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PostPosted: 27 Nov 2010, 15:28 
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Joined: 31 Dec 2008, 15:34
Posts: 441
SmittyHalibut wrote:
To be honest, I'm not sure why I got the bug to build a tube amp, but I did, and this design looked like a good place to start.

Hi SmittyHalibut

I guess you got the bug, because this is an easy build, which everyone, even beginners can make ! :up:
SmittyHalibut wrote:
I figure, if I've got an 18v supply from an old laptop, is there any reason I shouldn't just regulate 12.6v for the heater elements and run the plates at the full 18v? It's not a LOT more than 12v, but it's some...

You could try, but don't expect better performances. I've tried several times to modify this build to run 19 - 24 VDC, but never been satisfied, with the results. Make it running on 12,6 V as descriped in the original thread. It will work fine with low impedance headphones.

You can regulate the 18V supply of yours to 12 - 12,6 VDC, to get a hum and noise free PS.

About higher voltage experiments:
Through the last two years, i've tried to make different variations of this build. One variation were use of "two 12AU7 tubes" ..."one per channel". The purpose were to go for 24 VDC. The load were done by using the filament = around 80 Ohm load per channel, 12V/0,15A = 80 Ohm ( for this experiment i avoided use of LM regulators ). I won't say "try it", because it's not as good as the NP-100v12. Only purpose for this solution, should be use of high impedance headphones, where a higher voltage is needed ( ex. connected to my HD650 = 280 Ohms ) !


Last edited by KrammeAcoustics on 27 Nov 2010, 16:32, edited 9 times in total.

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PostPosted: 27 Nov 2010, 15:46 
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santik wrote:
I have made a power filter... capacitors in parallel.

1000uf, 1uf, 1000uf, 1000uf, 1000uf and 0.1uf.

that's is more than 4000uf. I have removed most of the hissing from the power supply but there is some light hum, very light that need attention to be able to listen to it. Is there any way to remove it? add more capacitors? how much capacitance do I need, I wonder.

Don't parallel them all
...try instead a RCRC or even better RCRCRC, see the ill. i've dropped earlier in this thread. Page 45

It could be following ex.:
3001uF (R) 1000,1uF
or 2001uF (R) 1000uF (R) 1000,1uF
Resistors (R) in the RC filter, depends of which voltage used ( try it out ).

You'll need a PS ( good of current, 1000 mA or higher will do it ) that gives a relatively high output voltage ex. 18 - 24 VDC or even higher and filter it down to the voltage needed.

If you're using a to low voltage PS ( typical 12 - 15 VDC ), it's difficult to get with of hum, nearly not possible. :exclaim:


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PostPosted: 27 Nov 2010, 17:43 
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Joined: 17 Apr 2010, 16:07
Posts: 39
Location: Huddersfield ,West Yorkshire,UK
SmittyHalibut wrote:
Let me preface this post by saying that I am _NOT_ a "true audiophile." I like good sounding audio, I just don't have any gear better than my Sennheiser HD555s that I just picked up from Amazon on GoldBox deal for US$75, and my Sennheiser SD280s before that.

The HD555 are great i had the chance to listen to some after i advised someone to get them as he was on a budget and i have to say they were great and they are often on offer you just can not go wrong with them i doubt theres much to touch them for double the price.

you might also be interested in this mod if you look at the HD595 and the HD555 specs they are the same apparrently they dumb the low end down with a bit of foam at the back of the driver .It wouldnt be the first time somethings been dumbed down and rebadged and sold cheaper for marketing reasons :lildevil:



koogar

Update: More info in this Sennheiser HD555 upgrade to HD595 thread.

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Head Amp On 555 Delay all in one
NP-100v12 - 12AU7 / IRF510 HeadAmp


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PostPosted: 27 Nov 2010, 20:27 
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Joined: 18 Sep 2010, 12:48
Posts: 81
KrammeAcoustics wrote:
santik wrote:
I have made a power filter... capacitors in parallel.

1000uf, 1uf, 1000uf, 1000uf, 1000uf and 0.1uf.

that's is more than 4000uf. I have removed most of the hissing from the power supply but there is some light hum, very light that need attention to be able to listen to it. Is there any way to remove it? add more capacitors? how much capacitance do I need, I wonder.

