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 Post subject: Re: True emission?
PostPosted: Mar Mon 23, 2020 6:00 am 
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Lou deGonzague wrote:
In the case of the 6C4 it could be the circuit was marginal with off spec components or poor design so only a "Hot" tube would function.

Lou, that 6C4/Hammarlund HQ-145A problem is not common to just HQ-145s or even Hammarlunds in general. It has happened to other brands also.

Now, it is always possible that no one can design a reliable HFO using a 6C4, but in that case, why use a 6C4?

John


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 Post subject: Re: True emission?
PostPosted: Mar Mon 23, 2020 5:16 pm 
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KX5JSC wrote:
Lou deGonzague wrote:
In the case of the 6C4 it could be the circuit was marginal with off spec components or poor design so only a "Hot" tube would function.

Lou, that 6C4/Hammarlund HQ-145A problem is not common to just HQ-145s or even Hammarlunds in general. It has happened to other brands also.

Now, it is always possible that no one can design a reliable HFO using a 6C4, but in that case, why use a 6C4?

John



Indeed, very common problem. Use a mil spec 6C4 or just find a 6100. That will solve the problem of borderline operation.

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 Post subject: Re: True emission?
PostPosted: Mar Tue 24, 2020 1:00 am 
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Vin Tageman wrote:
Are you trying to invent a better mousetrap? If so, you're a little late to the party, and as was said, there wouldn't be a market for it.

Vin,
Yes, a bit late to the tune of 70 to 100 years or so, but consider the perhaps millions of users of tubes in musical amps and stereo amps that are out there, not just vintage radios. Consider the user of just one guitar amplifier they have and use quite often, at gigs and such, and the sound is what that user likes about it - touch sensitivity, sustain, blend harmonics - and then suddenly, the tubes wear out, and upon a re-tube, the user cannot quite get back the sound it once had. Due to what? Not biasing correctly, possibly the amp changing its qualities due to degradation of capacitors, or perhaps the tubes themselves?

Consider all those that just roll tubes and find that from the same manufactured batch of tubes, some sound like nirvana, but others do not. Why? Some do this and can never get the sound back due to combinations they have changed and end up selling the equipment. Why? If they could see differences in tubes, and discern quality from one to another, they might choose to run a particular set as it gives the sustain, sounds, touch sensitivity, depth, or other qualities they are after from these imperfect devices (I fall in this category).

Users of tube use them because somewhere along the line they hear a different quality than that from solid state, whether it be from the distortions it gives, or from the extra details they hear in the sounds.

If a tube tester could show these differences, and one could see a difference in the analysis, and relate that back to the sound, well the market would be immense in my opinion. The current supply of tube testers do not show these nuances. What would the be market be if one could be developed? I read that David Gilmour could tell when one of his amps was not performing right, and would indicate this back to his tech to fix it. Probably tube related.

I have an original 64 Deluxe reverb and have been though all of this, and have just a Knight emissions tester which does not tell me these things, and thus started looking into other testers that might indicate these things which led me to ask these questions. I read as many posts as I can to get deeper into it (or whatever it ends up to be), so much out there to digest.


Last edited by Brobertson on Mar Tue 24, 2020 1:37 pm, edited 1 time in total.

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 Post subject: Re: True emission?
PostPosted: Mar Tue 24, 2020 1:25 am 
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If it's just for audio, a curve tracer will probably do what you want. But telling what "sound" you get from a particular curve would be another matter. But it could be used to compare one tube to another.

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 Post subject: Re: True emission?
PostPosted: Mar Tue 24, 2020 1:28 am 
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Quote:
If a tube tester could show these differences, and one could see a difference in the analysis, and relate that back to the sound, well the market would be immense in my opinion.

What you suggest would be tube Nirvana. In a word, it is impossible. Nothing you could ever test would tell you how a tube would "sound". This very debate goes on and on with capacitors as well, although with caps, there is a lot less to test. Two elements and some kind of dialectric.

With a tube, there are probably millions of different combinations of grid wire spacing, mica types, mechanical alignment, cathode coatings, filament coatings, plate coatings... you get the idea? You simply can not test a tube to this level of precision. Even if you could, you'd still not know how it would sound from one amp to the next.

