Problems getting the best out of my Berning

Hello fellow Agoners,

I beckon for help from experienced users of the Berning ZH270! I just received mine new a week ago, and although it is an incredible amp, it is not meeting my expectations. HELP!

First the good news:

This is the fastest amp I have ever head, and it has virtually no noise floor. I am truly impressed with these aspects. It handles most everything with ease and clarity.

Now my system:

Proac 2.5 loudspeakers
Cary CD308 and Arcam FMJ CD23
Kimber PBJ Interconnnects
Audioquest Type 4 cables

(I've also used Dynaudio Audience 72's and all MIT cables, and Triangle Titus + Audioquest Slate cables and PBJ IC's).

OK - now to the problem:

On all three setups mentioned above, the amp seems strongly biased towards the midrange and upper midrange, resulting in a fatiguing presention. There is a significant decrease in bass (not detail, but the actual movement of air) from the other amps I have used for comparison (Classe CAP 101, Pass Aleph 3, Adcom GFA 5400). While the detail and fastness are truly amazing, the midrange emphasis is getting the worst of me!

I've spoken with David Berning and Frank S (FS and both encourage some tweaking to get rid of this perceived (psycho?) acoustic bias. Frank is going to send me some interconnects to try. David mentioned that others have changed the tubes. He doubts anything is wrong with the amp.

Is this all in my head, or have others had similar problems and needed to make adjustments to get it right? While all my other amps are currently SS, I have trouble believing that this is the "tube sound" (I've heard other tube amps). Other threads mention system tweaking to get rid of a "glare" with the ZH270, changing tubes, sensitivity to cabling. My perception of the sound is pretty strong - currently I like my Aleph 3 a whole lot more with the existing setup.

I'm willing to put some time and money into making this work - because in all other respects, this is an absolutely amazing amp. Perhaps it doesn't suit my ear - but I want the advantages of this amp without the disadvantages I just mentioned. Please - suggestions on what to do from all you experienced Berning fans... so many high commendations cannot be that far off (right?).
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
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.
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 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.
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...I'm not saying that there is some sort of mismatch going on with your components or cabling (it sounds like there is), but I did want to point out that the Berning amps are an OTL amp...not a standard tube amp. OTL amps don't have a standard tube amp sound.

It might be worth checking into other interconnects and cabling. I haven't used Kimber PBJ for years, but I always found them to favor the upper frequencies. I never used them for my primary sources. I'm not familiar with the Audioquest.

I have never had a glare problem with the Berning. Actually it is only the second tube product I've ever owned that didn't have this problem which was usually fixed with rings and better tubes but never completely eliminated, especially the high frequencies which is damn annoying trying to correct. The Transcendent OTL was the only other tube amp that didn't do the ringing/glare thing. I also had this problem with several pre-amps as well. I suppose it can't be ruled out. I would be more inclined towards a bad tube being the culprit rather than the absolute quality of the tubes being used. The tubes are operated very conservatively in this circuit so while better tubes will yield increased performance a bad tube would present very audible problems. Peter if you have access to a tube tester, check out the tubes to see how they measure. Maybe you have a short in one or more.

If all else fails, I will recommend the following tube compliment I use 12AT7's Brimar Black Plates NOS 1950's, 5965's GE "5 Star" NOS Platinum 1% pair 1970's for the input/drivers and you may want to get in touch with Allan Bhagan @ for the cryogenically treated 6jn6 outputs. These tubes especially made a dramatic increase in performance, like a component upgrade. I still think you have a problem elsewhere, including the aforementioned bad tube (s).
Hi Phild

The Berning doesn't have a standard tube amp sound to be sure but it could never be mistaken for a ss amp. It has the soul of an SET with resolution of low level harmonic detail across the frequency spectrum. It is as airy and resolving of spacial information as any amp I've ever heard, period. Of course I can imagine it not sounding this way if everything else is not right in a given system.

The reason it sounds different from most other transformer coupled tube amps is simply that it is faster which is the OTL sound that you speak of, they all seem faster and more resolving. There is definitely a problem with Peter's system/amp that will be worked out, of that I am certain.
Hey Tubegroover, Nice Tubes! I just thought that I would pass along my "glare" info. I don't have a 270, so I was sort of just "extrapolating" the PP Microzotl circuit to the PP zh270 circuit. However, I did get a much better midrange smoothness when I got rid of the JAN Phillips 12AT7. So I thought that might help in this case. Of course, 1950's Brimar Black plates would be even better than my Mullard 6201's.
Jeez, I dunno what the problem is, Peter. I hate to say it, but perhaps your digital source is not a good match with the Berning. As you know, I tried to love the Cary 308. In the end, I thought it to be a good unit......for my bedroom setup. (Cary 308, Creek 5330, Dynaudio 1.1s)

I use an Audio Aero Cap MkI, zh-270 and Proac 2.5s. I rolled the tubes and absoluely LOVE my system. Still use Cardas Golden Ref interconnect (am looking at Silversmith) but replaced my CGR speaker cables with TG Audio HSRs.

