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Old 4th March 2009, 09:38 PM   #31
Marko25 is offline Marko25  United Kingdom
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Thanks for the links Rich!

Quote:
(Marko, I am TOTALLY off subject, but you will also learn from this here forum that us veterans afford ourselves liberties...)
No problem, glad my thread could spark some off topic debate
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Old 9th March 2009, 05:07 AM   #32
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'Links,are links nothing more;

ColdCathode, ( off topic)
Now, an open mind; that is something. I agree most of BH's music is of no use at all as a 'Ref' recording. I mentioned him only to set a 'stage', one that KT88 power belongs in. Give you credit for looking into him, and since you brought it up.... BH (being as 'weird' as it gets) is quickly becoming know as one of the world's greatest guitarists but is impossible to categorize; one never knows what style he'll be in next. This is a guy who put out 27 albums in 2007 alone. youtube mostly the kid favorites. 'Electric Tears' and 'Population Overdrive'(his best) are considered jazz recordings in some circles. Check him out on Wikipedia: Ozzy's comments (what a ref) show just how 'mainstream' old age can become. ... sorry,sorry ... so off topic.

Marko,
Bear with us; there are so many 'tangents' to tubes that 'off forum' is unavoidable. You've got enough to read, just funnin...

Johan,
Glad you weren't offended by my comment: Philo. is one of my favorite subjects, just that I use the 'tubes' to clear my head.
Back to topic....

My KT88's are Sovtek: a decent 'industrial grade' so I've read. They are tetrodes, in a pentode circuit; not sure if I've got that straightened out in thought yet!
As posted earlier:
"The KT standing for kinkless tetrode incorporated a form of beam shaping that actually amounted to another electrode to achieve a similar ..." result as the 6550's.
Back to the Russians: Wrong tube designations can/is a real issue: Don't want to think about plugging in the wrong tubes with some of the currents involved. Just did a 'google' on Sovtek: In 2006 an interesting/worrisome article came out in 'Stereophile'. From that article:
.....ExpoPul, a company whose factory in Saratov, Russia manufactures vacuum tubes under the brand names Sovtek, Electro-Harmonix, Tungsol, Svetlana, Mullard, and othersó If the threatened hostile takeover proves successful, two-thirds of the world's supply of vacuum tubesó
http://www.stereophile.com/news/052206tubes/

In ref to above article: 1) I was not unaware that Sovtek, Electro-Harmonix, Tungsol, Svetlana, Mullard were all under the same hat? Were you?
2) It appears something happened but not the worst: Its still owned by Mike Matthews but now called the New Sensor Corporation and still manufactured in Saratov, Russia.
Ref. Wikipedia
I've considered replacing the Sovtek's but seems such a 'cr_p-shot' and with '2/3's of the worlds tube supply under one hat'. Any suggestions?

Any comments on mods to Velleman K8010's? Especially on 'modjob' done for hire by http://diyparadiso.com/mod-k80101.htm? I was horrified by what at first seemed a 'hack job' but accepting that I'm overly proud of my amps, I'm opening up to some of 'mod's he suggests.

I've rambled on long enough......Charles
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I'm kinda curious about that myself........
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Old 9th March 2009, 02:31 PM   #33
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Quote:
I'm still running 807's which are now 50 yrs old
My best sounding (albeit 2 WPC) amp is running a pair of NX-483's that I pulled out of an old radio I got at a flea market. There was a sticker on one of the tubes proclaiming that the tubes were last replaced in 1931. The NX-483 is a relatively unknown 5 volt filament version of the 45 used in Sparton radios in the 1920's. They sound really good, but I can't find any more of them for a reasonable price.

