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Old 3rd Jul 2017, 8:28 pm   #21
Biggles
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Default Re: Audio amp on CV2799 ?

At least you wouldn't have to wait long for it to warm up. I remember looking after (GEC?) mobile equipment quite a few years ago with these bottles inside. The heaters were quick heat and only energized with the PTT. Why waste a VHF device with all it's design development on an audio amp? Can't understand it at all, although I admit I may be slightly biased towards RF. The bases may not be easy to come by either, which could have the knock on effect of cannibalization of even more good equipment.
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Old 3rd Jul 2017, 10:45 pm   #22
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Default Re: Audio amp on CV2799 ?

That'll be the QQZ03-20, quick heat but otherwise identical as far as I know.
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Old 4th Jul 2017, 12:36 am   #23
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Question Re: Audio amp on CV2799 ?

I would like to know in what equipment the QQV03-20 is currently used, either for new designs or maintenance purposes. I am under the impression that its traditional use has now been completely replaced by power R.F. transistors. If that is correct, then using these valves for audio is at least putting them to some use.

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Old 4th Jul 2017, 7:33 am   #24
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Default Re: Audio amp on CV2799 ?

Folk have been using transmitting valves in audio amps for years like the 807 and using TV valves like the 6DQ6B.

For myself as a builder of valve audio amps, I don't give a stuff for fashion but find the valve easier to work with at present. I'll use what I've learned building valve amps to tackle a transistor based one. One strong point in favour of the valve for a beginner like myself and others I guess is that a valve doesn't fall over and die when by some mistake you give it a few hundred volts in the the wrong place.

So whilst I can see the point of radio restorers being miffed at all the audio lads nicking all the PX4's etc, QQ type transmitting valves are unwanted, unloved and at least us audio manglers are using them. Though I doubt many amps will be made, they're tricky to use for the reasons given previously.

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Old 4th Jul 2017, 11:15 am   #25
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Arrow Re: Audio amp on CV2799 ?

Yes, since the "QQ" series of valves were intended for use at VHF / UHF, I can readily see that instability problems could easily arise when such are used in an audio application. But with careful construction - particularly aimed at making that construction "R.F. lossy" - and with ample by-passing, decoupling and filtering, I would have thought that such a project would be readily realisable.

I found this on the 'Net . . .
http://www.r-type.org/articles/art-138.htm

Al.

Last edited by Skywave; 4th Jul 2017 at 11:27 am. Reason: Add Internet reference
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Old 4th Jul 2017, 12:22 pm   #26
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Default Re: Audio amp on CV2799 ?

That's an interesting circuit Al. I see he's using a 12BH7 as PS to drive the QQV03-20 grids which will need some oomph that the 12BH7 provides. Still he's running it hard with very small anode resistors. Why is there such a mismatch between the OP stage grid R's though, R12 + 13, IE 390k + 47k? There's also a mismatch between grid stoppers.

Mr Carlson got 10w out of two QQV03 10's in PPin the video I refered to.

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Old 4th Jul 2017, 12:28 pm   #27
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Talking Re: Audio amp on CV2799 ?

Quote:
Originally Posted by Skywave View Post
Yes, since the "QQ" series of valves were intended for use at VHF / UHF, I can readily see that instability problems could easily arise when such are used in an audio application. But with careful construction - particularly aimed at making that construction "R
Hey Al, many things are possible but absurdly impractical. We could attempt one of the great cols of the Tour de France on a mountain bike, for example. No harm in it, but what's the benefit, and is it worth it?

I do think amps like this are essentially show -cases for what can be quite striking valves. That's a reasonable incentive, but it's hardly ever offered as the reason.

I think this would be really clear if someone proposed using near GHz-capable RF transistors in this application instead of some glass.

I can see why some earlier audio amps were modelled around TV line output valves for their cheapness , abundance , robustness /indestructability and anode dissipation, but this is another case altogether. Just because something can't be used in its original application doesn't make it mandatory to use it in another.

There's no harm in it, but to suggest that it has any innnate merit is another thing altogether .

I don't actually care if someone does make an amp from these or not; I'm just engaging with your line of reasoning, partly because I have spare energy to do while rattling around at home!
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Old 4th Jul 2017, 2:04 pm   #28
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Arrow Re: Audio amp on CV2799 ?

