Me too!! The PS 2 is a "Bucket List" piece of gear for me!!

Man this is the best tech vid i have seen yet, i need to pick up some more test gear, and get into this myself

Link to a schematic of aforementioned well designed power scaling circuit. please.

@@FryetteAmps talk to Mark Stephenson

what they say in the video is that sag is more stable set on a precise level on solid state rectifiers and mostly on amps with regulators than on tube rectified amps. They don't say the variac is useless without a tube rectifier they just say you'll have less range of changing the sag depending on the amp. great information

@Music_is_fun I was referring to "Power Scaling" which is very different to a simple variac. It's another attempt to get cranked amp sounds at low volumes: you could say a "rival" to Fryette products and I felt the dismissive comments directed at it in the video were basically not true: ask Suhr, Stephenson etc who know how to use the technology: it's far from sterile and sag is completely achievable in power scaling systems. Every solution to the tube amp volume problem has pros and cons

No. Tube nerds may disagree on esoteric technical grounds that typically do not apply here.

The speaker out from the amp into an 8 ohm load.

As we said in this video, we'll get into more detail on the related Malcontents episode, which we did. We also discussed manufacturers cross-marketing in the Mals tube episode. Not to this particular extent though because, you know, margaritas...

@@FryetteAmpsthanks for the heads up, I'll check out the other episides. There's so much history lost around the development, manufacture, patents, licensing, rebranding and distribution of tubes, and the inevitable mergers and corporate takeovers. Things got really weird in the late 70's and 80's with companies like National and IEC Servicemaster importing and rebranding tubes. They could be Mullard or Tele and they could be absolute crap from anywhere that was rebranded to look like good European imports (ServiceMaster was notorious for junk).

@@goodun2974 kzfaq.info/get/bejne/qd-ap92c3NK5mps.html

@@FryetteAmps , that was a good discussion. I would have liked ro see some discussion around heater-current draw and whether any of the re-labeled and "re-imagined" Russian (or Chinese) tubes exceed the original heater-draw specs sufficiently to cause overheated or blown power trannies; like those "weak" 6L6 types being relabeled as high-voltage 6V6's ---- do they draw .45 A per tube, or .9A per tube? And do "modern 6550's draw 1.5A, with modern 6550A drawing 1.8A, per the 1960's tube specs? Because I have a "DOUBT" rule pertaining to tube "substitution" and "upgrade" with modern production tubes: DOn't Unintentionally Blow Transformers! By the way I have never read anything scholarly about migration of air molecules, O2 or Nitrogen, into a tube over time unless the seal is bad around one of the pins or lead out wires, in which case usually it's quite obvious because the getter will turn snow white. The only info I ever read that possibly related to permeability or susceptibility of glass envelopes to air infiltration is that certain tubes were designed to withstand *low* air pressure in high-flying military planes (like the Chatham 5R4GY potato masher rectifier); and some transmitting tubes used special high temperature glass or quartz. Pertaining to contamination of the vacuum as tubes age, whether in use or stored away as NOS, water vapor was a particularly troublesome contaminant, and some tube types had their plates and other parts *baked in hydrogen* to drive out contaminants (according to the reference book "Tube Lore" by Lidwell Sibley). Hmm, would you want a high-temperature hydrogen furnace operating iin the neighboring industrial park? The quality and insulating qualities of the mica insulators is gonna be important as well (Russia supposedly has excellent quality mica) and the wafers are presumably baked to drive out moisture and then sometimes coated with compounds to increase their insulating factor. Having encountered tubes with interelement leakage, I have to wonder if some of the metallic materials in the getter got splattered on the insulators when the tube was flashed with the spot RF beam, or if the cathodes sputtered away some emissive material onto the micas or (worse) onto the grids, screens or plates, causing gassy behavior and thermal runaway. I also read somewhere that the KT series of kinkless tetrodes were purportedly originally built with gold plated or perhaps carbonized grids to minimize grid emission, but I don't know if such manufacturing techniques were ever applied to more modern Russian or Chinese tube manufacturing. 99.9% of my tube experience has been with vintage American and European tubes, and as you've pointed out, the original design, engineering specs and manufacturing processes used for our favorite vintage tubes is often merely a suggestion at best to the modern tube manufacturers.

@@FryetteAmps , ps, A discussion of the 6BQ5 beam power tube versus true pentode EL84, as well as their tougher semi-equivalent the 7189 and 7189A, seems in order. Especially germane to the discussion is whether there are any additional pinouts being used for heat dissipation of the grid and screen, or cases like the 7189A where the pin out is changed so that only the 7189A will work in certain amplifiers (like some older Magnatones) that run at voltages and dissipation well above what a 6BQ5, EL84 or regular 7189 can handle. And, does anybody make a usable "6973" these days?