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~misfit~[_3_] ~misfit~[_3_] is offline
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Default Introducing a New Horse to the Stable

On 10/09/2019 11:54 PM, Peter Wieck wrote:
OK, OK, I will bite! Minor rant to follow:

Tube vs. Solid State on reliability:

There are not so very many 60-year old components in operation these days unmodified since-new. My oldest tube item turned 100 this year and likely works better than when it was new based on a better understanding of antenna systems, optimum tube voltages and so forth. Other than moving parts (CD player), the newest component in my office system was made in 1963. The system runs 9 hours per day, 5 days per week. Oh, and the tubes are original as well.

On the other hand, and given my hobby, I see a large number of SS components that have blown transistors, exploded capacitors and much worse, irrespective of age and source. The well made, well designed stuff is serviceable, distinguishing it from the rest of the garbage out there.

I would make a fairly apt comparison: A tube amplifier is much like a mid-last-century Mercedes or VW - few things were self-adjusting, and they required regular and attentive care-and-feeding. With such, they were good for several hundred thousand miles of reliable service. A contemporary Ford, Cadillac, Plymouth would be considered remarkable were it to survive 100,000 miles without heroic measures. Might run very nicely when running, but that would be your basic solid-state device in comparison.

Put simply, they are different beasts designed with different things in mind, but for the same basic purpose. That one is or is not "BETTER" than the other is not relevant to the purpose in either case.

Now, when I here things like "Zero global NFB" and "Critically matched components", I can smell the snake-oil from a great distance, even the 10,000 miles from here to Australia. I am sure that process also contains descriptives of "interconnects" rolled on the thighs of virgins on Walpurgis Night...

Note that even "critically matched" solid-state components drift after a very short period of time in-service. All of them, such that that "less than 1%" is meaningful for perhaps 12 hours or so.

Being as this is a hobby for me, I get to try things that are otherwise unproductive, unprofitable or impractical. Such as shotgunning a device with single-value capacitors and then comparing it to the same device with carefully screened and matched caps. Or matching driver and output transistors and comparing to a similar device with disparate values. Guys and gals - you would be seriously shocked to discover how little difference some things make that the ALL-SEEING, ALL-KNOWING gurus will tell you are critical. Often no difference at all.


Thanks for your input Peter. If I may ask, do you have an opinion on 'storage capacitors' on an
amplifier power supply? What in your opinion is 'better', a single (or few) very large caps or
multiple smaller caps to the same / similar capacitance?

I have a long term project building my own amp based on PCBs taken from 100w MOSFET (two pairs of
J50 / K135 devices per amp) PA amps made by a New Zealand company in the 1980s. (Craft, Gary
Morrison's company before he went on to become head designer at Plinius until 2005 when he left to
set up Pure Audio). I got my hands on a rack of four of these mono amps and preliminary testing
using a clean source and good speakers suggest they will make a great stereo amp.

I need to put together a power supply to feed two of these and have some new 10,000uF caps but was
wondering if multiple smaller caps would be better. (In the PA amps they only had 2,200uF but
obviously weren't called on to reproduce much bass.)

As it is I'll be using fly leads from the rectifier PCB to the caps, then to the amps and I'm
building my own case. I was thinking of maybe using my 10,000uF caps as well as maybe some smaller
ones, perhaps 1,000 in a bank, the best of both worlds. (There are also 100uF electros across the
rails on the amp PCBs that I'll be replacing.) That said I could also just go to multiple

Cheers,
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy little classification
in the DSM"
David Melville

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