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KT88 schematic

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Miles Prower

Miles Prower

Member
Joined 2005
dolphin-hsl.com
22mannightstar said:
I am looking for a detailed KT88 mono schematic utilizing 8 KT88's in push pull with 6sn7's as drivers. Any help will be greatly appreciated. thanks
Click to expand...

Why? :bigeyes:

I don't like those designs that parallel finals. How do you get all those tubes pulling together? Obviously, you are not going to get all of them operating with identical characteristics. Just not gonna happen.

If you really want a bad-@55, high powered VT amp, you'd be much better off with a push-pull pair of 828s. Add 20db(v) of local NFB and the 828 can give 300W of audio at 1.0% THD. That can be pushed to 385W at somewhat higher distortion. Include gNFB as well, and the distortion will be even less. That'll sound a helluvalot better than these whacko designs.
 
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22mannightstar

Member
Joined 2006
Re: Re: KT88 schematic

Miles Prower said:


Why? :bigeyes:

I don't like those designs that parallel finals. How do you get all those tubes pulling together? Obviously, you are not going to get all of them operating with identical characteristics. Just not gonna happen.

If you really want a bad-@55, high powered VT amp, you'd be much better off with a push-pull pair of 828s. Add 20db(v) of local NFB and the 828 can give 300W of audio at 1.0% THD. That can be pushed to 385W at somewhat higher distortion. Include gNFB as well, and the distortion will be even less. That'll sound a helluvalot better than these whacko designs. [/

To tell you the truth I am not a big fan of large amounts of tubes in parallel either but this is my first foray into building an audio amp and I did research it but didn't really find a lot of tubes that would put out a lot of power besides these. I do have access to lots of tubes but not sure if they are audio friendly or not. I am familiar with the 813 because I have a Ham radio license and know that these are old transmitting tubes. I can research the 828. A pair would be user friendly also.
Click to expand...
 
Brett

Brett

Member
Joined 2002
Re: Re: KT88 schematic

Miles Prower said:


Why? :bigeyes:

I don't like those designs that parallel finals. How do you get all those tubes pulling together? Obviously, you are not going to get all of them operating with identical characteristics. Just not gonna happen.

If you really want a bad-@55, high powered VT amp, you'd be much better off with a push-pull pair of 828s. Add 20db(v) of local NFB and the 828 can give 300W of audio at 1.0% THD. That can be pushed to 385W at somewhat higher distortion. Include gNFB as well, and the distortion will be even less. That'll sound a helluvalot better than these whacko designs.
Click to expand...
Speaking for myself, I want one for bass guitar. A 1500V+ PS and thoriated tungsten DHP outputs (with platecaps) aren't practical for something that will get moved a lot.
sorenj07 said:
I'm partial to the 813 myself. Plenty of threads about those.
Click to expand...
Ditto, but same issues as above.
 
richwalters

richwalters

Member
Joined 2003
Re: Re: Re: KT88 schematic

22mannightstar said:
Miles Prower said:


Why? :bigeyes:

I don't like those designs that parallel finals. How do you get all those tubes pulling together? Obviously, you are not going to get all of them operating with identical characteristics. Just not gonna happen.
Click to expand...



Well here we go I'll say it now...to put oil on the fire... you all better change your way of understanding linearity of tubes.. thinking about this. I'm sure some of are getting jangled up by comparing with mosfet curves.....far from it..
Multiple parallel operation is by far the best way to get power for a modest B+ and the output tranny design is simplified and will give better performance. A drawback is a hefty heater supply.
The idea that multiple tubes in parallel p-p need be 100% matched is a complete fad with standard EI laminated cores. The odd 5mA drift per tube isn't going to make any difference to the sound..Why not use parallel tubes with todays makes. They are consisent enough ..I do it and it sounds way better than a standard pair p-p running at an exortionate B+.
I agree that the 400W Genelec design does need a better driving stage...otherwise I can commend it's simplistic arrangement.

I would also add that the cost of carriage for 15kg output tranny lump would probably come to around 1/3 cost of tranny unless one arranges own transport.

richj
Click to expand...
 
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