[Central-Electronics] Solid State Power Supply for 100V

[peter markavage]

Quote Jim - "There are those who believe that a power supply has an
audible effect on how an amplifier behaves....."
I won't dispute what you say here but I've used my 100V on both AM and
SSB with these solid-state devices for years. I've never observed any
unusual ripple on the carrier nor the audio component. Nor have received
any reports at the other end indicating my audio had some unusual
characteristics.

Pete, wa2cwa


On Thu, 24 Feb 2005 18:56:40 -0600 "Jim candela" <jcandela at prodigy.net>
writes:
> 
> 
>         Peter,
> 
>         There are those who believe that a power supply has an 
> audible effect on
> how an amplifier behaves. By amplifier I refer to audio amplifiers 
> with a
> tube basis. Push pull circuitry is more forgiving than high end 
> single ended
> amplifiers when it comes to the source impedance (Rs) of the power 
> supply.
> Lets say from DC to 1 Khz the power supply Rs is 350 ohms, and 
> decreases
> steadily above that frequency as the filter capacitance reactance 
> decreases
> with rising frequency. This will continue until resonance occurs 
> where Rs is
> near zero, and then starts rising again. All of this can occur 
> within the
> high fidelity 20-20,000 hertz audio range. Any ripple on the power 
> can also
> have noticeable impact on the sound as well. One source of ripple is 
> the
> solid state rectifiers. This is where in  a dual diode (FW-CT) 
> circuit the
> diodes themselves at crossover simultaneously conduct. This 
> momentarily
> shorts out the transformer, and when the reverse biased the diode 
> finally
> gives up, and the transformer releases a big voltage spike large 
> enough to
> blow many diodes. I've seen the 1N4007 variety where the overlapping 
> period
> can be several hundred micro-seconds. A suitable R-C snubber can 
> gobble this
> up to no ill effect. I have an old W6SAI Radio Handbook where this 
> approach
> was suggested. I think that was the 1970 edition. Another source of 
> ripple
> where the audio amplifier modulates the power supply due to the high 
> Rs of
> the power supply. This can be very apparent with heavy bass notes 
> that can
> drain the power supply maybe 20% in a few cycles at 20 hertz.
> 
>         The audio amplifier example closely parallels what we're 
> doing with
> the 100V with the 6550's. The big difference is parallel operation 
> at RF
> instead of push pull at audio. We still wiggle the RF at an audio 
> rate
> (SSB), so this is still is applicable. For those interested, here is 
> how I
> tackled this issue on a Sherwood audio amplifier (tube, circa 1962) 
> using
> power supply refinements to try to lower Rs to near zero across the 
> audio
> range.
> 
>         
> http://pages.prodigy.net/jcandela/Sherwood_S8000/HV_REG/regulator.ht
> m
> 
> Regards,
> Jim
> WD5JKO
> 
> 
> -----Original Message-----
> From: central-electronics-bounces at mailman.qth.net
> [mailto:central-electronics-bounces at mailman.qth.net]On Behalf Of 
> peter
> markavage
> Sent: Thursday, February 24, 2005 4:25 PM
> To: central-electronics at mailman.qth.net
> Subject: Re: [Central-Electronics] Solid State Power Supply for 
> 100V
> 
> 
> I solid-stated my 100V years ago. Found some old and weak tubes 
> with
> octal bases, broke the glass, cleaned out the base, epoxy a small 
> perf.
> board in it, mounted some 1N-4007's or something similar (bag of 100 
> for
> pennies at a flea market), and plugged it in. Been working ever 
> since. No
> variac, no thermistors, no power resistors, etc. Most of my rigs 
> have
> something similar.
> 
> Pete, wa2cwa