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Old 6th March 2013, 12:57 AM   #31
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Quote:
Originally Posted by GoatGuy View Post
ITPhoenix,

The original question was "what is that 1 ohm 17 watt wire-wound resistor doing in series with the 560 nF power supply distal capacitor? There have been a number of answers, but the best were along the lines of a high-frequency snubber. Indeed - if the amplifier sections are prone to HF (radio frequency) oscillation, then a whole lot of oscillation can travel down those power-supply wires. If the power supply has "naked caps" along the chain, they can aggravate - increase - the RF feedback problem. Having a moderately resistive cap could serve to quench RF oscillation before it gets carried away.

Apart from that though, it serves little to no other purpose. It might very slightly take the edge off the most spiky treble passages ... if the wiring from power supply to that last distal capacitor is long, and of thin-gauge wire (intentionally having a very low resistance element in series with the main power supply!) I've done this before, with results that are surprisingly good. But by no means am I advocating it. It takes careful calculation, and actually finding the right kind of wire to do the job in just the right way.

Anyone remember when all turntables had tall spindles where one could [horrors!] stack LPs to DROP onto each other automatically? Oh my, was that a bad idea.

Have fun, don't get wrapped up in the falderal, and keep your first attempts SIMPLE....

GoatGuy
Thank you for that. I agree. It reminds me of a scathing commentary on the opamp chipmakers. Their advertizing is designed to convince you that you would be out of your mind not to buy the latest chip to benefit from all its improvements. The writer quoted a double-blind study between an audio device with TL072s, and another with almost unbelievable specs. The result was that in some cases, the device with the older chip sounded better!!

My aunt had the 45rpm "stacker spindle". It jammed on occasian, but Chubby Checker's The Twist and The Singing Nun's "Dominique" sounded awesome at the time, as well as anything Phil Specter produced.

Just to clarify, my DC heaters are regulated. Nothing else is at the moment, except the AC power supply, which is regulated +-4% (don't ask). I should keep is simple at the moment so that debugging will be easier. I could always add the Zobels later.

I just ordered a rect/cap board with lower quality caps, higher ESR for sure. If they work, there is no point in purchasing audio quality. I hear you on the wiring. One way might be a blessing; but another may bring disaster.

What do you mean by the ZN filter taking "the edge off the most spiky treble passages". Do you mean the higher fundamentals plus their harmonics? The fundamentals with this project max at 1.3kHz, but losing whatever harmonics are generated by the overdriven tubes is prohibited, even if most people cannot hear them.
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Old 6th March 2013, 01:13 AM   #32
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Sorry, we went on to tangents. We have here an hybrid, high gain, treble guitar amp, 4 tubes in, with overdrive channel, feeding a 100w BJT power section.

Here's the Aikido manual which explains the regulated DC heater supply. It's very short. http://www.tubecad.com/2009/03/13/Ai...20in%20One.pdf

They are recommending elevation even with the DC, or letting it float on a capacitor to ground.

Yes, I know it's possible to obtain dead quiet with AC heaters, but I need DC because of the tube socket switches, where the wire separation will act as 60Hz transmitters. Moreover, my layout is experimental so I do not welcome the extra burden of testing various twisting and routing schemes.
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