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tube fanatic

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Posts posted by tube fanatic

  1. Bosco, I enjoy arguing with you!  So, you seem to be in favor of cutting off federal and/or state assistance for those who choose not to be vaccinated.  Many share your viewpoint.  In the supermarket I always see people walking around with a mask beneath their nose, as well as some food preparers.  What kind of sanctions would you impose on them?  Travis mentioned using drivers license eligibility as being contingent on furnishing proof of vaccination.  Do you agree with that too?   Will people who have not been vaccinated be required to wear an arm band so they can be avoided?  My whole point is that if a person chooses not to receive the vaccine after being educated with the pros and cons (and, yes, there are cons) that should be the end.  The NYPD and NYFD is not requiring the vaccine.  Should those refusing be fired?  
     

    And, Billybob, I have found that when such ideas are put forth by those who have the power to make them a reality, we better watch out.  
     

    I won’t be around the rest of the day, so feel free to criticize!  
     

     

    Maynard
     

     

  2. 11 minutes ago, Bosco-d-gama said:

    Maynard....   you’re not considering how much medicine and high tech medical care is required to keep the covid19 mortality statistics low. We do see where covid19 can overwhelm major cities and every hospital in those cities. We have the dead and we have many survivors with unknown futures because of how virulent covid19 is to our human bodies. Without any question covid19 needs to be stopped ASAP. Stopped before it infects and kills/injures more and stopped before the virus mutates into something more lethal, more infectious and even harder to manage. Everything the public can do to stop covid19 - the public must do. 


    I totally agree with you.  However, you need to consider the numbers of people who will die from suicide when their only source of income is cut off.  Look at the stats on drug overdoses (both legal and illegal) since the pandemic began.  How will society deal with the cost of millions more homeless people, or people who can’t afford food, if the government cuts off their income?  The philosophy of “get vaccinated or die” does not seem ethical, especially since there is no data on how long vaccine induced immunity will even last or whether the vaccine will prevent people from contracting the virus or spreading it.  

     

    Maynard

    • Like 1
  3. 8 hours ago, dwilawyer said:

    It's pretty simple.. They would have a Certificate of Vaccination like they do for all other types of vaccinations. They would start by requiring the certification for Drivers' Licenses, TSA checks screening, and school enrollment (every Texas college requires proof of meningitis vaccination for example) and it would go out from there if it needed to. 

     

    To drive, fly or go to school, you would have to submit proof of vaccination. Next would be, if you want to work, have to have a certificate in by a certain date, just like the two forms of id for an I-9. Then Social Security checks would require Certificate by a certain date if you want to continue to get them. About 60 to 70% will get it when it is available, if that isn't achieving herd immunity, they will start to implement certificates being required for certain things, and/or, they will require schools to do it (as one example) if they want to continue receiving federal funds. 

     

    The most significant thing about the new strain with a much higher R Zero, is that a higher percentage of people either have to have the antibodies (from exposure) or the vaccination. If they can get to herd immunity with the percentage that voluntarily receive it they won't have to look at alternatives to "encourage" people to get vaccinated.

     

     


    Cutting off SS (or food stamps as some have proposed) from those who refuse vaccination will kill more than the virus.  Using the Jacobson smallpox vaccine case from 1905 as the basis for such strong arm tactics is ludicrous imo given that COVID is killing 0.2% to 0.6% of those infected.  Smallpox in 1905 killed 30%.  A mandate from private industry is one thing, but government doing it is going to be unacceptable to many.

     

     

    Maynard

  4. 26 minutes ago, oldtimer said:

    Really interesting for those with family who have died from it.  Truly, bigly.


    If you understood how PCR tests work you would understand why Florida and NJ have raised questions and why a test with better specificity would be very helpful.  Enough said.......

