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Re: What is wrong with Futterman?

A few audiophile friends e-mailed me a link to this thread, and I wanted to add a few things to the continuing stream of negative posts regarding the Futterman amps. To preface, for those who do not know me, I was one of the original staff at NYAL, along with Ted Hammond, Jon Syder, Al Yarde, Harvey and eventually George Kaye. I currently own and operate my own company, which manufactures musical instrument amplifiers using tubes. It frustrates me to see these half-truths and inaccruate comments being tossed around.

To begin with, I'm not sure why Ralph feels it is constuctive or necessary to post such a constant stream of inaccurate information. Both Harvey Rosenberg and Julius Futterman are dead. These diatribes serve no constructive purpose other than to besmirch the legacy of a gifted Engineer who is no longer alive to defend himself. The only other advantage might be trying to sell Ralph's products and technology and to try to encourage potential customers to avoid purchasing products from companies making Futterman derived products, if such a benefit really exists at this point.

Like you Ralph, I too did not have a friendly parting with Harvey over a business deal involving NYAL that "went south", yet I have moved past this and have grwon to admire his unique marketing style and the enormous efforts he made to promote the Futterman legacy. I feel like I had a great opportunity to work with a unique "mad-genius". Like going to a unique, one of a kind liberal-arts university of sorts.

Was the Futterman "perfect" ? God-no. No circuit is, or likely ever will be. Some circuits do things better or worse, or use FET's or transistors. Was it a unique approach to addressing the limitations of a traditional tube amp with an output transformer ? Absolutely. Never having seen a KSS (although it was certainly of interest to me), and only seeing a Counterpoint amp at CES shows, I can't comment on those products. Perhaps my time at NYAL and these thoughts might clear some of this confusion up:

For starters, the "secret" of the power transformers was carefully handed off from Julius to the manufacturer of the Futterman OTL power transformers used in the NYAL Audio Labs products. [From what I'm told, Julius was not in very good health and realized if he did not help Harvey and his crew, his circuit and legacy would vanish. He was extremely open and I listened to many hours of tapes during which he described his circuit, the layout, how he chose parts etc.] In-fact, the transformer Engineer took Julius' designs and enhanced them for lower operating temperatures, a longer duty cycle and to apply modern (UL etc.) safety enhancements. It's clear that the NYAL transformers were more robust and hearty than the originals. The "secret" (if there really was one) was an extremely low impedance B+ winding that could kick serious current when needed. I know of no transformers that failed in our amps. I still have one OTL-3 power transformer I use on my bench to step up 120 to 240 for European voltage testing of my amps ! This is over 20 years old and still works fine, despite my abuses on a regular basis. Our supplier is actually still making power transformers for Krell when I last spoke with him.

Secondly, the circuit boards we used were designed to mimic (wire by wire) the physical layout of the original amps. As the amps had astounding frequency response (without the input filter they started to roll off around 100-K), they were prone to oscillation if the layout was not carefully followed. The circuit board designer was a very talented draftsman who's experience with in RF transmitter design and microwave circuit layouts was truly tested on this design. Sure, a number of prototype boards were made that oscillated, and had their share of instabilities. Both Ted and Jon were and are dedicated Engineers, and would not allow Harvey to start production until the products were stable and fully tested and approved by Julius.

Of-course Julius passed-on during this process, and Ted assumed responsibility for the design and it's execution. This was back in the days of "tape and doughnuts" on mylar, so this was not an easy project. Prototypes were costly and time consuming. Eventually, after a number of revisions, the boards reached a point of being stable into open loads, into speakers, and into test loads. They were constantly compared to a reference set of "real" amps during the process. We even took care to replicate the ground planes on the board to try to mimic the chassis metal in the original amps. These amps reproduced excellent square waves into a realm you would expect from a solid state amp, not a tube amp. The amps were burned for a full week into dummy loads, we matched all tubes, and also mechanically tapped each tube to make sure they were strong. The amps we got back for service (and there were very few) could usually be traced to a tube gone bad, or a photoflash cap having ruptured. In hindsight, we should have explored using alternative capacitors for the output and power supply.

Were they perfect ? No. There were clearly limitations and touchy areas in both the originals and the clones. The 6EJ7 input stage was running at a point so sensitive, the fan speed could actually impact the operating point of the tube ! The screen grid regulators clearly could have used a more robust design than the 6LU8 tube. Brian Clark did extensive computer circuit modeling and eventually designed a 6LF6 based screen regulator that we never actually put into production. The 6LU8 was clearly running a little close to it's limits in the Futterman circuit.

The other area that was a bit touchy was the use of adjustable zener diodes (VBE multiplier circuits) to avoid choosing zener values in the screen regulators. Ted Hammond designed these circuits, and they did their job well. Julius would actually measure and test each diode to create strings to set his screen regulator voltages ! Ted's alternative was simple and elegant, and worked well. Unfortunately, a tube failure would usually require these parts to be replaced. In a battle of tube and solid state parts, tubes invariably end up winning.

It should be noted that Harvey invested a great deal of time and money in R&D, paying Brian Clark to evaluate the circuits on computer (he was a true pioneer in a field that at that time was basically unheard-of), and it's unfortunate that his flamboyant marketing style perhaps made people not take the products as seriously as they desrved to be taken. We also suffered from being a great crew of guys who really felt strongly and passionately about what we were building and designing, but not being as well versed in the process of manufacture and execution. I always felt we needed to "get to the next level" in terms cosmetics and fit & finish. Our products clearly sounded better than they looked. The later units eventually started to acheive this, but I think it was too late to save the company.

It should also be noted these amps never required any active protection circuits or relays, nor blew any speakers from malfunctions to my knowledge. I think the confusion comes from the original Futterman amp (with the 6B4 outputs) who's circuit was published in a magazine, and actually had a DC coupled output. It ran a dual polarized power supply and had a "0" voltage DC coupled output. Rather daring in the late 40's early 50's I'd say ! These amps can (and did) on occassion have enough DC offset to blow out a speaker, with dramatic results. The later Harvard and NYAL amps did not.

I hope I've been able to shed a little light on the amps, their circuits, and our little community of builders.

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