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tube fanatic

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Posts posted by tube fanatic

  1. Richard, I am not the least surprised that you enjoyed an OTL amp as many audiophiles consider them the best.  Having a capacitor in the circuit does not in any way degrade the sound.  Remember, interconnect cables are capacitors as are the tubes themselves!  I am sure that Ralph Karsten and Bruce Rozenblit, both of whom sell some excellent OTL designs, would have a great deal to say about this.  All amps are flawed in some respect,  and OTL designs are certainly no more flawed than any other.  
     

     

    Maynard

  2. 3 hours ago, seti said:

    Gray amplifiers were among best available in 1956. It likely had more to do with quality than power.

     

     

     


    I have always thought that PWK favored Brook push pull triode amps but could be mistaken.

     

     

    Maynard

  3. This was done in 1956.  The results were not stated in the article.  I’m surprised that such powerful amps were used considering that PWK had once stated that far less power would be needed to fill a huge concert hall.  
     


    Maynard

    B5C5937F-9203-4DD1-B5FC-7ABB7D444EC9.jpeg

    • Like 1
  4. Fifty bucks could cover any needed parts if both output xfmrs are in good shape.  A tech’s labor would be another matter.  3 watts would power your speakers, but the unknown is whether it is enough to satisfy your listening levels. 
     

    You need to be careful with stuff like this since many have been stored in damp basements or sheds for long periods of time.  Can you post the link to the CL listing?  I can look at it this afternoon.


     

    Maynard

     

     

  5. If I recall, this one uses a single ended 6v6 per channel for about 3 wpc.  Correct me if I am mistaken.  Has it been restored professionally?  If not, you should factor in the cost of that.  Can you post pics of the amp chassis?  Would the seller let you pull the chassis to photograph the underside?  The gamble here is whether an output xfmr, or the power xfmr is blown.
     

     

    Maynard

  6. 14 hours ago, CECAA850 said:

    @tube fanatic Question Maynard.  Im currently running and loving the Grounded Grid pre in the system that previously had the Advom and briefly SYS.  Why is the gain structure so different on this than the other 2 preamps?  A quarter volume on the GG produces about as much volume as half volume (on the knob) on the other two. 


    A comparison with the SYS isn’t valid since it has no gain.  The gain of the GG is probably higher than that of the Adcom as a design choice.  As I recall, its maximum output voltage is far greater than that of the Adcom. The position of the volume control does not correlate with output voltage.  That can be measured if you have a signal generator or test cd.  
     

     

    Maynard

  7. 8 hours ago, Jeffrey D. Medwin said:

     

     

    I have this great sounding KT88 amp that is almost unusable, to hear at its best .  Why?  Too much gain.  The Volume Control feeding it needs to right now be set at about 6:30, rather than 3 O'Clock, and MOST of the source signal is getting shunted to ground. Additionally, if the Volume Control can be at 3 o'clock, the interconnect cable, going to the amp, will be operating at a much better, higher level of drive ( to the cable! ).   So, do you see the two edged sword here ??

     

    In 2019, we just much - misjudged the gain of a KT88 tetrode, operating as a tetrode, ( with it's separate G2 supply  ) - and without using any negative feedback, as everyone else on this planet does it. Thanks for posting.

     

    Jeff


     

    Jeffrey, I am surprised you are discussing your amp in a thread about George Wright’s amp.  
     

    I am confused!  When evaluated at Dennis’ house you and the others concluded that your KT88 amp sounded better than any amp in existence (including Dennis’ SET).  So how did it go from that to almost unusable to hear at its best?  Also, why does a cable need to be operated at a “higher level of drive” to sound its  best?  Are you saying that a cable performs better at the 2 volt RMS maximum output from a CD player than it does during a quiet passage at, say, 0.2 volts RMS?  Please explain the physics behind this to further my understanding.

     

     

    Maynard

  8. 6 hours ago, Jeffrey D. Medwin said:

     

     

    EDIT : 

     

    Jee,

     

    I did more research,  and see both amps use 12AU7.  What I am about to say is 100% OPTIONAL !!!   

     

    In my opinion, and from what I read on line, in the case of Simply Italy, that is likely NOT the very best tube choice, for the front end tube.  Usable, but it can be bettered. 

     

    I would look to eventually have a VERY EXPERIENCED technician replace the 12AU7 with a 6FQ7/6CG7.  It will require an internal wire change on the filaments.  It should sound nicer than the same amp with a 12AU7 as the input tube.  Would likely be superb.  Lovely tube, more linear.  Welcome to this Forum !! 


    The 12AU7 is a fine tube which will not detract from the sound quality of an amp.  If you are pleased with the sound I recommend that you do not seek modifications which are based on the opinion of someone whose auditory system is totally different from yours.

     

     

    Maynard

    • Like 4
  9. 2 hours ago, Jeffrey D. Medwin said:

    Not everything is pure science Maynard, nor can all things existing be explained today in scientific terms. !!!  