Quote:
I noticed the ghosting on the opening track i.e. the track starts before it actually starts.
The effect that you are referring to is actually a defect in analog recording tape called "print through". In the old days all music was recorded on tape then mixed down, mastered, and finally transfered to vinyl. There could be some considerable delay between the mastering and the creation of the plates used to press the vinyl. During this time the master tapes were stored in a cold vault, untouched. Tape is tightly wound on a reel, such that the tape is in contact with the layer below and above it for considerable time. During this time some of the magnetic information from one layer will "print through" to the layer above and below it. This causes a general signal to noise degradation to the whole reel of tape. It is most noticible at the very beginning of the tape because the beginning of the tape has no signal recorded on it, so any print through will appear as a direct (but noisy and weak) copy of the strong signal recorded on the layer of tape below it. This was discovered in the 1950's and several techniques were used to reduce it including thicker tape, paper spacers during storage, weekly respooling, etc.

New records and most CD's made from those old tapes are usually digitally processed to remove these known artifacts, but some are not, and most of us have old records where this effect can be found.

Quote:
I have always wondered when someone is going to start marketing USED tubes as "SEASONED" or "BURNED IN"?? LOL
How about "Previously Auditioned". I bought some tubes that were so marked, but the seller told me that they were actually returns that he had bought from a big Tube Store. They were cheap and all worked great.
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Old 10th March 2009, 12:19 AM   #34
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Quote:
Originally posted by cowboy99
Any comments on mods to Velleman K8010's? Especially on 'modjob' done for hire by http://diyparadiso.com/mod-k80101.htm? I've rambled on long enough......Charles
Hi Cowboy!

First nostalgia - thinking back to what we played at school age before there were computers, CDs, Walkmans (Walkmen?) and the like. Cowboys! That we didn't break each others' necks ...

Requested comments:

1. There were so many designs using the 'Mohican' topology that improvement by using an interstage transformer (what price?) can hardly be visualised. What about a Schmitt (long-tailed pair or LTP)? Not to condemn Benny, but when several things are changed at the same time, one needs to carefully analise which made what difference.

2. Using an ECC83 anywhere in a power amplifier is hardly the best option. Certainly not as a concertina phase splitter, and then at that required output amplitude. With respect, I must agree with B's analysis of the Velleman design. Sorry. (Draw the load lines and it shows that it would just about have overloaded as there.)

3. The use of an ECC82 in audio (despite its popularity with some) is however also debateable. You may have noticed elsewhere that it is comparatively non-linear. Small signal as here - mmmm - but rather ECC81, 12AY7 or a host of others.

4. There are two basic kinds of amplifier: Those without audible distortion, and those with low order harmonic pattern such that it 'enriches' the music (not all generated harmonics are objectionable!). If a feedbackless amplifier sounds better because of that, chances are that it is the latter kind. No feedbackless amplifier will have inaudible harmonic products. But if that is preferred ... it is your taste and money!

5. Now that I have showered on the parade, look for the silver lining. There are lots of that! My personal option would be for UL output stage (see further), LTP phase inverter using ECC81 or ECC88, and pentode input. [The eternal objection: pentodes generate more noise than triodes! Yes, about 5x more. But as power amplifier input tube this is hardly noticable unless you stick your hearing apparatus right up to the speaker. And as input tubes here, they generate about 4x lower distortion, are independent of input impedance, blah blah bloops).

6. Good quality components: Yes - but those are generally available these days. Boutique 'quality': Sorry Lone Ranger; 4 - 10x the cost, at no audible advantage. An audio amplifier is not a GHz device or super medical standard one. Beee-ware of legende urbanus.

7. As an aside: Distributed load (ultra-linear; UL) is often misunderstood. It offers the best of both triode and pentode operation. There should be little if any audible difference compared to triodes, but it gives about 2x the available output. At the same output of the maximum of triodes (other things being equal) UL gives about half the distortion - and still has further to go.

Also long post: Rather explain things well than having to go second time round.
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Old 10th March 2009, 11:42 AM   #35
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Quote:
Originally posted by Johan Potgieter


2. Using an ECC83 anywhere in a power amplifier is hardly the best option. Certainly not as a concertina phase splitter, and then at that required output amplitude. With respect, I must agree with B's analysis of the Velleman design. Sorry. (Draw the load lines and it shows that it would just about have overloaded as there.)

Johan:
Thinking technologically:- Was that a slip between the lines ? I use 'em as cathode follower as a HP 3rd order octave filter. Distortion = NiL. Noise in such config= NiL.

