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Old 19th June 2013, 05:23 PM   #2001
AndrewT is offline AndrewT  Scotland
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McBob,
that quote says nothing about an optimum minimum temperature.

Pass is generalising about the reliability of output stages.
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Old 19th June 2013, 05:30 PM   #2002
RKH is offline RKH  United States
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Bcmbob,

It looks like a prime candidate to host the F-5 Turbo, V3 . It certainly has me thinking and scrounging my parts pile...

Nicely done!

Ryan
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Old 19th June 2013, 09:54 PM   #2003
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bcmbob:
For mosfet output transistors, more and more bias means less and less distortion (until they blow up). See NP's paper 'Leaving Class A.'
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Old 19th June 2013, 10:24 PM   #2004
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Andersonix View Post
(until they blow up)
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Old 19th June 2013, 11:12 PM   #2005
bcmbob is offline bcmbob  United States
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O.K. Here's the story Andrew. I connected the same Walkman and DIY speakers that I always use for initial turn on testing. I soon realized there was some distortion that was not there with other setups using the same two boards.

My first thought was low power from the batteries in the Walkman. New batteries - no change.
Then maybe bad CD seating. Different CD - no improvement.
Source at max volume - lower levels = a bit better but still edgy.
Bad interconnects. different set - same problem.

That's when I considered low operating temps. Now whether it is the power transistor itself or the output stage as a unit, I had never experienced any amp measuring that low.

The new system is already disassembled for improvements, but today I was able to attach one board to the aluminum tube with no water flow, simple metal mass heatsink. There is none of the distortion that was present at the initial full flow test. I'll know if Mustang Sally is the cause of the problem once I get the smaller 120 mm fan and radiator installed. The F5s sounded great using the dual 80 mm liquid system I mentioned, but the heat removal factor was less than air/convection without increasing the fan speed to an annoying level. Certainly not adequate if I eventually want to take on a BA.
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Last edited by bcmbob; 19th June 2013 at 11:22 PM.
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Old 19th June 2013, 11:49 PM   #2006
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bcmbob:
Your liquid cooling experiments are very interesting and inspiring, and I think your reports deserve their own thread so they can be accessed easily in the future and not just randomly sprinkled about in this 200 page 'Pass Pictures' thread...

Either way, we'll find you!
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Old 19th June 2013, 11:55 PM   #2007
bcmbob is offline bcmbob  United States
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Thanks for the complements. The thread already exists. Just haven't made the transition yet. I will now.

Liquid Cooled Builds.

BTW: Other side of 80. Note different pump that pushed the water through the radiator too quickly.
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Last edited by bcmbob; 20th June 2013 at 12:01 AM.
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Old 20th June 2013, 01:15 AM   #2008
xrk971 is offline xrk971  United States
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Bob,
An easy way to control the temp if too cool is to use paper to block air flow to portions of heater core. You can also put a constrictor flow hole in the liquid circuit on the pressurized side. A needle or globe valve is useful for dialing in the temp. You can do this and measure temp and listen to or measure distortion if you have a distortion meter. Easy to do poor man's distortion measurement: record voltage into a load resistor using sine test tone using sound card mic input. Run that through FFT analysis in Audacity or other program. Measure peak amplitudes of harmonics of test tone as function of temp. The amplitudes of the freq sum upmto the total harmonic distortion. Usually second and third harmonic are enough to see.
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Old 20th June 2013, 01:40 AM   #2009
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Default Parting out your prototype

Bob,

If you ever tire of your last prototype, I think you can split it into two parts, and have:

1. A hefty welder, from the power supply.....

2. A small still, to make your own moonshine....!!


Very interesting work...... I'm wondering if cryogenics, liquid hydrogen, and superconduction is next......
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Old 20th June 2013, 02:11 AM   #2010
bcmbob is offline bcmbob  United States
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X, that valve addition sounds good. I will install one somewhere along the 5/8" tubing. I'll PM you when I get to the measurements phase.


" I'm wondering if cryogenics, liquid hydrogen, and superconduction is next......"

CanAm Man, Very funny, but I'll need you by my side tomorrow when I open the C-H-S thread.

The comments are helpful, informative and a kick to read, but let's move the conversation over to the other thread as suggested. We can post a link and picture back here if/when there is something significant to report.

Thanks All.
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Last edited by bcmbob; 20th June 2013 at 02:15 AM.
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