Greg Heumann
2520 posts
Dec 24, 2013
8:27 AM
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In THEORY they are supposed to work "just like tubes" and there should be no change in tone. I tried them in a Sonny Jr amp and Kalamazoo- I don't know if it was due to a change in voltage but I didn't like them. I swear it sounded harsher with the copper caps.
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/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
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HawkeyeKane
2228 posts
Dec 24, 2013
8:38 AM
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Glad you posted here Greg. I've been flirting with the idea of getting a WX4 for my Zoo to try different approaches. But harshness isn't an approach that's headlining my to-do list. LOL
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Hawkeye Kane
Last Edited by HawkeyeKane on Dec 24, 2013 8:38 AM
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Tblues1
50 posts
Dec 24, 2013
9:34 AM
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Thanks for the input, Greg.
Not sure I want to use them or not.
Just want to have a spare tube around.
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arnenym
247 posts
Dec 24, 2013
11:06 AM
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I test them in my Bassman.
I could not hear any difference between a GZ 34 and the replace copper cap. Nor on a 5U4GB and the replacement. Maybe it´s more in difference in smaller amps?
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Greg Heumann
2521 posts
Dec 24, 2013
1:43 PM
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Both of my Avengers have 5U4 rectifiers (I THINK - that's without looking.). Maybe I'm just a tube junkie, but I think the "attack" on notes at volume is less harsh with the tube rect. I can't claim to have done a scientific test and I'm freely willing to admit that I may just like the idea of tubes for other reasons - but since they work just great, I see no reason to switch to copper can rectifiers.
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***************************************************
/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
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Rick Davis
2794 posts
Dec 24, 2013
2:00 PM
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I agree with Greg. I prefer the sound of a tube rectifier, especially in a powerful harp amp.
A full-wave diode rectifier like the Weber copper cap can make a positive difference in a smaller class A amp, making it sound slightly punchier to my ear, and maybe a bit rattier.
In my opinion there is not really much advantage to the copper cap rectifiers in general. Some say they will last forever (not really true) but rectifier tubes tend to last a long time, too.
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-Little Rick Davis
The Memphis Mini harp amp
The Blues Harp Amps Blog
The Mile High Blues Society
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tmf714
2290 posts
Dec 24, 2013
2:14 PM
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From the Weber site-
"The Copper Cap emulates a tube rectifier, but it does not require filament power. In the case of a 5U4, for instance, this is a savings of 15 watts. The power transformer will run cooler and last longer. While the filament and coating on the cathode of a tube rectifier are destined to eventual failure, a Copper Cap will last the lifetime of the amp when used properly. Additionally, close tolerance parts are used in all Copper Cap models; no hand sorting is necessary."
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htownfess
283 posts
Dec 24, 2013
4:13 PM
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Well, the main advantage that Copper Caps have is that you can leave one rolling around in the bottom of the amp as a backup to a tube rectifier. The odds are very good that if the tube rectifier blows, it will do so when you first turn the amp on, and of course the laws of nature decree that it shall happen in a venue before a gig, not at home. If you have a safe way to pack a spare tube rectifier along, that's great; but a Copper Cap spare doesn't need careful handling. I think I actually left one under the front seat of my car for several years, but never needed it (laws of nature again).
Electrically, I believe that it's different inductance, or variation in resistance over time, that gives the two types of rectifier a slightly different sound and feel. The pattern of sag over time may be perceptibly different if you are sufficiently familiar with the amp in question, say if you developed the amp or test mics on it and perform on it often. IMO the difference is small enough that most people would have trouble identifying it in a blind test, or at least on a busy stage. I've never seen a comparison chart of the inductances, but from the way they behave, I assume the cap starts and finishes harder and makes a crisper note envelope, i.e., punchier, which has its uses sometimes.
The voltage is a related but separate issue. The Caps I've had have been more consistent than equivalent tubes, but tend to run at the high end of the expected voltage range, again meaning a brighter, punchier amp, especially compared to using a tube rectifier whose output is at the low end of the acceptable range. I think once the difference reaches 5-7%, most people are going to notice, and probably won't like the higher voltage as much for harp.
