Does anyone have a Williamson tube amplifier?

[DanielT]

Yes. A lot of unnecessary complication, and a lot of components that aren't really doing anything. I see you took out the schematic in an edit.

Sorry, that was not the intention. I'll put it back in.

You could certainly be right in what you say. I don't know what he's up to. He's a technical expert like you.
In practice, nothing that worries me because I won't be building that tube pre amp.

Index of /Morello/Tube-preamp

Edit:
OT.However, a DIY OP based pre amp with remote and built-in DAC would be fun to try. I think, anyway.

Just for fun, for example this Apple USB-C adapter plus some pre amp. Could probably be a fun project.

Amir:
"Note that my testing is all on Windows. I attempted to test on my Samsung S8+ and got odd results. Using both Google dongles, all they did was route the not so good sound of the internal DAC through the dongle (???). With Apple dongle I got music but level was very low. So if you plan to use the Apple dongle on an Android phone, you should do some compatibility testing."

Then you should add a pre amp. That should fix that problem. Maybe.
If I ever try to build something like that, I'll create a thread about it. Not something I prioritize now.

Review: Apple vs Google USB-C Headphone Adapters

This is a review, detailed measurements and comparison of Apple's USB-C adapter to the current and last version of Google Pixel headphone adapters. The Apple adapter costs just $9 including one day shipping for free. The Google dongle costs $12. Not that any of these are large by any stretch...

audiosciencereview.com

 

[firedome]

If interested in a garden variety (non-DIY) classic early '50s tube amp, then consider early Heathkit amps that were typically Williamson designs, hence their W nomenclature. W-1Ms are scarce. W-1M, W-2M, W-3M are all 2 chassis designs (power and output), W-4M were single chassis, the later produced in large numbers and all of them the "purest" Heath-Willimason designs. W-4M's are readily found on the usual suspect websites. The preamp for all these was the Heathkit WA-P2 which takes it's power from the amp. The power tranny of all of the W series was their weak point, but not hard to re-source. Not sure about W-5, 6, and 7s, but I believe at least the later 2 were Ultralinear, would have to see schematics, it's been a long time. The W-6M or W-6A's (updated design), both 70w, also, are rare and expensive and have some of the best output xfmrs ever measured by John Attwood EE PE, the Tech Editor of Vacuum Tube Valley Magazine back in the day. Years ago I had W-4, 5 and 6 models, all very satisfying to listen to with properly matched (high efficiency) speakers of their era.

 

[DanielT]

If interested in a garden variety (non-DIY) classic early '50s tube amp, then consider early Heathkit amps that were typically Williamson designs, hence their W nomenclature. W-1Ms are scarce. W-1M, W-2M, W-3M are all 2 chassis designs (power and output), W-4M were single chassis, the later produced in large numbers and all of them the "purest" Heath-Willimason designs. W-4M's are readily found on the usual suspect websites. The preamp for all these was the Heathkit WA-P2 which takes it's power from the amp. The power tranny of all of the W series was their weak point, but not hard to re-source. Not sure about W-5, 6, and 7s, but I believe at least the later 2 were Ultralinear, would have to see schematics, it's been a long time. The W-6M or W-6A's (updated design), both 70w, also, are rare and expensive and have some of the best output xfmrs ever measured by John Attwood EE PE, the Tech Editor of Vacuum Tube Valley Magazine back in the day. Years ago I had W-4, 5 and 6 models, all very satisfying to listen to with properly matched (high efficiency) speakers of their era.

I've heard Heathkit mentioned now and then. I looked them up. It was amazing what they were up to with various, fun things.

Heathkit - Wikipedia

en.wikipedia.org

 

[fpitas]

I owned several Heathkits growing up. They even had a kit version of one of the Altecs with an 811 horn.

 

[firedome]

Yes that was the Heathkit AS101, I had a pair, as well as a pr of the speaker that it was a clone of the Altec 846a Valencia, which had more elaborate cabinets. When listening it was difficult to tell one from the other as the components were essentially the same: 15" 416 woofer with the 806/811 driver/sectoral horn crossed over at 800Hz. . The Altecs came from my good collector friend Chong in Fairfax, the Heaths from a CL ad. The Heath came with a crossover kit that was home assembled. Both were optimal for low-ish watt tube amps but eventually went away due to a lack of WAF :-(

 

[egellings]

Or have had, listened to a Williamson tube amplifier? Impression?

Are they available?
What can one, in reasonable condition, cost?

