Problems getting the best out of my Berning

If your ZH270 currently has the JAN Phillips 12AT7 tubes in it, I would try to change them to NOS Mullard 6201 Gold Pins($35 each from Upscale Audio). In my MicroZOTL these JAN Phillips 12AT7's were the primary cause of the tube glare. I just looked up the ZH270 tube complement on the website, and found that indeed it does use 12AT7's, as I suspected, because Dave likes to use the 12AT7. When I did this with my MicroZOTL, the tube glare was gone. Substituting Sylvania GTA for the stock Sovtek 6SN7's made an improvement in detail and bass. But I feel in your case, the offender is likely to be the JAN Phillips 12AT7's.

Hi Peter

Initially I would be tempted to agree with Dan but there shouldn't be an impedance mismatch with the Berning/Pro-ac's. It must be elsewhere in your system or set-up. There is another proac/Berning user (Ian where are you?) that loves this combo. Obviously (at least to me) there is something wrong here beyond what you expected. There should be NO tube glare unless there is an interface problem with wire, certainly not from the amp unless you have a bad tube(s) which is possible, but somehow I doubt it, Berning is too meticulous to send out a new product with such a defect. Upgrading tubes will enhance performance but that is not the answer for tube glare with the zh270, break-in possibly.

An emphasis on the midrange is something more puzzling and I have no answer off the top of my head because I don't hear this in my system and never have nor have I heard it with other speakers and the zh270. I would agree that the bass through the Berning won't offer the slam of other ss amps but it should't be a problem, to the contrary. Bass should balance well with the mids and highs. This amp is all about superb tonal balance along with that clarity. You don't mention high frequency performance at all which with the right speakers and wire should be top shelf. So now all that is left is to troubleshoot.

Have you tried the 3 feedback settings. Do you note any changes between them.

What is the amp sitting on, how close to the digital source. The amp uses ultra high frequency so there could be a possible problem with the location of the amp that may be contributing to what you are hearing.

As Dan asked, are you running directly from your digital source to the amp or do you use a pre.

Certainly the MIT's in general are forgiving cables and shouldn't present a problem at all. The fact that you have tried so many different cable configurations leads me to believe that this isn't the foundation of the problem either but still...it wouldn't hurt to try something else, maybe Cardas. I am using Luminous Tech Syn Sig cables with superb results.

Lastly it could be a break-in of the amp. I wouldn't completely eliminate this. I have heard it first hand and it can never be ruled out. The bottom line is the Berning with the pro-acs should be singing in your system and you shouldn't be hearing any of what you are describing. Please keep us updated. I am confident you will find the problem so hang in there.

You need to get some NOS tubes. I have a MicroZOTL and I had the same problem with tube glare. The manufacturers cannot use NOS tubes in a production unit, because there is no guarantee of availability of the right tubes at any given time, and the price fluctuates too much.

Talk to A'gon member Tubegroover. He has a 270 and has some experience with NOS in it.

When I put Mullard 12AT7's and Sylvania 6SN7's in my MicroZOTL the glare was gone and overall sound and detail was much improved.

For the best bass control, use the Normal Feedback setting. It provides the lowest output impedance for best bass.

And trying different cables is a good idea, because, as we all know, cables are very synergy dependent on the amp and other components. When you change an amp, it is likely that cable changes may be in order also.

It is my opinion that the NOS tubes will give the improvements that you want. I know that it is a bitch to have to get NOS tubes when you have just bought a new amp, but that's the name of the game. I have come to expect to have to do that. They just can't put them into the amp for the reasons I described above. There is a limited supply of NOS and they are getting rarer, and more expensive, and eventually they will dry up altogether.

Peter, I can't offer specific recommendations for you but I do want to offer my sympathies. I have been in similarly frustrating situattons with new components many times.

I will say that I also have ProAc 2.5's and, for a while, drove them with an Aleph 3. That combination had a surprising amount of bass weight, more than I get from the Pass X-150, for example.

You are driving the amp directly from the CD player? You might want to try inserting a preamp (just borrow one) and see what kind of difference that makes. Could there be an impedence mismatch or some other form of incompatibility going on?

Good luck! -dan