     

    Maynard 

  5. When a lab runs a PCR test for coronavirus the number of cycles can greatly influence the result and yield many false positives if cycled too many times.  Florida is now requiring labs to report their test cycles.  It will be interesting to see if this yields far lower numbers of true positive cases than before.  Even NJ has raised some questions about validity.  Given that shutdowns are being based on positives as opposed to actual sick people this may get very interesting:

     

    https://www.flhealthsource.gov/files/Laboratory-Reporting-CT-Values-12032020.pdf

     

    https://www.nj.gov/health/cd/documents/topics/NCOV/APHL-COVID19-Ct-Values.pdf

     

     

    Maynard

     

     

  6. 21 hours ago, Søren said:

    It will probably be something like this:

     

    http://diyaudioprojects.com/Tubes/Junk-Box-Audio-Amp/

     

    but in a little more simple version. It started as a simple project but became more complex as modifications arrived. To start I will make it triode connected, no NFB and also a few other things. ECC82 and EL84. 

     

    Søren


    Inverterless (or self inverting) push pull amps were quite the rage back in the day.  In fact, a guy has been after me to resurrect a low budget version of my “Little Pee-Pee” SIPP (my wife named it and I have never had the nerve to ask about the source of her inspiration...).  I am vacillating but may consider it next build season.

     

    Maynard

    • Haha 1
  7. A worse situation was the ubiquitous hot chassis table radios of the 30s through 60s.  In spite of that hazard I never heard of anyone even getting a shock from one in spite of many having their backs removed for ventilation, knobs removed for whatever reasons, etc.  I am sure things happened but it was seemingly a rare occurrence.

     

    Maynard

    • Like 4
  8. Separating a p/s from a preamp or amp is different from separating an OPT from the amp chassis.  Will you be running a feedback loop from the secondary to the driver?  Even if you are not it is usually a good idea to ground the secondary in case there is ever a primary to secondary short (unlikely but possible).  Can you post the schematic of the amp?

     

    Maynard

  9. 7 hours ago, rebuy said:

    I have my Marantz and RF 82II's

     

    It sounds OK for Music but not where I desire.

    I'm thinking of adding a Primaluna Dialogue Power Amp

    Is this going to sound good through the Marantz?

     

    I need your Expert Opinion.


    What is your goal if switching to tubes?  What kind of sound are you looking for?  The RF-82s do extremely well in an all tube system.

     

    Maynard

  10. 46 minutes ago, henry4841 said:

    At first glance I thought it was a HP-87. The Eico HP-89 is a 50 watt per channel power amplifier made in 1960! The owner is a lucky guy. Leaving the old can caps is exactly what I am doing in my Eico ST-70 restoration as I install new caps in their place. 

     

    https://www.hifiengine.com/manual_library/eico/hf-89.shtml

     

    The one reviewer on hifiengine had this to say about his amplifier.

    "Took one to a Macintosh test clinic in the mid 60's. They laughed at it when they saw it, and stopped laughing when they tested it. Except for the area below 50 Hz (cycles,in those days), it tested out exactly like one of their Macs!"

     

    I agree with the Mac test clinic impression.  It's rare that I like a push-pull amp but this one really impressed me not only on the bench, but listening as well.  The synergy with the CWs is something to hear.  Eico was always a sleeper brand and didn't get the recognition they deserved.  The OPTs on this unit are massive and obviously of top quality.  I lived about half an hour from Eico and worked on lots of their stuff in the 60s and it was all excellent.

     

    Maynard

  11. 1 hour ago, Limberpine said:

    I used an extension cord and an outlet across the room. No change in noise. 

     

    I put my multimeter on the ACV 200 setting and the put the red on red and black on black terminals on the speaker and it just read 00.0


    A 200V range is too high.  Does the meter have a 2v range?  
     

    Maynard

  12. 5 hours ago, Limberpine said:

    Okay, I did the amp, direct to the wall outlet, hooked to the speakers, with nothing running into the amp. I used both the 3 prong and the 2 prong. The sound got louder with the 2 prong. 

     

    Video attached. 


    Two things to try- 1) use an extension cord to plug the amp in someplace else to hear if anything changes.  2) if you have a multimeter, set it to the lowest AC range and clip the leads across the terminals of either speaker and report your reading.

     

     

    Maynard

  13. On 11/30/2020 at 4:22 PM, dwilawyer said:

    Thank you for this thread, I was going to start one in a similar vein, but will hop on this one if you don't mind. I will start another one on the other topic I had in mind (the degree to which an amplifier plays in the total picture).