Quote:
Originally Posted by astral highway View Post
Just because something can't be used in its original application doesn't make it mandatory to use it in another.
In this particular thread, I am not aware that anyone has come even near to suggesting that using these valves in an audio application is "mandatory".

But more to the point: I 'fool around' with many an electronic idea: sometimes without any regard for its practical application; sometimes, something really useful develops. Many have been such avenues explored in Science and, occasionally, to the benefit of humankind. For myself - apart from satisfying my curiosity, now that I am retired - I have a bit more time to indulge in such pursuits. And that also keeps me out of the pub!

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Last edited by Skywave; 4th Jul 2017 at 2:09 pm. Reason: Add quote.
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Old 4th Jul 2017, 2:33 pm   #29
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Default Re: Audio amp on CV2799 ?

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Originally Posted by Skywave View Post
In this particular thread, I am not aware that anyone has come even near to suggesting that using these valves in an audio application is "mandatory".
Sure, Al. I was pushing the point a bit, partly for mischief, with a wink, but the ingredients were certainly in your argument earlier in post no. 23:
Quote:
Originally Posted by Skywave View Post
I would like to know in what equipment the QQV03-20 is currently used... I am under the impression that its traditional use has now been completely replaced ... If that is correct, then using these valves for audio is at least putting them to some use.
...Paraphrasing you here, it is better to use something [in a function where it is not actually fit for purpose] than to not use it at all. I don't agree; again, not that it really matters one hoot. But I'd say, if there's nothing to recommend a UHF+ valve for audio amp service, it's not essentially any better than putting it in a display case.

Quote:
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But more to the point: I 'fool around' with many an electronic idea: sometimes, something really useful develops....Many have been such avenues explored in Science and, occasionally, to the benefit of humankind.
Ah, come on now, Al, who are you kidding! Maybe in the days of Faraday, just about. But science isn't done in this haphazard way now, by one particularly enlightened individual tinkering around and getting a brainwave. Or perhaps could you cite one recent example?

On the other hand, tinkering about/ 'fooling around' is (potentially, given the right material circumstances) anyone's privilege or right. It's no better or worse than watching a TV series, painting, or walking the dog.
It doesn't have to have such a grandiose meta-purpose, surely? It can just be a thing that we do to pass the time, and that's ok. And yep, if that means keeping someone out of the pub, who doesn't really want to be there, great stuff.

Perhaps we can agree that much?
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Old 4th Jul 2017, 3:01 pm   #30
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Default Re: Audio amp on CV2799 ?

I agree with Al. These valves are plentiful and effectively obsolete for their original purpose. It does no harm at all to play around making audio amps with them, and if that raises the price a bit then they're less likely to get binned when people have clearouts of useless valves. It can be an interesting challenge to build an amp with what are theoretically completely unsuitable valves (though I've never done it).

Back when ECC82s were unloved and cheap, I remember a monoblock design which used 10 of them in parallel.
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Old 4th Jul 2017, 3:40 pm   #31
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Default Re: Audio amp on CV2799 ?

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Originally Posted by astral highway View Post
Ah, come on now, Al, who are you kidding! Maybe in the days of Faraday, just about. But science isn't done in this haphazard way now, by one particularly enlightened individual tinkering around and getting a brainwave. Or perhaps could you cite one recent example?

On the other hand, tinkering about/ 'fooling around' is (potentially, given the right material circumstances) anyone's privilege or right. It's no better or worse than watching a TV series, painting, or walking the dog.
It doesn't have to have such a grandiose meta-purpose, surely? It can just be a thing that we do to pass the time, and that's ok. And yep, if that means keeping someone out of the pub, who doesn't really want to be there, great stuff.

Perhaps we can agree that much?
Having some background in research (maybe some years ago but much more recent than Faraday ) I must disagree. Yes it is true that science is much more disciplined now but my experience tells me that many a disciplined hour is spent persuing a dead end, whereas the dreaming of a tuned in mind can, and still does, make a leap into hyperspace! A scientific team is essential to follow up an idea but it takes more to invent or take the abstract step into new dimensions.

Maybe using a transmitting valve for audio will produce a working but unimpressive result but so what. It is an interesting idea, similar to many that were followed by the valve manufacturers and implementing companies back in the day.

