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Old 16th November 2006, 08:23 AM   #1
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Default about newbies...and textbook..

I've been on this forum for a very short period of time compared with many of you guys!
I'm trying to get a better handle of this "technology" and......the quote to quote....takes me into the real topic of this post:


by checking the posts for newbies....i have downloaded and selected the informations that i need to increase my kwnoledge over this subject.
After awhile, i have stopped and reflect over this:

The whole source, i've found so far on Internet, is from the early 1950 or so...and the question it's a real consequence of this fact:

Is there any new thing on the valves design NOW (i'm talking about the last 15-20 years) that wasn't still discovered by then?

The modern valve equipments are still using the same schematics developed in the 50's -60's or even erlier (40's) ?


That is a question that i think most of the newbies would put to themeselves....because.....you see this source of information and you wonder if you have to study them or you have drop or skip them to pass for a better up-to-date source!

i hope you guys can help me to understand this point!


Thank's in advance.


Best Regards,
Stefano.
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Old 16th November 2006, 08:58 AM   #2
Nordic is offline Nordic  South Africa
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There certainly are new implementations, improving on things like noise rejection etc, look at the aikido for instance...

Ultimatly valves are very passive components it would seem (btw I'm also a noob, but an opinianated one). all they care about is the voltages, currents and impendances their respective pins see generaly. So its open to anyone to use whatever solidstate/integrated circuit to manage these attributes.

However you would still need to be familiar with what the old passive component arrangements were doing to begin to improve on them. So learning the old stuff is nearly inevitable.


I think on the other hand with minituarisation trends, it would be hard to find enough suitably rated components in the near future, wich would bring you right back to basics, using pasive components.
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Old 17th November 2006, 07:39 AM   #3
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I reply to it to put it gain to your attention....hoping in other comments!!
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Old 17th November 2006, 08:28 AM   #4
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Valve guys don't seem to like anything new. You only have to look at the deathly silence that follows the mention of something like solid state regulation to see that. Let alone something like SY's Heretical Line Stage, (one of the best preamps I have ever heard), that has an opamp servo as well!
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Old 17th November 2006, 09:27 AM   #5
ilimzn is offline ilimzn  Croatia
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I tend to agree. Even 'stranger', how amps thend to be less favorably received IF you tell the ones listening there are SS parts in them. Not so if you don't tell them, surprisingly.
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Old 17th November 2006, 10:30 AM   #6
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i'm not talking about valve guys or audience.
I'm referring of new type of shematichs, differente uses of the valve instead of the 10-12 c classic schematic.
I don't know....i'm totally guessing...... for instance...... the noise cancellation....if i'm not wrong was already developed on the 50's (around that!)
I mean...if i want to be a professional valve's projecter....do i have to study JUST the old books that i see on the net...or should i up-to-date my kwnoledge with something new.

I'm an engineer and it's a shame for me to study books that have more then the double of my age!

For instance...if i would study the digital technology on books from 90's...everybody would laugh at me....that's the concept that i'm tring to explain.
I would like to know if something new has come around ...at least...in the last 20years.
Is it possible that the research on valves's use it's already gotten to its climax a long time ago??
New patent....new use of the valve.....and so on??


Hope to clearify this point!


Thanks.
Stefano.
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Old 17th November 2006, 10:59 AM   #7
EC8010 is offline EC8010  United Kingdom
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As you say, classic circuits were developed and have stood the test of time. There are some differences between old and modern circuits...

(1) In real terms, valves are cheaper now than in the 50s. As a consequence modern circuits don't need to wring every last bit of gain out of a valve and if another valve would help, it is used.

(2) Low distortion sources are widely available, so amplifier noise and distortion are expected to be lower. This has tended to drive operating currents in pre-amplifiers and driver stages higher.

(3) Modern resistors and capacitors are far better. As one example, this has enabled tolerances in equalisation to be tightened up - it has also meant that design errors in equalisation can no longer be tolerated.