Morgan Jones valve amps 3rd edit page 500 fig 7.5 shows the perfect application for an ECC83 although an ECC82 is shown. Series feedback is an excellent way of using such tubes.
I use this config alot. Replacing the 1st stage with an even higher mu tube i.e EF86 pentode and 2nd stage with a pentode as triode gives excellent performance. However M Jones misses the more important point of bootstrapping the first stage grid to split loaded cathode creating an infinitum input Z.
The beauty is that with alot of feedback (36dB) the pentode thinks it is operating optimumally in such a way that thd is negligeable whatever screen volts is set !

Richy
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Old 10th March 2009, 12:21 PM   #36
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Default Re: The daunting world of tubes (where to start)

Quote:
Originally posted by Marko25
Hello everyone,

I have a previous post in the solid state section re: Class A and someone directed me to tubes so I'm hoping someone may help.<snip>
So now my search begins for a truly transparent amplifier that allows every ounce of detail to flow through.
<snap>
My speakers are the Wilson Benesch Arcs, 88db on axis 2.83V, 200W max unclipped, 6 ohms nominal 4ohms minimum, 111db max SPL.

Many thanks in anticipation,

Mark.
Ack, a tricky load to drive (I've not heard them so I can't say if the speakers are the problem)

What I can say is
a) look for the Fi Primer as an entry discussion into tubes
b) check Lynn Olson's postings on PP 300B class A. That's about as good as it can get
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Old 10th March 2009, 02:39 PM   #37
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Default My take on it.

First, get some efficient speakers. At least 96db/1watt/1meter, preferably higher above 100db/1watt/1meter. (Klipsch La Scalla, Heresy, K-horn, Belles, Lowther, Altec Model 19 or Valencia, EV Sentry IVB) Many of these speakers are not made any longer and you have to find used ones. If you do this then you ease the power requirement and prevent the amp from ever going into clipping or slew rate limiting. You don't ever want this to happen! The loudspeakers are your most important purchase and you should spend most of your money there. Just insist on very efficient loudspeakers!

True Class A operation is easy to find in a preamp but very difficult to find in a power amp. There are even fewer output transformers designed that can take the 0 signal demands ( In a Class A amp maximum current flows through the primary windings in a 0 signal state). To get good frequency response in a transformer it takes very fine wire and many turns, in the off the shelf common output transformer many times too fine to withstand the 0 signal condition current flow. Class AB is much more do-able and more common because you are not cooking transformers. Class A amps are only about 30% efficient at their best. You wind up consuming 100 watts of power from the power company to put out 18 watts of Class A audio power to the speakers.

The next opinion is that single ended Class A is much more enjoyable to my ears than push pull. Push pull cancels too much. Good luck! Ray
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Old 11th March 2009, 12:13 PM   #38
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Default Re: Re: The daunting world of tubes (where to start)

Quote:
Originally posted by thoglette


Ack, a tricky load to drive (I've not heard them so I can't say if the speakers are the problem)

What I can say is
a) look for the Fi Primer as an entry discussion into tubes
b) check Lynn Olson's postings on PP 300B class A. That's about as good as it can get
The Primer
The Amity, Raven, and Aurora
New 300B PP amp completed, phase shift questions
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Old 11th March 2009, 10:28 PM   #39
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Quote:
Originally posted by richwalters

Johan:
Thinking technologically:- Was that a slip between the lines ? I use 'em as cathode follower as a HP 3rd order octave filter.
Richy,

Er - no. I did say in power amplifiers, thinking of normal topologies either as Schmitt, or LTP, or whatever else driving power tubes like EL34, KT88 etc (highish amplitude, lowish following G1 resistor), or as input stage where the Miller capacitance could easily cause a variable loop gain h.f. slope depending on the driving input impedance, etc. I am sure you know what I mean; hope others do too.

In all these applications there always seem to be better candidates viz. ECC81, ECC88 and the like, or similar triodes, cascode circuit, pentodes or such.

Sure, I also used them in various topologies in pre-amps. I did not mean not useful in audio per se.
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