MS275 - revisions

KUB3 · Post by **KUB3** » Sun Dec 13, 2009 12:20 pm

I have two matched pairs of MS275 amps. One pair is revision "H", while the other two are revision "I", looking at the serials near the terminals part of the board.

So I assume these are all fairly new versions in the grand scheme of things. Does anyone know what the final revision was? Does this mean these are relatively more common, plus possibly better sounding than the older ones? (Assuming more revisions means improvements? Hopefully not cost cutting!)

It would be interesting to know the full story...

(It was interesting going through the last 50 pages, picking up some technical insights here and there on the MS series)

Post by **Eric D** » Sun Dec 13, 2009 12:34 pm

"I" is the newest I have found.

I personally don't like the "I" version as it uses clamp bars for cost savings. Yes these are more reliable than the older method, but they are far less attractive to look at under plexi.

KUB3 · Post by **KUB3** » Sun Dec 13, 2009 12:51 pm

I agree. It was a pain undoing all the individual bolts last time, but I prefer the look without bars. I haven't stripped them yet, but I assume these bars can be ditched, IF there are enough holes in the sink?

Is that the only difference? What about the earlier versions? Are some more sought after for one reason or another?

ps

I also have x2 new sinks with tons of holes, so I can use those if required too.

Pedi · Post by **Pedi** » Sun Dec 13, 2009 2:59 pm

One of the "H" revisions I have, was with clamp bars...

Post by **Eric D** » Sun Dec 13, 2009 4:25 pm

I had an "H" with clamp bars as well. I also had one without. I assume they made the change half way through that revision.

Post by **fuzzysnuggleduck** » Sun Dec 13, 2009 10:03 pm

What does the revision letter refer to exactly? PCB layout changes or just any change to the amp itself?

Post by **Eric D** » Mon Dec 14, 2009 11:16 am

PCB layout changes.

nico boom · Post by **nico boom** » Mon Dec 14, 2009 11:49 am

The rev. B boards are sought after more than the later versions for having "components with smaller tolerances".
Personally I never discovered any thruth in that, and I have had plenty of both grey and white MS-amps.
In some of the MPS2500 amps you'll find a few components soldered together, or even a small daughter-board under the powerbars; odd looking, but absolutely done by PG.... some boards did not have the correct [complete] layout, and PG found it a waste to throw them away. So beeing handmade as they were it was simple to make a few with a small correction.

For the comments about the clamp-bars; I prefer each fet to be bolted down to the sink seperately.
That provides optimum contact with the sink for all components and you're all right; it looks better when displayed.
So I do not have any preference in board revision; I only look for the "mint factor" the amp is in.

Post by **Eric D** » Mon Dec 14, 2009 12:00 pm

Nico, although I pretty much agree with you as to what people are looking for, they are not getting the whole picture.

The newer revisions of the amps are far better than the old. This is especially true for the MS275 style board. Around the G REV they added noise suppression to the power supply, and then on the H or I they added it right into the PCB. Also the parts used in the older boards are far less quality. Newer parts have far better tolerances and far better reliability.

As for clamp bars vs separate screws, I think you are completely wrong on this. PG went with the bars to improve reliability. I like you prefer the look of separate screws, but they put all the pressure on a small area of the device. The rest of the device has much less pressure and is more prone to failure because of this. The clamp bars put even pressure on the whole device (due a lot to the foam between the bar and the device) which greatly improves their thermal conductivity.

KUB3 · Post by **KUB3** » Mon Dec 14, 2009 1:30 pm

The top pair are "I" & the lower pair are "H"

The FET's on the older ones are a mix of black and green Toshiba. It would be better if they were all black

Post by **Eric D** » Mon Dec 14, 2009 1:49 pm

The one "H" on the right is older (the green transistors are some of the give away). It looks to also have the older terminal styles as well. And black optoisolators vs white on the newer ones.

It is likely a very early "H", and the one on the left is a very late "H" (but not so late as to have clamp bars).

Finding matching MS amps is nearly impossible. I bought 6 MS275s before I ended up with two which match. And even then some things don't match exact, like some resistors.

KUB3 · Post by **KUB3** » Mon Dec 14, 2009 2:58 pm

You have a keen eye for this sort of thing. I'd say the top ones look pretty identical to me with close serial numbers - both from nico. The lower two are from different sources - the newer left was supplied by Prestige in the UK.

I'd like to end up with 6 matching but I guess it may be impossible. I have a 5th on the way so I'll see what that is later...

Would it be crazy to swap out those green FET's to black. If so, would I need to replace all of them? Seeing as they will all have to be stripped apart anyway...

Post by **Eric D** » Mon Dec 14, 2009 3:54 pm

It would make more sense to swap the whole board than to just swap the BJTs. Since there are other parts which do not match, just changing the transistors would not be worth the effort in my opinion.

