Tubes - Fact and Fiction

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Postby oddioguy » Fri Aug 04, 2006 5:13 pm

gamblor wrote:okay....... i am currently in the process of replacing my tubes and ive got a slight concern

when replacing the el-34's.... on my old tubes, there are pins spaced evenly all around the bottom of the tube. on the new tubes, it is the same alignment of pins, but there is one pin missing where there would usually be a pin on the old one. also, there are numbers on each of the pins on the new tube.

so with this in mind, does it matter what way i insert the tube?

(From my post above) : EL34's ( the big tubes) are keyed so they cannot be inserted improperly.

There is a plastic key in the center of the circle of pins. It is the key, so the tube can only be seated one way.
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Postby Malcolm Boyce » Fri Aug 04, 2006 5:13 pm

gamblor wrote:so its okay that the new tube does not have the same amount of pins as the original?
I believe Pin6 is redundant. Some have it ommitted altogether, some just have it disconnected.
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Postby oddioguy » Fri Aug 04, 2006 5:15 pm

gamblor wrote:
Malcolm Boyce wrote:
oddioguy wrote:EL34's ( the big tubes) are keyed so they cannot be inserted improperly. The small tubes don't have an actual key, but the pins are arranged so that they can only be inserted one way.


ahh okay........ i just realized this.

so its okay that the new tube does not have the same amount of pins as the original?

So long as they are both EL34's. (Typically, there are unused pins on most tubes. Manufacturers have merely started to omit the unused pins to save $$.)
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Postby gamblor » Fri Aug 04, 2006 5:38 pm

Malcolm Boyce wrote:
gamblor wrote:so its okay that the new tube does not have the same amount of pins as the original?
I believe Pin6 is redundant. Some have it ommitted altogether, some just have it disconnected.


k sweet. this is the pin that is missing too.

thanks guys!
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Postby oddioguy » Fri Sep 01, 2006 1:59 pm

...and opinion!

I just swapped out the Sovtek EL84's in my project amp for a pair of JJ's. Very nice indeed. Fatter, and better definition when saturated.
I also swapped the Sovtek 12AX7WA's in the preamp for Sovtek 12AX7LPS's. The difference in plate size is audibly obvious, and they are quieter as well.
Last thing I am going to play with is the phase splitter. Currently a 12AX7, I am going to A/B some 12AU7's, 12AT7's, and maybe even a 5751.
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Postby Alain Benoit » Mon Sep 04, 2006 10:20 am

oddioguy wrote:...and opinion!


I also swapped the Sovtek 12AX7WA's in the preamp for Sovtek 12AX7LPS's. The difference in plate size is audibly obvious, and they are quieter as well.


Told you that the LPS's were it!!

Did a shootout with a dozen preamp tubes and in a microphone application the LPS was head and shoulders above the rest.
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Postby oddioguy » Mon Sep 04, 2006 11:00 am

U1176 wrote:
oddioguy wrote:...and opinion!


I also swapped the Sovtek 12AX7WA's in the preamp for Sovtek 12AX7LPS's. The difference in plate size is audibly obvious, and they are quieter as well.


Told you that the LPS's were it!!

Did a shootout with a dozen preamp tubes and in a microphone application the LPS was head and shoulders above the rest.

In my 10W guitar amp, they are quieter. (AC heater voltage...I may rectify that situation) They definitely have a fatter tone.
I've started stocking more of them, as they are now officially on my "to be recommended" list.
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Postby oddioguy » Sun Dec 17, 2006 5:23 pm

Here's something that I run into occasionally, but have not addressed....
Every so often I will get a request for help that begins with "My (insert manufacturer here) tube amp is doing (insert abnormal behaviour here). Blah blah, etc., ad nauseum....

As it turns out, little Johnny's amp is 100% solid state, but the filter caps are being identified as "tubes".

Where is this coming from? Wishfull thinking?

"Gee, I just got a "tube" amp for $99.00....brand new!!! Woohooooo!"

...or perhaps misleading sales people?

What gives?
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Postby weatherstation audio » Thu Dec 21, 2006 7:23 pm

Hey Thom,
can you explain what procedure and tools, one would need to properly match output tubes for a guitar amp ?
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Postby oddioguy » Thu Dec 21, 2006 11:54 pm

weatherstation audio wrote:Hey Thom,
can you explain what procedure and tools, one would need to properly match output tubes for a guitar amp ?

Well,
If you mean you want to be able to grab any old tube that is kicking around and stick it into an amp, and be able to have it work to the same potential as the other existing tubes, then "yes", I will post a little tutorial on modding your amp so that the bias of each individual tube can be adjusted to match any other tube.
If you mean that you want to set up a tube matching service...that would be impractical, based on the large quantity of tubes you would need in order to find pairs or quads that have near-identical properties.

It's late, I'm tired, I'll post the mod shortly.....
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Postby weatherstation audio » Fri Dec 22, 2006 8:47 pm

oddioguy wrote:If you mean that you want to set up a tube matching service...that would be impractical, based on the large quantity of tubes you would need in order to find pairs or quads that have near-identical properties.


that's what I'm talking about... although, no I'm not wanting to go into this business... just curious as to what companies like Groove Tube are doing to called a pair of tubes "matched" ?
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Postby oddioguy » Fri Dec 22, 2006 9:01 pm

weatherstation audio wrote:
oddioguy wrote:If you mean that you want to set up a tube matching service...that would be impractical, based on the large quantity of tubes you would need in order to find pairs or quads that have near-identical properties.


that's what I'm talking about... although, no I'm not wanting to go into this business... just curious as to what companies like Groove Tube are doing to called a pair of tubes "matched" ?