     

    Has anyone heard a direct coupled amp or built one? I have, at RMAF, and I wasn't that impressed, but attributed more to the speakers that were hooked up to it.

     

    In researching these kinds of amps I ran across this comment/observation: My one qualm with the LSES idea, is that by using a low-value choke and low-value cap- you're creating a resonant circuit that's likely got a corner frequency within the audio band.

    I've heard tube amp power supplies with this issue- and my usual complaint, is reduced low bass energy and impact- and what bass is there, tended to be tubby and ill-defined. I've modified such designs, with additional capacitance and/or inductance- getting the resonant frequency below the audio band, and reducing the Q of the resonant circuit to a low enough level to not overshoot- and the bass has almost always improv

     

    This is all way over my head, but what is a "resonant circuit"  and a corner frequency? (I get the "within the audio band part).


     

    Chokes and capacitors form a resonant, or tuned, circuit at a particular frequency (depending on value) and exhibit a -3 db point at a particular frequency (the corner frequency).  You are familiar with this from speaker crossover networks which provide a chosen corner frequency.  In an amp power supply you can inadvertently choose values which have a corner frequency which is much higher than the lowest frequency you want to reproduce.  You can demonstrate the effect with this calculator (select solving for frequency and the appropriate units):

     

    http://www.1728.org/resfreq.htm

     

    Try specifying an inductance of 0.3H and a capacitance of 50 uf (typical lses values as I recall) and you will see that the frequency falls in the low bass area.  Compare that with more typical values of, say, 5H and 100 uf.  
     

    The above is a very diluted explanation, of course, but should help a little.  I’ll try to explain a bit about Q when time permits.

     

     

    Maynard
     

     

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  14. Please describe the sound you are hearing in more detail and if it is from both speakers.  Does it change with the setting of the volume control or input selector?  If it has a phono input, do you hear the sound with only the turntable connected and nothing else?

     

     

    Maynard

    • Thanks 1
  15. 1 hour ago, babadono said:

    the crux of the biscuit:

    One thing that must be understood ... valves are non-linear, transistors (including FETs) are non-linear.  Live with it, and don't be fooled by claims that valves are linear, because they're not.  A valve is a comparatively poor voltage controlled current source, and a transistor is a very good current controlled current source.  The process of design is to create a voltage controlled voltage source (aka an amplifier), and while either technology can be used, ultimately (and I must include this with a touch of sadness), transistors win.  Such is life.


    But tubes have so much more charm😁.  Admittedly, I don’t agree with Rod on absolutely everything.  I am often asked why I bother with tubes given the performance available from SS devices.  The only answer I can give is that they attracted me from my first view of glowing filaments when the repairman came over to fix grandma’s console radio when I was 3 years old.  We all have our obsessions.....

     

     

    Maynard

    • Like 1
  16. We have been exposed to a philosophy of tube amp power supply design here on the forum which advocates very low inductance chokes, very low value filter caps, tube rectifiers, and high ripple.  I have expressed my personal disagreement with this philosophy.  Here, Rod Elliott explains very clearly (using proven electrical engineering principles) why such designs are inappropriate.  Scroll down to the section on power supplies for his explanations:

     

    https://sound-au.com/valves/design2.html

     

    The discussion is a bit technical, but the conclusions are very easy to understand.

     

     

    Maynard

  17. This was commonly done in console radios using field coil speakers.  I agree with Mike that long runs of wire carrying B+ are inadvisable. If you have mono amps, you could try placing them very close to the speakers.  But you would need very well shielded cables to connect the preamp or source to the amps.

     

     

    Maynard

  18. Eico has always been one of the best values in tube amps, even when they were new.  Restored, they typically can hold their own against almost any modern costly unit.   Like Lafayette tube amps, they are always worth picking up at the right price.  The “guy down the road”, a professional musician, said he wants to be buried with the HF-89 which I restored for him.  It drives his CWs to perfection, and he says it is the best sounding amp he has ever paired with them.

     

     

    Maynard

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