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Topic: More on Capacitors for Fender Twin |
Brad Sarno
From:
St. Louis, MO USA
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Posted 15 Apr 2002 2:01 pm |
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I've been working with the classic Sprague Orange Drops (series 716p or 715p) which are a "film and foil" type, not metalized film like the mylars are. The Orange Drops are nice and clear and sound great. BUT, there is a next level that I've discovered. The Tube Audiophile nuts are hip to these but guitarist tend to stop at the Orange Drops. I think steel players deserve to hear the next echelon of tube amp fidelity.
I've been using these Angela film and foil caps for a while and they are truly superior to the Orange drops. They sound a bit smoother and richer, perhaps less bright but no less detailed. Very warm and musical sounding. Highly recommended. BUT, here's what I'm really diggin at the moment.
They've got these foil caps that use paper in oil as the dielectric instead of polypropylene or mylar or polystyrene. The Paper in Oil cap's have always been expensive but now Angela has contracted a company to make them for much less. Still not cheap, we're talkin $4 to $6 per cap and on a Twin that can add up to almost $100. But wow the tone. These paper in oil/foil caps sound incredible. A hair brighter than the tinfoil caps, warmer than the Orange Drops but way way richer and more lively in the midrange where all the music takes place. I've never heard a steel sound so good thru my 15" Black Widow loaded '69 Twin.
Check out Angela Instruments at www.angela.com and look up the Sequa Paper/Oil caps or the Angela Tinfoil caps. Some people have no idea how beautiful and clean and musical a Twin can sound when they've only heard them with the old stock capacitors. The stock Fender is comparitively dark and unclear sounding. They can really open up.
Also, the most critical cap of all to upgrade is the .022 ceramic disk cap right after the vibrato channel. The whole signal gets bottlenecked in that cap and the crappy sound of ceramic disks gets smeared all over your tone. When you replace all the signal caps in a Twin with good ones, the results are astounding.
Brad Sarno
St. Louis
Mullen U-12/Twin/BW |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 15 Apr 2002 4:23 pm
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Brad, ever tried changing that .022 ceramic to a .05 orange drop?  |
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Rick Barber
From:
Morgan Hill, Calif. USA
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Posted 15 Apr 2002 5:07 pm
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You bring up some interesting comments. Listening to the amp results is good. No doubt a lot of this has to do with a capacitor that has resistive properties to it ( finite Q) and also nonlinear properties that may actually vary as the voltage is varied with the voltage across it. Probably another way to look at a cap would be to have it drive a slightly inductive load and look at its transient response using a step waveform and look at rise and falltimes and ringing amplitude and decay rate. Its internal resistance would certainly affect the rise and fall and insertion loss versus frequency. Is that to say that no capacitor is just a capacitor but its really a "network" of components that has capacitance and all kinds of excess baggage like "parasitic" resistance, inductance, nonlinearity with voltage, heating effects.
I have a question for you? If we took todays modern caps and added in some extra elements around it could we actually make them "sound" like the NOS vintage ones??
Why do we use caps --- for blocking DC and for affecting tone (frequency response)right. Since caps are constructed in all different ways using different materials then it figures that the results may sound different because a cap is more than just a cap (it is really a network between those 2 leads).
I guess if you think about it , I'm sure the manufacturer did his final Quality Insurance by listening to the original design using the best optimized parts that he/she could find at the time ---- like paper and oil. I'm sure circuits that have higher Q components driving inductive loads have a lot more high frequency content that maybe the ear picks up as "not" warm.
Could we take modern caps and add in some "baggage" like series and shunt resistance around them etc and start making them sound like the old ones. The problem I see in using old designs is not how good it makes things sound but rather how high a price do we pay for getting it all in one magic component.??
I'm rambling, I'm tired.
