A little off track, but, B&K also made mono versions of the ST 140. Not all B&K ST 140's are the same. Your success with mixing depends upon your system and how you do it. If you are mixing it's probably better to do it horozontaly as opposed to verticaly. The safest bet it to use as identical amps as possible. |
which of the B&K ST-140 amps are more desirered and why? is the one with the handles rated (power) the same as the one with the blue lettering? |
I don't have the expertise to be able to identify all the different incarnations, and there were quite a few. Many swear that the original 70 watt per channel ones were the best. I have to imagine the mono's have got to be up there too. I'm not sure but I think even the mono's had different versions. These amps have been made over quite a span of time. |
As far as a i know, there are at least five different ST-140's that B&K have produced. That is, they have the first model that was rated at 70 wpc with an "old school" iron core transformer. From what i've been told, this unit was quite limited in production. They then came out with the second version, which was rated at 105 wpc using a toroidal transformer. Sometime during the 105 wpc run with the original Hitachi devices, they changed quite a bit of the internal design / lay-out of the amp. One of the signs of the latter "third series" design is that they went to a "star ground" i.e. all of the ground wires tied to one point in the center of the chassis. According to what i've been able to find out, these design changes came into play appr 4 years or so after these amps were initially introduced, producing the third version of this amp. As such, the earliest versions PRIOR TO these changes are the most desirable in terms of sonics. The fourth version was this same amp but configured into a mono-block. They then switched output devices as the original Hitachi Mosfet's that they used were discontinued, resulting in the fifth version.
Having said that, it should be noted that the original Hitachi's are no longer available. If you end up blowing the output devices, you have two choices. You can send the amp back to B&K and they will rebuild it to current production standards for a very reasonable fee. They make use of the existing chassis, transformer, rectifiers and filter caps while replacing the amplifier circuitry and output devices. In effect, you end up with one of their current amps for about 40% of the cost.
The other alternative is to substitute some English made Mosfet's that are a direct replacement. This same company also manufacturers heavier duty versions of this device. It is essentially two Mosfet's in one case. Some fine tuning of the circuitry may be required, but this would result in a far more rugged amp.
As a side note, MANY, MANY other amps used these same Hitachi output devices. Earlier Perreaux's, Muse, etc... along with quite a few others used these Hitachi's, so there were tons of them on the market at one point in time. It has now gotten to the point of searching for "hen's teeth", so be careful with what you've got. That is, if you like the way that it sounds as it is. Changing the output devices and / or support circuitry will surely alter the sonics of the unit. Sean
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I am using a BK AV5000 to Bi-WIRE (actually tri-wire) a pair of Def Tech BP2000's for my Dad's home theatre. It sounds quite nice. I don't know if that helps you, I just thought I would throw that in.
Brad Day
Atlanta, GA |
Sean-
do you know which model represents what? i have a chance to buy two of the models with the gold lettering and handles. i believe that they are 105wpc each. how do i connect the two amps together? |
Sean, you never cease to amaze me! |
Sean's info is correct as far as it goes. All the different versions sound different and probably shouldn't be mixed in a bi-amp situation. The 70 wpc and the first 2 versions of the 105 wpc amps look identical on the outside with gold lettering and silver handles. To identify them you will have to pop the lid and take a look inside. The last version is the one with red and blue lettering and is a completely different design. As Sean said it uses different output devices. While still rated at 105 wpc it uses 2 pair per channel as opposed to the earlier use of 1 pair per side. The circuit boards and internal layout are also different. Because of it's use of more outputs the newer design does not have the problem of insufficient current delivery into low impedence speakers that the early 105 wpc units did. Sonically they are similar but not identical. The older amps have a very sweet & palpable midrange with a slightly loose low end and somewhat unrefined top end. The newer version has most of the midrange magic with a much tighter bottom and sweeter top end. I own an early and a late 105 wpc version and have compared them extensively. They are both really nice sounding amps but in the long run I prefer the newer red and blue version slightly on most music. You wouldn't go wrong on either one though as this amp is the all time greatest giant killer bargain amp. Here is a partial list of amps that have been bettered by the little B&K in my system. Aragon 2004, Hafler Transnova 9300, Meitner STR-50, Sumo Andromada, Counterpoint SA-12, Denon 2200, ASL 1003, and several others I don't recall at the moment. |
Perhaps B&K can give you the serial #'s that indicate changes? |
has anyone biamped any of the paradigm studio speakers with two B&K ST-140 amps? i have a pair of the Studio 60v.2 and a pair of the Studio 40v.3. they are both powered by denon recievers. i recently auditioned a B&K ST-3140 (3*140watts) with these speakers and liked it alot, but couldn't justify an extra $500 for the amp when my denon 3802 sounded almost as good. i am thinking that biamping with 2 ST-140 amps will make my paradigms sound the way i want (not bright). anyone tried this set up before? |
That darn sean!I thought that I was the B&K man because I use three in my HT rig,and have a spare in case one craps out.My serial numbers all range around #2900.They have a very warm sound that makes it quite easy to sustain three hours of lord of the rings.What my plans are for the three in active use is send them (drive them,I live near Buffalo)to B&K.Have them biased together.Then split the signal from my left,center,right and use one amp for each speaker up front.Remove the jumpers and one side will power highs and the other side will power the bass.Good luck. |
Kg: My Brother is using an ST-140 for his tweeters, an ST-202+ for his mids, a dual mono ST-202 for his woofers and a dual mono 442 for his subs. All of the amps are heavily modified and actively crossed over at 24 dB's / octave. The speakers are a vertically mirror imaged array consisting of a tweeter located in the center, a 5" mid above and below that, a 9" woofer mounted above and below the mids. All of these drivers are Morel's, which he chose for their very low weight to motor structure ratio i.e. transient characteristics. The subs are mounted off to the sides of this vertical array and down-loaded. Each driver is housed in their own sealed and stuffed PVC tube to minimize crosstalk and reduce internal standing waves. This also allowed him to dial in the proper time alignment for each driver since each driver is in its' own housing. We did this with the aid of a digital room correction device i.e. hooked up the test equipment and adjusted the speakers for the least amount of necessary correction and then removed the digital correction devices. Like most of the things we have going on with audio in my family, it is a never-ending project : ) Sean
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Why can't my brothers do cool stuff like that.One golfs and the other kills everything with fur and scales. |
I see 2 different 105W ST-140s with red & blue lettering. One has speaker outputs on opposite sides of the amp, the other has both speaker outputs and line inputs on one side, (the right hand side as viewed from the rear.)
Anyone know the difference between these 2 105W models? |
I have the blue with red lettering version (105w), non-balanced. My speaker outputs are on the right. I think the balanced version has the outputs on both sides. |