I thought the 308 was very "shrilly." Maybe it's a bad match going direct to the Berning.
Peter, my experience with the Berning would tell me that there is a problem somewhere. I have a ZH270 matched with AP Avanti III speakers. Some have commented that the Avanti's can be a bit bass shy, but I get terrific bass, clean, clear and musical, all the way down to the limits of the speakers. Part of that is my room, but alot has to do with the Berning's ability to handle bass extremely well.

I rolled the tubes to cryo'd NOS, but to my ears that primarily affected the soundstage, depth, and detail of the sound (more of the same only better)- the bass was there as well with the stock tubes. And it has never been out of balance relative to the midrange as you are describing.

I previously had an Adcom 5400, modded by Stan Warren, which is a decent sounding SS amp for the money, and the Berning is on a different planet, it is so much better. I have not heard the Classe or the Aleph, but I would be surprised if the Berning did not sound significantly better than either one.

Hang in there. Once you get it fixed, I am sure the sound with the Proacs will be pure magic.

Peter, I'll chime in too here. I have a 270 with the same tube configurations as Tubegroover, running Merlin Milleniums. I'll second tubegroover's opinion on the change in sound going with the cryo'd NOS tubes from ALlan--significant change for the better. Definitely worth the money. To my ears, changing the 6JN6's made a bigger difference than changing the input tubes.
I have also noticed a major difference in going from one CD player to another--at one point I had both an ELectrocompaniet EMC-1 24/192 and a Wadia 861 to play with, and the sound could not have been more different--not that one was 'better', just different presentation. The Electro. had more bass with more 'slam', for lack of a better word, but the Wadia seemed a bit less 'bright'--not that the ELectro. was bright.
Lack of bass was never a problem with the Berning in my system, even with stock tubes. I have never been able to run the Berning in the 'low' setting, because there is just too much bass in my room. THe normal setting has really tight bass, but maybe a little too sterile in the midrange, so I usually run the Berning in the medium setting--the best compromise for my system.
Hope you get this cleared up. For what it's worth, I also have a pair of Transcendent OTL monoblocks, and they don't match up with the Berning at all (although to be fair, the tubes are getting a little old).
Hello All,

Thanks for your suggestions! I’ll try to provide answers, and then highlight the remaining questions that arise from consideral all the responses:

1. As for the preamp – I’ve run it with and without a Rogue 66. In both cases, I still get the same undesirable tonal balance.

2. As for digital sources, I don’t think that is the problem, because I use the same sources through the other (pre-Berning) setups without ever having these problems.

3. As for impedance matching with the speakers: I’ve tried this with three different speakers (Triangle Titus, Dynaudio Audience 72 and Proac 2.5’s), and relative to the pre-existing amps on each speaker type, this same issue has arisen.

4. I have tried the three feedback settings. I get the best bass response, and an overall more controlled sound on the normal setting. I like the normal and the middle setting. The low setting is too “loose” for me, I perceive a slight distortion to the sound (maybe due to less driver control).

5. As for the tonal balance, I am pleased enough with the high end. A drummer friend of mine noticed that the cymbals and high-hat seemed a bit removed. We both thought that this is due to the psychoacoustics of the prominent midrange.

6. The amp is located at least 8” away from anything with steel in it. Sometimes on the carpet, other times on a wooden platform on the carpet, other times on a wooden bureau.

7. What about break-in time? How many of you who have purchased the ZH270 new had to break in? I take it few had similar problems as me? Anybody know how much break-in is required?

8. I will test all the tubes. I guess I’ll need a tube tester, or maybe one of the (few) electronics shops in town (Flagstaff) has one. There are many for sale on ebay – any suggestions on how to choose? How much would a decent one cost? Anybody wanna lend me one if I cover shipping (only half kidding!).

9. It sounds like changing tubes isn’t going to be the key for tonal balance, and I should start with cables. Any suggestions for good neutral sounding cables to try? The Proac’s are biwirable, and I would likely go that route (Ian, is that what you are doing?). I don’t have a tremendously unlimited budget. So far, recommended cables include: Cardas IC’s ($$$),TG Audio HSRs, Analysis Plus Oval 9’s, and Luminous Tech Syn Sig. Any other suggestions, with a total cable update cost of maybe $500 (IC’s and speaker cables) would be very much appreciated. Which Cardas to go for? Should I not biwire for now, to save money initially?

10. If I do make a tube change, it sounds like I should change the input tubes first (12AT7's) to see what happens. Or should I change the entire tube compliment at once. Again, I’m trying to be cost conservative. It was already a huge enough stretch to purchase the amp.

