Sprague vs. Mallory caps

[pvsage]

Hi all, I just joined this forum, and am brand spankin' new to valve amps, so please bear with me.

I just purchased a Valve Junior and am looking forward to modding it. I found a couple of articles from Premier Guitar about modding the VJr to sound like either a Fender Champ or a small Marshall, and among other changes, they recommend replacing the coupling caps with Sprague 715 Orange Drops (Fender) or Mallory 150's (Marshall) of the same value as the stock caps.

I was hoping you could help me understand how the different types of caps available from different manufacturers affect tone when used as stage couplers.

Peter

[Schwalbe]

I wouldn't expect Mallory caps to make a Champ sound any more like a Marshall than about any other capacitor would. Common lore states Sprague 715 are brighter and more hifi than Mallory M150's. If there is a difference it's fairly small, some folks find it inaudible.

[pvsage]

I wouldn't expect Mallory caps to make a Champ sound any more like a Marshall than about any other capacitor would. Common lore states Sprague 715 are brighter and more hifi than Mallory M150's. If there is a difference it's fairly small, some folks find it inaudible.

Aah...hence the use of the Spragues in the "cleaner" Champ mod and the Mallorys in the "dirtier" Marshall mod. I'm sure most of the difference in tone comes from other component substitutions that involve actual value changes, and the specific brands of caps were named to add a "mojo" factor. Thanks!

[yankeerob]

It's all much of a muchness - I use Vishay Roederstein MKT series - which for all intents and purposes are Mallory 150's - they're polyester film axial caps that are surprisingly close tolerance and have a generous voltage rating - they sound a little bit smoother where clipping is present whereas OD's can sound harsh but they all do the same thing

[pvsage]

I'm guessing the MKT's are also similar to the Cornell Dubilier 150 series? Just making sure I know what my options are at Mouser, in case they obsolesce the rest of the MKT's.

What is the easiest way to test for foil orientation?

[soundmasterg]

What is the easiest way to test for foil orientation?

I wouldn't even bother honestly. They used to have the foil orientation on the old paper and polyester caps but they got away from that, probably because it isn't necessary with modern caps. I certainly haven't noticed any perfomance issues hooking up the coupling caps any which way.

The difference between the Mallory 150's and the Sprague Orange Drops is in their composition and type of construction. The M150's are metallized polyester, while the Orange Drops come in a number of varieties and some are polyester and some are polypropylene, and all are film/foil construction. The 715P and 716P are polypropylene and the 225P's are polyester. The composition of the caps (polyester or polypropylene) and the type of construction (metallized vs film/foil) are what make the biggest difference in the sound and performance of a given cap. Film/foil caps are always a bigger physical size as compared to metallized caps because their construction method demands it. Polypropylene caps tend to have more high frequency content than polyester caps, but these are all generalizations, and they are best discovered by experimentation. The effect of changing from one cap type to another is a very subtle thing, that when added up, or done strategically inside an amp can affect the overall tone, but not to as great a degree as changing tubes speakers, or transformers. It is certainly more important in a hi-fi amp, but in a guitar amp it doesn't matter nearly as much to get the insert your "Best" brand here cap you can find. You'll get much more mileage out of tweaking voltages and circuit design. IMHO of course.

Greg

[Enzo]

ANd in a guitar amp, things generally are rolling off by 5kHz, so those mighty extended highs don't come out the speaker.

Cap brands will have a lot less affect than cap values. I'd say don't make cap brand a major focus.

ANd foil orientation? Oh my. At audio freqs, the cap looks like a wire with a lower freq limit. it doesn't matter which end goes where. If it were a bypass cap in a short wave radio, maybe then. But when the cap is taking a audio signal from one tube to the next, both ends are exposed to the ambient electrical fields, and shielding one end with the other accomplishes nothing. Neither end is grounded, so placing one end "nearer ground" is useless. It looks nicer if all the parts face the same way though.

I would suggest as a new convert to tube circuits, that it would make a lot more sense to focus on how the circuits work and what the parts do, than focusing on the little tweaks with the vanishingly small effects.

[dai h.]

Different types can make a bit of difference, but getting and trying a decade box so you can switch cap values would probably be a lot more effective in getting a sound difference (and fun) rather than trying out a billion different types of .02uFs, etc.

[pvsage]

Thanks for all the advise, guys! So far, I've made some modest mods to my EVJr to "Marshallize" it a bit (Hi-Z input, dropped the cathode bypass caps in the gain stages by a decade to tighten the bottom end a little), and I'm happy enough with it to leave it be for now...the next step for me will be building a Valve Junior/Les Paul Jr. copy on a custom turret board, then modding the f*** out of that. This is where I'll be applying what info I've been able to gather here.

I do have one more question related to caps: Mouser seems to like Cornell Dubilier for its M150-type capacitors, Vishay Sprague for 715 OD's, and Xicon for electrolytics. Are any of these sources known for lemons?

[dai h.]

I doubt in general that you'll get a bad mass-produced part especially for ordinary parts like resistors and capacitors which seem to be made in the bazillions ( = lots of $$$ incentive to make sure they get things right). Sometimes it happens as in the case of those aluminum electrolytics for computers a few years back, but I wouldn't expect new parts to be bad usually. New tubes might be one of the weak links since the quality control doesn't look very good (they need to be tested AFTER they leave the factory).

[pvsage]

Ah yes...The Capacitor Plague. From what I've read, that was a case of corporate espionage gone bad...but that's a different story, having little to do with tube amp design.

[soundmasterg]

By an M150 type part, I assume you are talking about a polyester cap? The M150 is made by Mallory and it is metallized polyester, but there are lots of companies that make that type of capacitor. Antique Electronics Supply (www.tubesandmore.com) is another good place to shop besides Mouser, and they have their own quasi house brand of polyester caps that sound and work just fine, and are a bit cheaper than Mallory 150's, which they also carry.

Vishay Sprague IS the manfacturer for Orange Drop caps of all types. The 715P is a polypropylene film/foil cap, as is the 716P, but the 716P is higher quality and generally is considered to sound better. Personally, I usually like polyester caps better for most guitar amp builds. YMMV on that score.

I've had good luck with Xicon electrolytics.

Greg