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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: 15 Apr 2018, 05:16 
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Joined: 13 Jan 2018, 21:33
Posts: 33
Location: australia
hi, i noticed this 5 volt regulator which seems to deliver a fixed 5 volts rather than needing to adjust it. has anyone had any experience using this to heat the 300b’s or other such valves? Does this have the right specifications to do the job? if so are there any benefits/disadvantages of the lm323t over the lt1085 used in this thread? thanks, woodo
https://au.mouser.com/datasheet/2/389/C ... 470641.pdf
edit: although i see it says voltage is adjustable

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PostPosted: 15 Apr 2018, 11:04 
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Joined: 06 Apr 2009, 10:08
Posts: 1442
Location: US Pacific Northwest
Woodo wrote:
Does this have the right specifications to do the job? if so are there any benefits/disadvantages of the lm323t over the lt1085 used in this thread?
Actually there is a big disadvantage; the dropout voltage.

The old LM323 design has a rather large dropout voltage which is exacerbated by increased junction temperature. There is no way a rectified 6.3VAC transformer, with rectification loss, and appropriate filtering will provide the necessary input voltage to maintain a stable 5.0v output using this regulator with appropriate design margin. Regulation margin would be severely compromised. I chose the LT1085 (new data sheet location: 108345fh.pdf) for this design due to it being first and foremost a low dropout regulator (>1.2v at Ia=1.2A) and it exhibits much better long term stability than the LM series regulators. Regulators like the LM323 require a higher input voltage, hence dissipate far more heat, and hence require a more comprehensive thermal design solution.

In post #127 to this thread (http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=2699&start=127) I discussed at length, all the design requirements that went into the 300B filament supply design process. I would strongly suggest that anyone wanting to change the filament supply design read this post so that they understand the various tradeoffs involved.

As always, questions and comments are more than welcome.

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PostPosted: 15 Apr 2018, 22:04 
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Joined: 13 Jan 2018, 21:33
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Location: australia
Great, thanks for the advice Matt.

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