Millett "Starving Student" hybrid amp - Page 168

The Tube Center is probably your best bet. Make SURE you order by phone - I sent my order from their website and got no response for about a week, then after two more weeks of phone calls I did get the tubes all in great shape and working. Orlando Vacuum Tubes

And when you call the guy will answer as ESRC so don't be confused - this is the place you are looking for.

Apparently the PCB's will be sold with a pair of matched tubes.

tube center

Thanks for the info. After a week I've not had a response from them so I'll give them a call.

So after about 40 minutes the case temps are ~110 degrees F and seem to be holding there. This is the surface temperature of the top panel, the sides, front and back are all in the high 80s. I'll try to leave the amp running for a hour or more and see if it goes up any more but so far using the case as the heat sink seems to be working nicely. Sounds pretty darn good too, currently being fed by a Buffalo DAC that's got my Arcam CD73 as a transport.

Well, you know Dsavitsk has been saying that all along - no heat sinks required.

Let's see if that holds for the smaller case, too - maybe 120 deg. on that one?

After another 45 minutes it was up to almost 120F so this definitely bears watching. If I can I'll bring the amp to work with me next week and let it run for 4hrs or more to see if the gradual escalation continues or if there's a plateau somewhere. 120 is getting to the borderline of what I'd feel comfortable with and makes me start to wonder about the junction temps.

Yeah, one thing I've noticed in other projects using the chassis as a heatsink is that it can take a few hours to stop rising in temperature and reach equilibrium. The more substantial the chassis, the longer it takes to reach that point, which can really give you a false sense of security.

It would be possible to just bolt on a heatsink to the outside of the case with some thermal paste, wouldn't it? Would it work well?

Certainly... just look at the link for the Menace in Nate's sig, that's exactly what he did there. The chassis will still rise up in temperature since it's still thermally coupled to the MOSFETs and heatsinks, but the cooling will be more effective than without.

All this prototyping talk is making me more excited and I can't wait to get a hold of a PCB... although to be honest I've also been kinda busy with my own prototyping

I had an idea about a certain enclosure design I wanted to build for my next mssh, so off I go and began to model my case:


Next, I headed over to the workshop and gathered some spare materials but all I had on hand were MDF boards, but that didn't stop me and I went cutting anyway The case came together nicely and I couldn't really wait to get building the internals so I decided why not build another P2P mssh for now, but this time I included ALL of the parts in the BOM (i.e. incl. all the optional parts).


Lastly, I had it all hooked up and fired it up in it's unfinished shell and wow... it sounds really nice!!! Thanks to Tomb and Dsavitsk for their additional design, and as always of course to Pete

I hate seeing perfect builds like that....damn my inadequacy.

That is one awesome build. Very well done!

You didn't mention what the room temperate is. I think you'd need to run the amp for several hours in a hot room (25C +) to get a feeling for whether this is a good idea.

For the BOM powerjack, which pin goes to the ground? I was able to use my MM to figure out which pin is which, but I am not sure whether to use the negative or the ground to wire to the ground.

Ambient room temperature is around 65 deg F (18.3 deg C), maybe lower. So basically after an hour and a half the amp is roughly 60 deg F (33 deg C) above ambient. That's not that bad in my book but if it keeps going up in could get to the point where I'm not comfortable any more. As it was you wouldn't have wanted to keep your finger on the chassis for very long.