Molded Mojo?

['64DlxRvb]

I've got a few early 60s blue molded caps set aside for me by a friend if I want them. There's enough to do my DR that I built with Orange drops because I didn't know better at the time and all I ever heard was Orange drop Orange drop Orange drop... Question: Worth the time and money? (He said I could have them for 10 bucks a piece.) They all test well within spec. I got bored the other day and decided I want to redo it and make as exact a copy as possible. I know the dual astrons won't happen, but other than that, an exact copy of a '64.

Thanks

[Tone Lover]

If your ears are like mine you wont hear the differance anyway. If there's something you dont like about the sound change the circuit
Bill
PS. this should start an interesting conversation. (LOL)

['64DlxRvb]

PS. this should start an interesting conversation. (LOL)

Yeah, I was afraid of that! But seriously, you guys know your shit, so I thought I'd ask here. It's not so much a sound thing as a "true copy" thing. Although mine does seem a bit brighter to me than an original right next to it. But that could be speaker age, wood type / age, any number of things. I am rewiring it to clean it up anyway, and that's what got me thinking. I want to do it as close as possible to the real thing. Correct wire type, color and all. I just think it would be neat I guess. And keep me from spending a ton of money on a whole new project!

[rp]

They should be saved for a righteous restoration where $10/cap would be bargain. IME any old molded, blacks, greens, reds, pretty much have the same mojo - addition of warm swirly 3Dness and that authentic organic balance to the tone.

To get what you want or at least to fully exploit the benefit of old caps you need to have everything else in place - carbon comps for starters but that's easy, harder is voltages need to be darn close to the schematic, iron that sounds right, nos tubes, and hardest of all speakers, most modern speakers are too sensitive. If your goal is a dead-on clone it's that last 10% that matters, if you aren't doesn't matter that much, 90% is still a pretty fine amp.

So, I bet shotgunning w/ all blues will improve your amp but seems a waste of rare parts, I'd worry first about voltages, iron, tubes. Did you use 715s or 6PS? Try 225s, or 150s to knock the edge off. Maybe those Jupiters actually sound right, though they cost as much as vintage so it's a wash there. Also the crappy old disc caps in the rev and vib matter too, upgrading these adds to the brightness, clangy skewed tone, and might cause you to hear the vib tic.

BTW old caps can leak and be WAY off spec, a whole batch can suck, so that's just a money gamble you must accept. Best here is get the amp perfect then start adding a stage at a time. If it sounds good keep adding. If it sounds bad you'll know which stage to check for a rotten cap.

[Gibsonman63]

I have a 1972 Super Reverb that never sounded right to me. It had been maintained for me by a few techs before I got fed up and learned how to do this stuff myself. After a couple of years of fiddling around with it, following bad advise and thinking I actually knew something, I ended up with metal film resistors and orange drop caps, which produced an unbearable ice-pick like tone.

I finally gutted the amp, replacing all of the PVC coated wiring with cloth covered, carbon comp resistors etc... The blue molded coupling caps were long gone (stupid me) so I went with Jupiter caps.

This amp is now easily my favorite Fender amp that I own. The ice-pick tone is gone and the tone is nicely balanced. I am sure that it wasn't any one thing that made all of the difference. The Jupiter caps were $3-$6 dollars each and I believe Sozos are in the same ballpark, so I would be tempted to spend a couple of bucks more for the blue molded. You could always swap them out in an evening or two if something more vintage and deserving comes along.

[rp]

I have a 1972 Super Reverb that never sounded right to me. It had been maintained for me by a few techs before I got fed up and learned how to do this stuff myself. After a couple of years of fiddling around with it, following bad advise and thinking I actually knew something, I ended up with metal film resistors and orange drop caps, which produced an unbearable ice-pick like tone.

Similar life trajectories.

I finally gutted the amp, replacing all of the PVC coated wiring with cloth covered, carbon comp resistors etc... The blue molded coupling caps were long gone (stupid me)...

Don't take it out on yourself, we must all start and learn somewhere, but never forget your sins and vow to respect and restore any old amp great and small that crosses your path. Luckily(?) old shit has gotten so valuable now that you probably won't have to throw yourself under a tank to save civilization.

[Tony Bones]

I've got a few early 60s blue molded caps set aside for me by a friend if I want them. There's enough to do my DR that I built with Orange drops because I didn't know better at the time and all I ever heard was Orange drop Orange drop Orange drop... Question: Worth the time and money? (He said I could have them for 10 bucks a piece.) They all test well within spec. I got bored the other day and decided I want to redo it and make as exact a copy as possible. I know the dual astrons won't happen, but other than that, an exact copy of a '64.

Thanks

Orange drops are OK in the signal chain but they really aren't suitable for driving the grids of output tubes where the voltage swing and mainly currents are higher. A good cap there makes more of a difference... might even say it's necessary.

