Crack w/SB - 50K stepped pot.

NightFlight · 6451

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Offline mcandmar

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Reply #15 on: February 03, 2014, 11:50:29 AM
90c sounds a bit extreme. I had a probe around my SEX amp and the highest i found was the main transformer ~60c, followed by the chassis plate in the high 40s.  Obviously inside the tube reads 100-140c but the elecy bits were easily half of that.

M.McCandless

Offline NightFlight

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Reply #16 on: February 05, 2014, 02:07:45 AM
My 80-90C was measured from non-heat conducting surfaces, with an infrared thermometer. I was seeing this temperature on the surface of the caps, black zip ties holding them, etc. I'll re-measure as I was taking measurements quick. Just to make certain I didn't get measurements from heat producing surfaces such as transistors, sockets or transistors.


Offline mcandmar

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Reply #17 on: February 05, 2014, 05:27:28 AM
Sounds like you were getting false readings to me, are you sure your meter hadn't switch over to Fahrenheit?

M.McCandless

Offline NightFlight

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Reply #18 on: March 08, 2014, 11:58:33 PM
Quote from: Caucasian Blackplate on February 03, 2014, 09:57:30 AM
Yeah, if the metal tab on the TIP50 is 60C, that's dandy!

Seeing 90C inside the amp would make me scratch my head about where all that heat was coming from, though perhaps removing the rubber feet and other unusual circumstances could drive the temps up.

I have the rubber feet on. I understand the need for the crack to breath.  The small fan under it certainly can't hurt. With the fan I see 54C on the largest board. Around 51C on heat sinks.

Taking the fan out now and letting it run. I've reverted to the CV4003 running the 5998. Its quite possible the 12BH7A was driving it a bit hard. I'd have check the plate voltages if/when I put it back in.


Offline NightFlight

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Reply #19 on: March 09, 2014, 12:00:27 AM
Quote from: mcandmar on February 05, 2014, 05:27:28 AM
Sounds like you were getting false readings to me, are you sure your meter hadn't switch over to Fahrenheit?

LOL yes. The big C or F are obvious.


Offline xcoolhandx

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Reply #20 on: March 09, 2014, 12:32:51 AM
nice stepper NightFlight...looks like this will be great build ,any chance for a pic of the Attenuator installed ?

P.S. I think your IR thermometer might be off ,I just measured mine

bottom pic is inside and top of the plate

 
« Last Edit: March 09, 2014, 12:37:01 AM by xcoolhandx »


Offline Mike B

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Reply #21 on: March 09, 2014, 12:04:27 PM
Hehe, I see we are all on the same page here.

I stuck my meat thermometer tip in the hottest cooling slot and after 3.5 hours its at 113F

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Ffarm8.staticflickr.com%2F7320%2F13044770864_f017f76df9_o.jpg&hash=5f1cb6f0e7794ff87c09601e0a9af476ace38a7c)

Yeah, I need to get another thermometer, I dropped this one.

Shows 111, but temp max was 113.  Ambient is 72, so looks like a 41F rise.

Far away from the bleeding edge

Offline xcoolhandx

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Reply #22 on: March 09, 2014, 12:11:07 PM
you are only 3C higher then me buddy ..lol  ;)
my ambient is 74F


Offline Mike B

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Reply #23 on: March 09, 2014, 01:06:37 PM
The transformer is so hot that you will remove your fingers after 5 seconds.

Crack runs hotter than my Stereomour, but after taking it's temperature I'm not worried.

Far away from the bleeding edge

Offline NightFlight

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Reply #24 on: March 10, 2014, 12:28:55 PM
I believe it was the 12BH7 pushing it hard. The CV4003 keeps the transistor package(s) max temp at 61C. The highest surface temp I measured on the surface of the caps as around 40C. I would call that ambient since they aren't generating heat, so far as I can tell.

However I'm in a small room and the ambient temp can creep up if I'm at it all day. The computer throws heat and the room will creep up to 28C. The house thermostat being downstairs - doesn't realize this and keeps blowing hot air in the room. *sigh*

I have the fan set up now anyhow - it should serve to keep the whole unit cooler and extend the life.


Offline NightFlight

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Reply #25 on: March 10, 2014, 12:48:13 PM
Pics as requested. Sorry - just really done quickly before I head out.


Offline JamieMcC

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Reply #26 on: March 10, 2014, 01:30:17 PM
Quote from: NightFlight on March 10, 2014, 12:48:13 PM
Pics as requested. Sorry - just really done quickly before I head out.

Ohh that looks a squeeze, I notice the small speedball board required a little creative offsetting.

Can I ask what sort of range in steps you are normally using out of 48 available?

Shoot for the moon if you miss you will still be amongst the stars!

Offline NightFlight

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Reply #27 on: March 10, 2014, 05:09:05 PM
It does. Board 'A' is currently floating. I'm looking to find something to cut and bind it down. A custom cut piece of plastic and replacement pair of screws.
 
As for the stepping, honestly I keep it at around half way around the dial.  With 48 positions, I get around 350 degrees of turn out of it.  I adjust visually with the screw hole more than the line guide.  :P  That gets the crack to the sweet spot and then I attenuate with Foobar, which is configured for WSAPI out.  The Khozmo is not the best for changing volume level. You get good snaps and clicks changing position.  However, it's possibly one of the best steppers out there - truly hardcore IME


Offline mcandmar

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Reply #28 on: March 10, 2014, 05:53:48 PM
Quote from: NightFlight on March 10, 2014, 05:09:05 PM
That gets the crack to the sweet spot and then I attenuate with Foobar, which is configured for WSAPI out.

From what i understand you really don't want to do that with a digital source as depending on the DAC it will either re sample and dither the signal, or just drop bits of data altogether.  I believe its less of an issue when playing 24bit audio as there is a greater range to work with, but its still preferable not to do it. Also almost all amplifiers are designed around a redbook input level of 2volts, if you start attenuating and feeding a weaker signal you end up either having to increase the gain, or crank the volume up at the amplification stage to reach the same output level, both at the expense of a higher noise floor.

In fact thats a great question to ask John Swenson to explain in the DAC thread...

« Last Edit: March 10, 2014, 06:00:07 PM by mcandmar »

M.McCandless

Offline NightFlight

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Reply #29 on: March 11, 2014, 08:05:03 AM
The differences I'm adjusting on the source is minimal. It really is imperceptible.  This is a totally different thread however.


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