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In Reply to: RE: These things are so system dependent... posted by viridian on May 24, 2020 at 22:11:35
Increasing the capacitance is a totally reversable mod.
If you're a purist, replacing a selenium rectifier with a silicon one and adding a series resistor to provide the correct voltage technically makes it a modified unit because it no longer matches the schematic. Marantz most likely would have used higher capacitances in the power supply when the 8B was in production except for the high price and large size of higher capacitance cans in the days of yore. What they used nevertheless worked well, and that's what we have.
I think the mods that cause the devaluation are the ones involving significant circuit changes. Even a mediocre technician understands why someone increases the capacitor values in a power supply.
...those things are mods plain and simple. Reversible, sure, so what? Still mods. And sometimes, mods beget more mods, so if I were increasing capacitance in the power supply, I would also add an inrush current limiter, that was appropriately sized.
Mod is not a dirty word, often we need to correct design flaws and problems with older material science in parts. Nothing wrong with that. It does tend to devalue the amp on the collector markets, but it can often be restored before sale. It is getting very hard to source some NOS parts that are 55 years old so true restoration has only become more challenging as the years go by.
I believe it would be impossible to find NOS power supply can capacitors identical to the ones used in the 8B. Even if you did, they likely would be bad after sitting on the shelf for decades.
If you bought a '53 Corvette, would you put API SA oil in it just because that is what was used in 1953? No, you'd put in modern grade oil (API SN) to assure long life and better performance (SA oil is why car engines wore out after 60,000 miles years ago). Same thing with replacing parts in an amp or preamp. Keep it as original as possible, but replace the bad parts with good quality modern ones unless you just want it to sit on a shelf.
....to keep it on a shelf. I have been dealing with collectors in Japan, and more recently, South Korea, for over 30 years. There are car collectors that do exactly the same thing. Though, just guessing, it is probably hard to find gas and oil from 1953, LOL, and you really wouldn't want to turn the engine over with that junk in it.
I have access to vintage can caps, and many can be reformed and are functional, but functional and performing to near original specs are miles apart, which is why restuffing can be a very attractive way to keep the original look while still providing a modicum of reliability.
Collecting is just a different part of the hobby. Many on this board deride it, but folks can spend their money any way they want as far as I am concerned. It's fine to appreciate the historical value, aesthetic and provenance of gear without actually wanting to play it. I don't imagine that many people are running down to the 7-11 for a pack of cigarettes in their Locomobiles at this stage of the game.
Restuffing is a major pain, especially with painted cans such as on the 8B. I just mount the new caps inside the chassis. However, I know anal people would have a fit over that. I also know several antique radio collectors who hollow out their old wax capacitors and restuff them. I guess they sleep better at night knowing that the capacitors that no one will ever see look original. To each his own...
You're exactly right. Back in the day material technology was very different. Upping a 600v cap wasn't a simple matter. As glorious as the 8b is, it still had an selling price point.
I always wondered what Saul Marantz would have done with the 8b today????
I still say restore the 8b as close to original with some minor tweaking in cap values (as needed). As long as you're not reinventing the driver board or some stupid thing like that - go for it and enjoy it.
I wouldn't hesitate to buy one in which someone had upped the power supply capacitor values. However, tweaking the values of coupling or bypass capacitors is a totally different matter as is changing the circuitry.
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