['64DlxRvb]

Thanks for the input guys. I think I'll pass on the moldeds, and like others said, let somebody who needs them to restore an actual original amp have them. It would piss me off if I needed them and they were in a clone. Anyway, mine are 715s. At the time I built the amp I though an orange drop was an orange drop. I may buy a few singles of different brands and try in one stage at a time as suggested. It could just be all in my head.

[Structo]

Orange drops are OK in the signal chain but they really aren't suitable for driving the grids of output tubes where the voltage swing and mainly currents are higher. A good cap there makes more of a difference... might even say it's necessary.

What type of Orange Drop?

Polyester or Polypropylene?

What working voltage?

[pdf64]

Orange drops are OK in the signal chain but they really aren't suitable for driving the grids of output tubes where the voltage swing and mainly currents are higher. A good cap there makes more of a difference... might even say it's necessary.

Except for a few >300 watt bass monsters, I can't think of any amps relevant to these forums able to pull the tube grid potential higher than its cathode (other than to a trivial degree), ie they're in class A1, AB1?
So I can't see that the current swing can be much, eg a peak value of a few mA at full drive.

I agree that it can be very beneficial to have good caps there. My feeling is that the output tube control grids are one place where I want coupling caps made in a modern high quality facility, rather than decades old 400V type (that have probably been subject to >400Vdc on numerous occasions).

[Tony Bones]

My personal experience is: Orange Drops in a tone stack sound OK but at the grids of even EL84's they sound harsh and wooly. The big molded caps sound good. Better yet, a paper in oil like Vitamin Q. On the other hand, a Vitamin Q is wasted in the tone stack and won't improve things much over an Orange Drop type of cap.

Just my experience, 2 cents, opinion, whatever.... that's all I'm saying.

[Leo_Gnardo]

2 things: the current Mallory 150 caps are supposedly the same as those 60's "blue hot dogs." I like 'em, nice clear tone and reasonably priced besides.

AND your film caps are basically doing two things. 1. Passing signal while blocking DC - you'll hear more of what a cap is doing in this position. B. Filtering - that's EQ whether a fancy tonestack or just a tone cap. In this instance you're throwing away frequencies you don't so much want to hear. The cap more or less acts as a conduit for that frequency range to ground, so it's a selective chute to the rubbish bin. Selection of cap "quality" less critical in this application. In order to not have to stock lots of different caps I use Mallory 150 for both purposes, as did Fender. But if you have to choose, I'd recommend putting your better quality caps in signal-pass positions, and lesser quality in the filters.

['64DlxRvb]

Thanks for that info. I think I'll give the 150s a try.

[rp]

2 things: the current Mallory 150 caps are supposedly the same as those 60's "blue hot dogs." I like 'em, nice clear tone and reasonably priced besides.

I've opened some moldeds but not blues or yellows, and they were film and foil, aren't the 150s metalized film? Be great to know that the Ajaxs were metalized film but then why so big? The ones that puzzle me are original mustards that are film and foil but as small as metalized films - secret patent formula from 1965?

And what does Jupiter use to make them intentionally big in 2014? After Gibsonman63's recommendation I will try Jupiters but I'd be less skeptical of Sozo or Jupiter if instead of cryptic pr they laid out construction details. I'm thinking both Sozo and Jupiter could do us all a favor and solve "the big cap debate". Apparently they KNOW why two similar caps of the exact same value can sound different - tone tuned caps is their business model, and they actually do seem to know how to knock the cold/bright/hard out of a cap. Sure wish they'd tell us. Info makes me spend my money.

[martin manning]

Gibsonman63's experience is more than just caps. "Icepick" is too much HF, which is remedied by bleeding it to ground. This can be done by putting small caps or R-C treble bleeds in selected locations, or following a practice of running leads close to the chassis to increase capacitive coupling. There may be some effect due to one insulation type vs. another, but I don't know how significant that would be. Carbon comp resistors are going to be noisier than MF (a negative, IMO), but may, in theory at least, contribute some favorable 2nd harmonic distortion in one or two locations where the voltage swing across them is high. There is more than one type of "Orange Drop," with PP 715P said to be brighter than 6PS, but then some prefer the more temperature stable PP, and presumably compensate for that elsewhere.

The volume of a cap for a given capacitance and voltage rating is determined by the combination of area, dielectric constant, and thickness of the film required, and the thickness of the foil. Caps of metalized film construction obviously have an extremely thin "foil" layer, and given a high-dielectric constant film would make a very small cap. M150's are an example. Boutique caps are typically film-foil, so if they are large that is simply a result of the materials selected. I've only seem pictures of opened-up mustards ( http://mhuss.com/Capacitors/ ), but they seem to have used a very thin film.