Don’t buy used McCormack DNA 1990s amps

@soix in response to your initial post. You're being extreme. All DNA amplifiers are not doomed to failure. Do original amps have a much higher failure rate than normal, probably so. However, I'd be willing to bet that 50% or more of them will still be kicking with their original input boards 10 years from now. Being that this is the internet you're going to hear more about failed units than about those that are still working because people go out in search of help when they fail.

I've worked on a couple of DNA-1's recently. They had clearly different manufacturers of the input boards, but the actual layout was identical. One I worked on was a full upgrade on a late model, circa 1997 or 1998, DNA1 Deluxe for a local audiophile. The other was a dead early model that I picked up off of Ebay and have since fixed and fully upgraded including the "C" mod. There are some problems with the input boards and the construction of them. If you have one and take a look at the few IC's on the input board you'll notice that the solder didn't flow through to the top side of the board and up on the legs of those IC's on the board. This is a big issue on the pins that have through-hole connections because those pins can lose contact eventually.

I contacted SMc Audio a while back asking for schematics for the amps and, in addition to saying no to giving me a schematic, they pretty much confirmed my observations. Here is what I was told "The problem is with the through-hole plating between the top and bottom copper layers of these two sided driver boards and attempts to repair them is not recommended or supported." 

All holes on the boards are not considered through-hole. Only about maybe 20% of them are. Through-hole is when a signal comes in on one side of the board and travels through the plated hole and then travels out the opposite side of the board to a different component on the board. Through-hole issues can be corrected and overcome. Its a lot of labor to do so, but the faults are not irreversible. Through hole connections need to have a solid solder connection on both the top and bottom of the hole. When these boards are upgraded care needs to be taken to offset the new capacitors about 1/4" off the board and apply solder to the leads on both sides of the board to make a solid and long lasting connection. 

I think its not a stretch to say that the impetus for the "C" mod initially was to eliminate the AD712 opamps that were driving the DC servo in the DNA amps because of failures. The reason was that if a through hole failure occurred due to a poor solder joint on one of these 2 servo opamps then the servo could drive the output into a heavy DC situation and smoke the speakers. Pulling the servo op amp and installing a manually adjusted DC offset trimmer (aka "C" mod) into the same location basically solves this issue. So IMO the C-mod was a reliability upgrade and not necessarily a sonic improvement. The DC servo works great, when its working properly.

I would ask how many of the amps that SMc upgraded from the late 90's up until about 2014 have failed? In those years SMc was upgrading the stock input pcb's. Has anyone heard of one of those amps failing? Probably not, because the stock amps were already randomly failing back then so Steve implemented fixes for some of the issues he was seeing. However, SMc is now selling a new product to go into your old DNA chassis. Its not easy to sell that new product if the old parts are repairable and if you were happy with how the amp sounded before. How many people would pay $2k+ (I've heard of costs approaching $4k for some) when they might pay $500 - $600 to just get it repaired and not just functional but more reliable than it was and sounding just as good as it did prior?

@fsonicsmith1 

I'm located near Dallas. I mainly do work for local audiophiles because I work as a research engineer M - F so this audio work is done in my spare time. I do some work on Acurus and Aragon preamps for folks around the country. I have a set of specific upgrades for those preamps. I used to take in various amps from people around the country but it became too much for me to keep up with so I had to stop taking in amps. I now only accept amps from local audiophiles. I have a full array of test equipment and can fully test amps up to over 1000WPC on my bench using an Audio Precision analyzer.

@soix 

You're correct I pulled that number out of my butt, using nothing but my 35yrs of experience designing and working on electronics in semiconductor manufacturing and research.

Guess what? Krell & Levinson amps of the same vintage are also very failure prone. In fact, probably more so for some models due to heat stress. The people buying those 30yr old amps for kilobucks do not seem to care? Does that make you angry too?

Anyone that is really concerned about one of these DNA amps failing should invest in having a true DC protection circuit installed by a competent tech. That includes the new input boards that SMc is selling because they do not have true DC output protection either. The DC protection in the older DNA amps is only an input muting circuit.

