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NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread
https://diyaudioprojects.com/Forum/viewtopic.php?f=10&t=1799
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Author:  christian_jennings [ 27 Jan 2020, 10:28 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

Looking at my parts I collected I noticed the MOSFET I had on hand is IRL510 not IRF510. That should be ok right? Or won’t work with this project? The IRL will work in place of IRF but not vice versa.

Author:  christian_jennings [ 29 Jan 2020, 22:15 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

The irl510 seems to be working fine. The first power adapter fried the 10ohm resistors before I got it shut down. I tried a couple other adapters and they worked but hum was really loud. I went to batteries plus bulbs and got a battery. Works awesome. Just amazed at the detail and the quality. ”Wish you were here“ at the beginning I’m hearing very subtle sounds that just weren’t there before. After he clears his throat (which I usually pick up) I can literally hear him close his mouth and then a slight groan then pause and pulls in a breath before the guitar comes in. crazy.
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Author:  christian_jennings [ 18 Feb 2020, 18:40 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

I built 2 of these and they work fantastic. Oven never been a big headphone guy but these little amps are making me a believer.

So I started a third to go in this enclosure that has a 12v power supply so it’s looking very cool. Problem it looks like one channel is getting nothing. I replaced both regulators no luck and one of the trimmer pots but still nothing.

All the components look ok and the circuit looks right so I guess I should try replacing the transistors?

Author:  ILoveHiFi [ 18 Feb 2020, 20:43 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

Measure the voltages in the circuit, if they are correct then the thing should be working.

Then it could be a input or output prolbem where something is not connected properly.

Or the circuit.

Author:  christian_jennings [ 18 Feb 2020, 21:38 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

User error. I had a problem with the circuit. Doh!

I think I got rid of the rf issues with this drive enclosure. Pretty snam dazzy.

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Author:  christian_jennings [ 20 Feb 2020, 22:35 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

There was a hiss at zero/low volume. I added a crc filter at 1000uf, 100ohm, 1000uf. See pictures. This seems to work it is dead quiet now. I had trouble finding information on the specific caps and resistor values.

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Author:  junkjer [ 21 Feb 2020, 05:51 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

If you mean specific values for the parts for this project (rather than the crc filter you added) there's a list here --

viewtopic.php?p=13962#p13962

Some have also found a sound improvement if you add a 0.1 microfarad capacitor (ceramic or film) between the drain of each mosfet and ground. A 1 microfarad film cap in parallel with each output cap (C3) might also improve the sound.

Author:  ILoveHiFi [ 21 Feb 2020, 06:21 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

Metalised polypropene, ERSE pulse x or more expensive are recomended for capacitors to get hifi sound quality.

Author:  christian_jennings [ 21 Feb 2020, 13:37 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

I was looking for values for the crc filter.

Would I want to use a non-polar crossover cap like the ERSE in this crc application? It sounded pretty good with these nichicon electrolytic.

Author:  ILoveHiFi [ 21 Feb 2020, 17:34 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

For powersupplies and voltages use cheap geniune metalised polypropene.

Direct audio signalpath then expensive stuff

You want small compact size cause normally what stopps me from installing more 0.1uF is the size of the metalised polypropelene, compared to ceramic or cheaper chinese stuff.

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