I could really imagine having one. Mostly for its HiFi history. Not as a main amp but in some nice secondary system. Then together with a subwoofer + LP/HP filter sub-speaker. Speakers that the Williamson tube amplifier would like to drive.
I might add that when I say have such an old amplifier as a general tip, you should be knowledgeable about electronics or, as in my case, have a friend who is knowledgeable (I help him with other things). Taking amplifiers to professional repairman, who charge by the hour, can be expensive.

Do you think the technical data in the Wikipedia link below is correct?:
15 W, 0.1% distortion, straight FR?
Good damping (factor) is mentioned. What kind of damping factor it is and what it is compared to, one might wonder.

The Williamson amplifier is a four-stage, push-pull, Class A triode-output valve audio power amplifier designed by D. T. N. Williamson during World War II. The original circuit, published in 1947 and addressed to the worldwide do it yourself community, set the standard of high fidelity sound reproduction and served as a benchmark or reference amplifier design throughout the 1950s. The original circuit was copied by hundreds of thousands amateurs worldwide.[1] It was an absolute favourite on the DIY scene of the 1950s, and in the beginning of the decade also dominated British and North American markets for factory-assembled amplifiers.

The Williamson circuit was based on the 1934 Wireless World Quality Amplifier by Walter Cocking, with an additional error amplifier stage and a global negative feedback loop. Deep feedback, triode-connected KT66 power tetrodes, conservative choice of standing currents, and the use of wide-bandwidth output transformer all contributed to the performance of the Williamson. It had a modest output power rating of 15 Watts[a] but surpassed all contemporary designs in having very low harmonic distortion and intermodulation, flat frequency response throughout the audible frequency range, and effective damping of loudspeaker resonances. The 0.1% distortion figure of the Williamson amplifier became the criterion for high fidelity performance[2][3] that remains valid in the 21st century.[4]

Or maybe one should let such an old amplifier remain in some radio museum for display only, considering this:

The Williamson amplifier was sensitive to selection and matching of passive components and valves, and prone to unwanted oscillations at infrasonic and ultrasonic frequencies. Enclosing four valve stages and an output transformer in a negative feedback loop was a severe test of design, resulting in a very narrow phase margin or, quite often, no margin at all. Attempts to improve stability of the Williamson could not fix this fundamental flaw. For this reason, and due to high costs of required quality components, manufacturers soon abandoned the Williamson circuit in favour of inherently more stable, cheaper and efficient three-stage, ultralinear or pentode-output designs.

Williamson amplifier - Wikipedia

en.wikipedia.org

Here is a video for the technically interested:

Edit:
I don't even really know what it looks like. There are pictures online but I think it mostly looks like variations on that amp. Can anyone produce a picture of the original? It would be nice to see what it looks like.

Williamson amplifiers tend to be motorboats.

 

[fpitas]

Williamson amplifiers tend to be motorboats.

Not surprising. Were I to try that kind of thing, I think I'd nest feedback loops for stability.

 

[egellings]

Not surprising. Were I to try that kind of thing, I think I'd nest feedback loops for stability.

The coupling caps from the additional driver stage between the phase splitter and the output tubes adds the destabilizing phase shift.

 

[fpitas]

The coupling caps from the additional driver stage between the phase splitter and the output tubes adds the destabilizing phase shift.

I'd probably feedback around the high power stages first, maybe split the cathode resistor at V2 and feed back to there from the output. Luckily though, I have enough hobbies without becoming a tuber

 

[Ken Tajalli]

From Audio Engineering, June 1952.

http://www.elektronikjk.com/Elektroakustyka/wzmacniacze/wzmacniacze_lampowe/Ultra-Linear_Operation_of_the_Williamson_Amplifier-2.pdf

2) Back then, if you wanted hi-fi, and didn't have a lot of cash, DIY/kits were the ticket.

Your link is for a different amp.

 

[anmpr1]

Your link is for a different amp.

The OP was asking about information on the Williamson design, and it's history in relation to early hi-fi. I linked to a famous 'mod' (I guess you could call it that), which discusses the Williamson. Thanks for noticing my hard work!

 

[fpitas]

The OP was asking about information on the Williamson design, and it's history in relation to early hi-fi. I linked to a famous 'mod' (I guess you could call it that), which discusses the Williamson. Thanks for noticing my hard work!

Yeah, but beam tetrodes. And ultra-linear!

/

 

[anmpr1]

Yeah, but beam tetrodes. And ultra-linear!