Sorry. :)

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 Post subject: Re: True emission?
PostPosted: Mar Tue 24, 2020 2:26 am 
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Barry,

Well said, but if you could identify the sounds you like or seek from a tube, would that not be half the battle?


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 Post subject: Re: True emission?
PostPosted: Mar Tue 24, 2020 2:48 am 
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More like 0.1% of the battle. (AKA 1/1000)

One of the first things you'd need is some consensus on what constitutes the best sound---probability of getting a measurable level of agreement maybe 1%---if only because there are distinct things that sound better than others--eg odd vs even harmonics.

Next, you'd need to make the connection between various metrics of sound and actual tube parameters. We know how to spec tubes and design circuits for simple stuff like harmonics---beyond that is the twilight zone. Suppose someone like their sound "bright and crisp": Do you know how to turn that into tube characteristics?

Try this:
First, study a tube data sheet to be sure you understand exactly what the various parameters are---including the biggies like plate resistance, transconductance, and inter-electrode capacitance. Next, define what additional parameters you need to specify---parameters that cannot be derived from the ones already in common use.


In the process, make sure your understanding of the basic physics is solid. For example, you don't control tube current by "modulating the cloud"....electrons follow the electric field lines, which is turn are defined by the vector sum of the fields generated by each applied potential.

In summary, the probability of improving or re-inventing this particular wheel is essentially zero....

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 Post subject: Re: True emission?
PostPosted: Mar Tue 24, 2020 5:40 am 
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Brobertson wrote:
Vin,
Yes, a bit late to the tune of 70 to 100 years or so, but consider the perhaps millions of users of tubes in musical amps and stereo amps that are out there, not just vintage radios. Consider the user of just one guitar amplifier they have and use quite often, at gigs and such, and the sound is what that user likes about it - touch sensitivity, sustain, blend harmonics - and then suddenly, the tubes wear out, and upon a re-tube, the user cannot quite get back the sound it once had. Due to what? Not biasing correctly, possibly the amp changing its qualities due to degradation of capacitors, or perhaps the tubes themselves?

High fidelity means getting out of an amp exactly what you feed into it, only with more power. At this point, you are really NOT interested in high fidelity, especially if the amp has tubes in it. Yes, there are a few, very few, OTL designs, but as soon as you put a transformer in the signal path, high fidelity goes out the window. The low response rolls off around 40 or 50 Hz because the inductive impedance starts dropping pretty badly and the highs start rolling off above 15 KHz or so due to the distributed capacitance in the transformer windings.

You can plot the frequency response of a GOOD solid state amp with a ruler. You put a dot at, say, 10 Hz (you NEED to roll off the subsonics), a dot at 100KHz, and draw a horizontal line between them.

The one place a vacuum tube amp shines is a musical instrument amp, especially guitar. Electric guitars sound great with a little bit of third order distortion. And an electric guitar just sounds a little "flat" when fed into a high fidelity SS amp. Otherwise tube amps just aren't that efficient. A 70 watt amp needs about 50 extra watts just to heat the thing up. And you are right about the other problem. Once a set of tubes start going soft, they can be difficult to replace.

John


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 Post subject: Re: True emission?
PostPosted: Mar Tue 24, 2020 6:01 am 
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re: guitarists..

This is a popular unit. Based on reviews across the interwebz, it seems to pretty much satisfy the needs of many guitarists.

https://orangeamps.com/products/accesso ... ve-tester/


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 Post subject: Re: True emission?
PostPosted: Mar Wed 25, 2020 12:27 am 
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. . .


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 Post subject: Re: True emission?
PostPosted: Mar Mon 30, 2020 12:19 am 
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. . .


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 Post subject: Re: True emission?
PostPosted: Mar Mon 30, 2020 8:18 am 
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How about applying a negative voltage to the plate, a positive voltage to the grid,
both referenced to the cathode. If it oscillates, the grid, plate and cathode are good.
Would this serve as an effective emission test ?

A 6C4, is a fine high frequency tube.


