Interesting Williamson article..

[DaveInVA]

Don't think this has already been posted here but found this while surfing, appears to be written by an old timer that doesn't like Williamson amps (and trying to push a design of his own).

http://www.cosmos2000.org/audio/william1.htm

Dave

[SY]

As soon as you read about the HF imbalance and distortion from the split-load, you know you're reading a very flawed analysis.

He does manage to mention the one actual mistake in the circuit, an insufficient LF margin because of the two RC couplings with similar time constants. A simple change of one of them by a decade fixes that problem very nicely.

[Giaime]

He also says that 6SN7 have inherently low bandwidth...

[tubetvr]

Hi,

This article has been discussed here several times before and as SY write there are several factual errors the text. For a better understanding of the Williamson amplifier and also to understand what the errors are in the White article I recommend to read the original build description from Wireless World that can be bought as a reprint.

When it comes to correct the insufficient LF margin I believe the best method is to use a phase corrective network between the splitter and the driver as can be seen here http://www.tubetvr.com/Williamson_comp2.pdf compare with the original amplifier here http://www.tubetvr.com/Williamson.pdf

Regards Hans

[DaveInVA]

Here is the same guy going after Dynaco amps:

http://www.stan-white.org/a_doc_dyna_1.htm

Dave

[SY]

Tsk, tsk. More howlers, more promotion for his particular idee fixee, a constant power amp. Unfortunately, speakers are generally designed for constant voltage amps...

There are valid things to criticize about the Dyna design, but he seemed to miss most of them.

[Kent Smith]

He also invented the ideal speaker cone.

And he's an astrophysicist that can explain how the universe began!

He says he's the only living engineer who was there at the beginning of hi-fi.

Sounds like he is the Zen-Master of Audio......

[DaveInVA]

It would actually be kinda funny if it wasn't kinda pathetic also...

Dave

PS- I'm sorry if that article had been posted here before. I did try 2 searchs here first and didn't discover it..

[Kent Smith]

PS: please don't take me seriously on that last line!

[Miles Prower]

He's got some legitimate complaints, but he's also over reaching quite a bit.

"As soon as you read about the HF imbalance and distortion from the split-load, you know you're reading a very flawed analysis."

With cathodynes, the unequal plate and cathode impedances become a problem that creates distortion when the load impedances become unbalanced, as they will during an overdrive situation where one grid cuts off as the other begins to draw current. Otherwise, no, it's not a prob. The reason I don't care for it is that a cathodyne always seems to be the "weak link" so far as headroom is concerned (unless you supply it with some insane DC Vpp's). Otherwise, from the balance and distortion perspective, there are lots worse phase splitter topologies out there.

" He also says that 6SN7 have inherently low bandwidth... "

Just plain nutz there. He said that this was due to the higher than normal r(p) of the 6SN7. Isn't so: the r(p) of this type is comparable to that of similar triodes: 12AU7 and 6C4. At ~7.0K, it's not all that high. It does, however, seem to have a highish reverse transfer capacitance, but at 4.0pF, it's not really a problem unless your Cmiller is way up there and you're driving from something like a 12AX7A with a very low plate current. Still, that could be solved by using an active load on the 12AX7A to get the plate current up if you have a very limited Vpp.

The 6SN7 was intended to be (amoung other things) an oscillator/buffer tube and/or an astable multivibrator. It could run all the way down to the 10M band with no probs.

"He does manage to mention the one actual mistake in the circuit, an insufficient LF margin because of the two RC couplings with similar time constants. A simple change of one of them by a decade fixes that problem very nicely."

I avoided that problem with one of my designs by using DC coupling as much as possible, and making sure that the one place where a coupling capacitor was unavoidable to make it a big one. A couple of 0.22uF/450Vdc Auricaps aren't all that expensive. Good open loop low frequency response and gNFB that consequently stayed effective made for excellent bass performance.