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Old 20th January 2009, 10:43 PM   #2341
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Quote:
Originally posted by RMS
they all sounded good except the Chinese 6L6GC "Coke Bottle"
That tube is super cheap and really rugged. However, in use, it's output is lower than any other 6L6 tube I've seen and it doesn't sound as good. It has it's place in guitar amps or radios, but probably not really in high-end stuff. Though I have used the Chinese KT66s and they are very nice tubes. Though my current favorite production tubes are the Russian KT88s -- Tung Sol, EH, GL...
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Old 23rd January 2009, 03:50 PM   #2342
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Location: Alps:Tube amp designs over 150W, SMPS guru.
A modified Mullard 7+7W amp as a just completed as an early winter project. By todays standards the original Mullard design is a poor performer, and this one with different phasesplitter and front end tube totally outperforms the original by magnitudes. THD now 0.035% at 1KHz at 7W each channel with -3dB at 50KHz. hum& noise -80dB.
Tube line up,12GN7, ECC88 (sections parallelled as concertina) and ECL82's, the triode section of the pentode dumped.
Since I've got several obscure 12GN7's these TV video pentodes were once up-market 12BY7 replacements and have excellent linearity.
With a B+ of only 270V, this amp offers brilliant easy listening.
The main distortion reduction is in the o/p stage. Fixed bias is used and 43% UL taps instead of 20%. With 20% taps, thd doubles. For those wanting to build this, note the ECL82 pentode grids will require distortionless drive capable of 15+15V rms. This is considerably higher when compared for an EL84.

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Old 23rd January 2009, 03:55 PM   #2343
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The 7+7W amp; The 12GN7 isn't recommended for low level mV signals, as it is somewhat microphonic and has no int shield. Graph of amp thd shown. Output transformers; coutesy Sowter.


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Old 25th January 2009, 06:07 PM   #2344
adamus is offline adamus  United Kingdom
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baby huey amp (circuit design by Gingertube).

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This is my first p2p build. Sounds stunning.

and the bijou headphone amp

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Old 25th January 2009, 08:20 PM   #2345
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Adamus, I'd bet your'e finding your little (EL84) amp sounds loud,as mine does. Put the 7+7 Watter up on top of the 150+150 main frame amp as shown in pic, these small amps are way more value for money. The log power scale puts the big ones at a massive disadvantage as also the ridiculous weight for an Altlas man. 5kg instead of 65 kg.
The ECL82 pentode is nice and tame to work with, the triode couldn't be more performance miserable, so I dumped this bit...

I expected the sound quality of the 7+7 Watter to be bit' lower than the 150+150W beast; No so.
I can recommend small amps for anyone.
I will have to dig out the Gingertube design and examine it.

richy
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Old 30th January 2009, 11:00 PM   #2346
noyan is offline noyan  Turkey
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Default My new GM70 SET monoblock amplifier

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My custom GM70 tube based 2x30 Watts monoblock SET amplifier. It was new built point-to point connections by using turrets. Amplifier has very loud and open sound, with lovely midrange and deep bass. Giving huge sound even without clipping at very high sound levels. No any audible hum with my 93db Tannoys even from zero distance from loudspeakers.

Explanation of design:

- Both halves of 6N8S tube are direct coupled to each other. The output of 6N8S tube also direct coupled to GM70 tube by using an anode choke to eliminate the sound loss especially in mid and high frequency bands. There is no any coupling or cathode capacitor used in this amplifier. Cathode leg of the GM70 power triode is directly connected to ground without any resistor or capacitor. Signal path is very short and design is so simple to provide extremely natural sound. Anode voltages for 6N8S and GM70 are separately provided by mosfet regulated power supply circuits. Filaments of both tubes are separately heated by regulated supply circuits to cancel the hum.

-Type: Mono block Single ended Class A1.

-Output Power: 2x30Watts to 6 or 8 Ohms.

-Feedback: No local or global feedback used.

-Bias: Adjustable fixed bias. One bi-color (Green-red) led and an adjustment trimmer is built on.

-Delay on circuit: Yes

-Tubes: Input tube; 6N8S (6SN7) , Output tube; GM70 copper plate.

-Output transformer: AE (Hi-end transformer company from Holland) Double C core 0,05mm laminations, max. 45Watts output, 6 and 8 0hms secondary.

-Speaker connectors: Gold plated, heavy-duty.

-Power consumption: 250Watts.

-Case/chassis: 2cm. thick polished hornbeam massive wooden case and 2mm thick steel chassis.

-Sizes: (Each mono block): 210mm(W) x 420mm(L) x 100mm(H); 19Kg.
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Old 31st January 2009, 07:55 AM   #2347
felixx is offline felixx  Romania
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Very nice.
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Old 31st January 2009, 08:54 AM   #2348
noyan is offline noyan  Turkey
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Smile GM70 SET

Thank you!
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Old 31st January 2009, 09:47 AM   #2349
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Default EL84 Red Light District prototype

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Old 1st February 2009, 04:33 PM   #2350
wicked1 is offline wicked1  United States
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Here is my finally complete tubelab 300b amp. Finished the amp a year ago. Finally got a nice drill press last week, and finished the chassis last night! Turned out better than I had hoped.


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