Also when an AC voltage is fed between the grid an cathode of a working
amplifier,the grid /cathode absorbs power from the driving source.
Attachment:
Let barking hausens lie.jpg
Let barking hausens lie.jpg [ 627.77 KiB | Viewed 347 times ]

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 Post subject: Re: True emission?
PostPosted: Mar Mon 30, 2020 11:00 pm 
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Sherman, is this a case of letting the wife fire this circuit up while I hide in the basement, or why are the neighborhood dogs barking?


Attachments:
images.jpg
images.jpg [ 19.39 KiB | Viewed 329 times ]
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 Post subject: Re: True emission?
PostPosted: Mar Mon 30, 2020 11:35 pm 
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Oddly enough as I read this again, I can see what you are saying as it does seem to isolate the cathode, and shows how the emission from the cloud is affecting the oscillation and strength of it. This could be an extra test added into a tube tester, along with proper resistances to drive a meter, or into some solid state device to show extra parameters of a tubes performance. Would be interesting to compare identical tubes and see the results, it is exactly along this sort of line I am imagining, a further test of how the control structures are influencing the cloud. The test would more clearly show the power and sensitivity of any ac signal pushed into a tube, a whole new perspective.


Last edited by Brobertson on Mar Tue 31, 2020 1:32 pm, edited 3 times in total.

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 Post subject: Re: True emission?
PostPosted: Mar Mon 30, 2020 11:51 pm 
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Methinks existing emission and transconductance testers already do show “the power of the cloud”.......whatever that means

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 Post subject: Re: True emission?
PostPosted: Mar Tue 31, 2020 12:50 am 
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Not arguing that all current tube testers show their quality, they do it quite well, but when you test two identical tubes with these methods and they test the same, then try them in the circuit you find one hits the mark much better, you begin to ask why. Tubes are basically all hand made (possibly archaic by today's stuff) devices, metals, materials on the cathode, all put through the same process of manufacture, and thus when you find one sounds so much better in the circuit, you doubt the tester. Current tube testers show to a certain extend their quality, but in the circuit they tell me nothing - and I have rolled many. There must be a reason.


Last edited by Brobertson on Mar Tue 31, 2020 1:46 am, edited 1 time in total.

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 Post subject: Re: True emission?
PostPosted: Mar Tue 31, 2020 12:57 am 
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No one doubts the tester. We accept that tubes vary and may or may not work the same in any given circuit

Going in circles here...... I’m out!

Best of luck to ya

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 Post subject: Re: True emission?
PostPosted: Mar Tue 31, 2020 1:17 am 
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Quote:
Bouncing back from the negative plate clearly shows the power of the cloud emission, a total isolation.

I have NO CLUE what you are saying....

My hunch is that you would benefit by reading up on vacuum tube theory.

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"Even if you don't understand Ohm's Law, you are still required to obey it."


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 Post subject: Re: True emission?
PostPosted: Mar Tue 31, 2020 3:54 am 
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Location: Powell River BC Canada
quote:

For ANY kind of tube test, you have to do 3 things:
--Apply a potential from plate to cathode
--Do something to control the potential from grid to cathode
--Measure the cathode current


After reading this thread, there is one more test, that might be considered.
It is the open element test.

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 Post subject: Re: True emission?
PostPosted: Mar Tue 31, 2020 3:57 am 
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Brobertson wrote:
Oddly enough as I read this again, I can see what you are saying as it does seem to isolate the cathode, and shows how the emission from the cloud is affecting the oscillation and strength of it. This could be an extra test added into a tube tester, along with proper resistances to drive a meter, or into some solid state device to show extra parameters of a tubes performance. Would be interesting to compare identical tubes and see the results, it is exactly along this sort of line I am imagining. Bouncing back from the negative plate clearly shows the power of the cloud emission, a total isolation. The test would more clearly show the power and sensitivity of any ac signal pushed into a tube, a whole new perspective.

You would need a microwave receiver to know if it was doing anything. Also, it won't test the capabilities of the tube since the power has to be kept very low to avoid overheating the grid.

Quote:
My hunch is that you would benefit by reading up on vacuum tube theory.

+1

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