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 Post subject: Re: Wavebourn Kaidan vacuum tube headphone amplifier
PostPosted: Thu Jun 25, 2009 11:34 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
If you take a couple of 1K resistors it will be much better than a floating filament. But I'm afraid it is not it, most probably your B+ filter creates too high ripples.
One option is to take 1K resistor and 100 microfarad capacitor and build a filter for 1'st stages (33K resistors in anodes of triodes).

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 Post subject: Re: Wavebourn Kaidan vacuum tube headphone amplifier
PostPosted: Sun Sep 13, 2009 9:36 am 
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Posts: 10
Hello again.
I've removed the redundant LEDs and have found some resistors/capacitors. Which rating should I use for the variuos resistors? I've got some 1Ks of varying sorts up to some wirewound 22W ones, so how do I add in the filter? Is it a case of transformer - resistor - cap to ground - valve? Or does the capacitor come before the resistor? Is the resistor in series with the capacitor? I vaguely remember discussing pi and L filters with someone but can't remember how they're laid out. Google's not proving helpful with regards to values!
Bests


 
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 Post subject: Re: Wavebourn Kaidan vacuum tube headphone amplifier
PostPosted: Mon Sep 21, 2009 10:48 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
Kaidanovsky wrote:
Hello again.
I've removed the redundant LEDs and have found some resistors/capacitors. Which rating should I use for the variuos resistors? I've got some 1Ks of varying sorts up to some wirewound 22W ones, so how do I add in the filter? Is it a case of transformer - resistor - cap to ground - valve? Or does the capacitor come before the resistor? Is the resistor in series with the capacitor? I vaguely remember discussing pi and L filters with someone but can't remember how they're laid out. Google's not proving helpful with regards to values!
Bests


Hi!

The filter should be made like on this picture (R7 and C3)

Image

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 Post subject: Re: Wavebourn Kaidan vacuum tube headphone amplifier
PostPosted: Tue Feb 28, 2012 3:37 pm 
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Joined: Mon Jun 09, 2008 1:10 pm
Posts: 10
Hullo again,

I'm sorry it's taken me such a long time to get back to this - University got in the way!

I'm working on the filter at the moment and thought that if the H.T. is running low already, then won't a 1k resistor drop it even further? Did you mean me to reduce the anode resistor to 32k so the 1k left over can form the RC filter?


 
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 Post subject: Re: Wavebourn Kaidan vacuum tube headphone amplifier
PostPosted: Tue Feb 28, 2012 8:03 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
Kaidanovsky wrote:
Hullo again,

I'm sorry it's taken me such a long time to get back to this - University got in the way!

I'm working on the filter at the moment and thought that if the H.T. is running low already, then won't a 1k resistor drop it even further? Did you mean me to reduce the anode resistor to 32k so the 1k left over can form the RC filter?


It would be actually insignificant voltage drop. If say the stage pulls 5 mA current on 1K it would be 5V only.

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 Post subject: Re: Wavebourn Kaidan vacuum tube headphone amplifier
PostPosted: Sun Mar 04, 2012 7:57 am 
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Joined: Mon Jun 09, 2008 1:10 pm
Posts: 10
Hullo again,

I put one channel of the audio on a separate board outside the chassis to make it easier to troubleshoot and took some more measurements. The filaments are at 16.1V while the H.T. is only at 107V (and that's with only one channel wired up!) It's coming off the 120V transformer at 115V so perhaps it's my filtering that's making it lose all that? I've checked the diodes for forward and reverse resistance and they all seem fine. They were from a computer PSU so should be able to cope. The rectified 120V then goes to a 220uF capacitor, then a 1K resistor then a 100uF capacitor. At that jump off point it's at 107V. I found the LED I was using (a blue one) was dropping 2.94V in my test circuit, so I replaced it with a red one at 2.2V. However in the amplifier the drop's only 1.6V, I assume because of the extremely low H.T.

So do you think the rectifiying/filtering's at fault or the transformers? They provide the filament voltage fine, so I'm hesitant to blame them, and they were both 50VA. I'm sorry my incompetence is making this so complicated!


 
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 Post subject: Re: Wavebourn Kaidan vacuum tube headphone amplifier
PostPosted: Sun Mar 04, 2012 5:45 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
No, I mean additional filter for the 1'st triode, not for the output cathode follower. Of course it would be too much to add 1K to power cathode follower!

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