Whoa - things are spinning here. There is a need for more discipline and rigour. Yes, adding sugar to wine is chaptalization or amelioration. But neither of those words appear in the standard of identity for brandy, which you find in §5.22(d). Fruit brandy §5.22(d)(1), is, among other things, “brandy distilled solely from the fermented juice or mash of whole, sound, ripe fruit, or from standard grape, citrus, or other fruit wine." The standard goes on to discuss pumice additions, etc., which are not relevant to the question.
If real estate is "location, location, location," regulation is "definition, definition, definition." So, you must ask, "What is "standard wine?"
Terms like "stand wine," which contain a modifier, almost beg the reader to look for a definition within the regulations. The regulation could have said wine, but it said, instead, "standard wine," and the notion that the wine must be "standard" reflects a conscious choice to include it. That sends us to part 24, the wine regulations (part 4, do not define the term). Part 24 defines it. Standard wine is "Natural wine, specially sweetened natural wine, special natural wine, and standard agricultural wine, produced in accordance with subparts F, H, and I of this part.. Now, that leads us on a merry chase, which I will not pursue to the end here, but "natural wine" "specially sweetened natural wine" and "special natural wine" are all defined too.
"Natural Wine" is The product of the juice or must of sound, ripe grapes or other sound, ripe fruit (including berries) made with any cellar treatment authorized by subparts F and L of this part and containing not more than 21 percent by weight (21 degrees Brix dealcoholized wine) of total solids. Natural wine is produced in accordance with subparts F and G of part 24.
Now,. things get deep. §24.176, which is headed " Crushing and fermentation," provides, in pertinent part, that , " At the start of fermentation no material may be added except water, sugar, concentrated fruit juice from the same kind of fruit, malo-lactic bacteria, yeast or yeast cultures grown in juice of the same kind of fruit, and yeast foods, sterilizing agents, precipitating agents or other approved fermentation adjuncts."
The addition to juice or natural wine before, during, or after fermentation, of either water or pure dry sugar, or a combination of water and sugar to adjust the acid level" is called amelioration. A winery may only do it within limits. What are those limit? Let's go a little further down the rabbit hole.
§24.178(a), which is headed "Amelioration," provides, "In producing natural wine from juice having a fixed acid level exceeding 5.0 grams per liter, the winemaker may adjust the fixed acid level by adding ameliorating material (water, sugar, or a combination of both) before, during and after fermentation. The fixed acid level of the juice is determined prior to fermentation and is calculated as tartaric acid for grapes, malic acid for apples, and citric acid for other fruit. Each 20 gallons of ameliorating material added to 1,000 gallons of juice or wine will reduce the fixed acid level of the juice or wine by 0.1 gram per liter (the fixed acid level of the juice or wine may not be less than 5.0 gram per liter after the addition of ameliorating material).
There's more on amelioration, but there is also a limit to how far down I want to go to make my point.
However, before leasing part 24, you can also add sugar to sweeten a wine. "§24.179 provides:
(a) General. In producing natural wine, sugar, juice or concentrated fruit juice of the same kind of fruit may be added after fermentation to sweeten wine. When juice or concentrated fruit juice is added, the solids content of the finished wine may not exceed 21 percent by weight. When liquid sugar or invert sugar syrup is used, the resulting volume may not exceed the volume which would result from the maximum use of pure dry sugar only.
(b) Grape wine. Any natural grape wine of a winemaker's own production may have sugar added after amelioration and fermentation provided the finished wine does not exceed 17 percent total solids by weight if the alcohol content is more than 14 percent by volume or 21 percent total solids by weight if the alcohol content is not more than 14 percent by volume.
(c) Fruit wine. Any natural fruit wine of a winemaker's own production may have sugar added after amelioration and fermentation provided the finished wine does not exceed 21 percent total solids by weight and the alcohol content is not more than 14 percent by volume.
So you can use wine to which sugar has been added to produce brandy.
However, before leaving the issue altogether, all of this that raises a question that is not answered clearly. Yes, you could receive in bond standard wine produced at a winery, with acceptable additions of sugar, and you could then distill it, as standard wine, to make a standard fruit brandy. But, could you, as a DSP proprietor, ferment juice, in the manner of standard wine, which would allow the addition of sugar within limits imposed on standard wine, to make distilling material.
I don't know.
If you can, and you did, you would create a need for a lot of records to prove that the addition of the sugar was within the limits allowed by part 24.
So ask TTB. But before you do, understand what the regulations say. When you understand, sort of - and I'd say that is the sort of understanding that I have, a sort of understanding - what the regulations say, you have a clue about the TTB employee to whom you are talking has a clue about what is required, prohibited, or allowed.