Thanks again for everyone’s input and concern. This excellent amp must meet its potential! Please keep sharing your suggestions and ideas.
Great summary in your last post. My TG Audio speaker cables use banana jumpers.
I have asked another guy to chime in here, too. He's on the west coast and has a Berning, Proac 2.5s and a Cary 306/200 with vol. control.
I heard what you said about the 308 being OK in OTHER systems. I'm sure that's true. But now - in your current system - something is wack. Out of the box, my Berning was great. I can't imagine cables being the culprit. You know the deal, peter - system synergy is key and, at the risk of being redundant, your cdp may be the culprit.
Who knows, maybe things will mellow in the next few days. When did you install it?
The amp only has about 10 hours on it total. The other CDP I'm using with it is an Arcam FMJ CD23.
Peter, don't spend money chasing cable upgrades until you figure out what is going on. In my experience, no cable change will fix a fundamental system problem, which is what it sounds like you have.

But do give the amp more time to break in. Do you have another amp you can try to see how much of the problem is directly related to having the Berning in the system?
Peter I'm with Ian, your summary was great and I think the problem is narrowed down. Based on what you said I believe there is a tube problem somewhere, more than likely the inputs. You should be getting more bass than you are. This amp goes down to 2hz, almost dc into an 8 ohm load. The bass performance shouldn't even be an issue. With the pro-acs 8 ohm load you should note a big improvement in the bass with the zh270. Further I am really mystified by this glare you are hearing; poor bass, tube glare from the zh270, its gotta be a tube problem.

Try Brendan at and just get the tubes recommended above, shouldn't be more than 175.00 or so to upgrade all 6. You'll want to do this down the road anyway, it is a great improvement and may just solve the problem. I really believe you have a tube mortality somewhere or a weak tube causing this anomaly. Try this FIRST and forget the wire for now. In the meantime see if you can locate a tube tester. I also don't believe the problem is with the Cary CD308. And keep up posted on the results.

When you get it right then you'll want to try those cryoed tubes for one of the best audio expenditures you'll ever make.
Tubegroover - would you go for the Cryo'd tubes first? Or do the NOS first? Thanks.

I don't think the problem is with the output's, the 6jn6 tubes. Generally, a problem as you are describing is in the input/driver circuit, not the output circuit. I would try the inputs first, the tube complement recommended above.

So far as the cryoed 6jn6 output tubes go, try to get in touch with Allan Bghan at the e-mail link above and see if he even has a set of them on hand. I'm not sure that he does but he is talking about producing another batch, mucho inquiries. These tubes are all individually tested prior to the cryo treatment. So he is using the creme de le creme before the process. They are probably a lot better tubes to start with than Berning uses. Twl's point in his first post is a good one and true. The cryoed tubes are well worth it and you might want to just get both the inputs and outputs. If neither of these upgrades turn out to be the problem you still aren't throwing away your money, believe me. You can be assured that there is a system synergy problem but when you find it, your zh270 will be ready and waiting :)
Waitaminute!!! No offense tubegroover, but he just bought a brand new, highly-respected and expensive amplifier, and now we're saying he has to upgrade the tubes in order to get even acceptable performance from it? Does this mean Berning sells a $4500 amp that basically sucks unless you do aftermarket upgrades? He should send the friggin' amp back to David Berning and have it checked out, or get his money back. The thing should be damn good as it is. Later on, he can look into extracting higher levels of performance with tube changes and the like.
Dan, maybe I didn't make my point clear enough. If there is a bad tube Berning should and will replace it. If one were to be conservative and not spend the money, the tubes should first be tested with a tube tester as noted above. I really believe the most ill advised thing to do at this point is to replace cables and cd players. Peter has 2 cd players and several sets of cables on hand and he is getting the same results. Process of elimination and common denominator leads to the prime suspect being the amp. Since David Berning's products have a legendary track record of reliability, my guess, based on the symptoms, is that there is a tube problem.

You are absolutely right, he should get acceptable performance from the amp stock. The problem is that he isn't so where does the problem lay? That hasn't been detemined yet. My recommendation is on the premise that there is a tube problem but this is not certain. Is the dealer readily available? How much would it cost to ship back to Berning to have him check it out? I am speaking of a 300.00-350.00 total expenditure for NOS and cryoed treated tubes that will improve the performance of the amp in the long run regardless of what the problem is now. If Peter's resources are limited I would recommend first getting the tubes tested to see if that is where the smoking gun is holing up.
I'm thinking I should ship it back to David. The shipping wouldn't be costly for such a light amp (insurance could be >> the shipping cost), and he would be most qualified to test the amp thoroughly (including the tubes). Perhaps that would be the best first step. He mentioned on the phone that he listens to all newly built amps for several days, but perhaps this was not apparent.
Peter If you can find someone in your area, maybe a dealer that has a tube tester or possibly a local electronic technician you might want to also look at that option. Infant tube mortality is not an uncommon thing. It usually happens within the first few months. Dr. Berning hand builds these amps himself. I doubt there is anything wrong with the amp itself. As a last resort you can ship it back but I would look into getting the tubes tested locally, if possible. Shipping always involves the risk of damage, maybe I'm too sensitive to it because I've had my share of damages, UPS!!
I loved my ZH270 and still miss it, but I couldn't afford to keep it after I bought a Siegfried...