One exception, however: The WY3GT Cap used to be configured to run 5-7% "lower" voltage output than a NOS 5Y3GT in order to compensate for today's higher AC voltage at your wall outlet. I know that for a fact, because about a decade ago I noticed my WY3GTs were doing that and remarked it to Ted Weber, who said he made them that way on purpose. This makes your small vintage amp's voicing shift back down towards what it originally sounded like in the 1940s-1960s, albeit possibly with the note envelope issue mentioned above--though IMO the lower voltage more than makes up for it, because you're not having to use a corrected power transformer or zener off some voltage or the other tricks we use to "correct" a vintage amp's running voltage. This does not apply to modern amp designs made for today's wall AC voltages, and the higher-power Caps like WZ34s were not made that way--it was just something Ted did with the rectifier most likely to go in a vintage amp played around the house back then, which says a lot about how practical he was. So I liked to use WY3GTs for harp in baby vintage amps, because in one way it gets you a "browner" and more authentic tone. I don't know if they are still making them that way; I would have to buy new ones and measure what they do.
I think the thermistor's effect on voltage inrush is negligible where tube warmup is concerned, as Barley Nectar says, but it is enough to go easier on the power supply filters, beats those up less than a straight SS plug might, and that may keep the amp sounding more consistent over the service life of the filters. YMMV. The thermistor is probably the weak point in the Cap mechanically; I've had a couple fail, but only when performing very unnatural acts like running a Bassman on a WY3GT or using a WR4 to run an AC-30 in true Class A mode (long story; just think about a 15 watt amp that weighs 70 lbs.), where I was using the Cap because I knew the tube rectifier couldn't handle it at all. I think the thermistor is just fine with the rolling-around-the-amp-as-spare mode.
If your amp has the tubes hanging down, like most Fenders, for example, then you really need to use a spring retainer to handle the extra weight of the Cap. Those are cheap and easy to install; otherwise the Cap will try to work loose.
Last Edited by htownfess on Dec 24, 2013 4:16 PM
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Tblues1
51 posts
Dec 24, 2013
4:47 PM
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Great information.
Thanks everybody.
My tubes do indeed hang upside down, but I have good tension in the sockets, as well as retainers.
I'm using a 50W Mission Amps setup.
My intent is to probably use the copper cap as a spare.
I like to keep a spare, but dropped one on the floor, so no more spare.
I'll probably do an A/B comparison when I get it, just to see if I can hear a difference.
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Barley Nectar
221 posts
Dec 24, 2013
8:10 PM
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Stephen, I know of no inductance that goes on in either a tube or solid state rectifier.
Inductance is the generation of electricial energy due to a conductor being in a varying magnetic field.
Examples of inductors are transformers, chokes and coils.
Maybe I'm missing something here. Please explain. Thanks old buddy...BN AKA Goose
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htownfess
284 posts
Dec 25, 2013
5:28 AM
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That's what I was trying to remember and why I qualified the statement, Goose--then it's not inductance itself but the lack of it that I was thinking of, like the way a resistor does not precisely mimic a choke when used as a substitute for one in a power supply, or the way a speaker's resistance varies under load despite what a multimeter says at rest. Those are analogous to how putting a sag resistor downstream of SS diodes as in a Copper Cap does not behave exactly the same as the tube rectifier with the same nominal sag does, I guess is what I should have said.
It reminded me that Monday I noticed a guitarist lamenting that he can no longer get certain alkaline 9v batteries for his pedal--probably more of a rarefied cork-sniffing phenomenon than the tube/Cap difference, but another example of how nominally similar power supplies can have perceptibly different characteristics if one is sufficiently familiar with/sensitive to the rig in question.
P.S.: I'm afraid that Gibsonette is still languishing, though my cat feels it makes a stylish pedestal for her food dish. Speaking of inductance, the big delay there is dealing with a field coil that needs reconing; thanks for reminding me to check on current reconers' reps and what people use for a choke when subbing with a p.m. speaker.
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LSC
563 posts
Dec 25, 2013
9:15 AM
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@Greg- I'm a tube junkie as well and would no doubt prefer a tube rectifier even if it's just perception. Is it a straight up swap on the Avenger?
Thanks kindly.
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LSC
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Udderkuz03
34 posts
Dec 25, 2013
9:28 AM
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I distinctly remember hearing that all amps(even from the same make or batch) will react differently...not trying to get you to throw away money...someone said you should find out for your amp, not someone else's experience....
Last Edited by Udderkuz03 on Dec 25, 2013 9:29 AM
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