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  1. Replies
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    The square-wave rise/fall time-switching...

    The square-wave rise/fall time-switching generates "infinite" number of odd harmonics. Filtering & shielding are needed.
  2. Yes, I gave you a 'thumbs-up' for that...

    Yes, I gave you a 'thumbs-up' for that one...which DOES work well IF the PI outputs are nearly balanced so they cancel each other; if not, whatever the difference is, it will want to 'bleed...
  3. Something to consider about the "standby"...

    Something to consider about the "standby" switching event:

    1) Switching B+ (between rectifier & first cap) involves highest voltage (B+) and highest current (all tubes)...lots of volt-amps
    2)...
  4. Unfortunately, he does, especially in the green...

    Unfortunately, he does, especially in the green book; for example, on page 66 in Chapter 3: "At full power, the Champ creates about 5W RMS in a 3.2Ω secondary load."

    And, there are a couple in...
  5. Richard sent me a copy (green cover) for...

    Richard sent me a copy (green cover) for review...he also sent me a copy of his newest (red cover) book: Fundamentals of Guitar Amplifier System Design
  6. Short answer: probably. Schematic indicates...

    Short answer: probably.

    Schematic indicates OT 4-ohm (minimum) load with ONE speaker, which is "switched" to OT 2-ohm when second 4-ohm speaker is plugged in.

    The 'rule-of-thumb' for vacuum...
  7. Unfortunately capacitors and potentiometers are...

    Unfortunately capacitors and potentiometers are bought in bulk...in advance...of production schedules, so those code-dates only indicate that the final product was built/assembled sometime AFTER...
  8. Replies
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    It's an "open" path when the switch is OPEN and...

    It's an "open" path when the switch is OPEN and thus no current passes through resistor R27, however, it WILL have a voltage when probed with a voltmeter, and it will be the same as that voltage at...
  9. Yep, "...non-inductive, "swamping" resistor in...

    Yep, "...non-inductive, "swamping" resistor in parallel with each amp's OTs winding input to switching circuit..."

    as I stated in my earlier post: ...
  10. Absolutely! "Opening" the OT output while signal...

    Absolutely! "Opening" the OT output while signal is applied is akin to "automotive breaker points 'opening' on older ignition systems," i.e.: reflecting a VERY high voltage...back into the OT rather...
  11. Replies
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    Adding a C to an existing R will create an...

    Adding a C to an existing R will create an RC-filter, you wanting to roll-off / reshape the bandwidth or something?
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    Excerpted from F. E. Terman[2] “1. To the...

    Excerpted from F. E. Terman[2]

    “1. To the extent that mu () is constant and that Eq. (6-10) is true, the plate resistance (rp) depends on the plate current (Ip),

    Eq. 6-10: Ip = K...
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    A single, SERIES resistor voltage "drop" is...

    A single, SERIES resistor voltage "drop" is solely dependent upon the output/load current passing through it; more current yields more "drop" and less current yields less "drop" producing poor...
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    The REASON for eqaul-sized "balancing resistors"...

    The REASON for eqaul-sized "balancing resistors" is to "EQUALLY" divide the voltage across the two caps at FULL/peak voltage and NOT during the initial "charge/pump" up when the voltages are smaller...
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    SINE-squared: 54093 COS-squared: 54094

    SINE-squared:
    54093

    COS-squared:
    54094
  16. Replies
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    Actually, you are correct -- I mis-typed -- the...

    Actually, you are correct -- I mis-typed -- the Vg "value" should be 35Vg, derived from one-half of Vgg; ie: Vg = (70Vpp/2). Hopefully, I haven't made other such errors in my previous posts, for...
  17. Replies
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    0.637 is AVG of fullwave rectified signal. ...

    0.637 is AVG of fullwave rectified signal.

    Because both ELECTRONICS engineers and ELECTRICAL engineers use the same physics principles and terminologies, people like National Semiconductor's Bob...
  18. Replies
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    Regarding amplifiers, I repeat "...there is NO...

    Regarding amplifiers, I repeat "...there is NO such thing as RMS power...it's AVERAGE power."

    The Root-Mean-Square (RMS) mathematics simply converts the peak VOLT or AMP value of a sinusoid to...
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    That value is directly quoted from the GE/RCA...

    That value is directly quoted from the GE/RCA 6L6GC datasheets...worked great from them back in the hey-day of vacuum tubes.

    For example:

    Po ≈ (%)*(Zoo/4)*(gm*|-Vg|)^2

    Where GE/RCA Class-AB1...
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    Your assertion *IS* valid when Vg(rms) exactly...

    Your assertion *IS* valid when Vg(rms) exactly equals Vg(bias.dc), which rarely happens; typically Vgg/2 is "less than" Vg(dc) by a couple volts, just for "good measure," For example, see GE/RCA data...
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    ...and he (me) also later explains that the DC...

    ...and he (me) also later explains that the DC bias voltage is assumed to equal the AC(rms) driving signal for estimating Po from the schematic values of Zoo (OT), gm (power tube), and applied BIAS...
  22. Replies
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    See this brief paper: ...

    See this brief paper: http://thermionic.info/mccaul/McCaul_PhaseInverterDriveVoltage_2008.pdf
  23. Good use for "past-useful-life" tubes...except...

    Good use for "past-useful-life" tubes...except those with "open" filaments (ha,ha)!
  24. Replies
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    Class-AB1 PP amps do not conduct 360-degrees,...

    Class-AB1 PP amps do not conduct 360-degrees, only about 190-205-degrees, or more generally 'slightly more' than 50% of a FULL sinusoid, so referencing a 'pure' sinewave is only valid prior to the PI...
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    First, there is no such thing as WATT(RMS)! ...

    First, there is no such thing as WATT(RMS)!

    Why? Because RMS is just the mathematical-equivalency operation (0.707*pk) that's applied to the peak value of sinusoidal VOLTS and/or AMPS to convert...
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    No, as Vg is BIAS (DC voltage), not Vgg which is...

    No, as Vg is BIAS (DC voltage), not Vgg which is AC peak-to-peak, which I believe you are thinking about.
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    *IF* you're wanting to 'guess-ti-mate' an...

    *IF* you're wanting to 'guess-ti-mate' an approximate output power for a Class-AB push-pull amp by simply looking at its schematic, here's an equation:

    Po ≈ (%)*(Zoo/4)*(gm*Vg)^2

    where:
    Po =...
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    Just to add some more mud to the waters: AMPS and...

    Just to add some more mud to the waters: AMPS and SPKRS are (unfortunately) spec'd differently, for example, on many Fender schematics, it's 400Hz for bass amps and 1kHz for guitar.
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