@soix

If you had any technical knowledge on electronics then you’d know that you do NOT have to build the exact same piece of electronics to understand the location and nature behind a failure. Especially when that failure is a mechanical issue in the basic board itself.

SMc isn’t saying there are deficiencies in their special top secret circuit design and they had to change this design. SMc is saying the basic board has mechanical problems. Manufacturers like SMc do not produce their own boards, they get PCB manufacturers to produce them. Whether that board is in a Kenwood, Marantz, Krell, McCormack, etc. most are from the same PCB manufacturers and run side by side on the same production line using the same processes. So anyone who has worked on repairing boards in electronics is qualified to make these statements about the repair of such.

Tell u what — I’ll go back to the guys WHO ACTUALLY BUILT THE AMP and tell you why you’re absolutely wrong..

If you do not understand that there may be a possible motivation of profit behind SMc telling people that their original amps input boards are not repairable then I do not know what to tell you. So yes, please do keep asking the fox to tend to the hen house. When you talk to SMc ask them to come onto this thread and post closeup images of the mechanical issues on these completely irreparable input boards. Certainly SMc has documented this issue many times over. There are other folks on this thread that seem knowledgeable about board repairs and I’m sure that they would like to see high resolution images of the failures too.

Your initial post reads as a person who needs to justify the expense of this purchase and is angry that others can still sell their functioning amps for a decent price.

So lets address your initial all or nothing statements,

While they’re great amps, and I happily owned a DNA 0.5 RevA for 20 years, they’re all gonna fatally fail.

No ALL DNA amps are not going to fatally fail, not by a long shot. Whether the number that survives a decade from now is my butt number of 50% or not, your statement is extreme and ridiculous. I personally believe that number will prove to be much higher than 50% and will probably be better than say a Krell or Levinson of the same vintage. BTW There’s a very good way to judge this reliability. When you begin to see far more dead DNA amp’s than working units for sale on the common audio sale sites then you can surmise that extremely high failure rates are present. I mean, based on your own opening statement, they cannot be repaired right? So they’ll remain dead until they’re sent to SMc to be upgraded or they’ll be sold as dead units and if they’ve been upgraded by SMc then the sales ad will state this fact.

Because their input board is at the end of its useful life, and when it fails your amp is dead and not repairable by anyone — not even SMcAudio. It’s a boat anchor.

Other’s have already pointed out your error in this statement. Unless a board has been completely burnt to the point it becomes conductive then it is generally repairable. However, I’ve seen boards that had burnt sections and people cut out the burnt section and P2P wired in that portion of the circuit. I’ve seen double-sided boards that literally snapped into two pieces and the tech repaired them by rebuilding each individual trace with a solid joining wire soldered to the traces and in the end creating a stronger board. In the end, whether or not a unit is repairable most of the time depends on the amount of a time and effort a tech wants to put into that unit. I’ve personally worked on a number of components over the years from the 1960’s and 70’s that had far more delicate and easily damaged circuit boards in them than the DNA input boards.

@mitch2

I believe you guys are making assumptions based on facts not in evidence, and unfairly casting SMc Audio in a negative light.  If you know Steve and Patrick, you would also know that there are not many folks in the audio industry who care as much about the satisfaction of their customers as they do, and you would also know that they have had more than a steady flow of work for years now.  Steve continues to move forward with new products benefiting from his 40+ years in the business and, for him, creating high quality audio playback equipment is clearly as much or more a calling than a business.  SMc certainly do not need to add clients by fear-mongering owners of old amplifiers manufactured by the former McCormack Audio into taking action before the inevitable failure of their amplifier's input boards. 

I do agree with you that most of us have no direct dealings with S. McCormack or Patrick and as such we are just making assumptions based on the facts we can see from our limited interactions (email) or reading of the direct interactions that customers like you have had. As such we may be making the wrong assumption. 

The one thing that bothers me in this current situation is the fact the SMc has stopped giving the schematics out for the old 1990's DNA amps to owners/techs interested in servicing them. If you do a bit of searching you'll find where Steve was noted as being quite open to supplying the schematics to folks for a number of years and that has stopped. I also talked with Conrad Johnson and they will also not supply the schematics, but I kind of expected that as CJ bought the rights to those McCormack amps >20yrs ago.

