Optimation PA/CA-250


I seek information on the load-driving capability of the PA-250 monoblocks from Optimation, Inc. (These amps preceded the Wolcott Presence monoblocks). Does anyone have experience with how the PA-250 monoblocks drive loads such as the Sound Lab A-1s or other difficult load types?

I currently use a pair of these monoblocks to drive Innersound Isis ESLs. The amps perform beautifully, however, they appear to exhibit signs of stress--in terms of the overload lamp flickering--as the impedance dips on some music passages. Audio literature indicates that the Innersounds present quite a stressful load in the low impedance range; yet, I wonder if the larger Sound Labs might not lead to a disastrous end to these wonderfully engineered amplifiers. Then again, 1970s technology backed with Mr. Henry Wolcott's sound engineering might stand the test of time and perform with aplomb.

Thank you for your time and patience.
I presently have a par of PA1002 power amps made by Optimation INC. They are very similar to the PA250 with the same lighting lamps. I have tried to restore these to original operation but have had great difficulty getting information from Henry W. I have the circuit diagrams for the PA250, and others in the series that was built by Optimation. Of course, not the diagram for the PA1002. There are differences and errors on the diagrams! I am driving Dynaudio speakers with no sign of stress, but they are easy to drive compared to what you have. According to the infomation manual I have, these amps should drive + or - 1.0 PF, at 250va. In other words, anything. The lights are lite if you draw excessive plate current, and not being an expert in the tube world I would assume some type of mis-match. My PA1002 had impedance taps for 3.75, 16 and 60 ohms. I have seen a host of different tape position availible on different models. I have moded the units with new signal caps, removal of the input pot and cap., new diodes, new Power supply caps., and some circuit changes. I also didn't have the feedback Transformer t3, so it has cause me a great deal of work to make the units sound good. I have bought a Tektronix 4084 distortion analyzer to do some adjusting of the local, global back/forward feed adjustment, but have just recieved the unit an it was damaged in shipping. So I am repairing it first!!!!

Let me know how you get on with them. Do you have any documentation you could share?

Thanks Rob... Not many of us out here working on these thing i guess. Mine sound really fast and clean for tube types....
Hello Mr. Optimationman:

Thank you for your response. I have my Optimation PA-250 monos running well, now that a local technician -- with expertise in engineering by way of working at some reputable firms -- has replaced some of the carbon resistors with updated metal film resistors and replaced some diodes. He apparently found the only information I have -- the Bible for this intricate point to point engineering via the Optimation PA250 manual and schematics -- quite invaluable to successful "surgery." If you need assistance, the gentlman's name is Joe Lalibert. Though he is confined by contract to work only on in-house equipment at his Company Sherbourn Technologies out of Billerica, MA, he is gracious enough to provide reasonable assistance one might need on tube amps and electrical engineering in general.

The PA250s we run have thus far performed beautifully, both from a technical standpoint and sonically. They are driven by 16 W. German EL34 tubes, namely Siemens derivatives. However, my quest for an all-out General Electric or Sylvania Fat Boy 6Ca7 configuration proves more of a struggle than I ever imagined. Should I get a hold of 16 Fat Boys, the Optimations should be an American Powerhouse to behold ad infinitum or at least until my passing. As Mr. Wolcott told me during a phone conversation, "These instruments you have exhibit numerous patented material coming together in performance that people have been trying
to achieve for 30 years. To this day, it has not been done."

Ultimately, a nice pair of Sound Labs should do justice to the Optimations' potential for power drive balanced with sonic composure. Nevertheless, with this in mind, I submit incredible respect to Mr. Wolcott's engineering and would not even let a mature adult within three feet of the PA250's for fear of voltage that can exceed a lethal 650 volts or more, at rest: Veteran engineers suggest donning one hand with leather glove and pocketing the other hand when coming into contact with these daunting masterpieces.

Hoping you prevail revamping your Optimation Series. Best wishes.