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Old 2nd July 2012, 01:07 AM   #4171
Cassiel is offline Cassiel  Libya
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Same color combo than one of the amps above - still doesn't look right to me for some obscure reason. Maybe because of the wedding colors.... the beige, the red. Hmmm. Kinda makes me feel uncomfortable.
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Old 2nd July 2012, 10:30 AM   #4172
56oval is offline 56oval  Australia
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Originally Posted by CSlee View Post
Here is an amp I built for a friends wedding present. It is an old bakerlight radio, gutted then a EL84 PP amp built inside. Engraved on the front is a lyric from Radiohead - True love waits and the date.

It sounds good, not amazing but good enough for a gift I think. And it took quite a while to get it all together - I thought my metal work was bad, it turns out my wood work is even worse! It is a little rough around the edges to say the least.

Right, now that is done I can finally get to work on my #26 preamp. I really don't know where you guys get the time for all your projects, you must all be retired!

Cheers

Charlie
Very cool .

Cheers
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Old 3rd July 2012, 06:24 PM   #4173
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Originally Posted by jervill View Post
Love the colour combinations and the art deco logo! Which wood for the cheeks?
Thanks, It's walnut, stained with some water-based red dye.

Beautiful amplifier Charlie! What a great wedding gift!
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Old 4th July 2012, 08:58 AM   #4174
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Default 2 x 10 W PP with QQE03/12

I built a prototype with a pair of QQE03/12 double tetrodes and pair of soviet 6F12P triode-pentode (which is a phenomenal tube).
Voltage amplifying stage is a CCS loaded triode and phase splitter is done with pentode section of 6F12P. Output stage has fixed bias and 10k to 8 ohms Indel output transformer.
Anode voltage is 300 V and screen voltage 220 V. Both bias and screen supply are stabilized. Output power is 10 W with 1 % THD. With one watt THD is some 0.1...0.2 % with 10 dB GNFB.
Input sensitivity is 600 mV. Hum level at the output is some 80 dB below max. Po. All heaters are done with AC.
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Old 4th July 2012, 01:07 PM   #4175
dady is offline dady  Argentina
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Default Amazing

Quote:
Originally Posted by artosalo View Post
I built a prototype with a pair of QQE03/12 double tetrodes and pair of soviet 6F12P triode-pentode (which is a phenomenal tube).
Voltage amplifying stage is a CCS loaded triode and phase splitter is done with pentode section of 6F12P. Output stage has fixed bias and 10k to 8 ohms Indel output transformer.
Anode voltage is 300 V and screen voltage 220 V. Both bias and screen supply are stabilized. Output power is 10 W with 1 % THD. With one watt THD is some 0.1...0.2 % with 10 dB GNFB.
Input sensitivity is 600 mV. Hum level at the output is some 80 dB below max. Po. All heaters are done with AC.
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Right now I trying to do some like this, beautiful finish. The PCB.
Nice election (couse i did the same) Can you publish the diagram?

Congratulations again



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Old 4th July 2012, 01:41 PM   #4176
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Default Diagram for the QQE PP amp.

Here it comes:

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Old 4th July 2012, 04:52 PM   #4177
dady is offline dady  Argentina
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Dear Artosalo, thankyou very much for the circuit. A couple of more questions. Does the +vcc at V3 plates 300V?
The tranies are from witch trade name?
Best and thanks again.
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Old 4th July 2012, 04:56 PM   #4178
dady is offline dady  Argentina
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Did you try to direct coupled between the 6F12 triode and pentode?
Did you try to use the pentode like amp and the triode like a phase splitter?
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Old 4th July 2012, 06:50 PM   #4179
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Supply voltage at the anodes of QQE02/12 is some 300...310 V. Optimum screen supply is about 220 V and quiescent anode current 30...32 mA.
CCS transistors are BF472 (PNP) and the NFET at power supply is IRF820.
Direct coupling of the voltage amplifying stage and phase splitter requires that the anode voltage of 1st stage should be some 80 V. The circuit I used give lower distortion.
I did not try to use pentode as 1st stage since the gain of triode section (mu = 100 ) was just what I needed. But ofcourse the pentode would work fine as an amplifier.
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Old 4th July 2012, 11:17 PM   #4180
dady is offline dady  Argentina
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Wonderfully cover, you are there, knowing your material your valves.
The 6f12 pentode like triode is so similar to the triode alone. They have both same transconductance and . Wavebourn likes this valve.
Best Regards and thanks for your fast reply
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