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Old 3rd March 2009, 09:16 PM   #21
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One thing that may become a problem is the thing that is keeping "Tubes" alive.

The many variations of tubes and circuits is great for the DIYer or "tinkerer" the problem is it does not translate as nicely upstream to the manufacturers of tubes.

Case in point:

It is pretty easy to find at least a few suppliers of 6V6 and 6BQ5 variants because of the relatively common use in "Guitar & Bass" amps.

With all the variations out there most people doing an "offbeat" design are either using some sort of variation of the common Sovtek tubes or using NOS or USED tubes. As the supply of NOS uncommon tubes dries up we all are going to face the prospect of limited choices when it comes to the tubes. It is basic "supply and demand" it is extremely costly to produce tubes (relative to SS) this results in 1 of 2 things. Either low production "boutique" manufacturers that because of limited production have to charge a hefty sum, or "mass production" of a limited number of tube designs. To maximize profit in a mass production run you usually sacrifice quality. (I said USUALLY not ALWAYS)

Basically what it comes down to is as a whole the DIY community needs to try to do the following.

Minimize the number of NOS & USED stuff that is ending up in landfills. (ie, search Ebay, Craigslist, Flea Markets, Tag & Estate sales etc) and get those tubes into the market.

Brace ourselves for the prices we will expect to pay once that stuff dries up.

and be sure to make purchases from the suppliers that are struggling to stay afloat in this economy.
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Old 3rd March 2009, 11:08 PM   #22
jzono1 is offline jzono1  Norway
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Remember that hearing stuff that you never knew were there is perfectly normal with akg k701's. They're reference headphones, and known for being VERY revealing. Fine details that normal speakers mask will be revealed by k701's.

As k701's are analytical and cold I'd suggest trying the whole tube deal with a small headphone amp first. It's a moderately easy load, and tubes play good with k701's because of their nature. k701's shine when amped with a current-strong amp, and that's exactly where tubes excel. You don't have to pay up for very pricey tubes and toy around with as high voltages as if you were to build an amp for your speakers.
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Old 4th March 2009, 01:30 AM   #23
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Marko25,

As intimated before, you will find a bewildering no. of options. Soon you will find contradictions, simply proving that folks' hearing is very different, even though there will be vehement protests against such a stance. Sometimes you will find topologies superceded by newer, improved topologies, to be preferred above the improvements. I am temted to quote from an article by eminent British designer and writer DRG Self:

"Most fields of technology have precise measurements of excellence; car makers compete to improve miles/hour and miles/gallon; computer manufacturers quote millions of instructions/second and cost/kilobyte, and so on. Any improvement in these objective quantities is regarded as unequivocally a step forward. In the field of audio design, many people seem to have difficulty in deciding which way forward is."
(From: "Science v. Subjectivism in Audio Engineering"; see his website.)

At the start of your 'journey', all of this just to raise awareness of genuine improvements vs. tastes/boutique designs. You can do no better than start with the AudioXpress 'Audio Classroom Series' quoted earlier, following a basic understanding of the vacuum tube. Anything by Norman Crowhurst is normative, and although I am less familiar with Marshall's work, the two contributions on power supplies there are equally instructive. That apart from the more recent book by Morgan Jones, which I understand gives quite extensive coverage.

Good luck!
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Old 4th March 2009, 06:16 AM   #24
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Default geesh!

Johan, Ok guess I loosely use Quads(a name given a circuit by its designer or manufacture) when quad(matched set of 4) would have been more accurate. Marko it can all pretty confusing: for example KT88 is technically an tetrode, whereas 6550 is a pentode. My amps and many other KT88 in Push-Pull are in pentode?
No offense Johan; philosophy and tubes::I can't hear you, Turn that s___ down Cowboy!!!!

\Ok Marko This your thread, back to it..

A push–pull output is a type of electronic circuit that can drive either a positive or a negative current into a load. A push-pull TUBE amplifier is accomplished by driving half of the output tube(s) with a phase-inverted signal that feeds the phase-inverted primary side of a center-tapped output transformer. (forgive me off main topic, threw it in to confuse- ah).

Back to Kt88 in pentode: It's actually as much historical as it is circuit topology. This little bit of history helps:

KT88 versus 6550
While developed independently on both sides
of the Atlantic, the KT88 and 6550 are broadly
speaking, electrically (and pin out) compatible,
although there are differences in the internal
construction. The KT88 has slightly higher
ratings in terms of absolute voltage (800 as
opposed to 600 Volts on the anode) but the
dissipation and electrical characteristics are
similar. Although the 6550 is classed as a
pentode, and the KT88 a tetrode (i.e. one less
electrode) there is an explanation for this.
During the time of development, Mullard were
applying for a patent on the ‘pentode’, where
the inclusion of a fifth electrode (sometimes
called the suppressor grid) connected to the
cathode was used to collect stray electrons
and reflect them back to the source. The KT –
standing for kinkless tetrode – incorporated a
form of beam shaping that actually amounted
to another electrode to achieve a similar
result, but avoided infringement of the
patent. As for the sonic differences, these days
I suspect that there is more difference
between different manufacturer’s product
than between the KT88 and 6550 per se. To
confuse the issue further, some suppliers will
produce an identical batch of valves and label
them according to the market demand; I have
had an example of each from the same
manufacturer, and breaking them open
revealed that they were absolutely identical.
From:http://www.euroaudioteam.com/pdfs/hi...morgasbord.pdf


