Krell iBias Amp Dependability: An Informal Survey

The Krell Duo 300 XD has been the biggest, brightest jewel in my audio crown for the past three years. What it does (when it does it), it does it superbly. But I'm about to send the unit back to them for the third time due to maintenance issues. The latest problem is a power supply failure, which is different than the previous two issues which both had to do with the amp overheating. I'm wondering if it's just this particular copy, this particular model or if there are broader quality control issues going on with Krell's latest generation of iBias amplifiers that others here are also struggling with. I'd prefer this not turn into a "let's all rag on Krell" forum just for the sake of venting. Rather, I'd like to learn whether this is a common issue that, to my knowledge, has yet to be discussed on this forum or if this truly is just a bad apple that I had the misfortune to buy. If anyone else has experienced repeat problems with their amp within the line of iBias products, please chime in. 

My system consists of:
PS Audio Digital Link III D/A converter
PS Audio NuWave phono preamp
Classé preamp
Krell Duo 300 XD (plugged into a dedicated 20 amp circuit) 
Mangepan 3.6 speakers
Nordost interconnects and speaker cables

I can only speak about my experience.  I bought the Duo 175xd a few months ago and have experienced no problems (knock on wood). Krell seems to have a good reputation for customer service based on Audiogon comments.  I you haven’t done so already, you should call and speak to Walter Schofield the COO. I spoke to him while trying to make a purchase decision and he was very helpful. Good luck!
Thank you for the response, fast. The lack of negative responses so far has been encouraging.

I agree with the notion that Krell's customer service has been strong, minus the repeat failures of this particular unit. But all the same, I'd prefer that I didn't have so much experience in this area! 

In the interest of staying within the normal chain of command, I'll forgo calling Mr. Schofield at this time. Although his reputation suggests that he's very approachable and helpful, and that speaks volumes to the reputation of the company as a whole.

The dealer I purchased the amp from is working with a Krell rep to try and get some relief from the shipping charges required to send the unit to them (Krell pays the charges to send it back to the owner). That will be most welcome given that I'll end up paying what a lesser amp costs just to have this one fixed repeatedly. 

Time will tell, but I'm hopeful. 
Dear 643,

Given that I am considering the purchase of a Krell Trio 300 XD amplifier, I am most interested in hearing how your problem was resolved.

Thank you!

Best regards,


No news to report as of yet. Due to the COVID-19 crisis, Krell has shut down operations at their service center as of late March. 

Before that occurred, the Krell engineer(s) suggested that it could be the preamp that was causing the problem. I did some basic testing on my own to try and determine if there was any significant DC offset in the signal path from the preamp. My readings indicated less than .5 mV on either channel, which is well below the threshold for what is typically considered unacceptable. I have since taken the preamp in question to a local electronics serviceman to put the unit under a more stringent evaluation. In discussing the amplifier issue with him, and based on his experience, it's not likely that the preamp is the culprit. Possible, but not likely.

Overall, and as you can see from this thread, there have been a lack of owners chiming in with similar problems to the ones I've experienced with the iBias line of amplifiers. This is certainly encouraging. 

My experience with Krell audio equipment is certainly not to the level that many on this forum enjoy as this is only the second Krell amp I've owned. However, my enjoyment of this particular amp has exceeded every other piece I've owned. The synergy in my system with the Krell providing the power suits my taste quite well. Whether or not the Krell TRIO that you're eyeing will do the same for you is, of course, not for me to say. But I would certainly give strong consideration to making the purchase or at least requesting an in-home audition. 

I wish I could be more help at this time. I'll likely follow up on this thread once the amp finds its way back to me. In the meantime, it's being greatly missed. 

Krell has resumed at least some level of operation, and the Duo 300 XD is back up to factory spec and on its way back to me. 

The preamp that it was paired with is also back from being given a thorough evaluation. The dc offset from the preamp outputs measured by the technician was in the microvolts, not millivolts. So dc offset in the signal path was obviously not the problem. The Krell engineering staff are concerned about a mis-match, nonetheless. They indicated that sometimes components of different ages don't always work well together. I have no details as to what technical issue that might refer to specifically, but I'm certainly going to take their word for it. So it's now time to shop for a new preamp. 

High on my list of potential replacements for the Classé preamp that it had been pair with, per Krell's suggestion, is the Krell Illusion II. Alternatively, but in a different realm of sound characteristics is an Audio Research LS28 that the local dealer is offering at an excellent price. I'm looking forward to auditioning these two and expecting that both will be capable of creating the same synergistic magic as the Classé. Whichever I choose, I'm hoping it cooperates with the Duo 300 XD and these faults don't recur. 

I had used Krell KSA 150 from 2000 to 2009 for 10 years without any issue.
I think you’ll be happiest w the Krell preamp. Would both units be connected using Krell’s CAST system? Just curious. 
@4425 I have yet to hear a system that uses CAST connections, but I understand that it's very well regarded by those who do use it in the older units where it's an option. Unfortunately, the Duo 300 XD does not have the ability to be connected using the 4-pin CAST cables. In fact, I don't believe any of the iBias amplifiers are CAST compatible. Perhaps the CAST system didn't have enough of a following for Krell to justify inclusion in their newer line of components. 

My dealer carries both ARC and Krell, but said that the Audio Research LS28 may have the potential to create a deeper, more convincing soundstage than the Krell. I must admit that I'm excited to hear the Krell amp with tube gear in front. I have precisely zero experience with tubes in any of my systems past or present, but the tech who works on my saxophones uses Lamm amplification fed by a Balanced Audio Technology preamp in his critical playback system, and the single word that always comes to mind upon hearing that setup is "mesmerizing."

Yet I'm concerned that with my preference for a more "clinical," or as some would say, "edgy" sound, the tube preamp may round things off a bit more than I'd like. Somewhat related to that issue, this combination will be powering Magnepans with full ribbon tweeters, and I've installed .5 ohm resistors in the Maggies to tamp down the tweeters ever so slightly. Maybe the Audio Research preamp will result in a sweeter yet tamer upper frequency output without the need for resistors. The way each of these preamps treats the higher frequency characteristics and sense of "air" will certainly be on my list of attributes to listen for. But who knows... Maybe the Krell will surpass the tubes.