[Jingo Lingo]

Great to hear Jarpy, I can't wait. Did you have any trouble with the build? And may I ask what phones you are using with the amp? I'm a bit worried about the high gain with my RS-1's.

 

[m0b1liz3]

You built one in one night Jarpy? Impressive! I will end up being a while on mine cause I need to rely on help from the shop at work to complete my case. Although I suppose I can still put together without the case... Thanks for mailing out the stuff!

 

[jarpy]

Quote:

Originally Posted by Jingo Lingo /img/forum/go_quote.gif Great to hear Jarpy, I can't wait. Did you have any trouble with the build? And may I ask what phones you are using with the amp? I'm a bit worried about the high gain with my RS-1's.

It seems to have worked straight away. I built it, double checked everything, found the 3 mistakes I had made, and fired it up. Actually, there was very strange distortion when I first plugged in my good cans, but I think the jack just wasn't seated right. Now it sounds great.

I'm running it into AD700s, which are also 32Ohm and very loud. Just like my last amp, i can only use the very bottom of the volume control without hearing damage.

Quote:

Originally Posted by m0b1liz3 /img/forum/go_quote.gif You built one in one night Jarpy?

Two really. I did the case work on Sunday. I used to build circuits and then try to fit them in a case. I now believe this is a very bad idea.

I completely ripped off the original Millet layout, and found his photo to be very helpful. I can post (higher-res) pics of mine if anyone is interested.

 

[m0b1liz3]

Yes. High res pics would be good.

 

[jarpy]

Here's some pics of my build. The workmanship is not as good as Pete Millett's (of course), but it's a high-res photo using exactly the parts you guys have so it may be helpful.

You can see that I ended up using more wire than I'd like. I think I will optimise the layout of my next one to minimise wire links.

http://assets.jarpy.net/images/linke...millet-top.jpg

http://assets.jarpy.net/images/linke...let-bottom.jpg

EDIT: If you follow this pic exactly, you will notice that I've wired my left/right pins wrong on the headphone jack. Since it's already disassembled for the pic, I think I'll go fix that now

 

[jarpy]

Quote:

Originally Posted by Jingo Lingo /img/forum/go_quote.gif I'm a bit worried about the high gain with my RS-1's.

I just added 100k resistors from the the RCA jacks to the the pot and the volume is now managable. It would be even better with 220k as suggested by rds, but I don't have 220k lying around right now.

This noise floor is still extremely low.

 

[Jingo Lingo]

Thanks for the pics. That will surely help when I begin mine.

 

[gz76]

Nice work. Your RCAs look a bit close together tho. Yeah, I'm holding off building mine until I've got a case sorted -- don't like the idea of having to retro fit a build to a case!

Quote:

Oh, a couple of other things. You will need thermal grease for the heat-sync insulators. They are the old-fashioned (and thermally superior) mica film kind. Also, the plastic volume knob does not fit the potentiometer, though I swear that I ordered exactly the ones that Millet himself suggested... such is life.

Anyone got some grease spare, or is it cheap enough to just go buy a tube?

I noticed the knob didn't fit while I was working on some layout ideas. I thought it might just need a little pressure to make it fit... good to know that's not the case!

 

[Pandaman]

For the grease, would thermal paste used for cpu's work the same?

 

[Daveze]

gz76: A 10g tube of the silicone based paste from Jaycar will cost $3.65, the 25% silver is $4.95 for 1.5g. I have a 10g tube of the silicone that's lasted me quite some time. If you're wondering how well the cheap stuff works: I'm using it for my MilletMAX with the highly biased BJTs and measure no temperature difference between the chip and the heatsink. I think the quality of the thermal paste is a bigger issue for amps like those Nelson Pass designs, where there is quite tremendous quantities of heat being dissipated.

Pandaman: The only concern is that the cpu stuff is often conductive (e.g. Arctic Silver), which isn't necessarily bad if you contain any runaway paste but can be if you apply it like I like to...liberally.

 

[jarpy]

Quote:

Originally Posted by gz76 /img/forum/go_quote.gif Anyone got some grease spare, or is it cheap enough to just go buy a tube?

I've got some grease. I've also got some TO-220 silpads that in retrospect I should have sent to people.

 

[jarpy]

Quote:

Originally Posted by gz76 /img/forum/go_quote.gif Your RCAs look a bit close together tho.

They are yeah

I didn't measure anything, it's all just eyeballed. It accepts my RCA cables though, so I'm happy.

 

[m0b1liz3]

Quote:

Originally Posted by jarpy /img/forum/go_quote.gif I just added 100k resistors from the the RCA jacks to the the pot and the volume is now managable. It would be even better with 220k as suggested by rjs, but I don't have 220k lying around right now. This noise floor is still extremely low.

If I did the same then, would I be able to switch the output to rca outs as a pre-amp?

My case is coming along nicely and may be ready by the weekend. Just have to sit down with all of these parts and figure out what I am doing with these parts. Never used clad board before but couldn't I get away with just half (3x4'). Have to think about what is the best way to proceed. What can I do before having the case ready?

 

[Pandaman]

Got my package this morning. Just started the case today, but should be good to start building tomorrow.

 

[jarpy]

Quote:

Originally Posted by m0b1liz3 /img/forum/go_quote.gif If I did the same then, would I be able to switch the output to rca outs as a pre-amp?

I dunno man. I'd ask the experts in the main thread. I'm just a beginner.

Actually, what I would do is try it out with some temporary wiring. Alligator leads are good for experimenting. I used a couple last night to resolve the "will it drive speakers" question that people have been chucking around. (Yes, it will drive tiny computer speakers. No it won't drive real speakers, but the distortion was kinda cool. Maybe I'll build a guitar amp with 19j6s

)