Best Regards,
Rick Barber (not a capacitor engineer)
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Steven Welborn
From:
Ojai,CA USA
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Posted 15 Apr 2002 5:07 pm
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| Brad, I'm no 'tronics techie but i can tell caps from resistors and such. So what are you doin...replacing ALL the various small, medium, large caps in both pre and power stages? Unsoldering and resoldering them into the circuit boards?(duh) Something I guess you can get away with only with these older type nonprinted board amps. I used to own a 69 twin ages ago but i forgot what their innards were like. I remember replacing a charred resister now and then.You do the big filter caps too? Thanks,SW [This message was edited by Steven Welborn on 15 April 2002 at 08:07 PM.] |
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Glenn Austin
From:
Montreal, Canada
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Posted 15 Apr 2002 7:19 pm
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| While I have never recapped a Fender Twin, I have recapped a couple of Neve modules and a couple of LA3A limiters. The difference in sound quality is night and day, and that's just with regular electrolytic capacitors. The biggest problem with older gear is that every part in there has a + and - 10% tolerance, if not more, and all those values will drift with time. So you end up with an amp that sounds very different from when it was new. Of course if Fender did the same thing as Brad is doing, they would end up with one very expensive amplifier! |
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Brad Sarno
From:
St. Louis, MO USA
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Posted 15 Apr 2002 10:03 pm
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To answer your previous question. This is what I do to every fender amp I have. Before I modify anything or alter any values, I simply replace old stuff with new. I first replace the power supply filter caps with Sprague Atom electrolytic caps of same value. Old electrolytic caps are the first to go bad. Then I replace ALL of the signal caps. Any cap that is directly in the path of the signal. You can recognize them in an old Fender as they are the fat round and often blue plastic ones usually of a value like .1uF or .047uF or .022uF. I also replace all the little white 25uF Mallory electrolytic caps that feed the bias circuit. It's really simple to find a schematic and block diagram on the internet. It's also easy to open the Fender and just read the old values off the caps and get new ones of your choice keeping all values the same. You can get caps with higher voltage ratings but not lower. They ALL sound different so it's really up to taste. No capacitor is without coloration or "tone".
You can pull out the old caps from the board but I find it easier to clip the leads of the old ones leaving about a half an inch and then wrapping and soldering the new caps to the old leads. This is easier and should be just fine.
Just remember that the caps in the amp can hold a very high charge after the amp is off. The zap can really sting sometimes. And remember that you should probably never have a tube amp open and plugged in unless you have experience around high voltage. If you must for biasing and whatnot, ALWAYS leave one hand behind your back. That's what they used to teach everyone in school. This prevents you from completing a 450v circuit thru your heart.
Enjoy,
Brad Sarno
St. Louis |
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Steven Welborn
From:
Ojai,CA USA
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Posted 15 Apr 2002 10:29 pm
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| Thanks for the tutoring Brad.Particularly a cool tip about clipping those leads. Any reason why an old transistor amp wouldnt benefit just the same as old fenders from a similar recap job? I've got an old HVfet500 Evans (purchased used few years ago) that doesnt seem to have all the stuff these amps are unanimously praised for, e.i. clarity, bass response. This amp has many miles on it. |
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Bill Terry
From:
Bastrop, TX
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Posted 16 Apr 2002 6:37 am
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| Quote: |
| Is that to say that no capacitor is just a capacitor but its really a "network" of components that has capacitance and all kinds of excess baggage like "parasitic" resistance, inductance, nonlinearity with voltage, heating effects. |
I remember a circuits class I took where the professor made the point that every component had inductance, capacitance and resistance, regardless of whether the component was an R, L, or C. His point was that if you ignore those factors, you may not get the circuit to perform the way you intended.
Ever stopped a circuit from oscillating by putting a finger on a cap or resistor (not even the actual lead, just the component body)? Doesn't take much sometimes.
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Brad Sarno
From:
St. Louis, MO USA
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Posted 16 Apr 2002 8:15 am
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To answer Stephen's question regarding upgrading the signal path in a solid state amp. Sure there are places to fix up a solid state amp but you'll probably find that there are far fewer signal capacitors in a solid state amp. In a tube amp, by its own nature, each gain stage or tone stage has very high DC voltage on the signal path and a capacitor by its own nature will block the DC voltage from passing on down the path. This is why your signal in a tube amp may pass thru as many as 10 capacitors. Thus the tone quality of caps gets multiplied.
In a solid state amp there is this issue of DC voltage bias on the signal path but usually it's much smaller and only needs to happen at one or two stages, not ten. But yes you can improve the path, I do it all the time. The problem you may run into is that often times the coupling stage in a SS amp uses a very high value cap, like over 10uF. When you get into values like this it's no longer practical to use a good audio film cap because it would have to be so physically large and expensive that it's not practical. What you'll often find is that an electrolytic cap is used for coupling. Sad thing is electrolytic caps generally suck for audio and sound quality. But what you can do is leave the original cap alone but add a smaller value film cap, say 1/10 the value, and solder it across the electrolytic cap. What this does is lets the electrolytic handle the bulk of the signal but the film cap will pass the higher frequencies is a much more clean way than the single cap could do alone.
Really this all depends on the particular design of the amp. The best thing to do is get a schematic and follow the path of the signal from the guitar to the output. If you see a cap in there, directly in the path, check it's value and see what you think you can do.
For whatever reason, I find that tube amps are more sensitive to caps with regards to tone. Maybe it's the high voltage or again maybe it's the fact that there are so many caps in the path.
Brad Sarno
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