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  #1  
Old 21st July 2021, 10:11 AM
rgccarter rgccarter is offline
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Default WAD KT88 Schottky and pi filter mod for LT supply

Just purchased a 2nd hand KT88 off fleabay, to upgrade - had a KEL84 for 12years which has been extensively modded but time for a new project


As the title says, can anyone point me to directions for schematic, build instructions, parts list to do this mod on a KT88?

know its on WD88VA as an XL upgrade - but would this be applicable to the KT88?

Thanks
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Old 21st July 2021, 12:03 PM
bob orbell bob orbell is offline
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Default Re: WAD KT88 Schottky and pi filter mod for LT supply

Yes, but I doubt you will hear any difference, did it to my WA88, but it was a pointless exercise. I got better results from low ESR capacitors on the HT line. Bob
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Old 22nd July 2021, 12:36 PM
Richard Richard is offline
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Default Re: WAD KT88 Schottky and pi filter mod for LT supply

Quote:
Originally Posted by rgccarter View Post
Just purchased a 2nd hand KT88 off fleabay, to upgrade - had a KEL84 for 12years which has been extensively modded but time for a new project


As the title says, can anyone point me to directions for schematic, build instructions, parts list to do this mod on a KT88?

know its on WD88VA as an XL upgrade - but would this be applicable to the KT88?

Thanks

Hello and welcome,


If yours is Kit88 the FAQ is here,


http://www.world-designs.co.uk/forum...ead.php?t=7644


I did it to mine and wrote it up along with the results. There was a measurable and audible improvement
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Old 22nd July 2021, 12:51 PM
Richard Richard is offline
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Default Re: WAD KT88 Schottky and pi filter mod for LT supply

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Originally Posted by bob orbell View Post
Yes, but I doubt you will hear any difference, did it to my WA88, but it was a pointless exercise. I got better results from low ESR capacitors on the HT line. Bob

If your amp is an WD88VA variant then all you need is the circuit diagrams for WD88VA and WD88VA XL to compare to yours and work to. Drop Greg a PM to see if he can send them to you. Peter Comeau used this modification to improve the heater suppy in the tweaked XL version.
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Old 22nd July 2021, 03:02 PM
Matthew Snell Matthew Snell is offline
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Default Re: WAD KT88 Schottky and pi filter mod for LT supply

Just for information, it gets my vote. You may not "hear" any difference, but the amp will be technically better. Of course you MAY even "hear" a difference.

Not trying to sell anything - although the parts are here (as well as being available elsewhere).

Also, Bob is right about the HT caps. Did you bypass the caps, Bob, as we do in the current KT88 XL?

Matthew
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  #6  
Old 22nd July 2021, 04:35 PM
bob orbell bob orbell is offline
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Default Re: WAD KT88 Schottky and pi filter mod for LT supply

No Matthew, I did not by-pass any capacitors, what I understand from books, by-passing PSU capacitors is a little more complex than just adding a smaller capacitor to the main capacitor, the connections must be made not at the main capacitor but at the load end and 0 volt line, this would have meant a lot more wire. If I am wrong about this, please correct me. Bob
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  #7  
Old 22nd July 2021, 04:40 PM
bob orbell bob orbell is offline
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Default Re: WAD KT88 Schottky and pi filter mod for LT supply

Richard, -- Peter Comeau used this modification to improve the heater supply in the tweaked XL version. -- of course, a regulated supply would be better, but I doubt many would hear any improvement. It is the HT supply to the valves that produces a better sound. Bob
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  #8  
Old 22nd July 2021, 07:25 PM
John Caswell John Caswell is offline
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Default Re: WAD KT88 Schottky and pi filter mod for LT supply

Please define "Better"

John
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  #9  
Old 22nd July 2021, 08:00 PM
bob orbell bob orbell is offline
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Default Re: WAD KT88 Schottky and pi filter mod for LT supply

I think we have been here before John, OK, more refined a touch more detail and less harsh, I hope that helps . Bob
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Old 2nd August 2021, 02:04 PM
rgccarter rgccarter is offline
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Default Re: WAD KT88 Schottky and pi filter mod for LT supply

Quote:
Originally Posted by Richard View Post
If your amp is an WD88VA variant then all you need is the circuit diagrams for WD88VA and WD88VA XL to compare to yours and work to. Drop Greg a PM to see if he can send them to you. Peter Comeau used this modification to improve the heater suppy in the tweaked XL version.

Thanks that's great. The amplifier arrived today, but I don't have a CD-ROM drive so instructions would be helpful anyway.
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