In addition to the many things you've already mentioned, I found that the ZH270 was sensitive to the type of feet it sat on. My best results were leave out the cones and spikes and use the standard plastic feet on hard, heavy surface.

Cables do matter! The Siegfried is merciless in revealing colorations in the input cables...more so than the ZH270. I get nice neutral sound from Kimber KS-1011. I found that my two "silver" cables had undesirable "zip" in the sound on the Berning amps. Also, I found that monowiring gave a more pleasing sound than biwiring. I use the same biwire cable as before, but I connect the the high and low end cables together again at the speaker end. This gives me a much smoother high end. Your experience will surely vary, but it might be worth a try.

Are you using any power conditioners before the Berning? If so, try without them. I get noticibly better results with the PS Audio Ultimate Outlet.

After buying my Siegfried, I horsed around with substituting NOS tubes of various types. David Berning warned me that it can be a "real adventure" in finding tonal balance...and he was right! I am now back to the original tubes, including the ordinary Sovtek 6SN7s, and all is well. I was able to get best results by choosing different cables and repositioning my speakers.

Do you get the same tonal balance from both speakers? Try right and left alone with a mono signal from your preamp. If they are strikingly different, try swapping right and left speakers to rule out differences in tone to speaker placement. If the problem is in one channel, then you may indeed have a problem with your amp.
Hi Peter. I'm the guy Ian mentioned with a setup similar to yours. For me break-in of the the ZH270 was an up and down affair, especially during the first 48hrs. Make sure you let it run continuously the first 2 days. Mine was a little on the lean side in the mid-bass to low-bass region in the beginning. That condition started changing around the 25-30 hour mark. Results may not be the same with 3hrs. here and 4hrs. there to achieve a collective 48. The Berning gear will let you know when the synergy is right in a way I have yet to experience with other mfgs. If a continuous and sufficient break-in period (no cable or equipment swapping during this time) doesn't satisfy I would then send it back to David and/or tube test inputs as suggested. Also, I would leave the Cary cdp running for at least 100hrs. non-stop as suggested in the Cary manual before any serious evaluation. Keep us posted.
The chances that there is something wrong with the ZH-270 is extremely low to nil, chances that there might be a problem with a tube is somewhat higher.

I recommend that you leave the ZH-270 on for the next week or so and play as much music as possible through it, it will break-in more.

The tonality of a ZH-270 is as neutral as it gets, any and everything you do will make a difference in what you hear, unshielded cable, metal shelves, stacking, will all hamper/change performance, this is not a short coming of this amp, it's ultimate performance without coloration.

However, ultimate performance without coloration might not be for everyone, wait a week or so, then contact me and let me know where it's at.

Changing tubes is for taste, not to bring up the performance, not everyone is ready nor do they want an amp that reveals everything, there must over 60 ZH-270 owners, all extremely happy, so much so that used ZH-270's have one of the highest resale values in audio, that is if you can find one.

The tube changes can be suited for your taste, while keeping the attributes of the speed and clarity that Berning has designed into these amps, it's not a performance upgrade but a taste that you might be more use to, I hope this explains it better.
Hi, interesting thread....I'm with Alan....the Berning is so exquisitely revealing and transparent. Personally, I think you're hearing the cables, or the Berning needs to burn in some more. When I first got my ZH270 the only RCA I had around was a BEL interconnect. Sounded edgy and shrill. I did replace the first two AT7s with Telefunkenn NOS - an improvement, but not earth shattering. I must say that I did take the Berning to a Proac dealer and tried it with the 2.5s. I actually did not think it worked so well. Before the Berning we listened to the Plinius 102 with the Proac. If I had the 2.5s I would prefer the 102 I believe. Just my opinion based on a very limited audition (I love that speaker by the way!). On a lark I recently bought a pair of Ref 3a da Capo's off Audiogon. HEAVEN!!! Current system - SCD-1 (w/Kern Mods)--> Quatro Fils (XLR) --> Aleph P --> Jena Labs Symphony --> Berning --> Red Dawn rev II bi-wire --> Ref 3a da Capo (w/AP Luna sub). (I also have AP Virgos, but I prefer the Ref 3as with the Berning)
I agree that the amp should be sent back to Berning and also agree that cables, cd players and tubes should not be changed yet. Acceptable performance should be achieved out of the box.

