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Old 8th June 2012, 07:18 PM   #21
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Hi there,

I am beginning to realize that this project will probably be nominated for the 'Slowest DIYaudio project ever' award.

But again, a little progress has been made, the cathode resistor assembly with the EL34 cathode resistors and the large bypass electrolytics is finished:

Click the image to open in full size.

And last month the output transformer for the test setup has arrived from Lundahl:

Click the image to open in full size.

So now everything is ready and waiting to complete the one-channel test setup, I hope I manage to do this in the next weekends, if there's not too much other work to be done...

Greetings,
Andreas
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Old 25th June 2012, 07:00 PM   #22
6L6 is offline 6L6  United States
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Just found this build journal, everything looks very good so far! I espically like the capacitor blocks. I am quite interested in this amp, and am considering building a version with KT88/6550 outputs.
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Old 26th June 2012, 10:51 PM   #23
smbrown is offline smbrown  United States
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For what it's worth, here is my build of the PP1C with CCS under the EL34s. They have been in regular use now for a long time. Love them!
Recently finished PP amps - SteveBrown - Tube DIY Asylum
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Old 7th October 2012, 06:51 PM   #24
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WHOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!

It works!

Click the image to open in full size.

Powered the test circuit up for the fist time after completing it this afternoon.
Very nice, seemingly undistorted sound via a single 8ohms fullrange driver.

A slight hum is audible when listening close to the driver, and it does not disappear instantly when switching off the mains. So I would think there is some grounding/shielding problem with stray noise picked up via the long, unshielded interconnects, not heater-related or too much ripple on B+.

Ideas for troubleshooting, anyone?

Greetings,
Andreas
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Old 8th October 2012, 05:27 PM   #25
ChrisA is offline ChrisA  United States
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Quote:
Originally Posted by Rundmaus View Post
....
A slight hum is audible when listening close to the driver, and it does not disappear instantly when switching off the mains. So I would think there is some grounding/shielding problem with stray noise picked up via the long, unshielded interconnects, not heater-related or too much ripple on B+.

Ideas for troubleshooting, anyone?
I assume you are joking. Having only a slight hum with a breadboard circuit is very good. The first thing to do is use shieled wire. I use RG-174 but anything would work if it can take the voltage. The RG-174 is rated for tube-type voltages and is not expensive. Of course yu only ground one end of the shield and use heat shrink on each end to prevent the shield from shorting to something. I use coaxial cable for EVERY signal that feeds a high impedance. It really will keep out environmental EMI.

Next step after that is to get a chassis with six metal sides. I go as far as to use star washers to close off the bottom cover plate to ensure the aluminum to aluminum conducts.

then be sure and use those aluminum tube shields over the preamp tubes.

Replace the IEC connector with an inlet filter. These are cheep and keep noise from getting in via the power cable
Welcome to Delta Electronics, Inc. - Components

But hum on a breadboard is to be expected. If it is only slight feel lucky.
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