/

I remember reading an interview with the man everyone loves to hate, Bob Carver. He was talking about the time he was talking to Stu Hegeman (of Citation fame). Stewart is reported to have told Bob that he was never a fan of the ultralinear circuit. On the flip side, I recall an interview with Hegeman, who quipped something to the effect that if Dave Hafler tells you something, you could take it to the bank!

The only thing I can say, is that I wish I had an old Citation kit to go with my Dynaco. Then I wouldn't have to think about this stuff!

 

[SIY]

The coupling caps from the additional driver stage between the phase splitter and the output tubes adds the destabilizing phase shift.

Yes, if you split the LF rolloff frequencies by a decade, the amp is far more stable, at the cost of a dB or two at 20 Hz,

 

[SIY]

I remember reading an interview with the man everyone loves to hate, Bob Carver. He was talking about the time he was talking to Stu Hegeman (of Citation fame). Stewart is reported to have told Bob that he was never a fan of the ultralinear circuit. On the flip side, I recall an interview with Hegeman, who quipped something to the effect that if Dave Hafler tells you something, you could take it to the bank!

The only thing I can say, is that I wish I had an old Citation kit to go with my Dynaco. Then I wouldn't have to think about this stuff!

Morgan Jones just did an article in AudioXpress showing perhaps why experience with UL is so split.

 

[egellings]

Yes, if you split the LF rolloff frequencies by a decade, the amp is far more stable, at the cost of a dB or two at 20 Hz,

Using asymmetrical RC coupling constants between stages helps with stability.

 

[anmpr1]

Morgan Jones just did an article in AudioXpress showing perhaps why experience with UL is so split.

As the last of the big spenders, if it's not available free after an on-line search, it's not available.

Historically, from what I gather, the first instance of the ultralinear design is traced to Alan Blumlein, in 1936. Hafler and Keroes (then of pre-Dyna, Acros) received a US patent in '51, refining the circuit in ways. That's probably another area for inquiry and comment.

Like most audio-related debates, in practice it's probably less of an aural issue, than it is simple grist for the intellectual debate mill. In any case, that's how I tend to approach this sort of thing. And as an audio history buff, I'd certainly prefer a Dynakit (or a Citation kit), than I would the latest and greatest Topping, which I wouldn't particularly care to own at all, although recognizing that the latter would fly rings around any Willamson, Hegeman, or Hafler, on the 'scope.

Since we are talking history, in the early '50s, today's debate was still raging, and had not been settled. In a 'back to the future' moment, Audio Engineering had published an article on 'advancing the ultralinear design' (July 1952), which led to comments from not only Hafler and Keroes, but also the esteemed English gentleman, and famous speaker builder, Gilbert Briggs (albeit the latter's issue with the article turned on a misuse of an earlier Elizabethan period bard's prose).

 

[fpitas]

As the last of the big spenders, if it's not available free after an on-line search, it's not available.

Historically, from what I gather, the first instance of the ultralinear design is traced to Alan Blumlein, in 1936. Hafler and Keroes (then of pre-Dyna, Acros) received a US patent in '51, refining the circuit in ways. That's probably another area for inquiry and comment.

Like most audio-related debates, in practice it's probably less of an aural issue, than it is simple grist for the intellectual debate mill. In any case, that's how I tend to approach this sort of thing. And as an audio history buff, I'd certainly prefer a Dynakit (or a Citation kit), than I would the latest and greatest Topping, which I wouldn't particularly care to own at all, although recognizing that the latter would fly rings around any Willamson, Hegeman, or Hafler, on the 'scope.

Since we are talking history, in the early '50s, today's debate was still raging, and had not been settled. In a 'back to the future' moment, Audio Engineering had published an article on 'advancing the ultralinear design' (July 1952), which led to comments from not only Hafler and Keroes, but also the esteemed English gentleman, and famous speaker builder, Gilbert Briggs (albeit the latter's issue with the article turned on a misuse of an earlier Elizabethan period bard's prose).


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I didn't realize Ultra Linear was so specific.

 

[anmpr1]

I didn't realize Ultra Linear was so specific.

That's the patent business for you. Legal specificity keeps the attorneys in business.

It's like a lot of things--think guitars. Anyone can copy the shape of a Telecaster (since that is public domain), but you can't call it a Telecaster, since that is a trademark of Fender. That said, I'd much prefer a Schecter PT Special in Aqua Burst, than the 'real' thing. And imagine how great this would sound through a Williamson amp and your Atlecs!

 

[SIY]

I didn't realize Ultra Linear was so specific.

It is; so much goes wrong when people use any old tube and some standard tap for the screen (43% being common). Done right, it's a great way to run an output stage.