However, being more than familiar with both the Z270 and the Proacs, I think that it might be a component mismatch.

Proacs are warm, smooth and laid back and use average drivers and cheap crossover components (yes, I know they cost $4500). They are not the last word in speed and transparency. The Berning, OTOH, is all about speed and transparency. This would leave me to believe that the Berning is not complementing the Proac's strengths, but revealing its weaknesses.

If the Berning does not work out try a Conrad Johnson Premier 11A (great relatively inexpensive amp and I regret selling mine) or Audio Research Vt100 (more power but has a fan in it). Stuart Tyler of Proac voices his speakers using Audio Research amps. Lastly, if you want the ease of solid state try the 47 Labs Gaincard; I was shocked by the musicality of this combination.
I am very happy with the Proac-Aleph 3 combo, but I would not say that the Proacs are very warm or laid back, atleast with my current cabling and the Aleph amp. Instead I feel that they are very forward and accurate. I've mentioned that before on Agon, and it was suggested that the perception of Proacs being warm and laid back may be due to the fact that most people use tubes with them. Anyhow, the perception of exaggerated midrange occurs with all the speakers I'm using - triangle titus, dynaudio audience 72 (both soon to be replaced). I really do like the Proacs, though I also look forward to listening to others at the CES in January (including the Ref 3).

Rhirsch and Ian - what can you say about the synergy between the Proacs and the Berning? The overall sound? Rhirsch - what type of cabling do you recommend?
By the way - the current strategy is to perform atleast 4 days of continuous burn in, have the tubes checked, and then assess the situation again. If it doesn't improve, I'll send the amp to David for a check up.
Im using the same speaker cable as Ian - TG Audio's and Silversmith Audio for the ic's. Bass really goes thru the floor with the TG thrown into the mix.
Yikes! I don't think I can afford the TG Audio Lab cables. Got any other suggestions for someting neutral that would be an asset? For speaker cables I currently have Audioquest Type 4, slates, and MIT Terminator 2's available. Of course, I'll do tube checks and break-in first, and maybe even tubes.
With my ProAc 2.5's, I alternate between a CJ 11A and a Pass X-150. Both work very well. I'm sure there is a poor amplifier choice for the 2.5's, but I have trouble imagining what it could be. (I'd love to try the Berning, by the way.)

Not to get too far off topic but as a long time Berning owner I would be interested in your comparison of the single ended zero feedback Siegfried to the PP variable feedback of the zh270. I'm sure Twl and others would be interested as well. Thanks.

Allan your statement changing tubes is for tastes, not to bring up performance is an interesting one. While I would agree that changing the inputs was more of a taste thing, my opinion is that it also improved performance.

So far as the cryoed treated 6jn6 outputs are concerned, there was DEFINITELY an improvement in performance, more resolving, more dynamic and just better across every parameter that I can describe, nothing subtle here. It seems Oneproof feels the same way. I really don't think this is a taste issue at all. And who should know better than you.
Tubegroover, I wish I didn't sell the ZH-270 quite so fast so that I could do proper justice when answering your question. I had been running a Sony SCD-1 cd player directly into my ZH-270 and then my Siegfried. After selling the ZH-270, I bought a used Berning TF-12 preamp--I needed the additional inputs. I expected no sonic improvement and hoped only for minimal degredation. The big surprise was that the TF-12 actually IMPROVED the sound, giving voices a organic wholeness and solidity that makes it sound "right". The Siegfried volume control is turned all the way up now. I guess that the TF-12 volume control is somehow more transparent.

I don't know whether the TF-12 on the ZH-270 would make a similar improvement or not. David Berning himself commented to me that he didn't see what a preamp could add. I was always thrilled with the inclusion of an A/B switch and volume control on the ZH-270 so that I didn't need any preamp. However, it may make a useful difference there as well. What is your experience here?

My speaker is the JBL 4344Mk2, a 95 db/2.83v 6-ohm speaker. There is an impedance peak of about 20 ohms in the bass register. I was using rather spindly speaker cables which suited the ZH-270. Going straight from the ZH-270 to the Siegfried without a preamp I immediately noticed enhanced dynamics, but weak bass and confused imaging. Switching to Harmonic Technologies heavy duty speaker cables firmed up the bass and gave an overall more open sound for the Siegfried. (I liked the spindly cables for the ZH-270, though). The other change I needed to make was to replace the Red Rose 1 interconnect between the SCD-1 and the amp with something smoother: the Kimber KS-1011 did the trick. There may be others, this one is fine.

