B&K ST-140 - Older vs. Newer versions?

Hi, I'm considering purchasing this amplifier and was wondering if anyone can tell me the easiest ways to distinguish older from newer versions, and what differences performance-wise there is between them.

Thanks in advance -Marc
I believe the older version had a pushbutton on/off switch, while later versions had a toggled switch. I owned a very early predecessor to the ST140 called the EX140. It is a true dual-mono version of the same amp. It was a great little SS amp and continued to perform well for me for twelve years till I sold it. I've never seen one being sold used. I bought mine at Singer in NYC back in 85'. At the time they sold both the ST and the EX and I did compare the two side-by-side there for some time and ended up liking the EX by a small margin. I think the ST is a great amp for the money on the used market, and I'm not a big fan of most SS in general. The 140's seemed to have a softer edge to them than other SS I've heard, and mine compared favorably to the tube amp I replaced it with, though I did prefer the tubes (Jolida 302B).

I'm not an expert but I run three in my HT system.The original had 70wpc.The next two versions had champagne rack handles and gray face plates.The fourth version had blue lettering.I like the gray with champagne rack handles.Serial #2300.Good luck
Do a search. You will find this subject discussed in depth several times.
The older EX version which is the best sounding, has a red rocker switch on the front. Gray face plate and champaign handles. It also has fixed, as in not detachable power cord. The old 442 I have was rebuilt by B&K due to a problem with the wife knocking the wires off an allowing them to touch, oh well, I sure do miss that wife, just kidding.

Mine is now in moth balls as I moved up to a Threshold, but I doubt for what I could sell it for I could find anything that performed as well.

B&K is an awesome company to deal with for service.

Loontoon - My EX-140 had a black faceplate, champagne handles and a pushbutton on/off switch. Purchased in 85' when they were discontinued and had already been succeeded by the ST. So there must have been more than one cosmetic version of the EX.

Marchomm, I picked up the ST2140 a year ago last fall to replace on old Hafler DH200. I only paid 450 bucks for it brand new. The salesman recommended 40 hours of burn in, so I played it 24/7 for a week. I didn't want to rush to judgement on this piece. After the week I settled in for some critical listening. To be honest, it was God awful. Contrained, harsh, unlistenable at anything more than conversation levels. No soundstage at all. It sounded like something was choking it. I re-inserted my Hafler. Sounded great. So I brought it back. Maybe it wasn't burned in enough. But I'll never know.