My strongest viewpoint though is that someone who thinks of ideas is thinking! That is opening the door to invention.
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Old 4th Jul 2017, 3:53 pm   #32
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Default Re: Audio amp on CV2799 ?

Quote:
My strongest viewpoint though is that someone who thinks of ideas is thinking! That is opening the door to invention.
Agreed. I think a lot of us on this forum enjoy thinking up ideas and overcoming problems. I'm certainly one.

Just saying, ultimately, that we don't really need to justify what we do. It is no better or worse than any alternative way of spending our time. And for me, there's a great enjoyment in debating these sorts of things in such a friendly and accommodating space.
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Old 4th Jul 2017, 6:16 pm   #33
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Arrow Re: Audio amp on CV2799 ?

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My strongest viewpoint though is that someone who thinks of ideas is thinking! That is opening the door to invention.
Which prompts me to state another quote from the great Niels Bohr:
"No - you're not thinking! You're just being logical."

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Old 4th Jul 2017, 6:22 pm   #34
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Arrow Re: Audio amp on CV2799 ?

Astral: It's quite clear to me that you and I do not overlap in our respective thinking. But that's O.K.: this world needs people who think differently: "thinking" being the important bit! No hard feelings: good luck with all your endeavours.

Ta Ta.
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Old 4th Jul 2017, 6:50 pm   #35
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Default Re: Audio amp on CV2799 ?

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Astral: It's quite clear to me that you and I do not overlap in our respective thinking.
Ahah, but is it? I think we can agree that based on this one example, we have a different viewpoint. And that's as far as the conclusion can go.

(Again, said with a wink. I'm not being pedantic, but I do like to draw appropriate conclusions from the information available!)

For what it's worth, I find your posts usually very informative and thoughtful. I'm definitely not agreeing that we are in stand-off!
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Old 4th Jul 2017, 8:37 pm   #36
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Default Re: Audio amp on CV2799 ?

The Mullard data sheet contains a set of operating conditions for the QQV 03-20 as an AF power amplifier (admittedly in class B) so they didn't think it was out of the question.
The Chinese have been flogging audio amplifiers using FU29s (same as 829B) for years.
Some people use 6080s as headphone amplifiers, not as series regulator valves. I quite fancy a couple of A2293s as a push-pull triode amplifier. Would that be de trop?
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Old 4th Jul 2017, 9:10 pm   #37
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Default Re: Audio amp on CV2799 ?

Pete Millet's build looks stunning. There is an obsessional eye for materials, layout and function.

I wouldn't mind owning such an amplifier, especially to attract comments on the build quality. With every detail covered with so much intention, it's hardly surprising that the valves chosen look particularly good.
I think there's a market for these in the headphone amplifier circuit especially? And who knows, maybe, the aesthetics of the build really do add up to deeper listening pleasure.

I understand this level of obsession; I think many of us do. It just may take different forms for each of us.

Nice post. Thank you.
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Old 4th Jul 2017, 9:36 pm   #38
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Default Re: Audio amp on CV2799 ?

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I quite fancy a couple of A2293s as a push-pull triode amplifier. Would that be de trop?
Now that's a stand -up -and -listen idea! From series pass to audio amplifier service!

I like it!

Don't get me wrong, I'm all for valves being put to all sorts of imaginative uses.
I only 'mind' (and that's just my Ego, so I'm learning to ignore it) when somebody asserts that the alternative application has some magical properties that it doesn't, on the face of it, actual have.

But as I say, that's just my Ego. It doesn't really matter. I often try using things in ways they weren't designed to be used.
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Old 4th Jul 2017, 9:56 pm   #39
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Default Re: Audio amp on CV2799 ?

My Topband AM transmitter, built in 1980, uses a QQV03-10 as a push-pull modulator. It was what I had available at the time and uses only one valve "space"

Cheers

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Old 4th Jul 2017, 10:03 pm   #40
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Default Re: Audio amp on CV2799 ?

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My Topband AM transmitter, built in 1980, uses a QQV03-10 as a push-pull modulator. It was what I had available at the time and uses only one valve "space"
Ah, that's fascinating, Aub! So you just built it round what you had to hand. I'd be interested to see the modulator circuit. Is it high-side, presumably?
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