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NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread
http://diyaudioprojects.com/Forum/viewtopic.php?f=10&t=1799
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Author:  mxweas [ 23 Apr 2010, 22:19 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

roggom wrote:
mxweas wrote:
I'm not quite sure how you have the potentiometer wired to the board. I'd like to out my potentiometer and input/output jacks on the same board as my amp.

Max, If I understand correctly, you want to mount input and output jacks to your amplifier chassis and have an external potentiometer? If so that is fine as long as you wire the potentiometer to the input. If you put a potentiometer between this amp and another amp, it will increase the output impedance significantly. So a good circuit would be cd or mp3 - volume potentiometer (audio taper, not linear) NP-100 amp then headphones or power amp.

For a really small and cheap inline solution, I have used these for CMOYS and other little amps http://www.amazon.com/Koss-155954-VC20- ... B00001P4XH. Use them on the input of the NP100.

Out = Put. Id like to put both the potentiometer and input/output jacks on the same board as my amp. I'm not sure how to wire it though. How do I hookup the potentiometer to my amps input?

Thanks,
Max

Author:  roggom [ 23 Apr 2010, 23:13 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

You will wire the input jack to one side of your potentiometer, the other side will go to ground and the center pin (wiper) will be wired to the input capacitor.

Here is a great tutorial on potentiometer types and how they are wired. http://sound.westhost.com/pots.htm

Author:  mxweas [ 24 Apr 2010, 00:17 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

That looks like a wonderful tutorial, I'll look over it. One last question. I would assume you'd hook the positive on the input jack through the pot and to the board, but how can I do that without bridging together my left and right inputs? Would I be putting ground from the input jack through the pot instead?

Thanks,
Max

Author:  li_gangyi [ 24 Apr 2010, 00:28 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

You'd need a dual ganged pot, it's 2 pots joined mechanically together (the shaft) but are electronically isolated.

Author:  mxweas [ 24 Apr 2010, 00:43 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

li_gangyi wrote:
You'd need a dual ganged pot, it's 2 pots joined mechanically together (the shaft) but are electronically isolated.

Awesome! Thanks for the info. So when the pot is turned to the full CCW position, the input on the amp will be grounded, where as the full CW position will have almost no resistance between the input jack and the amp, yet full resistance between ground and the amp. That's awesome!

Max

Author:  KrammeAcoustics [ 24 Apr 2010, 08:32 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

tombethe wrote:
"dgadling" asked the members to check his Eagle based schematic he posted (20 Apr. '10).
The hint on the e-caps was for his schematic. He had drawn his e-caps with the "+"
to the input... Now - that were the things we suggested to change on dgadlings scheme...
I also suggested him (not Rogers) to use something like the Audyns instead of e-caps.
MKPs have the advantage that they block DC on both sides.
I mean possible DC from the amp and possible DC from the source...

Hi Tom

Now i understand. It seems electrolytic caps for the input, have been up to discussion earlier in this thread. It's correct what mentioned, when the electrolytic cap is reversed, it will work.

Prost :mrgreen:

Author:  mxweas [ 24 Apr 2010, 15:07 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

W00t! I finished my amp today! However, it sounds a little choppy in the low end. I'm guessing it's due to my lower quality caps, but I'm thinking it might be the NTE66's. Any Ideas?

keechoon, could you post a pic of the underside of your amp?

Thanks,
Max

Author:  roggom [ 24 Apr 2010, 17:06 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

Max, you may be experiencing clipping. Measure the voltage at the positive pin of your output capacitor, should be about half of your power supply voltage. It looks like you went with the fixed resistor option, just may need to tweak the resistance. Let me know your power supply voltage and the measured at the output cap (+) side.

Author:  keechoon [ 25 Apr 2010, 07:32 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

mxweas wrote:
W00t! I finished my amp today! However, it sounds a little choppy in the low end. I'm guessing it's due to my lower quality caps, but I'm thinking it might be the NTE66's. Any Ideas?

keechoon, could you post a pic of the underside of your amp?

Max, here it is ;)

Image

Author:  mxweas [ 25 Apr 2010, 21:22 ]
Post subject:  NP-100v12 - 12AU7 / IRF510 HeadAmp in a old car stereo face

@roggom I think you're right. I got some trim pots today and that seemed to fix the issue. Thanks! Do you recommend I go for higher quality caps?

Made an enclosure for my amp today out of an old car stereo face case:
http://twitpic.com/1ij8ml
http://twitpic.com/1ij8mj

Max

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