It would be best to use other B+K amps to keep the sonic and imaging characters in tact.Depth and ambience cues are portrayed differently,depending on design.I assume that you will then remove the internal crossovers?
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Boy, the amps in your list sure do cover the full range in terms of pricing on the used market. From Monarchy's that can be had for a very reasonable price up to Krell's and Atma's, you've got quite a selection there. Whatever you choose, you have to remember that the amps should be gain matched or you have to find some way to vary the drive level to them. Many active crossovers have this feature but some don't. As such, you'll need to do one or the other if you want this to work out at all.
If you like your B&K amp, then stick with the older B&K series and go from there. These are all VERY simple circuits with a minimal parts count. This means a short signal path, which in most cases, is a good thing. As such, they are good candidates for upgrading via modifications as there isn't a lot of actual parts to change and most everything is easy to get to.
As a case in point, my brother is using an ST-140 to power his tweeters, an ST-202+ to power his mids, a 442 to power his woofers and another 442 to power the subs. All of the amps have been pretty heavily modified and he's quite happy with the performance. There's no reason that you couldn't be happy with a similar three way set-up if you are already happy with the performance of your modified ST-202 now. Sean
I'm not gonna make any recommendations, but I will say that tube amps will not necessarily 'cut off' your HF extension, or even your LF extension in many cases. Depends entirely on the amps in question, but there are lots of great tube amps which are known for their top octaves as well as their midrange. Remember, the division of the audioband into three 'ranges' is entirely arbitrary and without basis in physics, and any great amp must really be capable of covering the complete spectrum, or very close to it, with naturalness and cohesion from top to bottom. A design, whether tube or SS, which can only do great bass or great midrange, cannot really be considered a great amplifier, and I wouldn't use tri-amping with an outboard crossover as a bandaid to try and get around this. Your speakers and system will probably only sound their best if there is some kind of sonic consistency maintained across the spectrum, and running very different amps in the range above the low bass likely won't get you there.
TP-Yes,the Internal XO's are being Pulled in order to use an Active Outboard XO.
SEAN-I might just do as you say.I am reluctant to sell the B&K.I might try what your Bros. did.Looking at A-Gons Used list I saw a Krell for around $1400 and McCormicks for below $1K.I also have a B&K AV-2500 amp that I will use for the CC and Surround channel's.I am not in for the HT playback as much as the 2-channel so timbre matching might well be served using all B&K amps.
Zaikesman-Really not trying to bandaid,trying to get the best performance I can from the speaker's.I have seen alot of people try using Tubes for the Topend with mixed results,that is why I asked the question.Either way I go it should be intresting.
The Gain Levels will be controlled through the Active XO.
On a further note.I found some references to Hafler's and McCormicks being used with my speaker's.I might opt for an ST-120 on the Top or use the ST-202 on the top .Another way to go is Monarchy's for the Mids and a McCormick for the Bottom and ST-202 for the Top.
The speaker's are very power hungry and having amps to drive seperate driver's is the best way to get performance from them.
Thanks for the help everybody!
I don't know of any public source on suggested mods for the older B&K amps.
As far as amps go, you are asking for a LOT of headaches if you start mixing and matching amps. That is, unless you can have them all gain matched.
As far as mixing brands and / or different series of amps from the same manufacturer, you can run into various problems using that approach. You are best off sticking with one brand of amp or even identical amps unless you are technically knowledgable and / or know someone that is. Getting various amps to "blend" correctly can be a fine art and that is probably why some people have had problems when trying to mix / match tubes & SS amps.
Bare in mind that the ST-120 is a VERY different series from your ST-202. You should also find out what transistors are in your 202 as there were two different brands of output devices used in that amp. This is not to mention that there are different sized transformers that B&K used along the way. Sean