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Old 27th May 2012, 10:36 AM   #1
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Default QQV03-20A/CV2799

Hi All,

I have got myself some QQV03-20A/CV2799 and would like to make a Single-Ended Amp with them.

I have found a circuit on the net for the 829B which I can use as a guide. However, as this is/was a RF Transmitting Valve the Characteristics given online:-

CV2799 @ The National Valve Museum

and

CV2799

don't give much away as to the Anode Load Resistance and Cathode Resistor value, understandably as this was not its intended use.

Has anyone made an AF Amp with this Valve and wouldn't mind me 'stealing' their circuit or can give me clues as to the Values the O/P Transformer and Cathode Resistance should be?

All the best,

James.
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Old 27th May 2012, 01:03 PM   #2
DF96 is offline DF96  England
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See the datasheet for audio use. However, this is for Class B modulator service where power is more important that fidelity.

You will probably have to do the usual stuff with load lines on the curves.
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Old 28th May 2012, 01:23 AM   #3
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Default Audio Amps with VHF Double Tetrodes

Not SE, but perhaps still of some interest...

Steve Bench did one of his matrix amps using the YL1060, a dual tetrode designed for RF applications.

Fred Nachbaur did one with TT15's (basically a smaller oddly-pinned variant of the QQV03 types, but still an RF dual tetrode).

Jaz

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Old 28th May 2012, 08:44 AM   #4
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Thanks Folks.

Not much info out there then. I'm on my own I guess, well work will start in the not too distant future, just making my workshop in my new house at the moment.
I'll keep you posted.

James.
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Old 28th May 2012, 09:47 AM   #5
tricomp is offline tricomp  Denmark
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Look at the curves. They are nice looking for push-pull class AB2.
Doesn't take a lot of drive-power. Any 5687 cathode-follower will do it.
Probably with a CCS in the tail for Higher-Fi.
About AB2:
I just finished the better part of a guitar-amp, that is everything except the actual input pick-up amp section. Pre-amp, phase-inverter, cathode-follower and output (6AD10 Compactrons). What I made first was a traditional class A & AB and it sounded OK. Nothing special and flea-power watts. In the past I did AB2 with 2C34 with success so I thought why not try again with the 6AD10's? Let me tell you, IT WORKS. The sound is rich and full, bass you won't believe from a skimpy Hammond transformer and clean, undistorted highs. Flea-power gone! (I MAY have to work with this quality-level to bring it 'down' to suit guitar-use)
What I'm saying with this is, that if it's possible with tubes not exactly made for AB2 then it should REALLY sing with the QQV03/20A's.
Don't know about SE drive with cathode-follower; I never did one. In PP it works.
Schematic for the above mentioned amp attached. Disregard input-triode circuit and the 206V noticed below the volume-pot.

rgds,

/tri-comp
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File Type: pdf Mini_Gee-Tah_v2.2.pdf (27.7 KB, 70 views)
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Old 28th May 2012, 05:31 PM   #6
7N7 is offline 7N7  United Kingdom
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Quote:
Originally Posted by percival007 View Post
Hi All,

I have got myself some QQV03-20A/CV2799 and would like to make a Single-Ended Amp with them.

I have found a circuit on the net for the 829B which I can use as a guide. However, as this is/was a RF Transmitting Valve the Characteristics given online:-

CV2799 @ The National Valve Museum

and

CV2799



don't give much away as to the Anode Load Resistance and Cathode Resistor value, understandably as this was not its intended use.

Has anyone made an AF Amp with this Valve and wouldn't mind me 'stealing' their circuit or can give me clues as to the Values the O/P Transformer and Cathode Resistance should be?

All the best,

James.

Yes, I built a push pull amplifier with these. It was just to drive tweeters. I ran them as triodes - so of course I had to run both sections in parallel. I made some triode curves for them, but I don't know if I can find them at present. I can tell you that Ra is about 1k - it's basically an 832. My problem was connecting to the anode pins. The valves got so hot that in one case the solder melted! Pay attention to cooling. As triodes they were easy to drive - about -25V bias but I got very little power - only about 6W. I could have done better had I had more suitable output tansformers I suppose. The driver circuit used +ve and -ve supplies and was similar to Morgan Jones's Crystal Palace amplifier - I used 7N7s and 14N7s

Paul
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Old 28th May 2012, 08:16 PM   #7
7N7 is offline 7N7  United Kingdom
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Default A bit more

I recall that I had to make the anode connectors. I used nylon blocks at first but gave up - too fiddly to make. I just used connecters plundered from old computer cables and given the necessary squeeze with the pliers.

I think that the shape of these valves is the clue/ I wouldn't mind betting that they had heatsinks clamped to them and finned anode connectors to get the heat away, this is often seen on power valves of the RF type.

For those who don't know he valve, here's a snap I posted elsewhere on the forum. It shows l-r QQVO3-20, YL1071, YL1150, YL1071 and 832, ANd I still have the data for the triode curves for the 3-20, but not the curves themselves - my computer is resting abroad at present!

Paul
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File Type: jpg RF Selection.jpg (54.2 KB, 86 views)
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