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Old 5th November 2002, 07:58 AM   #1
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Default Tube rectifiers

i hear many things about tube rectifiers being better than solid state diodes. I tend to use them in the near future but just don't know which tube rectifier is good to go for. I hear that differents models have different sound.
i tend to use the tube rectifier for a pre- amp stage deliver juice to 2* 12 ax7 and 12at7
any help would be great
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Old 5th November 2002, 08:29 AM   #2
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I have a great fondness for the TV damper diodes like 6D22S, 6CH3/6CJ3, EY500A etc because they sound the best out of everything I've tried. Cheap too ($US5-7/tube). The two drawbacks are they are single diodes so you need 2, and they have a healthy heater requirement. If your power trans has a 5V 3A heater winding the 6D22S/6CJ3 will work fine even though it's under the 6.3V 3.6A nominally required. They are way overkill for the application, but are cheap and available.

If you just want an octal dual diode, 5AR4/GZ34 in whatever flavour you can afford.

Do yourself a favour and use a choke input irrespective of the diodes chosen.

Cheers
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Old 5th November 2002, 11:56 AM   #3
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Default RECTIFIERS

Hello,

In case you want to stick with the more classic types for preamp use:

The 6AX4/EZ81 and 6X4/EZ80 are both duo-diode types that were often used for this apllication.
Prices will vary so look around before you decide.

The TV damper types are an alternative and offer low voltage drop due to lower Ri but you'll need more of them:

I like to use them where I draw sufficient current and use a Graetz bridge full wave rect.



Quote:
Do yourself a favour and use a choke input irrespective of the diodes chosen.
I would even say don't bother with tube rectifiers if you don't want to use a good choke PSU.

Happy trails,
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Old 5th November 2002, 12:38 PM   #4
SY is offline SY  United States
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The bad things about tube rectifiers include cost, power consumption, heat, reliability, and inferior regulation.

The good things about tube rectifiers include slow warm up, which can extend the life of the other tubes in the circuit, and that they can look quite cool.

Sonic differences beyond the ability (or inability) to regulate? I'm skeptical.
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Old 5th November 2002, 01:01 PM   #5
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Default REGULATE

Hi guys,

Quote:
Sonic differences beyond the ability (or inability) to regulate? I'm skeptical.
Whether using solid state rectifiers or tubes to do that I will always provide good shunt regulation (lowZ) on a per stage basis.
I then rely on the capacitance put behind the regulated stage to provide the necessary current, not the rectifiers and the transformers which will be too slow for the task in most cases.
One major advantage of tube rectifiers is that they don't throw back all the switching noise into the powerlines.

And that is something that can be heard as well as measured.

Cheers,
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Old 5th November 2002, 02:46 PM   #6
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Hello all,

I have said it before (or maybe not here) and I will say it again... the rectifier shouldn't make the amp sound like anything but itself. If a different rectifier makes your amp sound different, then the power supply is badly designed. The power supply should not make the amp sound different. It should be transparent to the quality of the amp itself, which is what does the actual work.

Someone somewhere here said it before, and I have also heard it from school: an amplifier is nothing more than an adjustable voltage regulator. But the source voltage (power supply) should be stable (fixed unchangeable voltage) and have a theoretical infinite current capability.

As for the fast or slow startup... solid state rectifiers have been used in tube equipment since the fifties (selenium rectifiers) with little if any apparent reduction of tube life.

But I may be all wrong about this, in spite of the fact that I have a few items with the original tubes in my collection with SS rectification.

I use SS rectification in my amps and hear no difference, mainly because I use a large filter cap after the choke, so PS impedance is consistently low, even when I do use tube rectifiers. Also, I have been using it for at least three years with no degradation of sound quality, with hundreds of hours of use, powering on and off every day.

Now, if you do use a tube rectifier, I recommend the 5U4 for its low internal resistance and voltage drop. This way you get the most power from the supply. Other tubes tend to have a more radical voltage drop change for the load draw (AKA poor regulation). This is what makes the amp sound "different". But that is not a good thing. Not for accuracy and trueness of fidelity, IMHO. It merely puts the characteristics of the devices in different modes.

But that is only my opinion... based on fact.

Gabe
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Old 5th November 2002, 03:51 PM   #7
Joel is offline Joel  United States
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Default don't believe the hype

The whole idea that different rectifier tubes have different "sounds" comes from the (technically illiterate) guitar player community. They plug a 5AR4 into an amp designed for a 5Y3, and then claim the rectifier sounds different. No, it's the amp that sounds different, because you've just increased the B+ by 25 to 30 volts. "Thicker", "warmer", "louder", are the adjectives that follow - and are exactly what I would expect.

I use tube rectifiers as heatsinks and voltage droppers when I have spare power transformers with too much voltage. They also look cool. But there is no "tube rectified" sound, trust me.

Regarding "soft start" and all that - there are hundreds of examples of 30+ year old hi-fi's out there, with their original tubes intact. And I've never seen a single tube stereo with a "standby" switch. That's odd, isn't it? If cathode stripping were such a problem, wouldn't they incorporate that design?

Joel
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Old 5th November 2002, 05:58 PM   #8
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Default CATHODE STRIPTEASE

Hello guys,

Quote:
Regarding "soft start" and all that - there are hundreds of examples of 30+ year old hi-fi's out there, with their original tubes intact. And I've never seen a single tube stereo with a "standby" switch. That's odd, isn't it? If cathode stripping were such a problem, wouldn't they incorporate that design?
Stanby switches are there to kill the tubes so the industry can sell some more tubes.


Only to be installed on the gear of those customers you REALLY hate and know to be loaded.
OTH I love tubes too much to do that to them.

You could also poison them with some selenium rectifiers (if you can still find any)

Cheers,
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Old 5th November 2002, 07:22 PM   #9
SHiFTY is offline SHiFTY  New Zealand
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A lot of guitar amps have standby switches, probably more of a convenience thing though. I know when I have played a stadium gig, I dont want to blast everyone with feedback when I drop the guitar...

Why would standby switches kill tubes anyway? I realise they slam the B+ onto them, but tubes are pretty tough I think!
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Old 5th November 2002, 08:03 PM   #10
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STANDBY SWITCHES


While it's true tubes can withstand the surge of a nuclear blast... how many blasts would you want to live through to find out how durable the tubes are?

I think the point is that all electronic components suffer when slammed too often with full B+.

On the other hand... I have SS equipment over 25 years old...

Now we're getting a little off topic.

The coke bottle Sovtek 5U4 sure does look sweet in among my tubes.

Gabe
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