Hi, I'm looking to bi-amp my Infinity RS-IIb speakers and have a Threshold S500 amp and have been looking for a second, but have come across locally a Mark Levison 332,and a Krell KSA-200.I've only owned the Thresh equipment and have no experiance with either of the other brands.Can anybody tell their sound qualities, performance and how they compare to the Thresh?Any input would be great, Randy.

they're all good products...
it's really a though choice...

Ya, it is a tough choice, there is also a Perreaux PDF-2150, any opinions on this amp?

The Perreux has a transistor with no replacement, so I would buy one with caution. The KSA 200 is a beast. General wisdom is to use similar amps for top and bottom. Usually a good treble transistor amp will be good in the bass, and at these power levels I can't help but think you are in the grey zone of overkill. Are you sure you are starving for power? The S500 was very neutral.

Hi, I'm looking to bi-amp my Infinity RS-IIb speakers and have a Threshold S500 amp and have been looking for a second, but have come across locally a Mark Levison 332,and a Krell KSA-200.I've only owned the Thresh equipment and have no experiance with either of the other brands.Can anybody tell their sound qualities, performance and how they compare to the Thresh?Any input would be great, Randy.

Those big-name amps all have lots of power as the impedance drops, they usually double down at least once, if not two or three times. I'd also be skeptical of the need to biamp using something like the Levinson or Krell, etc. - I'm skeptical of biamp anyway...but even moreso with amps like that.

The Krell operates in Class A most of the time so it's going to be a real power hog and heater. It's bigger brother, the KSA-250, consumes 12 AMPS of current at idle and puts most of that out as heat.

Your RSIIb's will like tubes on the top. I've owned Infinity constantly since 1975 and had RSIIb's along the way.

I have IRS-Betas now and use a Levinson ML-3 on the woofers and a McIntosh MC2000 on the mid/tweeter panels.

I would give consideration to a McIntosh MC275 Series IV as a good tube amp for the high side. The Series IV amps have a variable control when using the single-ended (RCA) inputs, it'll make it easy for you to level match. Your current Threshold amp is fine for use on the woofers.

I used the same ML-3 and MC275 IV for quite a while on my RS1b's which I have since sold. In a word: Wonderful!

Best,

Paul :thmbsp:

Thanks for all the input, and I have read that the 2b's sound great on the topend with tubes, but I've never owned a tube amp and a little nervus buying a used one.Alot of questions come to mind like,type of tubes, how many hours on them, are they difficult to bias, alot of maintenance, on and on.Am I worrying to much?I would love to try the tube amp Beemer recommended, just not sure of what to ask?Randy.

Hello Randy, as said both are great amps. Being the age and not knowing the track record on the Krell KSA200 I would go for the ML332 if not that much
difference in money. The Krells are getting to the age when the main caps
should probably be replaced. Yes as said also 12 amps for these too at
idle. I have the mono versions of these KMA400's. After 1 hour with these
and the Krell MDA 500's the room temp goes up almost 15 degrees. As for
Biamping I like using different amps each has its strengths. If you lived by
IL you could compare some amps here:yes::thmbsp:

I've compared the Threshold S/300 and Krell KSA-100 head to head. In the end, I preferred the Threshold. I had it serviced, and after 18 years two small caps needed replacement and the bias had to be re-adjusted. All other components were on or even over spec.
The guy who bought the Krell had it serviced and the whole thing had to be revised. The revision cost more then the amp.
Not to sure about the ML. I heard a pair of mono's lately on a show and didn't like them much. Then again, I wasn't familiar with the speakers, acoustics etc., but a small tube-amp in the same rig sounded better to my ears. But it seems old(er) ML stuff sounds different, and to many better, then the newer gear.
So my advice is to keep your S/550, have it serviced if you haven't already done that, and look for another Threshold. That doesn't have to be a 550: a 300 or 200 would do the trick.
Oh, and if you still want to go with another amp, sent me a PM. I don't mind taking over your Threshold... ;)

Thanks for all the input, and I have read that the 2b's sound great on the topend with tubes, but I've never owned a tube amp and a little nervus buying a used one.Alot of questions come to mind like,type of tubes, how many hours on them, are they difficult to bias, alot of maintenance, on and on.Am I worrying to much?I would love to try the tube amp Beemer recommended, just not sure of what to ask?Randy.


The MC275 MkIV is self biasing. These are not so old that there should be a problem, and the tubes are reasonable, unless you start to get crazy with NOS tubes. Once you hear you RSIIb's with tubes, you won't want SS on the top. Trust me on this. :yes:

McIntosh is reliable, this particular amp sounds great, should be about $2300-$2500 used, and last but not least Mc holds it's value.

Good luck, if you do it, you will not be sorry.

Best,

Paul :thmbsp:

Krell is known for tight and well controlled bass.

I have heard Threshold in a number of systems, a few ML amps too. But I have owned Krell and you must temper my comments with that.

Infinity emits reveal all transistor hash in great clarity. It is best to listen to a solid state amp before purchase.

