From a Type 46 SET to a JJ 2A3 SET, in one weekend

Discussion in 'Tube Gear' started by dowto1000, Mar 5, 2018.

  1. dowto1000

    dowto1000 Junior Member

    Regarding a Type 46 tetrode, when triode-connected:

    I add perhaps 60 to 80 pounds of concrete mass loading to my SET amp. This prevents vibrating, which increases inner detail and definition.

    I use concrete Patio Paving Blocks, or concrete building bricks, placed on the Power transformer, Output transformer, and chassis ( in that order of importance ), to obtain this weight.

    Audiophiles will not mass-load their amps as I do, so they have not yet experienced what I have heard. .. ( the Triode-connected Tetrode 46's blurring of piano notes and diction-loss, on massed voices. ) That tube is never clear and pristine when my amp is mass loaded, not vibrating.

    The Type 46's wooliness, or poor reproduction of the lower registers of a piano, likely may not require the mass loading measures to hear, but.... it likely does require the wiring I use, to connect everything. I have posted wiring suggestions, on this Forum.

    The Type 46 tube fails there - just screws up - in relation to a JJ 2A3-40, which is both more linear and robust-sounding of a tube to my ears, in my system, top to bottom.

    My hearing is not much different than most others, but my amplifier and audio executions do differ.

    Buy some bricks and blocks, 100 pounds worth, and experiment some for yourself. Have fun hearing this. I have 400 pounds on each VOTT ALTEC. Mil Spec m22759/11 wire, beneficially, is both wideband and quite inexpensive.

    Have fun.

    Last edited: Mar 10, 2018
  2. Well said Sir. Erudite.
  3. dowto1000

    dowto1000 Junior Member

    Has anyone noticed there are two AC switches on top of the amp chassis? Any idea what that is for ??

    The second switch wires-out, ( shorts out ) the slow-start CL-90 thermistor ( negative temperature coefficient, current inrush limiter ) , and AC fuse, for better transfer efficiency from a home's AC line, to the power transformer, and hence, audio playback circuit.

    It can not be done in a commercial product, of course. I call it the " attended listening " switch.

    ' Sure improves audible performance, when listening.

    Last edited: Mar 14, 2018
  4. dowto1000

    dowto1000 Junior Member

    Good news on the output transformer topic. This morning, via FEDEX, arrived a nice pair of Magnequest DS-025 output transformers ( 2.5K to 4-8-16 Ohms ), for me to use my upcoming JJ 2A3-40 SET DC mono amps build.

    A couple of nice Hi Fi Haven Forum readers acted.

    One gave me for free, Bud Purvine's Level 1 O-Netics 4.5 K outputs for amateur-helping him in an upcoming SET build, and the other Forum Member sent me his MQ DS-025s, in even-exchange for the 4.5K O-Netics outputs. My cost is just the shipping.

    I have owned MQ DS-025s in the past, and typically hear them on the Serious Stereo 2A3 amps at RMAF shows each October in Denver. I know I will be happy having them. Good news !

  5. paulbottlehead

    paulbottlehead Active Member

    You know what they say about opinions...

    Superb results will not be what you get, especially if you are lower than you should be. The output transformer impedance/stepdown ratio is part of the circuit. A poor choice here makes for a poor circuit.
  6. paulbottlehead

    paulbottlehead Active Member

    Transfer efficiency is a term that is already defined, long ago, and means something completely different than what you're trying to imply. Perhaps you could come up with a different way to express yourself?
  7. dowto1000

    dowto1000 Junior Member

    More theory !!

    The Z of the output transformer of a triode finals stage, is but one of many many theoretical variables.

    There are a multitude of places wherein one can, and must in my opinion, digress from the textbook, in order to achieve superior performance. So, sadly, the technically-inclined theorists never seem to be able to build the best sounding SET amps, in all of my experience. They rely more on what they read in a book, and less on what they hear, when the amp is playing back complex music. This is typical in audio design.

    Since there are many places where a SET amp can lose music information, a rare design - that addresses most of these, will easily out-perform-musically, a design that has a " by the book matched Z ", and exhibits multiple sub- optimizations through out the rest of it's execution..

    A SET amp, built to perform to the maximum, assuming a person knew how to do that, is a VERY expensive piece of equipment to produce. Terribly costly. The average DIYer, and the average hi fi manufacturer, will not spend the money, to get the final result that is possible. The average DIYer is usually- but not always - too cheap, or, in most instances, doesn't know what to do. The average manufacturer, if he was smart enough to figure out how to engineer it, will never be able to sell the product, to recoup the parts cost.

    So, we have scores and scores of SETs that basically can play the midrange, or a little of the glory in the midrange. It might have been better result ( wider band, etc ) as a zero feedback two-stage Push-Pull 2A3 amp.

    I suggest we need to have SETs beautifully portray the mids, highs, and lows, and the maximum possible dynamic range on speaker playback.............those are my goals.

    Best results come to those who know basic theory, but can listen to their creations, with an open mind that will allow them to make changes, with the ear as the final judge...

    Its about what you hear.

  8. paulbottlehead

    paulbottlehead Active Member

    This is a lot of hyperbole. It's very easy to both measure and listen to how transformer impedance impacts SET amplifier performance, especially if you are leaving plate voltage and plate current fixed. This is incredibly well understood and well measured, and going too mismatched in one direction will either leave you with very little power or really poor bass control (damping) and a lot of distortion. I know that you don't measure either, and I haven't ever heard you address the damping issue.

    Again, these are audible and measurable quantities.

    If someone was to make a really poor single ended amp, then spend hours tweaking the crossovers in their speakers by ear to correct for amplifier issues, then some conclusions could be made that would end up being unique to a particular speaker and amplifier that only really work with each other.
    Alexz likes this.

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