• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

K8011/K8010 PCB build thread

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jamesfeline

jamesfeline

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well spotted ... yes you are correct did not think of that, but these will be OK for my next project (watch this space) as can easily extend the cables if needed. The transformers will be terminated local so no issues. But in the next batch will make the cables longer. many thanks for the observation, I have noted this ;)
 
jamesfeline

jamesfeline

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New batch of k8011/10 PCB's just been delivered :)
 

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jamesfeline

jamesfeline

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Hello fellow forum members

For some time now I wanted to make a k8011 amplifier with some 6CA7 NOS valves that I have .. also I wanted the valves to be on show safely ... so as you know all my existing valve amplifiers have the tubes fully enclosed .. like the picture attached
 

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jamesfeline

jamesfeline

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so the next pictures will hopefully speak for themselves as this is work in progress, please feel free to add any constructive ideas on the way through the build process. So currently this is just the internal chassis plate being fabricated .. and the valves will be on show in the completed project, so I am working this as I go along :scratch2:
 

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M

Matt BH

Member
Joined 2009
You are doing great work. Trouble with that is that you are copying an old design that had flaws. Adding a bias servo would be a good idea as your using toroidal output transformers. Maybe forget the input stage design and design your own?

Lovely work but just copying an old design won't bring much comment if any. Make it your own.

Cheers
Matt.
 
jamesfeline

jamesfeline

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Hi Matt ... good feedback, the design is old but all who listen to it really like it including me .. but I do have some improvements planned.
Like choke supply and some mods to the input and heater supply .. the transformers are now a new design with the output transformers will be by sowter ... some of the component values are now different based on my experiments.
But I enjoy making them .. so that,s the main thing I suppose ... :)
 
jamesfeline

jamesfeline

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Hi Samb

Hope all is OK ... all designs have flaws and is very subjective, especially on this forum .. I gave up worrying about statistics and software modeling for distortion etc etc .. I just use my ears and if it sounds nice I am happy ... all designs have their own distinct sound ... John Linsley hood for example with his shunt feedback phono preamp design most critics said it was a noisy design ... but in reality it sounded great when compared to other good designs of that same period, and who am I to challenge the great JLH as I am no designer and do not confess to be either, I just learn by reading and making real projects that I use ....
 
M

Matt BH

Member
Joined 2009
Building them is definitely the main thing and I applaud you for that. Most people get halfway and give up. I do apologise if if I came across a bit harsh.

As has been said all designs have flaws and the Velleman amps were designed with what was considered state of the art in the day. Time moves on. CCS and FET followers etc. are the norm now, that is why I suggested a bias servo.

So your going with some Sowters? Good choice! (Usual disclaimer) I have a pair of 100W Sowter output transformers. They are excellent. You may also like to try Majestic Transformers of Poole, Dorset. I have not used them yet but Rich Walters on here has. I can't find a link but a bit more of a search should do it. Excellent quality.

Cheers
Matt
 
jamesfeline

jamesfeline

Bespoke Constructor
Joined 2006
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Matt BH said:
Building them is definitely the main thing and I applaud you for that. Most people get halfway and give up. I do apologise if if I came across a bit harsh.

As has been said all designs have flaws and the Velleman amps were designed with what was considered state of the art in the day. Time moves on. CCS and FET followers etc. are the norm now, that is why I suggested a bias servo.

So your going with some Sowters? Good choice! (Usual disclaimer) I have a pair of 100W Sowter output transformers. They are excellent. You may also like to try Majestic Transformers of Poole, Dorset. I have not used them yet but Rich Walters on here has. I can't find a link but a bit more of a search should do it. Excellent quality.

Cheers
Matt
Click to expand...

Hello Matt

Looked at Majestic transformers look really good ... The Sowter transformers have arrived .. they are bloody heavy :)
 
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