Be careful with replacing the 4558s. The 4558 is slow but VERY stable, so higher speed replacements are likely to oscillate.
Do you own, or are able to borrow, an oscilloscope? Nothing too fancy, a basic 10MHz analog scope will do. Do not attempt replacing the opamps without an oscilloscope otherwise you may blow the tweeters if the amps oscillate.
Disconnected the limiter in my 50's today, one at a time, so I had chance to compare. Definitely removed some of that processed sound. Kick drums are less klicky and the low end extends a bit. "Screams" less at you, but the high-end is still a bit messy.
You probably mean the dual package OPA1642? Don't put single opamps in there or you will let the smoke out.
That BB part is probably the safest sub for that design. It draws little current and has a huge phase margin so it's hard to make it un-stable. If you examine the layout closely and see local chip caps from the power rails (pin's 4 and 8) to ground and see a small chip cap across the feedack loops of the opamp's (pin's 1+2, 6+7) you can try out higher test opamps in there. "Trust, but verify" with a scope.
Do check out the power supply regulators, if they are well heat sinked T0-220 sized parts you will be ok, if they are smaller SOIC versions soldered to the pcb for heatsinking, watch out for extra heat from higher draw opamps.
I mention that as I've not seen one of these before and don't want any of you to let any smoke out.
Don't overlook the 2134 (I will elaborate on this soon, but we did some listening tests today and inside this design as a replacement...wow). Stay tuned...but yeah give them a shot too.
*Edit: OK to elaborate...
The short story is that Bob brought in some 2134's to do a side by side mod test with before we ever shipped the first modified speaker, to compare with the 1642. For 2 days now we've tested and confirmed with our ears (not spec sheets): in this speaker and mod application, the 2134 actually delivers a more full and natural response. Therefore, without having actually shipped a unit yet (we launched this mod in the middle of a backorder with Yamaha, and none of the mail in units have even arrived to start on) our Burr Brown will be the OPA2134 for every speaker mod done here.
voidar: if you get the chance to try both, I'd love to hear your take on it. The presentation of music playback is better served, and is the best fit for this. I'm very excited about this actually, it makes better even more...better (either of these opamps will blow away the ones Yamaha uses stock).
Last edited by warhead; 30th March 2012 at 08:15 PM..
Oooo , not so good then .
Heatshield and small hotair blower if possible , or flood each side with solder and "walk" them out .
Try at your own risk , IMHO takes some experience to be doing this with an iron .
Never try without a temp controlled iron either .
Hi, i'm doing the mod with the chips i have on my stash. I the first to chips in each monitor with lme49722 and a opa1642 on mid eq and room control section.
I did the limiter snip and signal path caps with Pana FM's.
So much better sounding now, the bass is more extensive and natural and highs begin to became liquid instead of rough.
Loving so mucha that i'm thinking of swapping all opamps. In order to finish the mod in both speakers i only have 8 of the opa1612 type or ne5532 type.
Are 1612's less stable than 1642's? Worse sounding?
Same question for the NE5532.
I'd use the ne5532s cause I like the way they sound and you won't hear the improvment of other chips costing 10 times as much. The 5532 should be in all audio equipment 4558 and such are for stompboxes I'd never run serious audio through them.
Would swapping the active filter caps for lower tolerance ones like styroflex 2,5%, o some 1% ones, improve imaging? Since were reducing difference in a pair of speakers response i think it could make any sense.