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Tokyo Hy-Power Amp Best Practice

David HolmgrenDavid Holmgren Member ✭✭
Hello Fellow Flexers,

While I save my shekels for the new FLEX amp I'm using my  old Tokyo Hy-Power 1.5 amp.  It's a great amp and I'm using it successfully with my 6400M.  Like before with my previous Kenwood  TS-590S the amp would "kick out" with the over drive light turning on.  Cycling the power on the amp was a quick fix and I was back in business.  The amp is rated to accept 100 watts.  Until today even with my FLEX I would play with the radio mic gain keeping the radio drive power at 100 watts to keep from over driving the amp.  Today I tried something different that seems to be working better to prevent the over drive light from coming on disabling the amp.  I've reduced the output power from the exciter (the FLEX 6400M) to 50 watts and increased the mic gain.  Watching my power meter I'm still getting the same amount of deflection or power output this way.  The best part is no matter how loudly I talk the amp cannot be over driven.  So this part of my comment is a suggestion that seems to be working.  My next part of this is a series of questions about the elusive ALC discussion.  Some feel you definitely need it and other say it's not necessary.  I feel my amp has the necessary protections to keep is running safe so from that stand point I  don't feel it necessary.  Also my radio can't generate more that 100 watts so I don't have to worry about that happening.  I read the part in the FLEX manual about using the meter to see what the level of your signal looks like and I'm in compliance.  I also listened to myself on another radio in my shack with the RF gain cranked up and it sounds good on my headset. 

So my question is about the ALC hardware switch in the FLEX Smart SDR software. 

Should I use that as a protection method or would it not matter? 

Does this turn on the ALC jack in the back of the radio or does it have nothing to do with it?

I saw the warning in the FLEX manual saying that if the FLEX receives a control voltage lower than -4v that it could damage the FLEX ALC circuit.  According to the THP manual it could generate up to a -10V.  This looks like a scary option.  So does anyone use the ALC jack on their FLEX to control their amp or did you just skip it?  I don't use it.

Thanks and Best 73,




  • Pat N6PATPat N6PAT Member ✭✭
    edited September 2018
    I'm using a THP 450B amp with my Flex6700 and I do not use the ALC. Been using it like this for almost 2 years without any problems.  The amp accepts up to 50 watts and puts out 400.

    I'm also using an RM Italy HLA 305V amp for 160 again without ALC

    fyi...for both amps I use the Ameritron ARB 704 keying interface to key the amps
  • David HolmgrenDavid Holmgren Member ✭✭
    edited September 2018
    I think that's what I'm going to hear from other THP/FLEX users.  I think FLEX would refer to our amp as one of the "modern amps" they mention in the manual that doesn't require ALC.

    From the manual:

    Δ – Please note this input is provided as a safety measure for external amplifiers. It is NOT meant to be used in regular operation as an active power control input or to modify the “attack” of an external amplifier. Almost all modern HF amplifier manufacturers discourage the use of ALC in normal operation. In fact, many amplifiers do not have ALC implemented. The SmartSDR Software User’s Guide describes the recommended method for setting the power level on an external amplifier on a per- band basis.

    As a point of reference my amp does have an ALC **** to adjust.

  • Johan / SE3XJohan / SE3X Member
    edited October 2018
    Not using ALC on my 6700 regardless if I use my Acom 1000 nor my SPE Expert 1K-Fa. Never bothered with ALC on any of my Flex (6500, 6700) or any other radio I have had for last few years (Kenwood TS-590S, 590SG, IC-7300). Never had a problem.
  • Pete - W6OPPete - W6OP Member ✭✭
    edited September 2018
    I have been using my THP 1.5k amp first with the Flex 5000 and now the 6500 and never have hooked up ALC. I set the Flex for a max of 70 watts output on all bands (lower on 30 meters) and never have a problem.

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