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    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

On the cheap..Best coupling cap

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I'd like to find the best coupling cap I can afford on the cheap. Since I am retired that means the wife controls 95% of the money. What I would like to find is a coupling cap I can afford that will sound better than the stock wax covered paper variety vintage 1957-early 60's.

The amps are Model 75 Allen tube mono block's. The coupling cap currently is .1/600 VDC. I thought there might be something out there that is better than the normal "Orange Capacitor" that I generally purchase.
Any polypropylene cap (PP) with a suitable voltage rating would be ideal. About the lowest distortion for a film cap, self-healing, not subject to moisture absorption. Some "orange drop" capacitors are PP, others are mylar/PET - both will work and the low distortion of PP may be unnecessary in a valve amplifier (!)

With money-no-object then teflon dielectric might be worth considering - able to handle much higher ambient temperatures, and very low loss - in a hot chassis this is a consideration.
*ANYTHING* will work better than a 50 year old paper oil cap,

Sound? the new cap by itself will not sound "better" but not being leaky won´t mess with next stage bias which is far far worse, so there you will hear an "improvement".

A $1 cap will work and sound perfect;if you want to use a $10/100/1000 one there is up to you ... and the Wife of course.

Spend the $10/100/1000 on her instead and Life Will Improve [tm]
It would seem that people equate cost with performance. I had a pair of mono blocks a few years back that I purchased with the high dollar tube sockets the best wire and high dollar coupling caps and I couldn't tell any difference between that pair of amps and a identical pair I purchased. Quality wise I wanted some coupling caps that will last and not take out a set of new output tubes.
MKP1839410134HQ Vishay BC Components | Capacitors | DigiKey

The series. Obviously you don't need a 1k6V cap.

Off topic … but is it sanguine to deploy the kind-of-funky {major}{scale}{decimal}{units} notation for all numbers? It just … I don't know … I'm going to defend the practice … for practice:

№ 1 — 1k6V doesn't suggest a pronunciation, but probably most-everyone understands it anyway.

№ 2 — Would 3V6 be … 3.6 volts? Hmmm… I guess so. Still, it isn't as obvious. Or maybe it is. Dunno.

№ 3 — Is the {major}{scale}{decimal}{units} easier to type in than the decimal point notation?

… I am under the impression that it was invented to circumvent the mis-transcription of values from circuit schematics and other documents that tend to “drop the decimal” thru multiple generations of photocopying and image capture. 1.3 kV tends to “wear down” to 13 kV.

… I also get the impression that '1k3V' is preferred 'cuz it is 2 characters narrower than '1.3 kV', what with a decimal point and a conventional word-and-number space separator. Maybe that's the driver. Dunno.

All in all, I remain accepting-but-still-annoyed with the {major}{scale}{decimal}{units} notation. Maybe my foremost annoyance is that there aren't very many circuit-schematic-and-simulation-capture appliances that understand the notation, as typed in. They do understand 1.3 kV tho'. Usually. Unless Japanese or Bulgarian. Or Etruscan. Linear B.

Its one of those mornings.
GoatGuy ✓
Correct. It all started when someone misread a schematic because the decimal point was poorly printed.
1k6V would be pronounced (1 point 6 kilovolts)
3V6 (3 point 6 volts or three vee six)

When I get power resistors, they are printed like that, too. a 0.7 ohm resistor says 0R7.

Love it! Well said:
"And then a sociological aside: one major reason for the wire craze is that it takes absolutely no knowledge to swap wires, just a credit card. In fact, knowledge here is a detriment to the “fun” of applying exotic “solutions” to problems that only require simple and inexpensive solutions. Capacitors are not far behind- there is the additional barrier of having to solder, but beyond that, it takes no knowledge to read internet reviews, whip out a credit card, and swap in an expensive component with a good story. Follow it up with uncontrolled listening with a pre-existing bias and no actual knowledge to clutter up things, and you have a wonderful story to tell people on the Internet."
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