Don't parallel them all
...try instead a RCRC or even better RCRCRC, see the ill. i've dropped earlier in this thread. Page 45

It could be following ex.:
3001uF (R) 1000,1uF
or 2001uF (R) 1000uF (R) 1000,1uF
Resistors (R) in the RC filter, depends of which voltage used ( try it out ).

You'll need a PS ( good of current, 1000 mA or higher will do it ) that gives a relatively high output voltage ex. 18 - 24 VDC or even higher and filter it down to the voltage needed.

If you're using a to low voltage PS ( typical 12 - 15 VDC ), it's difficult to get with of hum, nearly not possible. :exclaim:

ok, it is a 12VDC regulated power supply, full of hissing. It is mostly gone now... just very very low frequency hum/hiss after that capacitor circuit. So, you say that with resistor capacitor circuit the hissing will be gone, better? I do have 1Ohm 2W resistor, is that wattage rating sufficient enough? and for 1 ohm in 12VDC, how much voltage will drop?


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PostPosted: 27 Nov 2010, 20:31 
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Joined: 18 Sep 2010, 12:48
Posts: 81
the sound from this amp will change digital sound to analog sound or not? I am thinking whether or not to get myself a USB DAC.
:)


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PostPosted: 27 Nov 2010, 21:09 
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Joined: 27 Nov 2010, 02:18
Posts: 34
Location: Arroyo Grande, CA, US
Koogar: thanks for that link! I'll give that a try on my HD555s and will report on it's effect.

As for milling a board, I found PCB-GCode (google it; I'm on my iPhone and cant easily link to it) and fed the Eagle file made by the author into it. I'll play with "etching" a board tonight after my daughter goes to bed. Unfortunately, I only have double sided stock which I don't want to plane off so I'll be "etching" wood tonight. :-)


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PostPosted: 27 Nov 2010, 21:10 
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Joined: 27 Nov 2010, 02:18
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Location: Arroyo Grande, CA, US
santik wrote:
the sound from this amp will change digital sound to analog sound or not? I am thinking whether or not to get myself a USB DAC.

This is not a DAC. It takes an analog signal in and amplifies it.


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PostPosted: 27 Nov 2010, 21:23 
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Joined: 17 Apr 2010, 16:07
Posts: 39
Location: Huddersfield ,West Yorkshire,UK
SmittyHalibut wrote:
Koogar: thanks for that link! I'll give that a try on my HD555s and will report on it's effect.

As for milling a board, I found PCB-GCode (google it; I'm on my iPhone and cant easily link to it) and fed the Eagle file made by the author into it. I'll play with "etching" a board tonight after my daughter goes to bed. Unfortunately, I only have double sided stock which I don't want to plane off so I'll be "etching" wood tonight.

No probs

wish i had a milling machine :mrgreen:

i often think about making a small CNC machine something around a few square metres would do me it would certainly earn its keep making front panels and boards :P :D

Koogar

_________________
Homebuilthifi Projects
runawaybrainz.blogspot
Head Amp On 555 Delay all in one
NP-100v12 - 12AU7 / IRF510 HeadAmp


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PostPosted: 28 Nov 2010, 00:26 
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Joined: 27 Nov 2010, 02:18
Posts: 34
Location: Arroyo Grande, CA, US
I started to post here a few ideas and plans for this headphone amp, but stopped myself, realizing that it's rather off-topic. So instead I created a new thread. If you're interested in discussing my 4 input (2x USB DAC, 2x Analog) mixer front-end for roggom's awesome amp, head over there.


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PostPosted: 28 Nov 2010, 10:55 
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Joined: 31 Dec 2008, 15:34
Posts: 441
santik wrote:
ok, it is a 12VDC regulated power supply, full of hissing. It is mostly gone now... just very very low frequency hum/hiss after that capacitor circuit. So, you say that with resistor capacitor circuit the hissing will be gone, better? I do have 1Ohm 2W resistor, is that wattage rating sufficient enough? and for 1 ohm in 12VDC, how much voltage will drop?

1 Ohm will give a low voltagedrop, but that will probably not be enough.

No, you won't go that way. If the PS you've got, are already regulated to 12 VDC, it don't bring sense, to go for a even lower voltage, because the amplifier and filament needs 12 VDC.

As told before, go for a higher voltage ( another PS ) and filter it down to 12 - 12,6 VDC.

Explanation of the RC circuit, read about it here:
http://en.wikipedia.org/wiki/RC_circuit


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