300b lovers

Since I’m on a roll (and thankfully nearly out of the woods on Covid), let’s talk about PP coloration. It exists, it is real, and if you spend time with top-quality (not junk) SET amps, the absence of that coloration is wonderful and refreshing. Compared to Golden Age amps, everything is so clear, so open, so natural with wonderful tone colors. (Again, you never hear this with junk SET amps, which are murky and dark.)

The magazine conventional wisdom would tell you that clarity and beauty is "euphonic coloration". That’s complete horse****. Euphonic colorations can’t add detail, resolution, more depth, and more in-the-room presence ... colorations can twiddle with subjective tonal balance, and usually adds mush, murk, or grain. They don’t remove it. Build your own amps and you find this out right away (I can see Don nodding his head). The magazines have had this wrong for forty years.

Back to PP coloration. The mainstream "alternative" view is that it is inherent to to all PP, so just build SET and forget about it. Entirely aside from power considerations, SET has its own universe of colorations unique to SET, and they can be quite severe. What I call "junk" SETs sound like old antique equipment. So designing a really good SET isn’t quite as simple as it appears at first glance. At the top of the performance spectrum, it gets fiendishly difficult, with costs and complexity reaching into the stratosphere, and all charm and simplicity lost.

I’m in the small minority that feels the colorations of PP are very real and not imaginary, but can be solved. The Golden Age amps of the Fifties and Sixties, and the modern copies from the big name vendors, all have remarkably similar circuits, boiling down to three types (Williamson, Mullard, and Dynaco, with a handful of variants). These were adopted because they were well understood, responded well to feedback, and were cost effective at the time. Even Marantz and McIntosh were part of the watts-per-dollar race, which only ended when the Crown DC300 and Phase Linear 700 came on the market, putting all tube amps in the shade. From then on, if you wanted Big Watts, you got a transistor amp. Still true today.

But Golden Age is not the only way to build a tube amp. There were other, pre-war circuits, before the Williamson wiped out everything in 1948. The pre-war "floating paraphase" phase inverter ... not as perfectly balanced as later circuits, but more powerful. Transformer coupling, which passively inverts phase, but demands ultra-performance transformers, and also rules out global feedback. And other methods.

The prewar era had a lot of interesting byways and interesting circuits, which all disappeared by the 1950’s. And they do sound different, and get away from the 1950’s monoculture which dominates tube audio. The tubes don’t care; they cheerfully work in any circuit, provided you pay attention to operating point, loading, and stability (part of any amp design).

At any rate, when you stop using Golden Age circuits, the "PP sound" changes. It’s no longer a thick blanket that lays on the sound. It might be a brand-new coloration, or might go away. That’s where the fun starts.

@lynn_olson Another nice to read recollection of a History of Amp Design and the connections made over the years 'pardon the pun'.

Some of the content once more Jogs my Memory.

I recollect my 845 Power Amp designer/Builder, requesting that I keep him in the loop if any EE support is required during ownership.

Again as a recollection, it was made known there was their own Hooks in the Circuit Design, that was beneficial to creating the perception the sound produced was transparent.

I am now wondering if this was a similar description to your own, where creative thinking has been used to produce circuits with the potential to align the SET - P-P sonic where there is seemingly a mimic, rather than a contrast.

I am due to spend time with the EE, in the not too distant future, My Balanced Pre-Amp will soon be complete. Which will then be passed onto the EE, who is to work on the 845 mono's, whare a Balanced Design is to be produced, with the Single Ended option retained.

I have been a friend and loyal to this EE's Services for more than 30 Years, I think that has proved sufficient as a 'NDA' about his early works. 

As an aside, a few individuals have asked to see inside the Power Amp. One  individual wanting to make a mark in the audio world, who I knew quite well, and have not at present not communicated with for quite some time, attempted on more that one occasion to be allowed to take the Power Amps Base off and see the Circuit.

My not being supportive, at one time lead to my being threatened that I was on my own with any future EE concerns, if l did not accommodate the request. For other reasons relating to this individual, I am on my own 'Hey Ho'. I'm pleased I 'stuck to my guns' and honoured the Designer /Builders request , and I certainly am not on my own where EE support is needed.

Lets hope owners of your New Amp design, do not find themselves meeting Pirates scheming to steal another's IP.       

@pindac 

There are only a few things one can do to keep someone from pirating a design.   Point to point wiring and manufacture avoids circuit boards.  When someone sends a PCB design for manufacturing, there have been cases when designs have been stolen.  That said, there is little that can be done to eliminate someone tracing out the circuit.  I used to restore vintage tube gear years ago and one major American manufacturer would actually use regulator and other chips whose labels had been erased so you couldn't tell what part they used.  They guarded the schematics of course, so you simply could not repair their gear unless the problem was obvious.  

One just has to hope that owners are honest.  I have never had a problem with the issue.  I suppose should this design become wildly successful, someone may wish to steal it.  The power supply is non-standard and would be a little more difficult to copy, but the possibility exists.  So be it.

I might add that these preamps and amps will be produced by Spatial Audio Lab in Salt Lake City, UT.  The builders are young and will be around for a long time.  Should they ever need repair it will be easy shipping.  They should be quite reliable though.

When time served EE's who have leaned toward and made Valves a Circuitry, they have dedicated themselves to, there is a lot on offer under the hood, that should be very reasuring.

As for reliability, my Amp's have been on the Oscilloscope for numerous Hours/Weeks prior to them being released to me.

Never have the Amp's in all the time of ownership needed to be returned to the Designer/Builder EE due to any change in their performance from general usage.

I do have a Balance Pot' that I have damaged during Transit coming home from a public attended event I exhibited at, they were incorporated to assist with correcting Psycho Acoustics.

This will be checked out when the EE, has the Amp's for the circuit change, where a Balanced configuration is to be added.

I am thinking these Pot's could now be removed?, as the Mono Pre-Amp's, which are my end game keepers, are each with a VC.