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Old 14th May 2012, 03:12 PM   #11
djn is online now djn  United States
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That is what I am hoping Mel. The only down side I've ever heard about the GM70 is there, in some cases, can be a lack of highs. I hope this is not the case. Time will tell. The only thing I am changing on the scheem is using a 1.5uf coupling cap instead of the .47uf. A friend of mine gave me a Seimans 1.5uf cap that is suppose to me the cat's nats.


Here is a link to my chassis build. That took some time in itself.


http://www.audiokarma.org/forums/sho...4&postcount=13




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Old 14th May 2012, 03:17 PM   #12
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WOWWW. Cool!
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Old 14th May 2012, 03:34 PM   #13
djn is online now djn  United States
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Thanks Radiostar. I am not looking forward to populating the GM70 filliment boards, but it should only take me an evening....and maybe a beer or 2
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Old 14th May 2012, 04:25 PM   #14
kevinkr is offline kevinkr  United States
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No lack of highs with my relatively recently completed (November last year, and still evolving) GM70 mono blocks so I think you will find your amplifier more than competent. Good enough overall that these amps have replaced my 300B SE amp. Very transparent, and well balanced spectrally speaking.

GM70s running 120mA/1kV fixed bias into 7K. Driver is IT coupled triode connected D3A running at 20mA.. About 20W out..

I'm also using the Rod Coleman CCS filament boards - work well.
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Old 14th May 2012, 04:39 PM   #15
djn is online now djn  United States
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Thanks for the vote of confidence Kevin. I figure I'll get 12 wpc out of it, which is fine with me. Here are pix of the speakers I will drive with this amp. I just finished them.
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File Type: jpg IMAG0095.jpg (65.7 KB, 341 views)
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Old 14th May 2012, 04:46 PM   #16
kevinkr is offline kevinkr  United States
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Very nice, and look a lot more attractive than my Onkens. Tell us more about the speakers. (I know it is OT.. )

The copper plate GM70 is worth the extra money if you can find a few..
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Old 14th May 2012, 04:55 PM   #17
djn is online now djn  United States
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I missed a pair of copper plates a week ago for free. The bass bins are JBL Barzilay cabs with JBL E140 15" woofers. They are tempoary until I get my Lambda TD15H back after reconing. The horns are 350hz tractrix with JBL 2441 CDs with Radian diaphragms, then the Big A$$ Heil on top. Currently I am running a first order passive crossing at 800hz and 8000hz. I have a Steve Bench 3-way crossover on the bench up next so someday I will be tri amping them.
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Old 14th May 2012, 10:44 PM   #18
djn is online now djn  United States
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I need a little advice. Because I like my junk to look cool it sometimes gets me in trouble. Here is a case in point. I run 1386volts to the front of my amp to the 6D22S rec tubes, but then I have to run the B+ from there back to the tall set of caps. I am concerned that I (geez I can't remember the term) will run a wire with more than 1000volts along the chassis and the volts can "jump" or arc to a ground. So how do I run the wire back to the caps without it arcing? How much space do I have to provide? Thanks.
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Old 14th May 2012, 11:24 PM   #19
MelB is offline MelB  Canada
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JBL E140's you say!
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Old 15th May 2012, 12:02 AM   #20
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I used 1500v rated wire. Then on the chokes and transformers which only had 600v rated wire I bought a roll of shrink tubing (600v rating) and added an extra layer of protection over all the wires. My chokes were all hi-pot tested to 2500v so I'm feeling pretty good about it all. Oh and rubber grommets for anything through the chassis.
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