Fairly extensive computerized, custom built test rigs.
See me next time you're in. I'll show you a flyer New Sensor sent around about how they do it.

It is my belief the the 3 main characteristics looked at would be:
- Plate current
- Cathode current
- Transconductance

Probably more, and I'm sure the screening process would include mechanical testing to exclude microphonic tubes as well.....
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Postby oddioguy » Sun May 20, 2007 8:44 am

Here's another point of interest....
Everybody is running around spouting off about the importance of matched output tubes.
Yup...with a common bias control for all output tubes in an amp, it is important that they all amplify equally.

...but...

Equally important in my view is a balanced phase splitter. This is a lot harder to achieve, as a typical phase splitter is going to be a 12AU7, 12AT7, or 12AX7, all of which are twin triodes. This means that each internal section of the tube must amplify equally.
Not exactly a small order as it requires sorting through mountains of tubes to find the ones that are closely matched internally.
There are dealers out there who will provide this service, but I wish more would...
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Postby Alain Benoit » Sun May 20, 2007 10:45 am

oddioguy wrote:Equally important in my view is a balanced phase splitter. This is a lot harder to achieve, as a typical phase splitter is going to be a 12AU7, 12AT7, or 12AX7, all of which are twin triodes. This means that each internal section of the tube must amplify equally.
Not exactly a small order as it requires sorting through mountains of tubes to find the ones that are closely matched internally.
There are dealers out there who will provide this service, but I wish more would...


Good point, never thought of the phase splitter but you are right.
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Postby oddioguy » Sun May 20, 2007 11:52 am

U1176 wrote:
oddioguy wrote:Equally important in my view is a balanced phase splitter. This is a lot harder to achieve, as a typical phase splitter is going to be a 12AU7, 12AT7, or 12AX7, all of which are twin triodes. This means that each internal section of the tube must amplify equally.
Not exactly a small order as it requires sorting through mountains of tubes to find the ones that are closely matched internally.
There are dealers out there who will provide this service, but I wish more would...


Good point, never thought of the phase splitter but you are right.

Applied to the Berelson, there may be a good reason why it is well balanced even though the 6GT5 power tubes are definitely not matched. The phase splitter is a 6C4, which is a single triode. There is no negative feedback, so no need for a 2nd triode section, therefore no worry about matched sections. Completely different topology than we generally run across today.
I am playing with the idea of applying this setup to the 10W project to see how well it translates.
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Postby oddioguy » Fri Nov 30, 2007 1:57 pm

Anybody tried the "Mullard" tubes from New Sensor? These are new tubes that are being built to the original Mullard specs.
I've had good feedback (pun!...) on the EL34's, but I'm looking for other opinions.

:?:
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Postby Alain Benoit » Wed Dec 12, 2007 12:40 am

oddioguy wrote:Lately I've been hearing that some people are warning purchasers of tubes to never touch the glass with thier bare fingers.
This has only started happening since the same warnings began appearing on halogen and xenon light bulbs.

Rule #1 - Tubes are not light bulbs.

Look at the filiment in a xenon bulb. I'd describe it as "white hot". Plus, the bulb itself is filled with xenon gas, which among other things, helps transfer heat from the filiment to the envelope.
It's true, skin oil on xenon or halogen bulbs can cause hot spots which shorten the bulbs life.

The filiment in a tube glows dull orange, producing far less heat, and it functions within a vacuum. Putting sound aside, I've seen tubes function for 30 or more years that have been handled more times than Madonna.
If that is the "shortened" life due to handling, I think I can live with it.

Personally, I've never worried about touching a tubes' envelope.


I was in Musicstop/Long & McQuades recently where I overheard a salesperson warn a customer who was purchasing some 34's that he should be careful to not ever touch the tubes while putting them in lest he caused them imminnent failure. He even said to handle them with tissue paper but not the lotioned kind. I proceeded to chide said salesperson that this was a pure myth. I was thanked with a huge hairy eyeball.
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Postby oddioguy » Wed Dec 12, 2007 5:14 am

That is some funny shit right there.

:lol:

This myth seems to propogating itself exponentially across the 'net, but there seems to be a common theme:

Don't touch your tubes...BUY *insert handling device here* THIS instead!!

All comes down to $$, doesn't it. :roll:

Again I reiterate; if 30+ years is the "shortened" life I can expect after repeated handling of my tubes, I'll live with it.
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Postby oddioguy » Wed Dec 12, 2007 9:08 am

...and remember kids, the $500.00 a piece wooden knobs sound WAY better than your stock metal or plastic knobs...

:roll: :roll: :roll:
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Postby Radio man! » Tue Dec 18, 2007 9:46 am

...and remember kids, the $500.00 a piece wooden knobs sound WAY better than your stock metal or plastic knobs...

Rolling Eyes Rolling Eyes


Alrighty then!!!!!! This sounds lie the proverbial Snake Oil debate about to start.
I personally have to have that green marker to put on the edge of my cd's.
This one is quite interesting(and cheap too) http://www.musicdirect.com/product/73105

And my all time fave The Golden Sound Intelligent Chip http://www.positive-feedback.com/Issue1 ... nsound.htm

And you can read the review at 6 Moons where they seem to be able to quantify the thing????
http://www.6moons.com/audioreviews/phot ... nnons.html
I'm sure the date should have been 1 Apr anyyear!

Thats it for me.

:lol:
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Postby oddioguy » Tue Dec 18, 2007 10:02 am

Bwahaha...forgot about the green marker dealie.

:oops:
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