Broadcast Audio limiter/compressor in audio chain for newbie

Discussion in 'Amplitude Modulation' started by KD6CXW, Jul 28, 2019.

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  1. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    I could never tell the difference between an AB1 push pull modulated signal and a ClassB push-pull modulated circuit in which the grid biases were properly calibrated to minimize cross-over distortion.


    Pheel
     
  2. K5UJ

    K5UJ Ham Member QRZ Page

    It's hard or getting harder (depending on the tube type) to find a pair that are reasonably close to each other--for example 813s and 810s are still out there at hamfests but 100THs seem to be drying up. 610 operators must be hoarding them away.
     
  3. K4KYV

    K4KYV Premium Subscriber QRZ Page

    And a good solid audio driver stage is used. A pair of 6L6s or 6146s without negative feedback and a good driver transformer won't cut it. Nor will a 20-watt tube type hi-fi amplifier backwards feeding another output transformer to the grids, especially if the backwards-fed output transformer is 8k-10k or higher to voice coil. A lower impedance (2500-3000 ohm) primary to voice coil or balanced line might be made to sound reasonably good if the amplifier uses plenty of negative feedback.
     
  4. N2DTS

    N2DTS Ham Member QRZ Page

    I built into my homebrew audio processor a pair of Williamson connected 6l6 tubes in AB1 to drive various modulators I have that take 8 ohm
    input.
    The 4x150 AB1 modulator and the push pull parallel 100TH class B modulator.
    It drove the 4X150's fine, but sounded nasty driving the 100TH class B modulator.

    I thought it was going to be a bad idea running back to back transformers, even if both are hifi units.
    A solid state (symetrix) amp drives the 100TH's ok, not as clean as the 4X150's but not bad.

    Others use back to back iron and it works/sounds good.
    Why?
     
  5. K4KYV

    K4KYV Premium Subscriber QRZ Page

    It depends on the quality of the back-to-back iron, and that of the amplifier. In any case, it's better to use higher input/output impedance, like 500/600 ohms, as the "link". This works analogous to mechanical advantage.
     
  6. K5UJ

    K5UJ Ham Member QRZ Page

    For you DAP 310 users, I found this website in support of the 310. I wish there were something like this for other processor make and models:
    http://dap310.com/
     
  7. K4KYV

    K4KYV Premium Subscriber QRZ Page

    I wonder if the 100THs in a 610 could be replaced with a pair of 4-125s, hi-mu triode connected by tying the screens and control grids together, as can be done with 813s. An adaptor could be made using 4-125 sockets and 4-pin tube bases, so that real 100THs could be used again if a good replacement pair was eventually acquired.
     
  8. N2DTS

    N2DTS Ham Member QRZ Page

    I find it hard to believe there is a shortage of 100TH tubes.
     
  9. K5UJ

    K5UJ Ham Member QRZ Page

    Maybe it is more like I don't see much in the way of BC610 parts in general now compared to a few years ago. I used to see 100THs often and they were not too expensive but around here they're MIA. Your area may be different.
     
  10. K4KYV

    K4KYV Premium Subscriber QRZ Page

    There seems to be more and more a shortage of nearly everything. You would be surprised at all the common every-day items we have taken for granted for decades, that have rather suddenly become unobtanium or horrendously expensive. I don't see that much even at hamfests any more.
     

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