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Post by RandomHero on Dec 8, 2006 8:00:50 GMT -5
I'm interested in their 50-watt combo. If it's got the same preamp as the Dual and Triple Recs, I'd be interested in buying it. But has anyone had any experience with it otherwise?
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Post by ChrisK on Dec 8, 2006 18:29:49 GMT -5
I've heard a lot of young'ins trying to play thru them at Guitar Center. ;D
Although I had a RectoVerb and liked it (the Recto moniker might indicate some familial relationship), and current have a Mark IV (and have played thru some others), I know that Mesa do voice their preamps differently betwixt the various models.
Sans real testing, you might want to give them a call. They tend to be helpful.
I actually like the (relatively) new Roadster myself.
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Post by ranchtooth on Dec 9, 2006 10:42:24 GMT -5
I've tried the single and the triple rectum friers, and in both cases I was impressed. There is quite an audible difference between the two however, being that the triple recto seemed to sustain for days and days. I don't really know the specifics of how the tube rectifiers work, but it seemed to me like they gave awesome natural compression to the guitar sound.
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Post by ChrisK on Dec 10, 2006 17:10:23 GMT -5
That they do since they're tube rectifiers and hence, fairly crappy rectifiers.
Like all tubes, they have significant plate resistance and plate saturation characteristics. As a result, the delivered plate voltage sags as a function from the effect of essentially limited plate current to the output stages.
Since the initial drive signal level is the highest, this current limiting occurs reducing the effective output power. As the drive signal is naturally reduced by note decay, the output power rises back to the normal level effecting a compression sound.
Also, the extra gain stages in the Mesa preamps give wonderful compression in that the stages are overdriven for most of the usable signal level. Once you fully overdrive a preamp stage (cutoff and plate current saturation), it sounds essentially the same as more overdrive is applied. Until the drive level reduces to that which does not cause full overdrive, compression is.
You know, that Santana "violin/saxophone-like" sustain.
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Post by vonFrenchie on Jan 2, 2007 17:06:12 GMT -5
Cant rectifiers be built with diodes instead of vacuum tubes? If so would this make the rectifier less... well in your words "crappy"?
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Post by ranchtooth on Jan 2, 2007 17:22:07 GMT -5
I think they use 4 diodes arranged in a diamond-ish formation... giving full solid state rectification. I believe its called a wheatstone bridge.
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Post by UnklMickey on Jan 2, 2007 21:46:54 GMT -5
...I believe its called a wheatstone bridge. that's just called a bridge rectifier. a Wheatstone bridge is a whole 'nuther animal. vF, using 2 solid-state diodes to replace the 2 tube diodes, in a full wave CT supply can and has been done. it gets rid of most of the losses seen across the tube rectifiers, and the most of the sag. the result is more power available, and a "stiffer" sound. this is not always seen as an improvement. cheers, unk |
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Post by ranchtooth on Jan 3, 2007 16:20:04 GMT -5
Thankfully the mesas allow you to switch between diode and tube rectification. Talk about versatility!
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Post by ChrisK on Jan 3, 2007 19:47:28 GMT -5
Indeed. A Wheatstone bridge is used for "balancing" purposes in older test equipment (not to mention sine wave oscillators).
A German fellow actually "invented" the full-wave bridge rectifier many years ago, but I don't remember his name.
True, since tubes are lousy rectifiers and the sag from a tube rectifier contributes to the compression in a tube amp (along with preamp stage saturation). You can buy diode-based tube rectifier replacements that emulate the lousy response of a tube rectifier.
Actually, the full-wave bridge topology is better than the full-wave center-tap topology since better transformer utilization occurs (current flows in the winding during both half-cycles) and only one winding is requires (no center-tap).
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Post by UnklMickey on Jan 3, 2007 20:03:21 GMT -5
...A German fellow actually "invented" the full-wave bridge rectifier many years ago, but I don't remember his name.... Graetz? |
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Post by ChrisK on Jan 3, 2007 20:31:32 GMT -5
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Post by UnklMickey on Jan 3, 2007 20:35:33 GMT -5
...A German fellow actually "invented" the full-wave bridge rectifier many years ago, but I don't remember his name.... A British fellow actually "popularized" the Wheatstone bridge many years ago, but I don't remember his name, either. 
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Post by sumgai on Jan 5, 2007 6:09:31 GMT -5
And so when is a tube rectifier not a diode?
Answer: all rectifier components are diodes, whether they operate in a vacuum or otherwise. There are only two elements in the component, hence the di in diode.
Remember (I wish I could!), in electronics, if you aren't on the same wavelength as the person you're talking to, one of you is very likely wrong. Such miscommunication just might cause a meltdown of something expensive - or worse!
sumgai
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