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Well I found a pristine pair of SMG-As and bought them. My first impression is that they are indeed, very musical and fairly efficient.I was able to power them with a 25watt LM3875 chipamp nicely but of course, the bass in pretty thin. I even got listenable levels out of a 15watt Tripath amp. Looks like 50watt is next.So, I have read about PGs mods but am unable to find any specification for them. Are the values left the same and just upgraded components used? And why is there a resistor in parallel with the tweeter fuse (per the schematic in the "tweaks" section)?
Follow Ups:
There's been a few differences of opinion over the SMGa parallel resistor, but it seems to me that, looking at the circuit diagram, the resistor is there to ensure that if the fuse blows it doesn't cut the treble signal completely but allows it to pass through the resistor - thus avoiding potentially damaging the amplifier. This would seem to be confirmed by those who have blown their fuses experiencing a "much reduced" treble rather than none at all. As Peter G says, if you're going to lose the fuse then lose the resistor as well, since it will obviously have no part to play any more.As for replacements for the crossover components, well take your pick - discussion on this topic has been rife over the past few years. For what it's worth (as the SMGa is in the upper mid-range price-wise) I decided not to go too overboard with top-end components and chose Solen caps (chateauroux) and Madisound Sledgehammer inductors (they can custom wind them to get the exact inductance)- the bass is definitely enhanced by these. However Peter G is fast approaching God-like status in the matter of SMGs refurbishment and enhancement so certainly worth taking notice of his recommendations.
Do bear in mind that any modification to the crossover components is likely to result in them not fitting within the frame of the speakers, so it will be necessary also to fabricate either a larger container or a separate box (as with the MGIIIas for example) to go behind the speaker. For me this was the most difficult and time consuming part of the process.
keep it in place temporarily, or just use an in-line fuse holder, to protect your tweeter while you're screwing around with different amps. This is especially important for someone like you, who is experimenting with a lot of different amps. Keep the tweeter fused for a long enough period that you know it's stable, i.e. run it at high levels, etc. Then, you can disconnect the fuse for the sonic advantages and feel confident your speakers will live.
...but maybe this guy likes living on the edge? :^ )
Joking aside, this is exactly what he should do especially if he is going to be experimenting. Good call.
After a lot of grousing, I found the stock values do work best, although you can play with them down to about 40uf depending on the caps you're using to alter the sound to your tastes and gear.If you remove the fuse (which you should) then remove the resistor as well.
I'd also stop trying to milk them with tube amps. If you like tube sound get a nice tube pre like a Mapletree or Bottlehead but use a good SS amp to drive them. It will work out better. There are some nice Conrad Johnson/ Sonographe units that mate beautifully with maggies and can be had used for $500 or so. 50 wpc simply won't do, so don't waste the time and money. Yes , it will play them, but not like a 200 wpc CJ amp will.
Great. I will simply replace the components and bypass the fuse/resistor and fabricate some proper stands.I only have but one tube amp, which was recently aqcuired. It was intended to possibly drive my ESL57s which are in pieces at the moment. I do have a pile of SS amp to play with so I thought Id start at the bottom of the power range for yucks.
If they really require big watts to sound their best, even though a 90db sensitivity would suggest that smaller amps should be sufficient, I will probably look into a UcD180 or Tripath based class D.
Bypass sounds like you're leaving them in and going round them. I just want to be clear that the word we want is remove, as in fuse and resistor out of the speakers and in the garbage can.Maggies are very unique in that yes, they can be driven with lower power as you observed, however what makes maggies special is their ability to what I call "light up". This only happens when they have tons of juice, and they sound entirely different then.
What's more, you actually run a greater risk of clipping and burning up your tweeter wire with less power than you do with more with the fuse out. More (good) power is actually safer, and sounds better. So go for the gusto. Just be prudent on your cap choices, it is very easy to have it become too strident. My rec is for the Obliggatos.
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