General improvement of a mass produced amplifier

[Pedro Vecino]

The term "upgrade" (systematic) to me makes no sense. The quality of the components can be regarded from several aspects: mechanical strength, response to different temperatures, electrical reliability, tolerances, etc. but the audio response (always dependent on circuit) is unpredictable if no exists prior experimentation.
Orange drops 715p are very good capacitors, but I prefer to keep them away from classic Marshalls, silver mica are very transparent, but I prefer to keep them away from classic Fenders, Russians 5881 are very strong but its compression (premature and non linear) do not invite me to use ... There are always exceptions, but everything must have a reason (musical, security, reliability, or whatever)
The basic idea is that with the change of any component that establishes a perceptible difference always sacrificing something. Have control over it is very important because the natural tendency is appreciate the new and forget the old. At the sound there are many things to attend.

[Chuck H]

So it's pretty much like I said, with a good addition. Speakers, tubes and transformers are the places to make improvements to stock cheap and mid priced amps. This, of course is because these are the most expensive parts and so this is where custs get made by MFG's chasing a bottom line. As to component quality I would illustrate by saying that with available parts the tonal difference between a cheap capacitor and a paper in oil boutique capacitor is truely tiny and in many cases immesurable. But not so with speakers transformers and tubes. With available offerings of these items there is a vast tonal difference between cheap parts and top shelf.

The addition being that circuit changes that alter an amps function can certainly improve performance. This is especially true because tone is a subjective matter and what works for you may not be how an amp was built, but could be how you change it.

[jrfrond]

I'd like to relate a recent experience with a large manufacturer's PTP reissue amp and a large profile client here in NYC. I won't mention either, because I don't need headaches from the manufacturer, so just follow me.

The client needed these two BRAND NEW amp combos split for separate cabinets and heads. No biggie. That's just a matter of ordering new head cabs and some minor woodwork. The manufacturer went ALMOST all the way on these $2K (street price) combos, including Mercury iron, but fell WAY short on the passive components, using the same cheap Asian carbon-film resistors that they use in their production amps, as well as crappy coupling caps. We won't even discuss the Chinese rectifier tube. I did a wholesale resistor and cap replacement with carbon comps and quality tubulars. I also installed NOS tubes. These amps, which were just OK and in the ballpark, really came to life with the vintage tone and feel that you'd expect from these 12W classics. I was actually so pissed off at the passive component issue that I complained to the manufacturer. Of course, I don't expect a manufacturer to install NOS tubes, but they turned out to just be the icing on the cake. The stock tubes even sounded much better.

I've replaced resistors and caps on other amps, and it DOES make a difference. You CAN improve a mass produced tube amp, no doubt.

[Chuck H]

I can get behind this better than most here, and I do believe I can hear the difference between caps of different construction. Enough so for me personally that I do have preferred caps for different amp types, but...

The difference really is tiny. I do have to question how stringent your comparison was. You did say that even with the stock tubes the amps sounded notably better, but was this after the full upgrade with NOS tubes, a bias adjust, possibly better filters, upgrade speaker, etc., and your sensibilities had already been swayed when you plugged the old tubes back in???

All I'm saying is that the mind can play tricks and other factors are at hand. IMHE: Same amp, same tubes, change only the coupling caps and the difference is really small.

And carbon comps do have properties that are audible but only in certain places where highish voltages drop across them. Other than that there is no measurable audible difference between resistor types. Noise being the exception. In the places where carbon comps have the most effect on tone they also contribute the greatest amount of hiss and noise. So it's pros vs. cons there. And again, the difference is tiny.

The ONLY way to judge is to build an amp with "adequate" grade resistors and caps, record the tone with a dummy track, then swap the components for more tonally accepted resistors and caps that have been checked for accuracy against the originals (with no other changes to tubes, filters, settings, bias, etc.) and record the tone with the same dummy track. Then have a group of listeners who don't know which is which grade the recordings. As far as I know this has never been done. And that's good news for the guys who pedal paper in oil voodoo caps at US $30 a piece.

Do what makes you feel confident in your product. That's what I do. But sometimes when I'm straining to hear the finite differences in any component I have to wonder if all things considered I'm not just blowing smoke up my own ass. I use Sprague 715P's or Mallory 150's depending on the amp. I do think I can hear a difference between the two (though I've never blind tested it) and I do think they sound better than bad caps (though I've never tested it) but all this paper in oil, cryogenic treated beeswax and NOS Mustard cap business is pure bullshit, IMHO. Polyprop's sound a little different from polyester and good caps sound a little better than grossly bad ones. But that's as far as I can take it by ear without stringent testing.

JM2C

[Five_E35]

I've read a number of improvement stories where someone compares a reissue to an original, then does a bunch of so-called upgrades, including some of the mods that have been used on that particular amp for years. And low and behold it now sounds better than before and more like the 'original'. Problem is, the original wasn't stock either.

IMO it's worth experimenting with tubes, especially NOS in critical parts of the amp. They do make a big differnce, plus they last a LOT longer. Large manufacturers can't use NOS tubes, otherwise there wouldn't be any available to the rest of us.

[Jazz P Bass]

In my not so expert opinion, the very least you can do for a mass produced amp is resolder it.
Some of the wave soldered crap I see day in & day out makes me want to scream.
The biggest fault is the preheat of the boards.
(don't even get me started on laid over leads that touch the next via)
Here is a nice place to skimp.
Production is up.
The amps work when final tested.
Now ship them 8000 miles.
Combo amps are the worst, everything in the amp vibrates.

[jrfrond]

In my not so expert opinion, the very least you can do for a mass produced amp is resolder it.
Some of the wave soldered crap I see day in & day out makes me want to scream.
The biggest fault is the preheat of the boards.

Not to mention RoHs solder!

Audiometric testing is all well and good, but you cannot quantify "feel" on a piece of test equipment, and THAT is what some of the best mods accomplish. The actual tonal variation might be extremely subtle and perhaps not even palpable, but the "feel" aspect can influence in player in a big way and make the PLAYER sound better as a result. Find THAT on an FFT!