ColdCathode: Have faith, I think all of us will 'run out' first. I'm 53
Check out the relatively "new" EAT Kt88 (I'm Santa for a matched quad)
http://www.tubedistinctions.co.uk/kt88_prices.htm#top

Yes Marko, you make your own, video
http://www.tubedistinctions.co.uk/video.htm


C
__________________
I'm kinda curious about that myself........
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Old 4th March 2009, 08:09 AM   #25
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That tube distinctions link ? OMO,
Those of us getting old and wise with onset tinnitus and other problems aren't really going to fall for cyrogenic treatment that is claimed to make a difference to the sound and is willing to pay the absurd price; there is no patent. Another snake oil remedy to ridicously tease the human brain. Why bother putting glass over the iceberg.

I'm still running 807's which are now 50 yrs old and still have 80% emission. Any need for snake oil remedy ? The output transformers are 60 yrs old and the iron hasn't changed.
richy
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Old 4th March 2009, 02:35 PM   #26
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Quote:
Those of us getting old and wise with onset tinnitus and other problems aren't really going to fall for cyrogenic treatment that is claimed to make a difference to the sound and is willing to pay the absurd price; there is no patent. Another snake oil remedy to ridicously tease the human brain. Why bother putting glass over the iceberg.
One doesn't have to be OLD to be WISE, just open minded! Not to knock Cowboy he obviously has strong opinions and beliefs about his tubes. But Cowboy, I had never heard Buckethead before so I checked out a couple youtube videos and a download or two. Pretty good for that type of music but I am pretty sure that I would have a hard time using anything of his as a track to evaluate tubes.

I have always wondered when someone is going to start marketing USED tubes as "SEASONED" or "BURNED IN"?? LOL

Marketing is such an art, it reminds me of a professor I had that told us all in class that there are 3 kinds of lies, "White Lies", "Damn Lies" and "Statistics". He was referring to the often used statistics in marketing and sales. You know like "XYZ car had the highest resale value among cars in it's class". Is it possible that XYZ car was the most expensive when new? This might indicate that even though people were paying more for it used than other models the original owner LOST more value than the others.
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Old 4th March 2009, 06:10 PM   #27
Marko25 is offline Marko25  United Kingdom
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Default Re: geesh!

I saw that link also in the favourites section, its great.

I am currently working my way through the AudioXpress lessons to get myself a bit more in the know on tubes. One thing I am wondering is when I make a start wheres a good UK online place to buy all the things I need. Any direction on this would be appreciated.

Quote:
Remember that hearing stuff that you never knew were there is perfectly normal with akg k701's. They're reference headphones, and known for being VERY revealing. Fine details that normal speakers mask will be revealed by k701's.
This is quite true hence why I bought them

The good thing about my search is that its re-sparked my interest in building my own amp and even though I may not be able to achieve what I originally would of liked I'm sure I will have fun trying.

Equally the knowledge and support on this forum makes me feel a great deal more confident about plunging into tubes, something I have always wanted to go but daren't.

Thanks everyone
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Old 4th March 2009, 07:02 PM   #28
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Default Re: Re: geesh!

Quote:
Originally posted by Marko25


One thing I am wondering is when I make a start wheres a good UK online place to buy all the things I need. Any direction on this would be appreciated.

www.hificollective.co.uk.
www.chelmervalve.co.uk
www.farnellinone.co.uk
For an expansive pocket: www.sowter.co.uk.

Maplin electronics (not sure)
RS components

richy
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Old 4th March 2009, 07:09 PM   #29
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Posts #24 and #25 ...

(Marko, I am TOTALLY off subject, but you will also learn from this here forum that us veterans afford ourselves liberties...)

Gentlemen,

Me hart be totally warmed by yon sentiments and convicshens ...
me being - respect please - all of 74 years young almost

From Richwalters
Quote:
Why bother putting glass over the iceberg.


Cowboy,

Oops - MY bad!!!! I guess when I see quad me mono-rail brain locks onto what little content is left over between me frequency challenged earlobes. You did spell 'quad' (low case).

Now back to the topic with an effort in me creaking old bones ....
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Old 4th March 2009, 07:31 PM   #30
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Default Re: geesh!

Marko,
AGAIN off-topic, but hopefully also informative to you.

Cowboy ...

Quote:
Originally posted by cowboy99
.... for example KT88 is technically an tetrode, whereas 6550 is a pentode. My amps and many other KT88 in Push-Pull are in pentode?
Hey??

This is where the sobering truth starts regarding labeling
of tubes. I have a collection of mounted 'di-sected' typical tubes, made up from duds carefully cut open to show the innards. There are a GE KT88 and a Tung-sol 6550.

They are both very much tetrodes, two grids, beam forming elements on the sides, etc. It would therefore appear that we have two types of 6550! What brand is yours, Cowboy?

This is actually not unique; some time ago there was talk of a 'beam EL34', and somebody actually showed a photo of one! (It never became clear of what exactly the innards were supposed to belong to.)

Marko,

This may seem trivial to you, but e.g. the Russians are quite free with their designations. I won't bore you with details at this point, and I do not know about serious cases, but one sometimes do want to know whether you are purchasing a 6L6GC or a KT66.
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