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  1. As Chuck H said, you still end up with flying...

    As Chuck H said, you still end up with flying leads. In other words, you can get some components closer to the tube sockets, but overall, the components themselves are spread out more. Unless you're...
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    My guess is that it has to do with elegance. To...

    My guess is that it has to do with elegance. To an engineer, the paraphase looks (on paper) like a bit of a kluge compared to the cathodyne and LTP, both of which look like they would work well...
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    I can see that making a lot sense depending on...

    I can see that making a lot sense depending on where you live. I take for granted fast/easy/reliable shipping and generally low tariffs. If I didn't have that luxury then I'd need to rethink how I do...
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    Well, of course. My semi-rhetorical question was...

    Well, of course. My semi-rhetorical question was about fab houses that are too lazy/cheap/shabby to plate holes that we would want plated.
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    Are there actually board manufacturers that make...

    Are there actually board manufacturers that make double sided PCBs without through plating on the holes? Single sided, yes. Maybe DIY stuff that's etched and drilled at home... But I can't imagine a...
  6. Two 1N4007 in series (for a total of four) will...

    Two 1N4007 in series (for a total of four) will give you the PIV headroom you need. Not as easy to mount on the tube socket though.
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    So, if you replace the pot with one with twice...

    So, if you replace the pot with one with twice the resistance, then the gain will double at all settings of the pot. Doubling R122 (4.99K -> 10K) will restore normal operation.

    C115 (0.68uF) puts...
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    Is the pot either VR1 or VR2 in the schematic...

    Is the pot either VR1 or VR2 in the schematic below? (Both in the feedback loop of an opamp.)

    http://schems.com/bmampscom/hartke/hartke_ha3500_power_amplifier_sch.pdf

    If so, then you can...
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    I don't think you can get more resistance at 7mA...

    I don't think you can get more resistance at 7mA with 1/2 of a 12AU7. Maybe both halves in cascode...
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    By my estimation, the plate resistance of your...

    By my estimation, the plate resistance of your 12AU7 CCS is only about 15K to 20K. Merlin talks about using the same tube to get 36K, but I don't see it. http://valvewizard.co.uk/ccs.html
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    I settled on a simple solution. I threw away all...

    I settled on a simple solution. I threw away all of my old socks and replaced them with a big pile of identical new ones. No more sorting. When they start to wear out, I replace the entire pile with...
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    Thanks. Apologies for not remembering. It was...

    Thanks. Apologies for not remembering.

    It was popular for PA amps of that era to run 6L6s at around 450V into an 8K load for 25W. Mismatch speakers and taps to get a 4K load, or run KT66s into 8K...
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    Those transformer part numbers suggest that they...

    Those transformer part numbers suggest that they came from a Heathkit A9 which was PP 6L6, ~20W. But that does NOT mean that this homebrew amp was meant to take 6L6's.

    The L shaped board looks...
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    Many of us here are more vintage than we'd like...

    Many of us here are more vintage than we'd like to admit.
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    The only problem is that to get the 12.5V grid...

    The only problem is that to get the 12.5V grid bias requires a 270R cathode resistor instead of the 470R shown.
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    Ghost notes with 100W Marshalls is not uncommon...

    Ghost notes with 100W Marshalls is not uncommon and is usually due to excess ripple on the screens. You cab try increasing the capacitance in the first two PS nodes. Maybe add a second choke in...
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    To add to Enzo's reply, the external strap...

    To add to Enzo's reply, the external strap doesn't see (thus doesn't affect) the flux that stays in the core itself, but it does see the flux that "gets away." For that flux, it is exactly a shorted...
  18. I don't mind people asking question that they're...

    I don't mind people asking question that they're merely thinking about. It was explained to me recently that if one can't travel on vacation, then it's still beneficial to their well being to...
  19. Look along the bottom row of your keyboard for a...

    Look along the bottom row of your keyboard for a function key that (probably) has the same color grey writing on it. You would need to hold down that key to activate the embedded numpad. So, while...
  20. If you're using Windows, look for an application...

    If you're using Windows, look for an application call "Character Map" (charmap.exe.) It's more cumbersome than typing alt-***, but it will let you copy any of a zillion weird characters to the...
  21. I've edited that part of the drawing by tipping...

    I've edited that part of the drawing by tipping up IR13, putting the power amp input at the top instead of to the left. Notice how IR13 and IR14 look like a potentiometer (volume control) set at less...
  22. All real 6V6GT tubes will handle 14W. Early...

    All real 6V6GT tubes will handle 14W. Early datasheets list the Design Center rating as 12W, but later datasheets show the Design Maximum as 14W for the same tube. And that's just the plates; the...
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    Ian makes a good point that the initial charging...

    Ian makes a good point that the initial charging current (at power up) is the same for both caps, so the DC voltage that they initially charge to is not shared equally, but split according to 1/C....
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    Right. The AC (ripple) voltage is shared...

    Right. The AC (ripple) voltage is shared according to the inverse of the capacitance (1/C). What are the balancing resistors there for? To balance DC, not AC.
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    Whatever switch you use, wire it as shown below....

    Whatever switch you use, wire it as shown below. The schematic looks more complicated than it is. The layout shows how simple it is.

    edit: Pay close attention to the polarity of the two windings....
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    With all the bad press that Watts Audio has been...

    With all the bad press that Watts Audio has been getting, I would avoid them.

    Doug Hoffman sells very good turret boards. hoffmanamps.com
  27. The signal path is just along the top of the...

    The signal path is just along the top of the drawing. Neither tube 'passes' signal.

    The top tube is biased super-cold with the 25K pot and 10uF bypass cap. An increase in signal level causes an...
  28. I'm going to admit that I can't follow the signal...

    I'm going to admit that I can't follow the signal path.

    Are the cathodes tied together? The grids?

    Does it work by increased (DC?) current lowering rp which acts as the lower part of a voltage...
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