KUB3 · Post by **KUB3** » Wed Dec 16, 2009 9:08 am

Another minty fresh 275 has arrived. It's anther "I" with bars. That's makes 5 in total. 3 of which look identical

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Wed Dec 16, 2009 4:20 pm

KUB3 wrote:Another minty fresh 275 has arrived. It's anther "I" with bars. That's makes 5 in total. 3 of which look identical

Hey KUB3, why do you have such a hardon for the 275's, Im just wondering because it is one of the smallest of the MS series besides the 250, youve peaked my curiosity

KUB3 · Post by **KUB3** » Thu Dec 17, 2009 1:36 am

Because it IS the smallest

It's compact and so makes instal very easy, it weighs less, makes cap change easier, less strain on the battery. Yet it still has useful power too. I will get one larger sized amp later on. I have my eye on a 2250 for my subs

ps

Have you ever noticed the best sounding M series is the M25?

I don't really fancy the largest amps made. For me they are simply too huge to be practical. Besides cars are getting smaller in future. Amps like the MS1000, Frank, etc will not be much use in these...

Post by **joerg** » Thu Dec 17, 2009 3:30 am

KUB3 wrote:I don't really fancy the largest amps made. For me they are simply too huge to be practical. Besides cars are getting smaller in future. Amps like the MS1000, Frank, etc will not be much use in these...

You just got to buy the right cars to fit those amps

Look at my trunk

KUB3 · Post by **KUB3** » Thu Dec 17, 2009 4:45 am

Charger

Very cool. But that is also likely to be obsolete in the near future. It may be too big to run on electric power by then

Post by **Eric D** » Thu Dec 17, 2009 8:01 am

Instead of the MS275 you should consider the ZX350. Lighter, more power, maybe even physically smaller, and on board defeatable crossover so you don't need an external one. Or even better try the Aluminum Ti amps. Though rare they weigh almost nothing compared to a MS amp, and a Ti400.2 is still better than a MS275.

KUB3 · Post by **KUB3** » Thu Dec 17, 2009 10:19 am

My first amp was a ZX250. I've had a couple of the ZX over the years. I think they're very good but look a bit too modern for me. I don't really like the cheaper method of cooling, thin case work, or slightly jumbled up circuit board to be honest. They look more like a computer inside, rather than an old school amp. If I went for any ZX it would be a 0.5 or 0.3 as they look much better, in a futuristic way. But they are WAY too complex for me.

I much prefer the M25 to any ZX, mostly for their cool looks, very sweet sound and also the simplicity of construction. But my personal favorite of all small amps is not surprisingly the 275. They are just so solidly made, dead simple, with good looking circuits, proper old school retro looks. I also don't need x-overs or any other gadgets as my HU will do all that.

So I am an MS fan through and through.

If I could spec a dream amp, it would be a small MS, with a heatsink milled from titanium, thick gold tracks and top level audiophile components, all hand soldered. But for that cost you may as well by a new Brax X4. Now that is one sexy modern small amp!

marko · Post by **marko** » Thu Dec 17, 2009 10:33 am

i can't wait to get my ms amps back in, i miss the ultra sweet sq from them! the hifonics are just brute force that sound ok but the ms are something else

KUB3 · Post by **KUB3** » Thu Dec 17, 2009 10:50 am

I've always fancied the Hifonics Colossus in pure white, ever since I saw it in John's ODR scorpio way back in the day. That is probably the king of sub amps, don't you think? There is also something about plain white amps (and many other things for that matter) that just flicks my switch

I started stripping all my MS apart today. I've done three, down to every nut and bolt. I spent an hour just polishing the white terminals. Next all gold and screws will be dipped in cleaning product. These will be better than new

marko · Post by **marko** » Thu Dec 17, 2009 10:56 am

KUB3 wrote:I've always fancied the Hifonics Colossus in pure white, ever since I saw it in John's ODR scorpio way back in the day.

i got an earlier blue one, still series viii of course, it spent most of it's life in a cabinet on show, i have yet to see a "minter" one! if only my wife would let me have it in the living room on display

Post by **Eric D** » Thu Dec 17, 2009 10:58 am

What do you mean by cheaper method of cooling? ZX amps have far superior cooling than a MS. They use less aluminum, so maybe that makes it cheaper in the long run, but their plates are anodized, so they don't use the crappier and more unreliable heat pads like the MS do. They have a fan, which does add noise, but is variable speed and also keeps the amp more reliable.

MS amps are simple and too the point, but they are not very high quality. The way the board is mounted using the fiber washers, plastic sheet and self tapping screws is really pretty crude. The way the transistors are mounted with individual screws puts uneven pressure on them. And the very worst part of MS amps is the loose wiring in them. The RCAs break off with very little effort, the power wires are loose, and the speaker wires are not only loose they have their output inductors soldered into the speaker wire and heatshrunk, which really is downright tacky. At least the larger version of these amps have those soldered on the board.

I am by no means saying MS amps are junk, but if you list the flagship PG amp lines, MS, ZX, ZPA, Ti, and Xenon, hands down the MS is the least quality of the bunch. Xenon may have lower reliability than MS, but that is likely more perceived than actual. Just having the gold plated circuit board does not make the MS amps better quality.

KUB3 · Post by **KUB3** » Thu Dec 17, 2009 10:59 am

If I saw a mint white one I'd be so tempted to buy it. Just for the sheer nostalgia and cool factor, even if it wasn't to be used. I bet they are better than any modern ten bazillion watt digital amp! I wonder how a 2250 compares to this for pure sub control?