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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: 09 Jan 2019, 19:35 
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Joined: 21 Oct 2015, 23:26
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Hello

Any opinions or suggestions about this hybrid tube preamp ?

Thank

Bye

Gaetan


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Last edited by gaetan8888 on 09 Jan 2019, 20:01, edited 1 time in total.

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PostPosted: 09 Jan 2019, 19:54 
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Joined: 23 Feb 2017, 02:02
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Can't really tell by schematic have to listen yourself, two gain stages one mosfet then 12ax7. Plently or some feedback depending on the overall gain and the ammount feedback allows for low distortion and listen to only the tube.

A quick guess is R5 R6 is boost strapped by the vaccumtubes gride cathode which could mean the impedance is very high so large open loop gain and lots of feedback for low distortion, not 100% sure though

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PostPosted: 09 Jan 2019, 20:02 
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Hello

I've repost the circuit with now the parts values in my first post.

Thank

Bye

Gaetan


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PostPosted: 09 Jan 2019, 20:46 
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Same impression as before

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PostPosted: 10 Jan 2019, 11:16 
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Joined: 04 Jun 2008, 20:59
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Hi, Probably would work. Hard to tell how it would sound. I much prefer stages with zero nor nearly no negative feed back and this one has a bunch. Probably very linear and low distortion, but might not be "musical" in sound. Then again that brings up the can of worms on how things should sound....to each their own.

Good listening
Bruce

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PostPosted: 10 Jan 2019, 14:20 
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I typically find valve only schematics to have high distoriton and the valve distortion is too much to be warm anymore.

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PostPosted: 10 Jan 2019, 17:20 
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Joined: 21 Oct 2015, 23:26
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Hello

Yes, there's a lot of negative feed back, maby replacing the 12ax7 by a 12au7, may need to change R4 value ?

But it could be more linear and less feedback.

Thank

Bye

Gaetan


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PostPosted: 10 Jan 2019, 19:55 
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More feedback is more linear in most cases

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PostPosted: 10 Jan 2019, 20:12 
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ILoveHiFi wrote:
More feedback is more linear in most cases
True.

However, in audio amplifiers, linearity is not the key to good sound. Harmonic structure and controlled intermodulation is the key.

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