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  #11  
Old 6th October 2020, 11:01 PM
bikerhifinut bikerhifinut is offline
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Join Date: Jan 2006
Location: Penrith, Cumbria
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Default Re: KAT6550 schematics

I've donned my suit of armour before bob aims his crossbow at me!
The excessive gain issue on the Pre3 and pre4 variant can be got round quite easily and our very own John Caswell talked me thorough this very kindly on here and also at a show in person.
Basically you can fit a potential divider between stage 1 and 2 which will attenuate the signal to whatever you set it as.
I reduced the value of the grid leak on the second stage in order to keep the overall resistance down to 1meg as a hedge against noise, its not really that critical and if you think the bass response may be affected just increase the coupling capacitor value.
John C can explain the method in a far simpler and concise way than I and I think theres a thread in here what does it.
Anyway I got mine down to a manageable level,and bear in mind that although I build my power amps to have a lower sensitivity than most, I find this method to be very effective.
I do believe the current production pre3 and pre4 boards have this facility built in.
So all is not lost, you can adjust the gain should you feel it is needed.
By the way Bob you are not alone in not being a fan of the shunt mod. I think its a fudge rather than a solution and carries its own issues, for me the "log Law" seems to not function properly. My lug 'oles and its an opinion NOT a statement of fact. Its a bit like the way I find the standard polyester coupling caps to suit me better than expensive ones. I could be deaf.

Andy.
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  #12  
Old 6th October 2020, 11:12 PM
A Stuart A Stuart is offline
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Location: Selkirk, Scotland
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Default Re: KAT6550 schematics

Quote:
Originally Posted by bikerhifinut View Post
Its a bit like the way I find the standard polyester coupling caps to suit me better than expensive ones. I could be deaf.
A bit like I find eating the food with the reduced price sticker so much more satisfying.

Alastair
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  #13  
Old 6th October 2020, 11:34 PM
bikerhifinut bikerhifinut is offline
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Default Re: KAT6550 schematics

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Originally Posted by A Stuart View Post
A bit like I find eating the food with the reduced price sticker so much more satisfying.

Alastair
I'm sure I don't know what you mean......
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  #14  
Old 7th October 2020, 08:23 AM
bob orbell bob orbell is online now
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Join Date: Nov 2009
Location: kettering northants.
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Default Re: KAT6550 schematics

Thanks for this info Andy, I can't remember reading such information, but I will look, my chum has and uses my Pre III and even he commented on the gain, I had it back and fitted dividers in the output just before the output phono sockets, it works fine. Bob
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  #15  
Old 7th October 2020, 10:32 AM
Chris Chris is offline
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Join Date: Dec 2005
Location: Peterborough
Posts: 302
Default Re: KAT6550 schematics

Looking at a high-end pre amp this week, I noticed that it had 3 options of differing gains, 3 pairs of phono sockets each with a different gain. Perfect for those wanting and needing the option, easily applied.

Chris.
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