(4) Computers. Classic circuits were designed using a slide rule, but a computer can be used to model the circuit at the design stage then measure and analyse results at the prototype stage. FFT analysis has enabled home investigation that wouldn't even have been possible in a laboratory in the 50s.

The Internet has broadened the choice of components available at the design stage. Traditional designs used components from one country, but a modern design might use a British special quality valve, an American TV valve, and a German telecommunications valve. The same argument applies to passive components, Soviet PTFE capacitors from the Cold War are popular - definitely not available in the 50s!

(5) Semiconductors. Modern circuits can incorporate semiconductors when it seems useful. Mostly, this tends to be in power supplies, but they're also common in constant current sinks.

(6) Oscilloscopes. In the 50s, an oscilloscope was a rare beast but a 20MHz dual channel oscilloscope is now peanuts. This has meant that modern designs have far more attention paid to HF stability.
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Old 17th November 2006, 11:23 AM   #8
SY is offline SY  United States
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I'd emphasize EC's point 5. We can use solid state to set operating points and do circuit housekeeping in ways the guys in the '50s couldn't.

For example, a proper current-sink for a long-tail pair was a significant problem in 1956 (requiring an extra tube, an extra power supply rail, and an extra heater supply), which is why they were used in approximately zero power amp phase splitters at that time. A couple of transistors and LEDs or a couple of depletion mode MOSFETs accomplish that function today for about 2 bucks and 3-4 square centimeters. So in 2006, we can easily build a phase splitter with far better balance than we could in 1956.

Or take the notorious servo that pinkmouse mentioned: we can direct-couple from the output of a cathode follower without running the signal through a big, messy capacitor using an opamp and a handful of small Rs and Cs. The servo handles nothing but DC to 1-2 Hz, freeing the tube to do its thing properly.

And regulation- we can do triode amplifiers with far less dynamic distortion these days by regulating the B+. In theory, that could have been done in 1950, but it would require a regulator four times the size and expense of the amp. So even for the "classic" amps, it just wasn't used. The B+ regulator in my small triode amp (20W) is about the size of my fist and cost less than $10. The transistors only handle DC and subsonics. The tubes are left to run optimally.

In terms of tube topologies, there's a limited number of ways to connect them, and they were all done by 1960. Now, most topologies weren't used in audio, but creative guys like John Broskie are trying to remedy that.
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Old 17th November 2006, 12:48 PM   #9
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it's exactly what i was talking about: the topology (which as you conferm me, was totally develoved by the end of 60s).
About the components, i agree with the fact that there are higher quality's components than back then due to the lower tolleraces and other factors.

About the OP amp i'm sory but i don't agree with you at all.
If we were solely talking about performances rather than sound i would do agree with you guys, but for me the target is the sound and not the wave form on an oscilloscope.
If an amp sounds great and have a great responce...then good...otherwise i could care less if an amplifier with havier components sound better than one made with op ampl but worse responce.

The op amp technology is smaller, cheaper and less noisy and so on than valves.

The point is that i'm noticing that you guys are likely to be not very considering about the sound, if i'm wrong you can correct me.
According to my experience, Amp with IC inside don't sound very nice and fine.

About the oscilloscope, the FFT, the simulators and so on....i completely agree.
Now it's easier and faster to develop a very good and stable amplifier with all this tools now avalable.
Regarding on the simulator, i will open in the future a 3d, since i have allegro cadence 15.5 and orcad 10.5 and would like to know if anybody uses this particular program.

Just one more thing:
whose John Broskie? (sorry for my ignorance!)


Best Regards,
Stefano.
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Old 17th November 2006, 12:54 PM   #10
SY is offline SY  United States
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I would maintain that an op-amp based servo, which just handles DC-2Hz, will have far less impact on the sound than a 10uF coupling cap.

John Broskie is the proprietor of the excellent site www.tubecad.com .
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