F5 / Mezmerize Integrated

[McQuaide]

Originally Posted by 6L6

McQuaide -

Congratulations on a fantastic build!!

Everything looks great! I'm so happy that your project has turned out as good as it did!

Have you decided on adjusting the F5 feedback resistors to get a bit more gain? Or is everything working out well?

Thanks for the nice words, and thanks for answering my never-ending questions.

I'm still deciding on the gain question. Honestly, the gain is plenty for normal listening, especially with a MM (actually MI) cartridge like my Stanton 681ee. No, it's not like a dance club with 110 watts times 5.1 channels from a HTR, but that kind of volume isn't really necessary for serious listening anyway. And as I get older, I think more and more about protecting my hearing.

So I'll give it some time before considering any changes. Plus I want to get out of building, fiddling, hardware store runs, etc and actually enjoy the thing as it is for a while.

[McQuaide]

Originally Posted by Salas

Here is what to roughly expect from elecrolytics and temperature:

"When you will pack it up in its final box measure the temperature on the electrolytics. Rule of thumb is you double half a quoted cap's spec sheet lifespan for each 10 degrees decrement from printed max temp on the cap's sleeve. Example: If you got a 2000 hours 85C electrochemical capacitor working in a 55C environment, then 85C-55C=30C i.e. 3 times 10 degrees less than its max. Half 2000 hours is 1000 hours. 1000*2*2*2=8000 hours. That is how long it will live if the manufacturer is accurate and reliable. "

Quoted from a post I did in the SSA thread once. Of particular interest to all Class A amps builders of course.

Interesting. I have an instant-read food thermometer that will go right down through the top vents and down to the Mezmerize.

[Salas]

Let it cook for long enough with the lid on. Then remove the lid without powering down and quickly sample main PSU caps, Mez caps, and F5 Mosfets. So the temps can read near to closed box conditions before it cools down a few degrees with lid off. If one's got a DMM with a thermocouple wire probe, it may be fastened on parts of interest passing through a ventilation hole for gathering better temp cycle info.

[McQuaide]

I can tell you that at full song, the PS caps are barely warm to the touch. This case dissipates so much heat I would be surprised if there was a problem.

[Salas]

Sure its a big box that dissipates well. Just because we discussed temperature and electrolytics useful life, your class A integrated is a nice example and thank you for checking it out empirically for the topic to be complete.

[MASantos]

Awesome, this is exactly what I have been planning in my head, but using a second case to house the PSU section for the pre and power sections.

Really nice build!!!

[McQuaide]

Originally Posted by Salas

Sure its a big box that dissipates well. Just because we discussed temperature and electrolytics useful life, your class A integrated is a nice example and thank you for checking it out empirically for the topic to be complete.

OK Salas, I played music for a couple of hours with the case closed up, then took some temperature readings in degrees F:

F5 Mosfets: 143.5
Mez PS cap: 93.6
PS cap: 92.6

How does that look?

[McQuaide]

Originally Posted by MASantos

Awesome, this is exactly what I have been planning in my head, but using a second case to house the PSU section for the pre and power sections.

Really nice build!!!

Thanks! I have the Pearl 2 on input 1 and a Panny RP-91 DVD-A player on input 2. Was listening to some Donald Fagen on DVD-A and it sounded tremendous, and with plenty of gain.

[McQuaide]

Originally Posted by Salas

Sure its a big box that dissipates well. Just because we discussed temperature and electrolytics useful life, your class A integrated is a nice example and thank you for checking it out empirically for the topic to be complete.

Following on from this, I saw in Nelson's article that the heat sinks should run about 25°c above ambient room temperature. 25c=82f, 82+72=154°f. So it looks as though the temp of the F5 mosfets is right in range.

For the caps I just put the probe on the top of the cap until the temp reading stabilized.

[Salas]

I see some pinkish Mosfet insulation pads in your photos. Are those Keratherm by any chance? Which brings the discussion to the local temperature on the power semis cases is the best criterion. Thermal bonding from semis cases to sinks can vary depending on method and materials.