I assumed he was going to drive the woofers with Threshold/ML/Krell and the rest with something sweeter.

I guess I didn't read well enough.

Yes, your right Grainger, I'm keeping the Threshold for the bottomend.Also as far as the power ratings on the tube amps, is the performance similar to ss i.e. 100 watts tube equal in output"volume" as 100 watts ss?The S-500 is putting out 500 aside into the 4ohm 2b's, I don't want the bottom to be over powering the top.Randy.Would the Mc 275MKIV be a good match with the Thresh?Randy.

Oh Beemer, do the 2b's like rock on the Mac tubes?I listen to rock7o% jazz30%.

Oh Beemer, do the 2b's like rock on the Mac tubes?I listen to rock7o% jazz30%.

I had my RSIIb's back in the late 80's. I used to drive them with Haflers.
I like my rock but these days more classical/jazz. I like full range classical, not the sleepytime stuff.

I ran RSIb's with the MC275 Series Iv, and the Betas I have now for a little while.

With only 3 EMIMS and 3 EMITS per side, the 275 will work excellent with the RSIIb, and I loved it on the RSIb, so if you get a chance to upgrade you haven't wasted any money.

Best,

Paul :thmbsp:

I know I can adjust bottomend output with the LF EQ that can with the 2b's, but should a guy consider active EQ "Marchand" or is the Infinity box good enough?Also, would there be any other considerations for tube amps, brands,power, or are they fairly similar in the 75watt and up area.You guys have me thinking!Randy.

I know I can adjust bottomend output with the LF EQ that can with the 2b's, but should a guy consider active EQ "Marchand" or is the Infinity box good enough?Also, would there be any other considerations for tube amps, brands,power, or are they fairly similar in the 75watt and up area.You guys have me thinking!Randy.


That's why I recommend the MC275 Series IV, as it has a pair of level controls for the single-ended inputs. Between those and the Infinity box, you should be fine to level-match. An outboard crossover such as the Marchand is great, however you'll cross over twice, as you will still be using the xover in the RSIIb's.

Best,

Paul :thmbsp:

Well it looks like I'll be Mc 275 hunting.Also any good sites to read about tubes in layman terms.Would like to learn more.Thanks, Randy.

Well it looks like I'll be Mc 275 hunting.Also any good sites to read about tubes in layman terms.Would like to learn more.Thanks, Randy.

There's the tube forum here, and the McIntosh forum. there's lots of tube boards out there. a very active tube forum at www.audioasylum.com

Happy reading!

Best,

Paul :thmbsp:

Thanks for all the help and input I'm going to look into this sites and try out some tube equipment.Randy.

I used a triamplified system throughout the 70s and 80s. There is always level control to compensate for different gains of each amplifier used for the speakers. So you don't have to have matched power on each range of the speakers. I used 120WPC (mono) on the bass, 400WPC on the mids and 200WPC on the tweeters. Before that I was using a ST-70 (~30WPC) on the tweeters and I raised the tweeter level control. It all balanced.

If you don't have volume controls on your crossover, you can use a simple passive attenuator (100k pot and 4 RCA jacks) between the crossover and each amp.

A warning I should give you is that you need to know if each amplifier inverts absolute phase. The scenario you could get in to is a bass dynamic, drum strike, that carries into the midrange, maybe the treble, the bass wave should be positive (forward moving) and the mid/treble part of the wave should move forward first also. If the mid/treble amps are out of absolute phase, it will sound really odd, but it will be hard to put your finger on it.

Thanks Grainger so how does one determine what phase the amps are running in?Also I don't have a active x-over , I just have the LF EQ that came with the speaks.The passive attenuator you talk about is this a diy unit or can you buy it retail?So how was the tri-amping, bi-amping, better than running one big amp?Randy.

Thanks Grainger so how does one determine what phase the amps are running in?Also I don't have a active x-over , I just have the LF EQ that came with the speaks.The passive attenuator you talk about is this a diy unit or can you buy it retail?So how was the tri-amping, bi-amping, better than running one big amp?Randy.

What it has to do with is the number times the signal is inverted throughout the amp. If it is an odd number, the amplifier inverts absolute polarity. If it is an ever number of times, it is non-inverting.

But you will probably hear an obvious difference. Try listening to one speaker with the tweeter unplugged, invert (swap) the input to the midrange listening to mid and woofer only. (This is the hardest to get)

If it suddenly sounds really odd, the mid is out. If it sounds far more coherent, it was out and now is in.

Then move on to the tweeters. You will be able to adjust it by ear. Both sides of course would end up the same.

Nelson Pass is one of the most clever engineers in the business, so I'd lean towards one of his designs.

I've also liked the Threshold and Pass Labs stuff I've heard. I was never very impressed with Levinson, Krell, or Rowland - although the prices are pretty impressive.

Nakdoc said there was a transistor problem with the Perreaux 2150 amp, would this relate to there other amps like the 3150, a friend is looking at a used one.Can this transistors be upgraded?Randy.