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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 10 Nov 2019, 20:21 
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Joined: 06 Jun 2008, 18:23
Posts: 5174
Location: Australia
Gio wrote:
Thanks Bruce. I've got your project posted on the site now:

JBAA - High Fidelity Tube Junk Box Audio Amplifier - http://diyaudioprojects.com/Tubes/Junk-Box-Audio-Amp/

I've also got a submission from Mark now and will get that posted soon.

Cheers,
Gio

Good work Gio.

Bruce, some good looking amps. Nice!

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Projects:”Image” - Low Profile 100W Class D amp | ”fiih” - 150W Holton inpsired power amp | "Precision" - 300W Class AB Holton power amp | ”Gothic” - FET Push-Pull headphone amp


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PostPosted: 13 Nov 2019, 21:36 
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Joined: 04 Jun 2008, 20:59
Posts: 4078
Location: Arizona, USA
Hi Mark, Thanks, The 6Y6 one sounds the best to my ears, but the 6AQ5 one is prettier. I like wood and chrome for current builds mostly. But JBAAs are from what ever is on hand. Each of the two amps were built on chassis that were from defunct projects. Even I (especially accourding to the "other one who is all knowing") make mistakes and dud projects. 8-)

BTW, many of your offerings are really nicely done too. :beerchug:

Good listening
Bruce

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PostPosted: 16 Dec 2019, 06:45 
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Joined: 08 Dec 2019, 04:20
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Hello everyone!
Maybe my project is interesting, it seems effectively removing the Class-B crossover distortion,
it's discussed at
https://www.physicsforums.com/threads/c ... ng.981712/
The idea is to combine a current driver, a current-pumping coil and a precision power follower like this
Image
(of course, a small LR parallel circuit ought to be added between the follower output and that big coil, for HF stability)
The input current driver, in my simulation, looks like this
Image
The 2 Ohm resistor is connected to the diodes limiting the output (unipolar) between 3 and 37V.


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PostPosted: 16 Dec 2019, 21:28 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, An interesting idea....but since few hi-fi audio amps use class "B", I don't actually know of any. AB or A or even D, but not B largely IMO because of the crossover distortion. The only application I know of is in modulators for transmitters and even then that is not common any longer. Good submission though. Thinking out of the box....it might be good for a power inverter as it would cut down noise and EMI in the output and thus reduce filtering needs.

Good listening
Bruce

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PostPosted: 18 Dec 2019, 07:37 
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Joined: 08 Dec 2019, 04:20
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Hmmmm thanks -
Then I rather adapt it for 12V supply, 1 or 1/2 Ohm speaker - since it's low load resistance that makes the crossover problem challenging, especially . The power MOSFETs shall be powered from the 12V battery, the opamps from the secondary -10 and +22V. So the coil ratio can be 20 rather than 50 as the low-voltage Class-A current driver won't dissipate too much power.


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PostPosted: 30 Dec 2019, 00:00 
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Joined: 23 Feb 2017, 02:02
Posts: 584
It only takes bias of few 1-5mA per transitor of 125W - 300W to get amps from Class B to Class AB.
Now its efficent and on scope you cant see or measure the diffrence between A or AB but can hear the diffrence.


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