torroids in addition to the differences you noted...

 

[ratten46 10+ year member]

Id bet that the 400 uses heavier duty Fets along with larger torroids in addition to the differences you noted...

That's what I expected as well. I looked over all 6 pages, and the only noted difference in the schmatic are 2 additional capacitors in the HV rail, 2 in the 12v rail, and a pair of resistors on the HV rail. The differences are called out plain as day, and the schematic is for both amps. :shrug:

 

[ratten46 10+ year member]

Not that I'm willing to risk damaging this amp. If I really want a 400a4, I can pick one up on ebay for 80 bucks. It's just an interesting find...

 

[Tehgregzor 10+ year member]

My guess is the profit theory. I very much so doubt that a few caps and resistors will do anything to an amp's output. Most homebrew mods are to take out the impendance shutdown and keep it cold.

 

[ratten46 10+ year member]

Well, these amps are pretty highly underrated to begin with. From my measurements, my 200a4 is putting out just under 50 watts RMS per channel in 4 channel mode. The 400a4 is rated for 50x4 RMS, so if they raise output by 15%, they've exceeded the 400a4 specs and underrated it.

 

[ATF 10+ year member]

are you partial to retaining this amp? If not, why not try it and bench test it?