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Can anyone please identify this mechanism and tell me if it has any value
Thanks
Follow Ups:
https://www.technicalaudio.com/pdf/Gordon_Clark_folder/Stancor_Ultra-Linear_Williamson_Amplifier_w_A-8072_xfmr.pdf
John Kuthe...
"Williamson Amplifier PDF"
That is not exactly the whole thing. There was a version with cathode taps on the output transformer. It provided negative feedback directly to the output tube cathodes. This was in addition to any other feedback.
With that scheme you need much more grid drive voltage so after he phase splitter was another stage. Some, probably many of those rare birds floated the drive booster stage on the cathodes of the outputs which acted as sort of a booststrap.
A Chicago BO-15 is one such output transformer. I had such a pair of amps. Not bad at all, in fact I ever thought I would like tubes because of what I'm into.
I have a schematic of it on my now dead PC but it isn't the harddrives so I can get it back. I don't know where my copy came from and can't seem to find it again.
Obviously the cathode taps reduce the maximum power output, but you could lower the plate load and get it back because the tubes see the same thing from anode to cathode. Of course it is possible the cathodes are feeding the output as well in that configuration, I would need information that I'll probably never get. All the schematics I find now are mostly all the reprint from one magazine and doesn't show that one.
If I ever find it I'll let you know.
NT
It's going to be for sale in December. Thank you
Thanks
Seems like an historical artifact. Is there a special way to make it known to museums and such?
I've visited computing museums and far less interesting stuff.
It will be for sale in December. Care to make an offer? Thanks luke
Thanks
Williamson amps appeared in the UK circa 1947. Stateside, we slowly received kit versions at first. IIRC, the earliest kit offered stateside was the late 1940s/very early 1950s Harvey Radio Williamson kit; this was another two chassis amp that included the precious Partridge WWFB opt tranny. It was available to be ordered with 807s or KT-66s as opt tubes.
What the OP has is quite rare and was actually even quite rare back in the 1950s. Acoustical Quad (QUAD stands for Quality Unit Amplifier Domestic) made this "Hallmark" Williamson two chassis version amp for "British Radio Electronics" looking very much like massive Quad II chassis. Allegedly, a Partridge opt tranny lurks inside. Collecting for nearly four decades, I have only seen one of these up close. Internally, the wiring is exemplary and challenges the neatness of any valve/tube Quad or Leak amp. This is actually the third of this Hallmark type amp I have ever heard about stateside.
While many collectors have undoubtedly heard about other early appearing stateside Williamson type amps, like the early 1950s Stancor and Heathkit two-chassis Wmson kit amps, as well as the "updated" 1953 "Ultralinear" output transformer type amps (Heathkit W4, W5, Brociner and so many other brands), the "Hallmark" was quite elusive. UTC and Freed Transformer companies even offered kit amps and everyone should know about the Acrosound TO-290 and later TO-300 equipped Williamson amp types.
Since the OP now has some basis for his knowledge, perhaps he can take the time to open the amp chassis and shoot a pic or three of the fantastic quality inside. We would all enjoy that...
It is a Williamson Amp which undoubtably has a Williamson Circuit, which is a circuit designed to have low measured distortion. It uses 2 6SN7's driving triode wired output tubes KT66 tubes with global negative feedback. I have a mono Radio Craftsman version of this. I have read that Williamson designed it as a "Laboratory" amp. Perhaps that is why output hookups look very strange to me. Input is a regular RCA female.
I was not aware that DTN Williamson actually manufactured amps, but his article in Wireless World is quite famous. I am not sure what to make of the label. It certainly would be a find if it was actually made by Williamson himself. You should research the address. This is still a popular DIY design.
Dave
An Actual Williamson amp. Not the design but the real thing.
Historically valuable as the Williamson design had vastly reduced distortion over the prior art, by using differential amplifiers (back in those days known as a 'long-tailed pair') as the driver. This reduced distortion as push-pull normally has some distortion cancellation in the load, now you were getting distortion cancellation driving the power tubes as well.
A venerable and very copied design!
But, the phase inverter is not a long tailed/differential type. Williamsons used the cathodyne phase splitter, aka: split load phase inverter. The Mullard and some McIntosh amps, as well as other vintage and historically important amps did use the long tailed pair arrangements. The split load inverter was one of the "features" of this long lasting Williamson design.
BTW, DTN Williamson was also the designer of the Ferranti ribbon phono cart pickup/tonearm in the mid-1950s. Why do I mention this, you all ask ? Because, that pickup was the first phono cart to offer an elliptical stylus. DTN Wmson was quite clever...
Actually we're both right on that. The Williamson amp uses both. The cathodyne drives the differential driver circuit.
Looks like a two chassis mono tube amp w/ KT-66 (5881/6L6G) output tubes and a small octal twin triode(?) driver-
The hallmark of this design was low distortion at full power and the use of negative feed-back to achieve this along with a good damping factor.
Some oil/paper 'motor run' caps and decently sized transformers-
probably ~25 wpc in AB1
has a strikingly similar layout to the original Quad Tube amp -
the name plate indicates a provenance to Davit T. N. Williamson - which is the the design most copied in audio-
Should be a great amp- might need some parts replaced - carbon-comp resistors, old caps and the usual suspects
Happy Listening
Nobody goes to tubes forum anyway. I don't much.
Here is some information. The amplifier configuration looks pretty modern to me, for a tube amplifier.
Post that over at the tube forum.
Interesting if anything?
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