After all these changes, I am not sure whether we are comparing amps anymore! However, the overall effect was a much more articulate and dynamic sound for most music at moderate volumes. When I say "articulate" I mean, for example, that you can hear the words of songs that much more easily without any bizarre artifacts like siblance, etc. When I say "dynamic" I mean that the inflections of various instruments are that much clearer, even when they are playing all at the same time. Music is more lively and interesting. It sounds that much more like people are playing it rather than it just "happening". Does that make sense? I don't think that it is a tonal change.

Tonally, the two amps are similar, but the Siegfried has, I think, a more open high-end and somewhat more resonant bass on my speakers despite the lower output impedance. Is the high end difference related to feedback? Maybe. Listen closely to how the fine details of cymbals, etc. are rendered at different feedback settings. I found that the high treble fell off at the low feedback setting on the ZH-270, yet paradoxically there was very a subtle improvement in clarity. Overall, though, on my speakers, I found the high and medium settings best: the high setting gave me a tight, fast sound and medium a more organic sound. Low feedback was sometimes alluring, but didn't hold my interest in the same way.

The ZH-270 beats out the Siegfried when it comes to volume. It can get louder and louder without any noticible strain on my speakers. It just "puts out" the sound and remains confident, open and tight. The Siegfried, by contrast, starts to sound a little hard and compressed on peaks if you push it over its limits of a few watts average. That happens on large orchestral work including, ironically, Wagner's Siegfried!

People often comment about the "speed" of the ZH-270 and I noticed it, too, especially at the high feedback setting. I rather liked the effect, but don't believe it is particularly natural. After all, when was the last time you listened to live music and remarked that the sonics were really "fast"? I suppose I prefer fast sound to slow, but the best of all is one which doesn't even raise the question. I have forgotten all about this with the Siegfried: it just seems to get it right.

Can I have the best of two worlds of high dynamic contrast and power? My current project is to build a more sensitive (100db/w) speaker to see what happens. In the meanwhile, the answer is to play at moderate volumes and enjoy the sound even if it means giving up visceral impact.
Ken, I am doing just that. I have a pair of Lowther EX3's in modified Voigt Pipes(100db), and I have a special order cutom amp coming from David Berning. It will be a battery powered, choke-loaded, SET ZOTL, with type 45 output tubes, and 2 watts nominal. I will be using the Emission Labs VV45 Mesh-Plate tubes. It will be loosely patterned after the Siegfried, but with the obvious differences of battery power, and choke-loading, and of course the type 45 tubes. Some people I've talked to are calling it the "Holy Grail" of amp designs. Probably pretty close.
Ken I find many of your comments interesting. So far as sibilance is concerned I have often found this to be the result of interaction of components and wire and have experienced my share of it. I have never heard this emphasis through the zh270 or the previous Transcendent OTL amp I used. The system is wired with copper interconnects and Millersound speaker cable which is aluminum with covered with a copper flex wrap. I have been using the Millersound in my set-up since I had the Transcendent and it works extremely well to the point that I have stopped looking for "better" speaker wire after going through numerous ones.

The interconnects (Luminous Technology Synchestra Signature) were a notable improvement over the Harmonic Technology Truthlink. The Berning allowed me to hear that Truthlinks are intrinsically smooth sounding cables but somehow there is a sameness to all music, much of the subtle nuance of the performance is missing in action. As it happened a friend bought a pair of Luminous cables and his system transformed, I don't use the word lightly. There was that organic wholeness and a separation of instrument lines ala live music that you speak of that were revealed when one cable from the pre to the amp was installed. It was the most significant improvement I have heard his system make and this includes even swapping the Berning in. To put this in some perspective, he has tried numerous cables including MIT, Exos, Harmonic Tech Pro-Silways and Truthlinks, Tara labs, etc. each resulting in differences and some improvements in one area at the expense of another. The Luminous was a revelation and trying to analyze what happened took a back seat to listening to the music prior to which I had a difficult time doing with this system because I always was drawn to the artifacts of the reproduction, in a word, fatiguing.

I don't want to get into a cable review because my point is to emphasis not only do cables make a difference as you note above, they can make a DRAMATIC difference in bringing out not only the musicality of a system but the artistry of the performance. After hearing this in his system I did some research on the cable to see if there is a reason why it should make such a difference. Pretty straight forward, 6 nines continuous cast, (the truthlink are also continuous cast) with a special termination that may come into play. He brought the cable to my place the next weekend and while it didn’t transform my system like it did his, it was certainly a big improvement in the areas that I felt the truthlinks to be weak. Nuance or realness conveyed much better, which I attribute to greater resolution of harmonic detail, tighter and better control of bass, and probably the most notable, to me an incandescent, airy natural portrayal of the upper frequencies.