Because these schematics were at one time given out that tells me that Steve didn't consider them proprietary back then, so that wouldn't have changed. If he's worried about the safety factor of these amps then he should've put out a service bulletin and supplied a replacement input board at a reasonable cost many years ago because some of these amps input boards failed early on back 20+ yrs ago. Irregardless, in the interest of safety if that's what SMc is worried about, a large red lettered addendum on the front page of the service manual could be added stating the fact that the amps with input board problems should be considered due for board replacement and should not be repaired.

There are plenty of qualified technical people out there that are capable of servicing these amps. The thing is that many techs will not touch an amp if they cannot get the schematic. The reason is that the amount of labor/time goes up dramatically when you're working on a piece of electronics without a schematic.

BTW, To anyone interested. CJ will still service the DNA amps. When I asked them for the schematics I was given a quote for a full recap and a replacement of the input board.

@mitch2

I suspect this is heading way deep into proprietary business issues. Since C-J acquired McCormack, it would seem that any notifications about the equipment would be the responsibility of C-J and likewise any sharing of equipment schematics would be their prerogative.

You would expect that this was the case but there is a thread on Audioasylum with a 2009 date on it where Steve Mc. himself responded on a thread telling a user that PDF schematics were available and he normally responds immediately to email requests for them. That date was about 10yrs after CJ bought the rights to the DNA amps, so if a legal limitation was in effect then the last thing he would be doing is posting and publicly offering schematics to the amps on audio forums. There are also other threads on alternate forums with later dates where people supposedly emailed him and received the schematics. Suddenly in the last few years this openness is no longer the case. I should add that I did ultimately find the schematics by contacting users on DIYAUDIO, but it shouldn’t have to come to that for a 30yr old electronics design. They should be public info after a certain period of time.

My suggestion of safety was not due to your prior statement. I understood your intent. I was just covering the "safety" aspect in case that was the motivational factor for SMc.

@jetter 

Sorry I should've been more clear on that. What I meant is that CJ is still repairing and restoring amps that are sent to them. I only contacted CJ for schematics and they offered a full rebuild in response. For my own DNA1 amp and another unit brought to me by a local audiophile, I've done the repairs and upgrades myself.

@davidbeagrace 

CJ is still working on the DNA amps. When I contacted them a couple months back for schematics they offered to upgrade and rebuild the DNA1 I was working on. Here's an excerpt from that email.

"The only repair/update we offer is the R1 main board replacement.
At the same time the amp components are upgraded to the Deluxe level.
The price is $1050 plus shipping for the R1 board replacement.
This is a 25-30 year old amp.
Also the main power supply capacitors have reached their time limits, 20-30 years is normal.
The insulation deteriorates over time, as a result there is more
internal resistance. The resistance causes heat, the heat causes the deterioration to accelerate.
Many times the metal can expands as pressure inside builds up.
There are 16 capacitors in the main power supply.
The supply capacitors replaced at the same time is recommended, and adds another $550.
Replacing the caps would normally have 3hrs labor charges.
However I'll waive the labor for the cap replacement if done with the upgrade, since some of the labor is duplicated.
So around $1600 total, plus box and packing and shipping"

However we didn't go that route so I cannot attest to the work they perform, but at least you know the cost.

@jetter 

The one amp brought to me was fully functional. It had been back to CJ about 20 years ago for the input board replacement. That was just prior to the current owner purchasing it. It's worked perfectly for him during his time with it. He just wanted it refreshed and upgraded. 

The amp I bought as non-functional was killed by someone that tried to upgrade it. I was told "it smokes when it's turned on"  They broke a couple of traces and with their botched repairs ended up burning up the voltage reg circuitry. The DNA amps are not a good amp for a beginner to try and modify, especially when it comes to the input board.

So no, neither of these amps came to me due to the protection error from the input board problem. But it sounds like the first one I mentioned had been repaired for that issue prior.

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