     

    To answer your other question, the need for precise matching is pretty rudimentary.  Our ears hear unmatched paralleled resistors as a SKEW in the music, as they are not equal to each other.  It will sound inferior, because " one is always fighting the other " so to speak. We can hear that Maynard.  It is " funky " sounding, compared the NO " fighting", or just one resistor in that circuit location.    Particularly, it becomes audible in the better executed SE amps,.... readily evident.   The less differences in resistances between the two resistors in parallel, the better, the less skewed, the final result will be.  I suggest 0.1% or better matching.  It is audibly superior to 01%.

     

     


    This is where we definitely part ways!  Resistors in parallel do not “fight” one another as the voltage across them is identical.  It does not matter if you use 50 in parallel- the voltage across each is the same.  As a plate load for a voltage amplifier, the tube will not know if you use a single 100k resistor, two 200k resistors in parallel, or 500k in parallel with 125k.  The dc plate voltage and ac signal voltage will be identical.  I, and every amp designer or builder I know, cannot hear the phenomenon you describe.  And we have tried this many times to determine if what you are saying is real.  Have you ever evaluated your concept blind?  If not, have a trusted friend do some changes for you to determine if what you perceive is real, or wishful thinking.  Further, what is the advantage of using resistor wattages vastly greater than what is needed?

     

    What is a “skew” in the music?
     

     

    Maynard

    • Like 1
  10. 1 hour ago, hcnelly said:

    Just wondering, I have my newer Vrd stereo amp set at ultralinear 100% of the time. I was wondering, once my vrd amp is warmed up, if I could switch to triode mode on the fly? Or do I need to have it set at triode before I fire the Vrd amp up? Thanks,

    Chad


    The best thing is to call Craig and ask him about this as well as the best kt88 tubes to use in his amps.  We designers get insulted if folks ask others for advice about our creations 😀😀😀

     

    Maynard

    • Like 1
  11. 1 hour ago, babadono said:

    If the resistors are the same type i.e. metal film, wire wound etc... then this is definitely a case of perception bias. i.e. you want to believe that this will change how it sounds so you convince yourself(your auditory cortex) that you hear a difference. As the old man said "it won't make a dimes worth of difference"


    Of course!  We know this.  I want Jeffrey to explain why he believes his assertion to be true.  I am also confused by some of his recommendations which presumably are meant for hum reduction.  Yet, he insists that some hum is needed for music to sound good.  I look forward to reading his responses.

     

     

    Maynard

  12. I share your frustration.  Occasionally, Barnes & Noble or CD Universe has had better prices.  It seems that those in charge are trying to force streaming as the only source of music.  I prefer a physical medium.

     

     

    Maynard

    • Like 1
  13. Jeffrey, I’m going to need to see some science which supports many of your recommendations.  Let’s start with your belief that using multiple resistors in parallel is better than using a single resistor.   Why will that make an amp sound better, and why do they have to be matched so closely?  I will have many other questions as this proceeds.  
     

     

    Maynard

  14. I still remember my amazement at the astounding bandwidth of Carl’s GG preamp.  When inserted between my CD player and any of my amps there was no change at all in sound quality.  I’m not easily impressed!

     

     

    Maynard

    • Like 1
  15. Jeffrey, to me the salient point is your incessant bashing of any amp design which does not conform to your vision of what an amp should be.  Your designs may sound terrific, or they may not.  That is a purely subjective assessment and will not be universal.  I have never discredited your recommendations but have questioned them from technical viewpoints.

     

    For me to have a technical discussion with you about what you promote you will need to present supporting information such as measurements, or computer simulations which prove that your assertions work.  An example of the latter is how a choke input filter with inductance way below critical value, and low value caps, does not have high ripple.  I believe our past discussions about such matters amounted to a dog chasing its tail.  But, I am willing to listen...

     

     

    Maynard

  16. Jeffrey,  bashing every amp out there because it isn’t constructed as you see fit does not endear you to many who follow your posts. It is not necessary for a person to hear your, or Dennis’, amp to know that they are totally satisfied with what they have.  Do you remember saying this on another forum:

     

     “Of course as soon I write I think that 99.99% of the amps are unsatisfactory I have just alienated myself to anyone who reads my post, and has carefully, thoughtfully paid their money for whatever amp they own.”

     

    The presumption from your statement is that you have indeed heard 99.99% of the amps out there.  Forgive me for finding that a bit hard to believe.  I’m sure that the followers of this fine forum are just as astute as those on the forum where you made that statement and were ridiculed for doing so.

     

     

    Maynard

    • Like 1
  17. Roberto, with all due respect for Jeffrey who is very passionate about what he believes, I urge you to seek advice from others before you implement his proposed changes and modifications.  I can’t count the number of amps out there which do not utilize the Medwin/Fraker philosophy which are truly outstanding in every respect.  
     

     

    Maynard

    • Like 1
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