My litmus test of how my system is performing is massed vocal recordings, Ode to Joy Beethoven's Ninth John Elliott Gardner on Archiv is a good example. Nothing is more difficult to reproduce and very seldom do I get goose bumps listening to a choir on a stereo system. It is generally so far off the mark of the real thing. The speed I speak of with OTL’s and the zh270 is the ability of the system to reproduce instruments and vocals without overhang or adding a richness and to keep everything together yet to reveal the air, space, image focus and separation of the performers as we might hear it in a live performance. I would think if an amp is too fast, if this is possible, it would have the same effect as a tt platter going too fast, there would be a chance in the pitch of the instruments and voices. What could be perceived as artificial is if the dynamic shadings of the music aren’t keeping up with the above, this could certainly lend a perception of something being amiss. At this level of performance in an audio system, each element of the chain has to complement the others or whatever area has a shortcoming will draw attention to the whole.

Your insight was most welcome. I am currently going direct from the digital source to the amp. Prior to installing the Luminous cables, I was going from my CAT SL-1 pre to the amp and preferred it somewhat better with the truthlinks. There really wasn’t an earth shattering difference. With the Luminous cables there is a big difference and I much prefer direct. The presence on a great performance is palpable. Performances can swell you with emotion. It is a level I’ve never experienced before and it is consistent with music I love and the effect I get when attending a great live performance. I now realize that the pre-amp has to go and have just ordered a new one recently. I wasn’t particularly happy with the phono stage and the line stage is now just ok. I sure hope this new pre can keep up with what I am currently hearing. If I’m real lucky maybe it will be an improvement. What I’m really looking forward to is the phono stage. The bottom line with the zh270 is that I have finally found an amplifier that can showcase the potential of my system. Of course it doesn’t hurt that my speakers are a nominal 8 ohms with no dips that could alter the tonal balance. I generally prefer the normal setting with great recordings. I listen equally as much through the medium setting going back and forth often trying to decide. I only listen to the low feedback setting on overly dry recordings. As Peter notes, it is a bit too ethereal, not real but still pleasing. It’s nice having the flexibility. I sure would love to hear the Siegfried on Siegfried (Wagner’s)

Tubegroover and those interested.
Yes, I hear the improvements that the tubes make, yes, it's certainly a big hell of an improvement to me and most of those that hear it an have them, it's shocking how good but not everyone prefer it, believe it or not, some may want that glare, it's not a tube glare, it's a true glare, it's there in live amplified music, it's there in digital recordings.

One person preferred the stock tubes in all, a very small amount but still shows that improvements are a taste thing, there is no other explanation for it.

So to call it an upgrade, it would have to be better for everyone.
One thing in Audio I have learnt is, for every one thing a person upgrades to, another upgrades to the opposite, if you have speaker cable A, an you hear speaker cable B an love it, there is always someone that had speaker cable B and now loves speaker cable A, so the only logical explanation for this is personal taste but then I suppose there is no logic in audio :)
October 10th Update!

Hello to all you helpful Berning owners! Well, it's been a couple of weeks and here is what I have to report.

1) I took the unit to an electronics expert person who just happens to live in Flagstaff (used to work at UC Santa Barbara), and he took it through some bench testing. The results were interesting, much of which above me. But the tubes were working fine.

2) I have kept the amp on for over 100 hours, and the break-in has improved the bass response to that of (or near that of) my other amps: Pass Aleph 3 and ARC VT100-mk2. Still dominant in the midrange though, and a bit fatiguing.

3) Alan B (see posts above) lent me a quad of Cryo'd Sylvania output tubes, and I popped them in and listened today. There was a significant improvement. The bass got more detailed and stronger. Overall detail increased, openess increased, and soundstage improved. Despite a ground problem with my Rogue 66 preamp, the noise floor still seemed way, way down there! Listening to Nora Jone's "Come Away With Me", the cymbal brushes lost a bit of excess metalic nature and became more "brushy". There was a reduction of the midrange emphasis, but it is still a bit there to my perception. Now at the point where I could see adjusting to it, as a different sound approach.

4) I'm away for four days vacation, but when I get back, I will be doing more listening comparisons between the amps. A quick impression now: while the Pass sounds flatter than the Berning, the Berning sounds clearer (e.g. clearer vocals and kick drum). Anyhow, I'll also be working with system synergy. Newly arriving are a pair of Cardas Neutral reference biwire speaker cables, two Neutral Reference interconnects, a Golden Cross interconnect, and some Harmonic Tech interconnects. All are on loan in order to work with the synergy. I will keep y'all informed.

5) I'm really wondering whether I should be trying different input tubes, while I'm trying to make this decision. Any advise? Where to get them...

