GM-70 Amplifier

[dberning]

Beautifully constructed amp, Dave. With the weather the way it is, I am sure that you can get the second one done shortly. Look forward to hearing it.

David Berning

[David McGown]

Made good progress on the second amp this weekend. Nothing like the motivation of a completed and nice sounding amp, and looking forward to stereo. A couple of in-progress shots.

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[Stuart Polansky]

Pictures don'e do this amp justice. It is MUCH bigger in person than it appears. It sounds amazingly powerful, and is of course, constructed with David's usual meticulous craftsmanship.

The choke, power transformer and oil caps are enormous!

Great build David!

[KLH007]

Another beautifully made amp, great work David!

[Grover Gardner]

Terrific, Dave! Glad you were able to put that iron to good use!

[David McGown]

Another progress report. Wanted to show the copper ground buss for the power supply, since that is hidden from view when the amp is fully assembled. Using 22 or 24 gauge (don't remember offhand) copper sheet, cut down to 1" wide strips running from the HV power transformer to the capacitor terminals, and finally to the input jack. Using bronze external tooth lock washers between the terminal and each buss layer to ensure a good mechanical/electrical connection when the terminal nut is torqued down.

Attachments

[Stuart Polansky]

David, I'm surprised, the clamp screws for two of those oil caps are installed in opposite directions. Tsk, tsk!


Laugh out loud, even David is not perfect. I can sleep better at night knowing that!

[ratbagp]

What a great idea for those of us who use wood for the top plate. I have a bunch of these copper strips that I could use though I suppose a single run like you have done would be better.

http://www.leevalley.com/US/gifts/page.aspx?p=10459&cat=4,104,53211,10459

ray

[tomp]

Have you ever thought of lining the inside of the wood case with copper screen? I have done that in low level applications to create a Faraday cage. It is a great way to keep out RF if you ground it.

Tom

[David McGown]

Have you ever thought of lining the inside of the wood case with copper screen? I have done that in low level applications to create a Faraday cage. It is a great way to keep out RF if you ground it.

Tom

Tom,

I have never had a problem with power amps and RF using my wood chassis construction. Low level (phono stages) are a problem, and I have used copper shielding with wooden chassis in those cases, but even with a metal enclosure grounded to earth, I have problems with the ham radio operator up the street. When he is working his rig, then I fall back to digital.

David