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PostPosted: 03 Jul 2017, 15:42 
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Joined: 03 Jul 2017, 15:35
Posts: 7
hey guys, so ive just build my first tube amp namely this one : NP-100v12: 12AU7 (ECC82) / IRF510 Headphone Amp

works great, very nice sound !

Just a question as im new to tube amps

How much is the output power more or less?
And anyway to increase the bass a bit more?

Im currently running my Sennheiser HD420's off the amp, very nice sound indeed but needs a bit more low end as compared to my laptops output.
I know the HD420s' doesnt have a very low low end but my laptop output has more bass though.

Also can the amp be run on 19v? and the tube heaters on 12v? what difference would it make ?

The Sennheisers are 600ohm headphones as i found out in the specsheet

thanks , and a awesome wright -up on building the amp.


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PostPosted: 19 Feb 2018, 15:58 
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Joined: 09 Oct 2012, 19:43
Posts: 297
Location: Vancouver Canada
OK the spec sheet on the HD420's says the normal power required is 100mW. Your amp then would have to output an 8 volt signal just to produce that 100mW sig for "normal listening". (8 x 8 / 600 = 106mW). You could use a filter to attenuate the high freq then turn the volume up a bit. This is all a bit complicated for such a simple amp system though.
I would not connect the amp to 19v as it is designed for 12 volts. 19 volts would cause all kinds of problems just before it blew.
Your best bet is to:
A --Run it the way you are and put up with less bass. (is there an equalizer in the chain you can boost the bass?)
B --Try and find some lower impedance headphones. (most now days are 32 ohms).
C --Build something like Bruce's 6DJ8 headphone amp which can be built using a 600 ohm output transformer which matches your 600 ohm headphones.


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PostPosted: 27 Jun 2018, 04:09 
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Joined: 03 Jul 2017, 15:35
Posts: 7
I have changed the amp a bit (still experimenting and learning). I added a 12v DC regulator to the heaters to keep them at 12v volt seperately. The rest of the amp runs at about 20v. Ive checked the spec sheets of the LM317 regulators and IRF 510 and they can handle a bit more power, they do get a bit hotter as well. I could always add heatsinks.

The sound has changed, bit more output power .
Ive been running it for a few months now. No noticeable problems, except the heat being slightly more.

If i were to change the 12au7 valve for a 12ax7 ( more gain) , what would be needed to run the 12ax7 and what would the benefits be?

Sorry for all the questions, i'm still new to valves and still learning as i go.


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