Thanks All. Peter
Peter, your perceptions of the effects of the cryo'd tubes match mine perfectly. I also have cryo'd NOS input tubes. I'm posting from work, so off the top of my head I can't remember the exact designation of them--G.E. 5 star platinum and Brimar Black Plates? I'm sure that the other berning owners will correct me. Anyhow, I got them from Tubeworld. If you contact him, the guy at Tubeworld (Brendan?) knows exactly what you want because apparently all Berning owners go for the exact same set of tubes. They were a little pricey, but as far as I know that is the only source. In my opinion, and I'm not sure that this opinion is shared by the other Berning owners, the cryo'd 6Jn6's made more of an impact. However, I have to say that at the time I was changing other system components too--interconnect, CD player--so I don't have a very good baseline to compare them to.
Peter, check out my 2nd 9/26 post it gives the tube set. I certainly hope matters improve with the amp. I really don't think the inputs will change any of your general perceptions. Since you have had the tubes checked and they are fine my guess is you have either a break-in issue or a serious synergy problem. What you are describing I can't remotely attribute to this amplifier. It is the antithesis of fatiguing or tonally out of balance, especially with an 8 ohm load like the Pro-acs. I am also familiar with the sonic characteristics of the ARC and Pass amps you speak of although not in my system nor in yours ;^).

I had quite a lot of set up problems in the beginning. I don't think it is tubes, however the amp does sound even better with better tubes. I would carefully read the operations manual again to make certain you haven't missed anything silly (like I did), and then I would look to cable synergy as the culprit. I was very close to sending mine back, but I am very glad I stuck with it, as it is now the heart and soul of my system. I have never heard the SS amps you own, and it is true the ZH may never equal them in bass slam, but it certainly should not sound as if the mids are overwhelming the bass. In fact it is a bass demon in my experience.

It takes getting use to, for sure, the amp really has no sonic signature per say, it's most timber correct, as Bobby from Merlin will attest to.

So it really does not smoothen, brighten, add bass or anything, you get exactly what you give it, that really needs getting use to.
My earlier response was written without having read all the posts, my apologies...

Mine did take quite a while to break-in, and it went through some wild gyrations while doing so. It does keep getting better, and better, AND BETTER.

Allan is right on the mark about the Berning. It doesn't really have a "sound". What ever changes I make in my system, the Berning will highlight them, good or bad. I am in the middle of trying some new cables, so I can attest to fact that everything you do will have either a positive or negative effect on the ZH. Set up and synergy are everything! On a side note, I have found the Berning to be fantastically stable, and user friendly. Shes never uttered so much as a burp.

Well, I guess I am wearing my heart on my sleeve here, but I really think is a great real-world amp.

Good luck
Peter S, the TG HSR speaker wire isn't horribly expensive at $800 for 8'.....Let the amp break in for a few weeks is the best suggestion I have for you, but wanted to set the record straight as the speaker wire is a bargain compared to anything else that it competes directly with.....
-Its an easy mistake to make and it would give you the results you have. Try reversing the phase of *one* speaker cable and leave the other alone. Don't pay any attention to the markings on the amp- its possible that it could have an internal phase problem in one channel. Give it a try.
I really don't think it's phase, he's not complaining of imaging, which would be the first obvious thing, he also has issues with his pre-amp, he just needs to get it all together and get use to the clarity, as Gbeard stated, he also was set back by the sound for the first little while, it's that different, an very much so from what he is use to.
Peter, I must say this is an unusual description of the Berning. Out of curiosity, what is the amp sitting on? This amp is EXTREMELY sensitive to any metal. I had an experience like this once with my 270. It turned out that one of the binding posts on the amp was touching the rack and shorting out. (thats right, shorting out with out blowing up!) I ran it this way unknowingly for almost two days. I don't know of any other tube amp that would not have turned into a mini nuclear reactor when shorted out for extended period. Also, make sure the other components are at least a foot away from the amp(again due to its sensitivity to metal). I have tried many different tubes in my amp with incredible results as well. Don't give up on the 270 just yet. When the problem is solved, you won't believe your ears.
Since the cryo'd NOS output tubes created an audible improvement, I decided to go ahead and do the entire tube compliment replacement. From Brendon at Tube World, I got the input compliment that Tubegroover recommended:

12AT7's Brimar Black Plates NOS and 5965's GE "5 Star"

A QUESTION: Brendan sent me two matched pairs of Brimars. How should I arrange them in the amplifier - vertically (pair per side) or horizontally?

Allan will be sending me a new set of Cryo'd tubes shortly.

Thanks Kriskosiba, I am keeping the amp away from steel things, atleast a foot if not more.
Kriskosiba and all,

Do you think Symposium Rollerblock isolation devices would be a no-no under the amp?? My experience with other tube amps usually really likes the enviromental isolation they provide. Would the steel ball contact on the chasis bottom be a problem?

The steel ball, I assume would be a stainless non-magnetic type, you should have no problems putting them under your Berning.
However I do recommend the new Still Points, if no one yet is using isolation.