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Old 22nd December 2011, 07:30 AM   #641
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Now thereīs equal pieces of sand and glas in the amp

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Old 22nd December 2011, 07:44 AM   #642
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by flatheadmurre View Post
Now thereīs equal pieces of sand and glas in the amp

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Interesting....

Have you done any measurements yet?

I guess no ....

I see a difference two of them have more diodes?
So is the bias setting different?

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Old 22nd December 2011, 08:03 AM   #643
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Iīm fiddling around with bias.

Lets say one channel is heating the house better then the other right now.

I want to run them a bit hotter but i have no clue where they perform the best and when they start dieing prematurely.

Iīll try some different settings and see how it goes.

Please chip in with some guidelines here
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Old 22nd December 2011, 08:20 AM   #644
M Gregg is offline M Gregg  United Kingdom
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Well max Anode is 60W,

I am told that 400mA is pushing it (tube life) ..The higher the bias current the shorter will be the tube life..Then again up to 60 Watt is the design..

The heat will be very high..In the box temp will be higher than with it open..
What power out are you getting now what bias current are you running?
Probably a good idea to check mains power taken just so your aware of the electric meter rotation speed....
Have you used chassis as a heat sink?


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Old 22nd December 2011, 09:26 AM   #645
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All mosfets attached to top plate.

I was dissipating 43w this you should try itīs an excellent toaster !!!

This is wintertimeonly setting

Specs say one heater should be able to manage 45w but i donīt dare to flip the switch
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Old 22nd December 2011, 09:29 AM   #646
M Gregg is offline M Gregg  United Kingdom
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Just for interest..

Whats the sound like?



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What is the sound of one hand clapping?

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Old 22nd December 2011, 09:48 AM   #647
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To descride sound is hard.

More distinct donīt wonders of when driven harder.

Now i can turn it up more before it gets ugly.

The power is enough for my needs but the russians are capable of twice as much.

Iīll try raising B+ for PI by adjusting the reg i got 30v more before regulation starts dropping.
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Old 22nd December 2011, 10:17 AM   #648
M Gregg is offline M Gregg  United Kingdom
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I guess possibly,

A fixed bias servo control creating an auto bias...
(Probably not worth the effort)..
I will try the Fet just for fun..
I also want to try some polycarb caps....can't remember what they sound like..


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Old 22nd December 2011, 11:15 AM   #649
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My first approach was a 1ohm resistor and a servo that adjust the bias but space is not there for it.

This is a brilliant KISS solution Alistair has a good eye for the nononsence approach of things.

Next step is higher b+ for PI.

For another go iīd like to raise the rails a bit higher for more OP.

Iīm running 350mA right now keeps the cost for firewood down.
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Old 22nd December 2011, 11:59 AM   #650
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Quote:
Originally Posted by flatheadmurre View Post
To descride sound is hard.

More distinct donīt wonders of when driven harder.

Now i can turn it up more before it gets ugly.

The power is enough for my needs but the russians are capable of twice as much.

Iīll try raising B+ for PI by adjusting the reg i got 30v more before regulation starts dropping.
At 320V on PI with 47K loads, I get around 65V P-P from the PI before it starts to clip.
This should be enough to drive the O/P pair to the point where they would start to conduct G1 current,--although this PI cant source that sort of current.

Worth remembering, When running 150V +-B rails, the O/P pair are only 'seeing' 110-120V each, as the bias voltage is coming off the full +B value.

To get More power, a higher +-B volts to o/p would be needed to compensate for the Bias loss--With the attendant Extra Heat, both in the valve and the cathode-components and possibly reliability issues--Is it worth it?
--Alternatively, you can try out fixed-bias, but you'll need an extra neg supply referenced to the neg rail for bias of the bottom valve....
--The top valve could use a well de-coupled supply from the neg rail....
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